334155066-TNB-Planning-Guide-LV.pdf

Low Vol Low olta tage ge Planning Guidelines

LOW VOLTAGE PLANNING GUIDELINES November 2012

Asset Management Department Distribution Division, Tenaga Nasional Berhad Wisma TNB Jalan Timur, Petaling Jaya Selangor

Disclaimer This guidebook does not confer legal rights or impose legal obligations obligations upon any member of the public. While TNB has made every effort to ensure the accuracy of the discussion in this presentation, the obligations obligations of the regulated community community are determined by statues, regulations or other legally binding requirements. In the event of a conflict between the discussion in this presentation and any statute or regulation, this presentation presentation would would not be controlling. controlling.

LV PLANNING GUIDELINES

ACKNOWLEDGEMENT We would like to express our deepest gratitude to the management of the Distribution Division, for the successful publication of this Low Voltage Planning Guidelines. Our special thanks to Hj. Ismail Mohd Din, Senior General Manager, Asset Management Department for his full support and motivation to establish the revision of this guide book. We would like to express our gratitude to the ever-committed LV Planning Guideline workgroup members, comprising Ir. Tan Siew Hwa, Mr. Kok Sheng Kheun, Mr Ideris Shamsudin, Mr Lim Chia Yih and Dr Rahman bin Khalid for their 2 years of hardwork in successfully completing this new edition of Low Voltage Planning Guidelines. Our appreciation also goes to Assoc. Prof. Dr. Ir. Au Mau Teng, Ir. Lau Chee Chong, Ms Teo Siow Kim, Mr Ruslam Hussin, Mr Azmi bin Husin, Ir Rekha A/P Perumaloo, Ms Fadhlillah Adnan, Mr Fazely Haron and Ir Woo Chiew Chonng for their guidance and feedback in developing the guidelines. Special thanks to Dr. Marayati Marsadek for her untiring efforts in proof-reading this guide book. Lastly, acknowledgement and thanks to all other distribution planning community members whose names are not listed above for their valuable contributions and ideas in preparing the contents of this handbook.

Thank you.

Dr. Abu Hanifah bin Azit Chief Engineer System Planning & Development, Asset Management Department, Distribution Division, TNB

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FOREWORD Objective of the power distribution system is to deliver electrical power to customers in a safe, reliable and most economical way. Several parameters of electricity supply such as frequency, continuity of supply, voltage level etc. should be within allowable limits to ensure that customers obtain satisfactory performance for their electrical equipment while ensuring that the demands of the customers are continuously met. The capital and operating costs of doing so should be kept at the most optimum level, taking into account the total cost of ownership and losses in the system. This document details out and standardizes planning methodology in TNB Distribution, which provides TNB Distribution Planners with a basic understanding of theory and practical application. This latest edition of Low Voltage Planning Guidelines also introduces additional requirement to adopt the changes in technology and expansion of network. With this revised Low Voltage Planning Guidelines, I am confident that TNB Distribution Planners would be able to produce the most efficient LV network to meet customer’s service expectation.

Hj. Ismail bin Mohd Din Senior General Manager Asset Management Department TNB Distribution

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TABLE OF CONTENTS ACKNOWLEDGEMENT......................................................................................................... i FOREWORD ........................................................................................................................... ii TABLE OF CONTENTS........................................................................................................... iii CHAPTER 1 GENERAL INTRODUCTION ..............................................................................1 1.0 INTRODUCTION ..................................................................................................... 1 1.1 SCOPE ..................................................................................................................... 1 1.2 DOCUMENT LAYOUT ............................................................................................ 2 CHAPTER 2 QUALITY OF SUPPLY ........................................................................................3 2.0 OBJECTIVE .............................................................................................................. 3 2.1 DEFINITION OF QUALITY OF SUPPLY ................................................................... 3 2.2 SYSTEM AVERAGE INTERRUPTION DURATION INDEX (SAIDI) ......................... 4 2.3 SUPPLY SYSTEM STANDARDS ............................................................................... 5 CHAPTER 3 LOADS ...............................................................................................................7 3.0 OBJECTIVE .............................................................................................................. 7 3.1 TYPES & CHARACTERISTICS OF LOAD ............................................................... 7 3.2 LOAD GROWTH ..................................................................................................... 7 3.3 LOAD DEMAND..................................................................................................... 8 3.3.1 Typical Load Demand for Domestic Residential Premises ................. 9 3.3.2 Typical Load Demand for Commercial Premises ................................ 9 3.3.3 Typical Load for Commercial Complex ................................................. 9 3.3.4 Typical Load Demand for Industries ..................................................... 10 3.4 COINCIDENT FACTORS ...................................................................................... 10 3.4.1 Sample Calculation of Coincident Factor .......................................... 10 3.5 LOAD FACTOR ..................................................................................................... 11 3.6 ALTERNATIVE SUPPLY ..........................................................................................12 CHAPTER 4 DISTRIBUTION SUBSTATIONS ........................................................................13 4.0 OBJECTIVE ............................................................................................................ 13 4.1 DEFINITION............................................................................................................ 13 4.2 SUBSTATION SELECTION CRITERIA .................................................................... 14 4.2.1 Indoor Substation ...................................................................................... 14 4.2.1.1 Indoor Standalone Substation .................................................. 14 4.2.1.2 Indoor Attached Substation ..................................................... 15 4.2.2 Outdoor and Semi-Indoor Substation .................................................. 15 4.2.3 Pad-Mounted Switchgear H-Pole .......................................................... 15 4.2.4 Compact Type Substation ...................................................................... 16 4.2.5 Summary of Substation Characteristics and Usage .......................... 17 4.3 SUBSTATION REQUIREMENT & TRANSFORMER SIZING ................................... 18 4.3.1 Domestic Development .......................................................................... 18 4.3.2 Commercial Development .................................................................... 20 4.3.3 I ndustrial Development ........................................................................... 22

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4.3.4 Multi-tenanted Buildings/ Development.............................................. 23 CHAPTER 5 LOW VOLTAGE NETWORKS ..........................................................................24 5.0 OBJECTIVE ............................................................................................................ 24 5.1 DISTRIBUTION NETWORK COMPONENTS ......................................................... 24 5.2 DISTRIBUTION TRANSFOMERS ............................................................................ 25 5.2.1 Configuration............................................................................................. 25 5.2.2 Transformer Cable Tail ............................................................................. 25 5.3 LV FEEDER PILLARS ..............................................................................................26 5.3.1 Configuration............................................................................................. 26 5.4. LV FEEDERS ...........................................................................................................28 5.4.1 Loading Limits ............................................................................................ 28 5.4.2 Configuration............................................................................................. 28 5.5 FIVE FOOT WAY MAINS ...................................................................................... 29 5.5.1 Configuration............................................................................................. 29 5.6 SERVICE CABLES .................................................................................................. 29 5.7 STREET LIGHTING.................................................................................................. 29 5.7.1 Configuration............................................................................................. 29 5.8 DISTRIBUTION NETWORK TYPES ......................................................................... 30 5.8.1 Domestic Overhead ................................................................................ 32 5.8.2 Domestic Underground ........................................................................... 33 5.8.3 Commercial Overhead ........................................................................... 33 5.8.4 Commercial Underground ..................................................................... 34 5.8.5 Industrial Overhead.................................................................................. 34 5.8.6 I ndustrial Underground ............................................................................ 34 5.8.7 LV Supply for Premises with Separate Owner / Landlord and Tenant Meters .....................................................................................................34 5.8.8LV Ring System ............................................................................................ 35 5.8.9 LV Auto Transfer Switch System.............................................................. 35 5.9 ECONOMICS .......................................................................................................36 5.9.1 I nitial Cost of Implementation ................................................................ 36 5.9.2 Operation and Maintenance Cost....................................................... 37 5.9.3 Replacement Cost ................................................................................... 37 5.9.4 Technical Losses ........................................................................................37 5.10 OTHER CONSIDERATIONS .................................................................................. 37 CHAPTER 6 LOW VOLTAGE PROTECTION AND EARTHING ..........................................38 6.0 OBJECTIVE ............................................................................................................ 38 6.1 DEFINITION............................................................................................................ 38 6.2 PROTECTION PLANNING.................................................................................... 38 6.3 FUSE PROTECTION ............................................................................................... 39 6.4 SURGE ARRESTORS ..............................................................................................41 6.5 NEUTRAL EARTHING IN LV SYSTEM ................................................................... 41 6.5.1 Feeder Earthing for Overhead Lines ..................................................... 41 6.5.2 Feeder Earthing for Underground Cables ........................................... 42

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CHAPTER 7 LOW VOLTAGE METERING ...........................................................................43 7.0 OBJECTIVE ............................................................................................................ 43 7.1 DEFINITION............................................................................................................ 43 7.2 CUSTOMER SUPPLY AND METERING ................................................................ 44 7.2.1 Metering Criteria ....................................................................................... 44 7.2.2 Whole Current Metering.......................................................................... 44 7.2.3 C.T. Metering ............................................................................................. 44 7.2.3.1 C.T. Meter Loading ...................................................................... 45 CHAPTER 8 LOW VOLTAGE TECHNICAL LOSSES ...........................................................46 8.0 OBJECTIVE ............................................................................................................ 46 8.1 DEFINITION............................................................................................................ 46 8.2 POWER FACTOR CORRECTION ........................................................................ 46 8.3 TYPES OF TECHNICAL LOSSES ........................................................................... 47 8.4 CONTRIBUTORS OF TECHNICAL LOSSES IN LV NETWORK ............................ 47 8.4.1 Strategies .................................................................................................... 47 8.4.1.1 Reactive Power Management - Supply Side ......................... 48 8.4.1.2 Reactive Power Management - Customer side ................... 48 8.4.1.3 Efficient Low Voltage System Design ...................................... 48 8.4.1.4 LV Load Monitoring ..................................................................... 49 8.4.1.5 Smaller Transformer Design Rating and Initial Installation Practise ........................................................................................................ 49 CHAPTER 9 POWER QUALITY ............................................................................................50 9.0 OBJECTIVE ............................................................................................................ 50 9.1 DEFINITION............................................................................................................ 50 9.2 VOLTAGE DIPS ..................................................................................................... 50 9.3 HARMONICS ........................................................................................................51 9.4 VOLTAGE UNBALANCE ...................................................................................... 51 9.5 TRANSIENTS ...........................................................................................................51 9.6 VOLTAGE FLUCTUATION AND FLICKER ........................................................... 51 9.7 REMEDIES ..............................................................................................................52 9.8 POWER QUALITY MANAGEMENT MONITORING ........................................... 53 CHAPTER 10 DATA MANAGEMENT .................................................................................54 10.0 OBJECTIVE ............................................................................................................ 54 10.1 DATA CATEGORIES .............................................................................................54 10.2 LOAD AND DEMAND DATA .............................................................................. 54 10.3 SYSTEM NETWORK DATA ....................................................................................55 10.4 SYSTEM PERFORMANCE DATA.......................................................................... 55 10.5 DATA MANAGEMENT MONITORING ............................................................... 56 10.6 INTERACTION BETWEEN VARIOUS UNITS IN AN AREA ................................... 57 APPENDICES.......................................................................................................................58 APPENDIX 1: TYPES OF LOADS AND THEIR CHARACTERISTICS .................................. 59 APPENDIX 2: TRANSFORMER SIZING COMPUTATION.................................................. 60 APPENDIX 3: STANDARD MULTI-TENANTED BUILDINGS DESIGN ................................ 62

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3A Multi-Tenanted Buildings (< 5 storey) without Substation .................... 62 3B Multi-Tenanted Buildings (< 5 storey) with Substation .......................... 63 3C Multi-Tenanted Buildings (> 5 storey) without Substation ..................... 64 3D Multi-Tenanted Buildings (> 5 storey) with Substation (Landlord & Tenant takes LV supply) .................................................................................... 65 3E Multi-Tenanted Buildings (> 5 storey) with Substation (Landlord & Tenant takes MV supply) ..................................................................................66 3F Multi-Tenanted buildings (> 5 storey) with Substation (Development takes MV supply with Landlord load >1600A) .............................................. 67 3GMulti-Tenanted Buildings (> 5 storey) with Substation (Development takes MV supply with Landlord load <1600A) .............................................. 68 APPENDIX 4: FEEDER PILLAR ............................................................................................ 69 APPENDIX 5: STREETLIGHT TYPICAL CONFIGURATION ................................................ 71 APPENDIX 6: O/H DOM A ................................................................................................ 74 APPENDIX 7: O/H DOM B ................................................................................................ 75 APPENDIX 8: O/H DOM C................................................................................................ 78 APPENDIX 9: U/G DOM A ................................................................................................ 81 APPENDIX 10: O/H COM A ............................................................................................. 84 APPENDIX 11: U/G COM A.............................................................................................. 85 APPENDIX 12: U/G I ND A .................................................................................................87 APPENDIX 13: U/G RI NG .................................................................................................. 89 APPENDIX 14: LV-ATS ........................................................................................................91

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CHAPTER

1 GENERAL INTRODUCTION 1.0 INTRODUCTION The design and development of supply system are critical in delivering quality supply to the customers. The quality of supply includes security, reliability and power quality. To provide quality supply, the issue of cost needs to be considered. The optimized distribution system planning and development is introduced in order to achieve overall effective services to the customers. The objective of this Low Voltage Planning Guidelines is to help the technical staffs at the district (kawasan) to plan and develop low voltage (LV) distribution system, so that TNB’s distribution systems: i. ii. iii. iv.

Can fully meet customer expectations. Can achieve the corporate quality and reliability targets. Is optimally planned at the most economic overall cost. Is capable of satisfying customer demand growth for the foreseeable future.

1.1 SCOPE The scope of this document covers: i. ii. iii. iv. v.

Definition of security, reliability and power quality for LV network. Compliance with the Regulatory Requirements. LV Planning criteria. Typical LV network design. Guidelines on “what to do”, and “how to do”.

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GENERAL INTRODUCTION

1.2 DOCUMENT LAYOUT This document comprises of 10 CHAPTERS, addressing separate topics for ease of use and future reference. Each chapter is arranged in several sections, each of which addresses a specific aspect of the chapter topic. The chapter topic is summarized below: Chapter 2

Refers to “Quality Of Supply” and TNB Corporate Standards

Chapter 3

Indicates the types and magnitudes of loads that can be fed from the LV network

Chapter 4

Describes the types and sizes of substations used by TNB and includes criteria to decide on the number of substations required to feed expected loads.

Chapter 5

Details the planning criteria and design for the LV distribution network, including services fed from the substations.

Chapter 6

Refers to the planning criteria for the LV network protection and earthing.

Chapter 7

Details out several main strategies to reduce LV technical losses

Chapter 8

Deals with the implications of “energy metering” on LV network planning.

Chapter 9

Redefine PQ phenomena in a simpler manner and includes the possible mitigations.

Chapter 10

Details data that needs to be monitored and managed for the LV distribution system development

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CHAPTER

2 QUALITY OF SUPPLY 2.0 OBJECTIVE The objectives of this chapter are to: i. Define “quality of supply”. ii. State the related LV system regulatory and engineering standards that need to be complied with.

2.1 DEFINITION OF QUALITY OF SUPPLY The term “Quality of supply” means security, reliability and power quality of supply to the customers. Security of supply means availability of supply to customers following the occurrence of a supply interruption. This aspect is measured by Security Level 1 – Level 4 as follows: i. ii. iii. iv.

Security Level 1 - Less than 5 seconds. Security Level 2 - Less than 15 minutes. Security Level 3 - Less than 4 hours. Security Level 4 - Less than 24 hours.

Reliability means ability of the distribution system to perform its required function under stated conditions for a specified period of time. This also describes the continuity of electricity supply to the customers. This aspect is measured by SAIDI. Power quality refers to any power problem manifested in voltage, current or frequency deviations that result in failure or misoperation of customer equipment.

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QUALITY OF SUPPLY

2.2 SYSTEM AVERAGE INTERRUPTIO INTERRUPTION N DURATION INDEX (SAIDI) Service reliability in TNB Distribution System is expressed by SAIDI. It is derived from the product of SAIFI (System Average Interruption Frequency Index) and CAIDI (Customer Average Interruption Duration Index). In TNB system, only loss of supply exceeding 1 minute is termed as “outage” and will be counted in the computation of SAIDI. The equation to compute com pute SAIDI is as follow: n

∑ C i d i SAIDI =

i =1

(2.1)

N

The equation to compute SAIFI is given as: n

∑ C i SAIFI =

i =1

N

(2.2)

The equation to compute CAIDI is as follow: n

∑ C i d i CAIDI =

i =1 n

(2.3)

∑ C i i =1

where: i n Ci di N

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= = = = =

interruption event total number of interruptions number of interrupted customers for each interruption event duration of each interruption event total number of customers served for the measured area


QUALITY OF SUPPLY

2.3 SUPPLY SYSTEM STANDARDS The supply system standard associated to voltage regulation and frequency variations for quality of supply adopted by TNB is shown in Tables 2.1and 2.2 respectively. Table 2.1 Voltage regulation Nominal Tolerance Under Normal Condition Tolerance Under Contingencies Condition

400V/230V + 10 % to – 6 % (MS IEC 60038) ± 10%

Table 2.2 Frequency variations Nominal

50Hz

Tolerance Under Normal Condition

±1 %

Tolerance Under Contingencies Condition

47 – 52Hz

The average restoration period is given as follow: i. Less than 5 seconds. ii. Less than 15 minutes. iii. Less than 4 hours. iv. Less than 24 hours. The acceptable permissible values for quality of supply at the point of common coupling are summarized in Table 2.3. Table 2.3 Acceptable permissible values at point of common coupling Type Of Disturbance

Voltage Step Change

Indices

∆V %

Acceptable permissible values at point of common coupling 1% - Frequent starting / switching and/or disconnection of load. 3 % - Infrequent Inf requent single starting/ switching or disconnection of Load – once in two (2) hours or more hours. 6 % - Starting/switching once or twice a year.

Reference Document

UK’s Engineering Recommendation P28

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Type Of Disturbance

Voltage Fluctuation and Flicker

Harmonic Distortion2

Voltage Unbalance

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Indices Absolute Short Term Flicker Severity (Pst) Absolute Long Term Flicker Severity (Plt ) Total Harmonic Distortion Voltage (THDV) %

QUALITY OF SUPPLY

Acceptable permissible values at point of common coupling

Reference Document

1.0 (at 132kV and below)

0.8 (Above 132kV)

0.8 (at 132kV and below)


0.6 (Above 132kV)

5 % at

≤ 400

Volt

4 % at 11kV to 22kV 3% at 33kV

Engineering Recommendation ER G5/4

3% at 132kV

Negative Phase 2% for 1 minute Sequence Voltage %


CHAPTER

3 LOADS 3.0 OBJECTIVE The objective of this chapter is to: i.

Provide methodology for the estimation of maximum demand (MD) for the purpose of LV planning.

3.1 TYPES & CHARACTERISTICS OF LOAD There are various types of loads such as lighting, electronic gear, heating and motor. Types and characteristics of these loads are tabulated in Appendix 1. It is important for distribution LV Planners to understand the characteristics of these loads in order for them to plan appropriately.

3.2 LOAD GROWTH All loads supplied are subjected to growth over time. Load growth can be divided into: i. Natural growth. ii. Step growth. The respective growth rates depend on: i. ii. iii. iv.

Economic environment and growth. Customer category. Customer affluence. Electrical appliance penetration. Page | 7


LOADS

v. Life styles. vi. Presence of step loads. LV systems need to be planned such that it can cater for credible load growth for the foreseeable future. The area load growth must be taken into consideration when designing supply infrastructure in a new development area. Normal load growth pattern in a certain area is represented by the graph shown in Figure 3.1.

Figure 3.1: Typical load growth pattern

3.3 LOAD DEMAND The estimated load demand is based upon load declared by consumer and TNB’s own information on load profile characteristics for various consumer classes. Range of values is given as demand profile is known to vary according to geographical location of consumers around the TNB service areas in Peninsular Malaysia. Fairly accurate assessment of individual and group demand of consumers is critical for correct dimensioning of network or facilities to meet the initial and future demand of consumers imposed on the network. MD range in this section is meant for reference as the minimum value. MD declared by Consultants must be accompanied with the connected load and design calculations of the development.

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LOADS

3.3.1 Typical Load Demand for Domestic Residential Premises Table 3.1 indicates the range of typical individual domestic loads in urban, sub-urban and rural areas for different types of premises. Table 3.1: Typical range of loads for domestic premises (kW per Unit) No. 1 2 3 4 5 6

Type Of Premises Low cost flats, single storey terrace, studio apartment ( < 600 sq ft) Double storey terrace or apartment Single storey, semi-detached Double storey, semi-detached Single storey bungalow & three-room condominium Double storey bungalow & luxury condominium

Rural (kW)

Suburban (kW)

Urban (kW)

1.5

2.0

3.0

3.0 3.0 5

4.0 5.0 7.0

5.0 7.0 10

5

7.0

10

8.0

12

15

3.3.2 Typical Load Demand for Commercial Premises Table 3.2 shows the range of commercial customer’s load density. Table 3.2: Typical range of loads for commercial premises (KW per Unit) Type Of Commercial Premises Single storey shop house Double storey shop house Three storey shop house Four storey shop house Five storey shop house

Min.

Ave.

High

5 15 20 25 30

10 20 30 35 40

15 25 35 45 55

3.3.3 Typical Load for Commercial Complex For other commercial premises such as supermarkets, shopping complex, etc., the load demand is computed using the total floor area. The load density with respect to load environment is as shown in Table 3.3. Table 3.3: Load density with respect to load environment for commercial complex Load Environment Low load density areas Average load density areas High load density areas

Load Density 6 watts / sq. ft. built up, 8 watts / sq. ft. built up, 10 watts / sq. ft. built up.

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LOADS

3.3.4 Typical Load Demand for Industries Generally the demand for industries is declared by the consultant/developers. However, as a guide, Planners can use an average of 20 watt / sq ft (215 watts / sq m) for Development Order Plan comment. Table 3.4 summarizes the load density associated to the load environment for industrial. Table 3.4: Load density with respect to load environment for industries Load Environment Low load density areas

Load Density 16 watts / sq. ft. built up

Average load density areas 20 watts / sq. ft. built up High load density areas

24 watts / sq. ft. built up

3.4 COINCIDENT FACTORS Multiple loads fed from a distribution network will experience diversity between different of occurrence in their peak demand. Hence the total demand fed will be less than the sum of the individual load demand. This factor is important in estimating the total maximum demand in a development. Coincident factor (CF) is considered as the ratio of coincident maximum demand of 2 or more loads to the sum of their non-coincident maximum demand for a given period (the reciprocal of diversity factor). The CF depends on the number of customers of a group, as well as the different customer groups involved. CF is always less than or equal to 1.

3.4.1 Sample Calculation of Coincident Factor Proposed coincident factors for different groups of customers are shown in Table 3.5. Table 3.5: Group of coincident factors Customer Groups Residential Commercial Industrial Residential + Commercial Residential + Industrial Commercial + Industri al Mixed Group

Coincident Factors 0.90 0.87 0.79 0.79 0.87 0.79 0.75

*Source: Development of End User Load Model for Distribution Planning by TNBR

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LOADS

If sufficient data is available, the following template can be used to compute coincident factor for any categories of customers: - 17:00 24:00 90% 30%

- 00:00 08:00 50% 5%

-

kW 5 10

08:00 17:00 10% 90%

- 17:00 24:00 900 1000 0.90

- 00:00 08:00 500 1000 0.50

-

Domestic MD CF

08:00 17:00 100 1000 0.10

08:00 17:00 Commercial 1800 MD 2000 CF 0.90

- 17:00 24:00 600 2000 0.30

- 00:00 08:00 100 2000 0.05

-

unit Domestic 200 Commercial 200

Group MD Total MD Group CF

1900 3000 0.63

1500 3000 0.50

600 3000 0.20

Max CF

0.90

0.90

0.63

3.5 LOAD FACTOR Load Factor (LF), is a ratio of average power consumption (kWh) to the peak demand over a period of time. It is reflected by the formula: L.F =

kWh (Over specified period) MD (kW ) × Hours (for the period)

(3.1)

Load factors for different customer category vary according to the business type and operating cycle but generally are within recognizable values. Table 3.6 summarized the typical values of load factors that can be used for planning purposes.

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LOADS

Table 3.6: Typical load factors CUSTOMER TYPE

Typical Load Factor

Residential premises

0.35*

Commercial

0.44*

Industries

Single shift

0.15-0.25

Double shift

0.40 – 0.60

Triple shift

0.60 – 0.95

*Source: Development of End User Load Model For Distribution Planning By TNBR

3.6 ALTERNATIVE SUPPLY Customers having critical/essential loads such as lifts, operating theaters, dialysis machines etc. should have an alternative source of supply in case of utility power failure. The common sources of alternative power supply are: i. Battery (connected directly, or through converters). ii. Uninterrupted power supply (UPS) from dedicated battery and engine-generator set. iii. Stand-by generating set. This alternative supply is to be designed and installed by the customer / developer.

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CHAPTER

4 DISTRIBUTION SUBSTATIONS 4.0 OBJECTIVE The objectives of this chapter are: i.

To describe TNB's "standard" practices on the use of substations in LV distribution system. ii. To describe the selection criteria for substation types.

4.1 DEFINITION Distribution substation is defined as the substation that converts power from medium voltage to low voltage. Some typical distribution substations are as follows: i. 33/0.4 kV ii. 22/0.4 kV iii. 11/0.4 kV TNB's standard substation types include: i. Indoor type – stand-alone buildings or attached to customer’s premise. ii. Outdoor type – in fenced enclosures. iii. Semi-indoor type – with transformer installed outdoor and switch gear indoors. iv. Pad mounted switchgear H-Pole (PATOD) – with the transformer mounted on 2 pole, or 4 pole structures and pad mounted RMU Switchgear. v. Compact substation.

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DISTRIBUTION SUBSTATIONS

In urban areas, substations are often equipped with more than one (1) transformer due to the high load density.

4.2 SUBSTATION SELECTION CRITERIA The choice of substation type depends on several technical and nontechnical factors. Amongst the factors that need to be considered are: i. Physical location of the proposed substation. ii. The control and other peripheral components to be installed, e.g. SCADA equipment, RTUs, power factor (p.f.) correction capacitors, etc. iii. The system, and overall protection requirements for the substation, e.g., fully switched or RMU type, need for fire-fighting equipment, etc. iv. The relationship of the substation to the overall distribution development plan of the area. . v. The magnitude and growth potential of the load to be fed.

4.2.1 Indoor Substation Indoor type substation is the most favorable type of substation to TNB with the following advantages: i. Public safety. ii. Less chances of v andalism. iii. Enable VCB installations. iv. Reduce exposure to environmental impact on equipment and operation maintenance personnel (eg: UV ray, rain & moisture etc). Indoor substations may consist of single or double chambers. It can be either constructed as a standalone building or attached to customer premises. Indoor type substations can be equipped with SCADA system (RTUs and other communication equipment), capacitor banks and load monitoring devices. All substations in the industrial areas must be planned to use indoor type substations. For operation and public safety purposes, indoor substations must also be used in all strategic and critical substations. 4.2.1.1 Indoor Standalone Substation Indoor Standalone substation has the following additional advantages: Page | 14



i. Easy transfer of land title from customer to TNB. ii. Portable fire extinguisher is sufficient and it does not require extensive fire-fighting system. iii. Easy access. iv. Compliance to Uniform Building By-Laws 1984, By-Law 139: Separation of Fire Risk Area. 4.2.1.2 Indoor Attached Substation Indoor attached substation has similar advantages to that of a standalone, except for: i. The substation is part of customer’s building. ii. Automatic and comprehensive firefighting equipment must be installed and maintained in order to meet the fire safety requirements. iii. Land is leased to TNB for a limited period with the risk of lossing the substation site upon expiry of the tenure. Due to these reasons, indoor attached substations are only allowed by TNB only if: i.

Domestic and commercial or industrial bulk supply customers with substation supply dedicated to them only. ii. Customers must incorporate fire fighting facilities in their premises. iii. Customers without sufficient land to build indoor stand alone substation.

4.2.2 Outdoor and Semi-Indoor Substation Outdoor and semi-indoor substations are mainly used in rural areas due to their cost advantage. These types of substations require smaller land area, and easy installation. However, there are several disadvantages for these types of substations: i. Installations are exposed to public access. ii. Higher chances of v andalism violation. iii. Exposure to environmental effect on equipment and operation and maintenance personnel (eg: UV ray, rain & moisture etc).

4.2.3 Pad-Mounted Switchgear H-Pole Pad-mounted switchgear H-Poles (PATOD) is normally used for system improvement in rural areas where substation land is difficult to be acquired. The maximum capacity of pad-mounted switchgear H-Poles, limited by the physical load bearing capacity of the support structure is 300 K VA. Page | 15



There are several issues related to the conventional pole mounted substations (with link /drop out fuse as isolators) such as: i. Difficulty in isolating supply. ii. Difficulty in fault finding. iii. Safety of switching below a transformer. iv. 11kV drop out fuse is no more in stock. In order to deal with the above mentioned issues, RMU switchgear is installed at the base of the H-pole to replace the traditional isolator link and drop out fuse design.

4.2.4 Compact Type Substation Compact type substations are physically small and consequently require small sites. Therefore, it is unobstructive and can be erected quickly. Currently compact substations are available in 500 kVA and 1000 kVA capacities. Compact substations are encouraged for domestic development (500kVA only) and commercial development (500kVA & 1000kVA) owing to the following advantages: i. Require smaller substation land size hence can be placed closer to the customer loads. ii. More efficient load distribution. iii. Shorter LV network. Usage of compact substation is considered as ‘special features design schemes’ in which special features cost is charged to the consumer as per Clause 8.0 of Statement of Connection Charges 1994/1995. Appropriate distribution network design is required to ensure security and restoration time to consumers will not be affected: i. If the housing development is more than 5MVA, 11kV switching station shall be provided by the developer within the housing development to support 11kV network connection to the respective distribution substation. ii. For housing development that is less than 5MVA, requirement of 11kV switching station depends on the existing network configuration and constraints. iii. One unit of 11kV switching station is able to support a development of maximum 10MVA only. Compact substation for non domestic and commercial development must obtain approval KJOW office (Surat Pekeliling PBK Perkhidmatan Page | 16



Kejuruteraan & Logistik, Perkhidmatan Dan Amalan Kejuruteraan A7/2004) and is to be strictly applied in selective situations under the following circumstances: i. Genuinely limited space at site. ii. Upgrading of load for existing customers. Compact substation is also allowed to be used for system reinforcement projects for highly built-up areas where substation land is difficult to acquire.

4.2.5 Summary of Substation Characteristics and Usage Table 4.1 summarizes the substation characteristics and their respective usage.

Table 4.1: Substations Characteristics and Usage No 1

Type Indoor Standalone Substation

2

Indoor Attached Substation

3

Outdoor & Semi Outdoor Substation

4

Pad Mounted Switchgear H-Pole (PATOD)

5

Compact Substation

Characteristics Standalone building. Requires biggest footprint. Attached to customer’s building / premises. Substation land is leased to TNB for a limited period. Small footprint with easy installations. Exposed to public access, easy vandalism & environmental effect. Smallest footprint. Limited physical load bearing capacity. Compact and requires small footprint. Unobstructive & can be erected quickly.

Usage Suitable for any types of development, especially industrial customers. Domestic, commercial or industrial bulk supply customers with substation supply dedicated to them only. Rural non domestic development.

System improvement in rural areas.

Domestic & commercial developments are allowed to use compact substation. Appropriate distribution network design is required.

Page | 17



4.3 SUBSTATION REQUIREMENT & TRANSFORMER SIZING Every development area must have sufficient number of substations with appropriate transformers sizing (including PMU or PPU where necessary). To determine the number of sufficient substations and appropriate sizing of transformer, the following requirements have to be considered: i.

Maximum demand of the load to be supplied, including the estimated load growth in the foreseeable future of 15 years. ii. Possible contribution to reinforce the LV network in the vicinity iii. TNB’s standard transformer ratings.

4.3.1 Domestic Development For domestic development (tariff A), transformer size must be planned according to the load requirement with maximum of 1 transformer at each substation site. 500kVA compact substation is also allowed to be installed in domestic development. The utilization of installed transformers capacity will reach 100% in 15 years assuming that the average growth rate as stated in Appendix 2. Hence, the planned transformer capacity is computed based on 85% of transformer loading. Table 4.2 provides the details on the number of substations required in residential development based on this principle. Table 4.2: Computation on Number of Substation Required MD with GCF Up to 85 kVA Up to 250 kVA Up to 425 kVA Up to 638 kVA Up to 850 kVA > 850 kVA

(Domestic Development) Transformer capacity at 85% loading 1 substation @ 100kVA (for rural supply) 1 substation @ 300kVA 1 substation @ 500kVA 1 substation @ 750kVA 1 substation @ 1000kVA More than 1 substation is required

For MD >850 kVA, the number of substations required can be computed as below:Step 1:Calculate the minimum installed capacity (a) based on the principle of 85% transformer loading using the following relationship: a=

MD (in KVA) 0.85

(4.1)

Step 2:Determine the number of 1000kVA transformer required to meet the capacity calculated in step 1 using the following formula: Page | 18



b =

a 1000 kVA

Number of substations = roundup (b (b)

(4.2) (4.3)

Step 3:Transformer 3:Transformer capacity is selected based on the closest match of kVA to a, taking into account the possible MSVR in the area. Example 1: 1: Computation on Number of Substations Required (Domestic Development) Each terraced house in a housing scheme which consists of 250 terraced houses has an MD of 4 kW. The total MD by considering 0.9 group coincident factor is 900 kW (i.e (i.e (4 x 250)x 0.9 = 900kW). Assuming 0.85 p.f., the MD in kVA is 1059 kVA. The number of substations substations required is determined using the following procedures: Step 1:

a=

Step 2:

b=

MD (in KVA) 0.85

a 1000 kVA

=

=

1059 0.85

= 1246 kVA

1246 kVA 1000 kVA

= 1.25

Number of substations = roundup (1.25)= 2 Step 3:

Required transformer capacity 1 nos 1000kVA + 1 nos 300kVA Or 2 nos 750kVA

Example 2 : Computation on Number of Substations Required (Domestic Development) Each single-storey semi-detached house in a housing scheme which consists of 500 single-storey semi-detached houses has an MD of 5 kW. The total MD by considering 0.9 group coincident factor is 2,250 kW (i.e (5 x 500)x 0.9 = 2,250 kW). kW). Assuming 0.85 p.f., the MD MD in kVA is is 2647 kVA. The number of substations required is determined using the following procedures: Step 1:

a=

Step 2:

b=

MD (in KVA) 0.85

a 1000 kVA

=

=

2647 0.85

= 3114 kVA

3114 kVA 1000 kVA

= 3.11

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Number of substations = roundup (3.11)= 4 Step 3:

Required transformer capacity 3 nos 1000kVA + 1 nos 300kVA OR 3 nos 750kVA + 1 nos n os 1000kVA

4.3.2 Commercial Development For commercial development (tariff B), transformer size must be planned according to the load requirement with maximum of 2 transformers at each substation site. The utilization of installed transformer capacity will reach 100% in 15 2. years assuming that the average growth rate as stated in Appendix 2. The planned transformer capacity is computed based on 60% of transformer loading. Table 4.3 provides the detail of the number of substation required in commercial development based on this principle. Table 4.3: Computation on the Number of Substation Required (Commercial Development) MD Up to 180 kVA Up to 3000 kVA Up to 450 kVA Up to 600 kVA > 600 kVA

Transformer capacity at 60% loading 1 substation @ 300kVA 1 substation @ 500kVA 1 substation @ 750kVA 1 substation @ 1000kVA Require > 1 substation with 1 substation or double chamber substation

For MD >600kVA, the number of substation can be computed as below: Step 1:Calculate 1:Calculate the minimum installed capacity (a ( a) based on the principle of 60% transformer loading by using the following relationship: a=

MD (in KVA) 0.60

(4.4)

Step 2:Determine 2:Determine the number of 1000kVA transformer required to meet the capacity calculated in step 1 by using the following formula: b =

a 1000 kVA

Number of substations = roundup (b (b) Page | 20

(4.5) (4.6)



Step 3:Transformer 3:Transformer capacity is selected based on the closest match of kVA to a, taking into account the possible MSVR in the area.

Example 1: Computation on Number of Substation Required (Commercial Development) Each single-storey shop house in a commercial development which consists of 80 units of single-storey shop houses has an MD of 10 kW. The total MD by considering 0.87 group coincident factor is 696 kW (i.e (10 x 80)x 0.87 = 696 kW). kW). Assuming 0.85 0.85 p.f., the MD in kVA is 819 kVA. The number of substation required is determined using the following procedures: Step 1:

a=

Step 2:

b=

MD (in KVA) 0.60

a 1000 kVA

=

=

819 0.60

= 1365

1365 kVA 1000 kVA

kVA

= 1.365

Number of substations = roundup (1.365)=2

Step 3:

Required transformer capacity. 1 nos 1000kVA + 1 nos 500kVA

Table 4.4: Transformer Loading Computation (Individual Commercial Customer) MD <180kVA 180kVA up to 300kVA >300kVA up to 500kVA >500kVA up to 750kVA >750kVA up to 1000kVA >1000kVA

Transformer capacity base on customer’s maximum demand Nearby substation (LV 4C Al cable <240m) or 1 substation @ 300kVA 1 substation @ 300kVA (1 circuit of LV 500mmp Al 1C PVC/PVC cable < 30m) 1 substation @ 500kVA (2 circuits of 300mmp Al 1C PVC/PVC cable < 30m) 1 substation @ 750kVA (2 circuits of 500mmp Al 1C PVC/PVC cable < 30m) 1 substation @ 750kVA (2 circuits of 500mmp Cu 1C PVC/PVC cable < 30m) 11kV Bulk Supply Intake

Page | 21



For individual commercial customer where the substation is dedicated to individual customer the computation of transformer loading tabulated in Table 4.4 applies. Example 2: Computation on Number of Substation Required (Individual Commercial Customer) An individual commercial application has an MD of 350 kW. Considering 0.85 p.f., the MD in kVA is 411 kVA. Based from Table 4.4, supply has to be given through a new substation with 500kVA transformer capacity. 2 circuits of 300mmp Al 1C PVC/PVC cable is to be laid in concrete trench from transformer tail to customer MSB (<30m away).

4.3.3 Industrial Development For industrial development area, the planning principle is similar to the commercial development area. The planned transformer capacity is computed based on 60% of transformer loading. The computation of required number of substations is as shown in Table 4.5. Table 4.5: Computation on the Number of Substations Required (Industrial Development) MD Up to 180kVA Up to 300kVA Up to 450kVA Up to 600kVA > 600kVA

Transformer capacity at 60% loading 1 substation @ 300kVA 1 substation @ 500kVA 1 substation @ 750kVA 1 substation @ 1000kVA Require > 1 substation or double chamber substation

Table 4.6: Computation on the Number of Substations Required (Individual Industrial Customer) MD <180kVA 180kVA up to 300kVA >300kVA up to 500kVA >500kVA up to 750kVA >750kVA up to 1000kVA >1000kVA

Page | 22

Transformer capacity base on customer’s maximum demand Nearby substation (LV 4C Al cable <240m) or 1 substation @ 300kVA 1 substation @ 300kVA (1 circuit of LV 500mmp Al 1C PVC/PVC cable < 30m) 1 substation @ 500kVA (2 circuits of 300mmp Al 1C PVC/PVC cable < 30m) 1 substation @ 750kVA (2 circuits of 500mmp Al 1C PVC/PVC cable < 30m) 1 substation @ 750kVA (2 circuits of 500mmp Cu 1C PVC/PVC cable < 30m) 11kV Bulk Supply Intake



For single industrial customer, the transformer capacity is based on customer’s loading. The calculation of the number of required substations and transformer sizing shown in Table 4.6 applies. Example 1: Computation on the Number of Substations Required (Individual Industrial Customer) An individual industrial application has an MD of 200 kW. Considering 0.85 p.f, the MD in kVA is 235 kVA. Based on Table 4.6, supply has to be given through a new substation with 300kVA transformer capacity. 1 circuit of LV 500mmp Al 1C PVC/PVC Cable is to be laid in concrete trench from transformer tail to customer MSB (<30m away). Individual LV bulk customers are not allowed to take supply from substations with 2 or more transformers due to the following reasons: i.

Paralleling of the LV sides of the transformers can create potential hazards due to high fault level on the system. ii. Any bulk customer with MD>1000kVA is required to take 11kV bulk supply so as to reduce the technical losses (one of the initiatives to reduce technical losses in TNB system) . Customers with high load factor can benefit from MV and HV supply as their electricity tariff would be lower. Furthermore, they would also have direct control over their incoming supply.

4.3.4 Multi-tenanted Buildings/ Development For multi-tenanted buildings / development such as condominiums, apartments or shopping complexes, where the substation is dedicated to such development, the computation of transformer loading tabulated in Table 4.4 applies.

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CHAPTER

5 LOW VOLTAGE NETWORKS 5.0 OBJECTIVE This chapter addresses the planning design requirements of TNB LV distribution network, such as: i. Magnitude of the demand to be fed. ii. Types of network components. iii. Types of LV network design. iv. Technical and economic considerations and network suitability for an appropriate “life-time” operation. This chapter also includes guidelines on public streetlighting which stipulates the relevant guidelines to help Engineers satisfy TNB’s stated standards of quality of supply to customers. In this chapter, the guidelines are arranged according to the following groups: i. Distribution network components. ii. Types of premises. iii. LV reticulation design.

5.1 DISTRIBUTION NETWORK COMPONENTS Distribution network components comprises of : i. ii. iii. iv. v. vi.

Distribution Transformer. LV Feeder pillars. LV feeders, can be underground cables or overhead cables. Five-foot-way mains. Service cables. Public Streetlighting.

Page | 24


LOW VOLTAGE NETWORKS

The guidelines for each of the distribution network components mentioned above are explained in the following sections.

5.2 DISTRIBUTION TRANSFOMERS Transformers used to step down medium voltages such as 33kV, 22kV, 11kV or 6.6kV to LV is known as distribution transformers.

5.2.1 Configuration The LV tail from a distribution transformer can be connected to TNB Feeder Pillars or directly connected to customer’s Main Switch Board (MSB) depending on the connection schemes. Feeder Pillars are used for distributing electricity to multiple customers as well as LV bulk supply to multi-tenanted buildings; whereas direct connection is for single customer with loads not more than 1000kVA. Distribution transformer usage and size must adhere to the requirements as explained in section 4.3. It is mentioned that single commercial and industrial customer with MD>1000kVA shall take 11kV bulk supply. This is to eliminate multiple transformers connected to a common busbar at the customer’s side. Separate MSB must be installed at the customer’s intake side for the owner and tenant supply when it involves multiple tenants and owner intake, such as condominiums, apartments or shopping complexes. Detailed design scheme is shown in Appendix 3: Multi Tenanted Building Design. However, multi-tenanted building customers are encouraged to take bulk supply with Independent Distributor license from Energy Commission. Independent Distributor is licensed to sell electricity to the tenants in a building / development. In the case where multi-tenanted building requires supply through LV service connection from two transformers to customer MSB, interlocking facility must be provided at customer’s incomers to prevent parallel operation of two transformers.

5.2.2 Transformer Cable Tail Table 5.1 indicates standard cable sizes used to connect the transformers to the TNB network.

Page | 25



Table 5.1: "Transformer Tail" Cables Transformer kVA Rating

LV Tail HT Tail 11/.4 kV Phase(sq mm)

Neutral(sq mm)

100

70 mm 2 1C XLPE 1x300 AI 1C PVC/PVC 1x300 AI 1C

300


500

70 mm 2 1C XLPE 2x300 Al 1C PVC/PVC 1x300 Al 1C

750


1000

70 mm 2 1C XLPE 2x500 Cu 1C PVC/PVC 1x500 Cu 1C

The recommended LV connections summarized in Table 5.1 are applicable to both connections to the feeder pillars or directly to the bulk customer's installations.

5.3 LV FEEDER PILLARS LV feeder pillars are used to split the output from the secondary winding of the distribution transformers to several different circuits. LV feeder pillars provide fusing facilities for each circuit as protection where it can be used to disconnect or isolate supply to that particular circuit. The usage of LV feeder pillars are not restricted to after the secondary transformer tail but can also be used to further split the circuit from main feeder pillar. The usage of LV Distribution Board has been discontinued since it does not comply with the Factory and Machinery (Fencing of Machinery and Safety) Regulation 1970, and Regulation 11 (Revised -1983), due to existence of exposed busbar. In the current substation design, LV Distribution Board has been replaced with Feeder Pillars. All new substation layouts have been designed to enable the Feeder Pillar usage.

5.3.1 Configuration LV feeder pillars should accommodate a sufficient number of outgoing feeders in order to allow optimal distribution of LV system to meet the expected customer demand. The number of outgoing feeder pillars with respect to feeder pillar current carrying capacity is given in Table 5.2.

Page | 26



Table 5.2: Typical Number Of Incoming & Outgoing Feeders In Feeder Pillar Feeder Pillar Current carrying capacity (A)

Typical Number of incoming feeders

400A (Mini) 800A (Main / Sectional) 1600A (Main / Sectional)

2 2 2

Typical Number of outgoing feeders 6 5 8

At the planning stage (for commercial, industrial or mix development), it is recommended that spare feeders are made available at every substation, for customer upgrades in the future. The number of minimum spare feeders for each type of customer is listed in Table 5.3. Table 5.3: Minimum Spare Feeders at the Planning Stage Customer type Group Commercial Group Industrial Mix Development

Minimum Spare feeders per substations 2 2 2

However, Planners should determine the necessity of spare feeders according to the needs of a particular development area. If the development area has the potential to become a busy commercial hub, then the Planner should plan for a higher spare capacity to cater the increase in the commercial customers like banks, eateries or convenient stores. If a double chamber is planned, the number of minimum spares made available at the planning stage is required from one (1) of the transformers only. Appendix 4 shows typical outlook of different sizes Feeder Pillar. A typical LV underground network design entails the following: i. Transformer tail to main feeder pillar. ii. Main feeder pillar to sectional feeder pillar • Incoming cable 2 x 300mmp 4T Al. XLPE (max fuse Amp = 250A) • J-slotted fuse / DIN type fuse iii. Main/Sectional feeder pillar to mini feeder pillar • Incoming cable 1 x 185mmp 4T Al. XLPE (max fuse Amp = 200A) iv.From mini Feeder Pillar, lay LV service cable 70mmp or 25mmp XLPE Al 4C cable (depending on MD per unit) to individual unit. Page | 27



v. Loads connected must not exceed incoming feeder fusing rating. vi.Location of feeder pillar must comply with local authority requirements and location agreed by developer. Planners should take into account the extention of LV networks at the planning stage. To reduce the length of LV network, Planners should consider acquiring additional substation if high numbers of feeders or feeder pillars are needed. This requirement should be prompted during Ulasan Pembangunan stage.

5.4. LV FEEDERS The outgoings from main feeder pillars which are used to distribute supply to customers are called LV feeders. LV feeders include underground and / or overhead cables.

5.4.1 Loading Limits All LV conductors’ mains loading at planning stage must be at a maximum of 50% of their thermal capacity in order to achieve distribution technical losses at 4%, To avoid having joints in the circuit, the length of LV underground cables must not exceed 240m. The length of LV underground and overhead cables are also limited by maximum voltage drop of 5% from reference voltage of 415V at the end of the circuit. Effective and efficient planning of the LV distribution network is critical as: i. It affects the cost of LV network, which forms a substantial portion of the project capital cost and is described in Section 5.9. ii. It influences the magnitude of technical losses in the system. iii. It has an impact to the reliability of supply to customers.

5.4.2 Configuration LV network is designed with security level 4. However, higher level of security can be designed based on consumer request at an additional cost and with special agreement from TNB.

Page | 28



5.5 FIVE FOOT WAY MAINS From the LV feeders, the circuit is further extended to LV services or Five Foot Way Mains, which is the last section of the circuit before terminating to the customers intake point. “Mains” along terraced premises are often in the form of Five Foot Way Mains comprising of PVC single core insulated conductors or ABC insulated cables.

5.5.1 Configuration Five Foot Way Mains configuration is currently standardised to three phase plus neutral in which it consists of four wire layout throughout its length using 7/.083 (25mm 2) for PVC Al. or 3 x 16mm 2, 3 x 95mm 2 and 3x185mm2 for ABC cables. Due to the increasing load demand by customers, it is necessary to use high capacity conductors. To facilitate the increasing load demand by customers, larger ABC cables are used instead of single core conductors. Five Foot Way Mains normally do not include feed back supply features.

5.6 SERVICE CABLES Service cable includes all means of connection from TNB mains to customers’ installations. This consists of overhead cables, underground cables inclusive of direct connections from transformer terminals to the customer’s switch board.

5.7 STREET LIGHTING Street lighting, given at a special tariff to local authorities, is part of the “local government’s” provision of public amenities. The intention is to encourage lighting up the public area, especially roads or streets at night. TNB has recently extended the provision of street lighting to include such supply to domestic customers, also at a special tariff. The lighting equipment used can be of standard TNB design, or of special design at the Local Authority’s cost.

5.7.1 Configuration The configurations of street lighting are divided into three categories.

Page | 29



i. Street Light for individual domestic customers and maintained by TNB • The application of street lighting in this category is by individuals and billed to the customer’s account at a determined flat rate per month. • It is installed by TNB on the existing LV lines (i.e. 5-wire Aeriel Bundled Cables (ABC)) ii. Street Lighting for Local Authority but maintained by TNB • This category of street lighting is installed by TNB upon request by the Local Authority. • It is installed on TNB poles and is maintained by TNB. • It is metered and paid by Local Authority unlike the previous category which is paid by individual customer iii. Street Light for Local Authority and maintained by Local Authority • For this category of street lighting, a dedicated LV underground cable is used to supply to the street lighting system • It is metered and paid by Local Authority • It can be supplied from TNB feeder pillars, existing or new substation Planners should plan for the street lighting supply at the initial stage so that the distance from the source to the street light meter panel can be optimized. The distance is restricted by voltage drop and technical loss of the service cable. Refer Appendix 5 for typical streetlight configuration.

5.8 DISTRIBUTION NETWORK TYPES Network configurations with respect to types of premises and metering locations are designed to suit a particular development. Table 5.4 summarizes the network configuration associated with customer type, meter board location and design requirement. Table 5.4: Network Configuration Associated with Customer Type, Meter Board Location and Design Requirement Customer Type Residential Overhead

Residential Overhead

Page | 30

Meter Board Location Five Foot Way

Pole

Design requirement Conductor PVC Al 1C 35mm2 (19/.064) as the five foot way mains Services drop Conductor PVC Al 1C 25mm2 (7/.083) into 3 houses (max) with meters installed at the pole


Customer Type

Meter Board Location

Domestic Overhead (with gate pillar)

Gate Pillar

Domestic SemiUnderground

Five Foot Way

Domestic Fully Underground

Gate Pillar


Meter Pillar

Group Commercial (U/G)

Stair case



Bulk Commercial

Group Industrial (U/G)

Upper front wall of the commercial premise Supporting vertical pillar of the building Meter Room in TNB Substation. Upper front wall of the industrial premise


Gate Pillar


Meter Pillar

Bulk Industrial

Meter Room in TNB Substation.


Design requirement Use LV underground service cable from pole and junction box if looping of service cable is required (3 houses max). The bottom of meter must be >3 feet from fl oor level. UG Cable LV XLPE Al 4C 185mm 2 terminated on the pole with service drop 35mm 2 Conductor PVC Al 1C 35mm2 (19/.064) as the five foot way mains Fully underground design with junction box for looping of 3 houses max. The bottom of meter must be >3 feet from floor level. Fully underground design where developers prefer centralized metering scheme Ensure grill gate installations at staircase is after the centralized meter panel (by developer, before V.P. stage) 3 phase & 1 phase meters installed between 0.7m to 1.65m from floor level Aesthetic design by the developer’s architect. 3 phase & 1 phase meters installed between 0.7m to 1.65m from floor level C.T. & voltage input to meter tapped from transformer tail 3 phase & 1 phase meters installed between 0.7m to 1.65m range from floor level Fully underground design with junction box for looping of 3 houses max. The bottom of meter must be >3 feet from floor level. Fully underground design where developers prefer centralized metering scheme C.T. & voltage input to meter tapped from transformer tail

Page | 31


Customer Type

Owner / tenant (LV)

Meter Board Location Owner’s main meter installed at TNB Metering Room, tenant’s meter installed at centralized meter room at ground floor (5 storey & below) or every floor (> 5 storey)


Design requirement

Splitting of owner and tenant feeders at TNB’s installations

Different types of premises need different types configurations. LV networks types can be grouped into:

of

network

i. Residential Overhead. ii. Residential Underground. iii. Commercial Overhead. iv. Commercial Underground. v. Industrial Overhead. vi. Industrial Underground. vii. LV Multi Tenant and Owner. viii. LV Ring Circuit.

5.8.1 Domestic Overhead LV reticulation using overhead lines to housing developments are the method preferred by TNB. Reticulation using this method is the most costeffective when compared to other methods and also the easiest to maintain and repair. Ring system through overhead should be provided, wherever possible, as it can be easily incorporated into the system via jumper or connection at sectional poles. Services can be distributed mainly using five foot way mains or directly from poles to individual premises.

Page | 32



Detailed design is shown in Appendix 6 Standard Design O/H Dom A: Consists of 185mmp XLPE 4C from feeder pillar in substation to pole; 3x185+120+16mmp LV ABC as Overhead Mains; 7/.083 PVC/PVC as Five Foot Mains; Metered at five foot way. Alternative Design O/H Dom B is shown in Appendix 7: Consists of LV ABC as Overhead Mains; 7/.083 PVC as Five Foot Mains; Metered at pole. Alternative Design O/H Dom C is shown in Appendix 8: Consists of LV ABC as Overhead Mains; 25mmp 4C underground cable as service cables to the meter s; Metered at gate pillar (pipings are required and provided by developers. Loopings to 2 other units are allowed through junction box)

5.8.2 Domestic Underground This method is used upon request by developers or as per the requirement of the Local Authority. Both would request for this method due to aesthetic reason of not having poles and overhead lines along the road. However, this method is expensive to construct due to extensive road excavation and involves erection of large numbers of feeder pillars to serve the customers. It is also difficult to maintain and repair. Hence, this method is treated as special features and the cost difference compared to overhead method (O/H Dom A) is chargeable to developer. The meter is required to be installed outside the premise and normally at the gate pillar or metering pillar. Detailed design is shown in Appendix 9 Standard Design U/G Dom A: Consists of 2x300mmp XLPE Al 4C cable from main 1600A Feeder Pillar in a substation to 800A Feeder Pillar; 1x 185mmp XLPE Al 4C from 800A Feeder Pillar to 400A mini Feeder Pillar; LV service cable 25mmp XLPE Al 4C or 70mmp XLPE Al 4C from mini Feeder Pillar to customer meter panel; Looping of 3 houses max is allowed through junction box.

5.8.3 Commercial Overhead For shoplots at sub-urban area or rural area, supply can be distributed to commercial customers using overhead poles from the source to the shoplots. Overhead lines can be used for this situation if the load requirement is of low to medium density. The Planner must decide whether sufficient spare capacity is available to cater load growth for the shoplots.

Page | 33



Five foot way mains for commercial lots will not pose a problem because meters and cut outs are accessible to TNB. Detailed design is shown in Appendix 10 Standard Design O/H Com A (meter at individual lots).

5.8.4 Commercial Underground This is the main method used to distribute electricity to shoplots in urban areas. The design fully utilizes underground cables with feeder pillars providing distribution outgoing to MSB of each l ot. Detailed design is shown in Standard Design U/G Com A of Appendix 11: Meters at individual lots.

5.8.5 Industrial Overhead For industrial customers, it is seldom supplied through the overhead line unless it is small scale industries producing things like clay pots, ice plant, rubber products etc. Most of these factories are located sparsely and this is the reason supply is given through overhead system. The design is similar to commercial overhead network design.

5.8.6 Industrial Underground The LV network design for this category is usually planned at early stage and it is found mostly in dedicated small and medium industrial area. Initially numbers and location of sub stations are determined during Ulasan Pembangunan stage and each factory is supplied with 100A 3 phase or 200A 3 phase. Spare capacity for this category is important as growth potential is tremendous. Customers requiring loads beyond the available spare capacity shall be required to provide additional substation. Detailed design is shown in Appendix 12 Standard Design U/G Ind A where meter pillar is located at customer’s front gate.

5.8.7 LV Supply for Premises with Separate Owner / Landlord and Tenant Meters This type of customer consists mostly of apartments, condominiums or shopping complexes. It is required to have separate MSB for landlord / owner and tenants for ease of disconnection. Detailed design is shown in pin Appendix 3 Standard Multi-tenanted Buildings Design.

Page | 34



5.8.8 LV Ring System LV ring system is an LV network designed with N-1 element. N-1element is the possibility of distribution system to feed back from a different feeder when the main feeder is down. It is installed only upon customers request and the developers must have special agreement with TNB. It is special features and cost difference is chargeable to the ring system, labeling of feeders is very important in order operation.

customers or considered as customers. For to ensure safe

Detailed design is shown in Standard Deisgn “U/G Ring” as shown in Appendix 13.

5.8.9 LV Auto Transfer Switch System LV auto-transfer switch (LV-ATS) system is an LV ring system which enables automatic switching of source when an interruption occurs. Two (2) LV feeders from different substations with different MV supplies need to be connected to the LV-ATS. The design principle is as follows: i.

To ensure the shortest possible service cable, the LV-ATS panel is to placed as near to customer’s MSB / meter panel as possible. ii. Lay 2 circuits of LV feeders to ATS panel from 2 different substations. iii. These 2 substations should be connected from different MV source. iv. The transformer capacity of both substations is sufficient to provide the customer load when LV-ATS operates. The sample network with LV-ATS is shown in Appendix 14. Similar to LV ring system, LV-ATS is installed only upon customers request and the customers or developers must have special agreement with TNB. It is considered as special features and cost difference is chargeable to the customers. Proper labeling of feeders at ATS and substation is very important in order to ensure safe operation. This system is suitable to provide secured supply to VIP customers such as Istana, Prime Minister’s or Chief Minister’s residents.

Page | 35



5.9 ECONOMICS The decision of selecting a certain network design in a project will have an economic impact to TNB throughout lifecycle of the installation. The economic consideration shall include: i. The initial cost of implementation. ii. The operation and maintenance cost. iii. The replacement cost. iv. Technical losses. v. Other cost such as aesthetic, safety.

5.9.1 Initial Cost of Implementation Initial cost of implementation for LV network depends upon the network design. This cost includes : i. ii. iii. iv.

Land acquisition cost. Material cost. Contract cost. Supervision cost.

TNB standard design for LV system is overhead network since it is the most cost effective network design. Overhead network system reduces the need to acquire wayleave and permits for road excavation from local authorities and therefore shorten the duration of construction. Furthermore, the unit price of ABC is cheaper when compared to the underground cable. Any change from the standard overhead network design is treated as Special Features and is chargeable to customers. Table 5.5 shows the summary of the cost comparison between an overhead system design and an underground system design taken from a project supplying 38 units of 3 storeys semi-detached and 1 unit of bungalow. From the example shown in Table 5.5, the initial cost of implementation for underground system LV network is 131% higher than the overhead system. Table 5.5: Network Design Cost Comparison Type of cost Land cost Staff cost Material cost Contract cost Permit cost TOTAL Page | 36

Overhead system (RM) 10 2200 76000 34562 0 112772

Underground system (RM) 10 1700 162000 82270 15000 260980

Difference (%) 0 23 -113 -138 -1,500,000 131



5.9.2 Operation and Maintenance Cost The operation and maintenance cost of an LV network depends on the type of system design. The cost of repair which is part of the operation and maintenance cost differs significantly between the overhead and underground systems. For example, a fault in the underground system requires specialised equipment such cable fault locating equipment and cable tracer in order to pinpoint the fault location whereas fault in the overhead system can be detected visually. The material used to repair the fault for underground cable is more expensive compared to overhead line and its accessories. Furthermore, repairing underground cable fault may require permits from local authorities and contractors for excavation works.

5.9.3 Replacement Cost All materials will deteriorate after a particular period in operation and need to be replaced. The cost of replacement for underground system is higher compared to overhead system.

5.9.4 Technical Losses Generally, underground system has more losses than overhead system due to method of construction. Underground cable will be affected by rate of heat dissipation where high operating temperature will increase the technical losses. The heat dissipation depends on the depth and laying methods (in ducts or directly in soil).

5.10 OTHER CONSIDERATIONS There are other considerations for Planners to explore and advice customers during the network design stage. Planners should lead in determining decisions listed below: i. ii. iii. iv. v. vi.

Supply security requirement. Location of installation (such as LV poles and feeder pillars). Utility reserves such as manhole and ductings. Wayleave for cables. Meter location. Advising customers on power factor control such as requirement of capacitor bank where applicable.

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CHAPTER

6 LOW VOLTAGE PROTECTION AND EARTHING 6.0 OBJECTIVE The objective of this chapter is: i. To describe the protection and earthing requirements for the LV distribution system, and to be employed as standard TNB practice.

6.1 DEFINITION System protection is the combination of devices and features that ensure safe operation of the system when abnormal conditions occur by isolating the fault, or dangerous components to eliminate potentially dangerous incidents. System earthing, or grounding is the intentional electrical connection to ground of the neutral or star point of four wire LV system. Effective earthing is an essential requirement for system protection. Commonly, TNB practise multiple earthed neutral (MEN) system in LV network. The neutral conductor is grounded at all poles. Besides that, the star points of substation transformer and the end of each LV feeder are also grounded.

6.2 PROTECTION PLANNING Planning of the LV system protection must address the following issues: i. Safe operation of the system. ii. Adequate capacity to meet customers load. Page | 38


LOW VOLTAGE PROTECTION AND EARTHING

iii. Definite operation of the protection devices. iv. Proper discrimination of protection settings.

6.3 FUSE PROTECTION Fuses are TNB’s standard LV distribution protection system, usually with time delay characteristics, or thermal detectors. They are normally used for short circuits and over-current. Fuse protection uses various “housing”, such as feeder pillar carriers, fuse switches, cut outs etc. Fuses provide low cost and effective protection for short circuit and over load. The types of fuses used in TNB LV distribution system are of HRC (high rupturing capacity) J-slotted, HRC NH (or Blade type) and barrel fuse. Table 6.1 presents the types of fuses used in TNB distribution system and its respective usage. Table 6.1: Fuses in TNB network Fuse Type HRC (J slotted type) HRC (NH type)

Usage Feeder pillar Feeder pillar, black box

The Low Voltage ABC Manual provides detail guidelines on the selection of fuse sizing and location as well as the examples of short circuit current calculation. The sizing and location of fuses must satisfy the following criteria so as to conform to the LV protection philosophy: i. ii. iii. iv.

v.

The fuse rating must be higher than the maximum load to be carried. The fuse rating must permit fuse failure under the “minimum” fault current occurrence. The fusing current must not exceed the conductor current carrying capacity. Fuses in series along a feeder must be suitably graded to provide discriminated failure so as to limit the supply outage extent to the minimum. Fuse rating selection is based on the following, whichever is lower:•

1 3

×(

Lowest short circuit current of the feeder ) -

This is with reference to Pekeliling Timbalan Pengurus Besar Kejuruteraan (Perkhidmatan Pengguna), Kejuruteraan Bil 3/1991

Page | 39


•

1 1.5

×(


Conductor current carrying capacity) -

This is with reference to mean HRC fuse time-current characteristic

For proper fuse grading: i.

J-slotted type and NH type fuse requires up stream fuse to be 2 times higher than down stream fuse ii. NH type and NH type fuse requires up stream fuse to be 1.5 times higher than down stream fuse The grading Table for LV overhead system is shown in Table 6.2 . Table 6.2: Grading Table for LV Overhead System Nearest location Fuse Fuse Fuse Size allowed Fuse Size Size Size Transformer Conductor (J-slotted for (NH at (NH) (NH) Size ABC at st st 1 Substation) 1 2nd Substation) Section Section Section Fuse 2 16mm Tiang 1 n/a n/a 50 n/a 100kVA 2 95mm Tiang 1 n/a n/a 100 50 H/Pole 2 185mm Tiang 1 n/a n/a n/a n/a 16mm2 Tiang 1 60 50 n/a n/a 100kVA 95mm2 Tiang 1 160 160 50 n/a G/Mounted 185mm2 Tiang 1 n/a n/a n/a n/a 16mm2 Tiang 1 n/a n/a 50 n/a 300kVA 95mm2 Tiang 2 n/a n/a 125 50 H-Pole 185mm 2 Tiang 3 n/a n/a 200 125 2 16mm Tiang 2 60 50 n/a n/a 300kVA 2 95mm Tiang 2 160 160 50 n/a G/Mounted 2 185mm Tiang 3 200 200 100 50 2 16mm Tiang 2 60 50 n/a n/a 2 500kVA 95mm Tiang 3 160 160 50 n/a 2 185mm Tiang 5 200 200 100 50 16mm2 Tiang 2 60 50 n/a n/a 2 750kVA 95mm Tiang 4 160 160 50 n/a 2 185mm Tiang 6 200 200 100 50 2 16mm Tiang 2 60 50 n/a n/a 2 1000kVA 95mm Tiang 4 160 160 50 n/a 2 185mm Tiang 6 200 200 100 50 * Source from LV ABC Manual

Page | 40



6.4 SURGE ARRESTORS Surge arrestors are used on TNB overhead LV system to minimise possible risks from lightning strikes causing serious damage to the utility’s or customers’ installations. Surge arrestors must be installed at cable terminators, connections to other installations (e.g.: transformers, feeder pillars, five foot way mains), at the T-off and end of LV overhead mains. The satisfactory performance of surge arrestors depends to some extent, on the integrity of the system earthing. In TNB LV system, the surge arrestors are installed at every phase and neutral conductor is of metal oxide varistor (M.O.V) type.

6.5 NEUTRAL EARTHING IN LV SYSTEM Earthing of the LV Distribution system neutral is of paramount importance to ensure safety to users and equipment connected to the system, as well as its operation. Neutral earthing provides a deliberate earth path for fault current to be directed back to the source to operate the protective devices. The protective devices segregate the faulty components from the supply, so that the rest of the electricity supply system operates in a safe and stable condition. The system neutral is grounded so as to: i. Provide constant reference for the supply voltage. ii. Enable safe ground leakage path for fault currents to clear the faults. iii. Minimize unbalanced voltages due to “floating neutral”, if the neutral earth path becomes disconnected.

6.5.1 Feeder Earthing for Overhead Lines For LV overhead lines, the system is grounded at the distribution substations, via transformer neutral, and at every LV pole. With ABC cables, the MEN practice still applies, with the earthing via pre-installed SWG stay wire inside the pole. This stay wire needs to be connected to the neutral and make up at the bottom of pole. ABC cable installation is designed to prevent breakage by allowing the cables to fall off their supports through mechanical fusable link.

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6.5.2 Feeder Earthing for Underground Cables For underground cable feeders, the system is grounded through substation neutral busbar at feeder pillar.

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CHAPTER

7 LOW VOLTAGE METERING 7.0 OBJECTIVE The objectives of this chapter are to: i. Provide guidelines on LV supply metering methods according to customer categories and load dem and. ii. Summarises TNB’s policy on metering schemes, especially for LV customers, including LPCs.

7.1 DEFINITION Metering of electricity for billing is the measurement of the amount of electrical energy that is consumed by the installation. Metering in TNB is based on measurement of active energy as kilowatt-hours (KWH), and reactive energy as kiloVAR-hours (KVARH), where power factor penalty applies on the supply tariffs concerned. Meters used are of several types: i. Whole current meters for single & three phase customers. ii. LV current transformer (C.T.) meters for the LV customers. iii. HV C.T. meters for the customers. TNB customers with C.T. operated meter are classified as Large Power Customers (LPCs). In TNB, power factor penalty charge is imposed for all customers’ with monthly average load at power factor value < 0.85, except for domestic customers and street lighting.

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LOW VOLTAGE METERING

7.2 CUSTOMER SUPPLY AND METERING The mode of supply connections to customers is dependent on the load demand as indicated in Chapter 3, i.e.: i. Direct (whole current) • Single phase • Three phase ii. Through LV C.Ts via : • LV from mains • from dedicated Substation • MV or HV supply

7.2.1 Metering Criteria The metering criteria depend on the: i. Mode of supply ii. Supply voltage iii. Respective tariff iv. Magnitude of load fed (i.e. energy consumed)

7.2.2 Whole Current Metering In TNB LV distribution system, for loads not exceeding 100 amps, whole current meters (single phase and three phase up to 100 Amp) are used. Currently, the whole current meters are all electronic type and their designated accuracy tolerances are: i. kWH meters – class 2.0 ii. kVARH meters – class 3.0

7.2.3 C.T. Metering For load exceeding 100A, supply must be metered through Current Transformer (C.T.), with 5 Amp secondary windings in order to enable the supply to be measured within relevant accuracy class tolerances. The accuracy class standard adopted by TNB is presented in Table 7.1. Table 7.1: Accuracy Class Standard for C.T Meter Category Voltage

Description

1 2 3 4

CT size CT size CT size CT size

Page | 44

400V 400V 11kV 33kV and above

400/5 and below 500/5 and above 50/5 and above 100/5 and above

Meter Class 2 2 0.5 0.2

CT Class 0.5 0.2 0.2 0.2

PT Class

0.5 0.2


LOW VOLTAGE METERING

Check meter is required for all Category 2 customers and Category 1 customer with more than 50,000kWh monthly consumption. Details of metering installations required for LPCs are set out in Arahan Naib Presiden Pembahagian C4/2007. 7.2.3.1 C.T. Meter Loading Meter has a limited overload capacity with regard to their accuracy range, which is 120 % of the nominal rating. This means that the measurement accuracy can be severely affected if the input current exceeds the limit value. For planning of supply connection and selection of metering installation, the primary current of C.T. metered installations must not exceed 120 % of their nominal rating. Thus planning of supply must ensure that for C.T. metered customers, their protection trip settings do not exceed the metering C.T.’s accurate measurement limit.

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CHAPTER

8 LOW VOLTAGE TECHNICAL LOSSES 8.0 OBJECTIVE The objective of this chapter is to: i.

Provide a brief overview on LV technical losses from the planning perspective in TNB Distribution.

8.1 DEFINITION Losses in TNB distribution systems are divided into 2 main categories:i. Technical losses. ii. Non technical losses. Technical losses are the electrical energy dissipated in the conductors and transformers while supplying electricity to the customers. These losses are inherent in the processing and delivery of power but can be minimized in order to maximise returns. Losses represent a considerable operating cost, estimated to add 6-8% to the cost of electricity and some 25% to the cost of delivery. Non technical losses are due to un-audited account or billing, meter errors or theft of electricity.

8.2 POWER FACTOR CORRECTION Indoor substations serving residential and commercial loads are planned to accommodate switched LV capacitor banks for power factor correction. Currently, 3 phase supply to commercial and industrial customers are imposed with power factor penalty for load with p.f. <0.85. Page | 46


LOW VOLTAGE TECHNICAL LOSSES

However, most domestic and commercial customers do not have power factor correction capacitors installed at their premises, although they often have low p.f. loads. Capacitor banks used in TNB are rated at 300 kVAR and 150 kVAR with 50 kVAR automatically switched steps. Capacitor banks need only to be installed in substations with p.f. measured less than 0.85. Appropriate system studies are to be conducted before installations of the capacitor banks.

8.3 TYPES OF TECHNICAL LOSSES There are 2 types of technical losses: i. Fix losses due to iron losses : varies with the square of voltage. ii. Variable losses due to current flowing in the resistive component ( I 2 R ).

8.4 CONTRIBUTORS OF TECHNICAL LOSSES IN LV NETWORK The following are the several main contributors of technical losses in LV network in TNB distribution systems: i. Overloaded feeders. ii. Long and extensive LV network. iii. Low power factor / high reactive customer loads. iv. Unbalanced load. v. Under-utilized transformers.

8.4.1 Strategies There are several main strategies to reduce LV technical losses and they are listed as follows: i.

Reactive Power Management • Supply side • Customer side ii. Efficient Low Voltage System Design iii. LV Load monitoring & mitigating actions iv. Smaller transformer design rating

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8.4.1.1 Reactive Power Management - Supply Side A comprehensive reactive power planning methodology is used to obtain the most optimum location and size of capacitors to be placed in TNB distribution network. This methodology requires placing of the capacitor at LV side of 11/0.4kV substations first, then, the 11kV side of the substations, before opting for the placement at PPU / PMU. This is to ensure reactive power compensation is done closest to the customer loads. This methodology ensures the coupling point of transmission and distribution is maintained at a minimum of 0.95 p.f. LV capacitor banks that are installed in TNB distribution systems are of the following specifications: i. Rated voltage of 525V. ii. 300kVAr 6 steps. iii. 7 % detuned reactor. However, if the LV network consists of overhead systems, LV pole top capacitors are to be installed prior the installation of LV capacitor bank at the substations. LV pole top capacitors that are installed in TNB distribution system are of the following specifications: i. Rated voltage of 525V. ii. 30kVAr - fixed step. More details can be found in PSI procedure ENGR-750-55. 8.4.1.2 Reactive Power Management - Customer side All customers except with domestic and street lighting tariff are subjected to power factor penalty if customer’s power factor is less than 0.85. Hence, these customers are encouraged to reduce their reactive power consumption by installing appropriate sizes of capacitors. 8.4.1.3 Efficient Low Voltage System Design LV planning design principally aims to supply quality electricity to customer with the shortest possible service cable and appropriate sizing of conductors and transformer. All substations / transformers must be placed as close to the load centre as possible in order to reduce technical losses. Smaller compact substations are encouraged especially for domestic development areas. All LV conductors (mains) are planned to be loaded at 50% of their thermal capacity at planning stage.

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8.4.1.4 LV Load Monitoring All matured substations where occupancy of the area is more than 50% are required to: i. Take a 24 hour feeder load profiling using data-logger. ii. Spot reading. Based on the load reading data logged at every 15 minutes interval, corrective and preventive activities below shall be taken: i. Reduce overloading of LV feeders. ii. Load balancing. iii. Installation of LV pole top capacitors. iv. Installation of LV capacitor banks. 8.4.1.5 Smaller Transformer Design Rating and Initial Installation Practise Distribution transformers are planned to load to the customer’s declared MD at the following percentage: i. Group domestic: 85%. ii. Group commercial and industrial: 60%. iii. Individual bulk commercial and industrial: 100%. However, it is recommended, where it is originally planned for double chamber transformers, a single transformer is to be installed first. Feeder pillars and LV network reticulations are to be installed as originally planned with interconnection cables of LV 2x300mmp 4C XLPE between the two (2) main feeder pillars at the substations. This is to ensure the Transformer Utilisation Factor (TUF) is high so as to minimize no load loss in transformers.

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CHAPTER

9 POWER QUALITY 9.0 OBJECTIVE The objective of this chapter is to: i.

Provide a brief overview on power quality issues and the remedies.

9.1 DEFINITION In the context of LV network planning, power system quality is the ability of the LV system to deliver electrical energy to consumers within limits specified by the Electromagnetic Compatibility (EMC) standards. Common phenomena related to EMC includes voltage dips/swells, waveform distortion (harmonics, notching), voltage unbalance, transients, voltage fluctuation and flicker.

9.2 VOLTAGE DIPS Voltage dips can be caused by: i.

Short circuits in the LV networks cleared by fuse operation lasting several milliseconds. ii. Switching of large loads, such as motors and capacitor banks. It is recommended to perform transient simulation for LV system with low fault level supplying industrial laods with large motors to determine severity of any voltage dip due to fuse operation and/or motor starting.

Page | 50


POWER QUALITY

9.3 HARMONICS Harmonics in LV network are produced by nonlinear loads which are expected to increase in numbers due to advancement in the application of power electronics to improve energy efficiency level of electrical loads. Inverter air conditioners, refrigerators, washing machines are examples of highly nonlinear loads which have penetrated the electrical loads market recently. Other nonlinear loads are the compact fluorescent lamps, personal computers, television, etc. The above mentioned single phase nonlinear/harmonics loads are known to produce high third order harmonic currents which cause additional heating of distribution transformers, cables and neutral conductors of the LV network. Consequently, a derating factor should be applied to distribution transformers, cables, and fuses where necessary. In cases where power factor correction capacitors are installed at LV distribution board and/or pole top, parallel resonance may occur in the presence of harmonic currents.

9.4 VOLTAGE UNBALANCE The main effect of voltage unbalance is the heating of machine windings. Voltage unbalance may be significant particularly in cases of long LV feeders with highly unbalance connection of single phase loads. Steps must be taken to ensure that single phase loads are distributed as evenly as possible among phases.

9.5 TRANSIENTS Transients are caused by capacitor switching or lightning.

9.6 VOLTAGE FLUCTUATION AND FLICKER Voltage fluctuation is characterized by the amplitude of voltage changes and the rate of repetition usually caused by welding devices (arc furnance) or dynamic loads.

Page | 51


POWER QUALITY

9.7 REMEDIES Table 9.1 details the possible electromagnetic phenomena.

remedies

for

power

system

Table 9.1: Power Quality Disturbances, Causes and Possible Remedies Disturbances Causes  Incorrect voltage settings  Mal-operation of voltage regulating equipment, e.g., transformer On Load Voltage Tap Changers (OLTCs) regulation  Inadequate system development design  Excessive VAR on the system  Heavy loads, fed far from substation injection points Under Voltage regulation failure voltage  System faults and emergency operation  Unbalanced loading  

Overvoltages

 

Waveform variations and harmonics

Voltage spikes and voltage dips

Floating neutral “Ferranti effect” of long lightly loaded cables Sustained single phase to earth faults Voltage regulation failure

Possible Remedies 

  

        



Customers’ nonlinear/harmonic loads



System faults Lighting interference Switching operations Third party interference, e.g., arc furnaces strike effect, motor starting etc

  

  



Voltage flicker

Page | 52



Intermittent heavy load starting, or pulsating loads

Correct voltage settings and verify correct operation of OLTCs Adequate system design Power factor control Adequate VAR management Provide additional substations Distribute loads over more feeders Reset voltage regulation Balance loads Rectify neutral conductor continuity Reset fault clearance or voltage regulation Effective load management Effective system planning Suppress harmonics through filters, otherwise may have to derate equipment Surge arrestors, filters Minimizing system faults System reinforcement

Review starting arrangements, or system capacity and configuration


POWER QUALITY

9.8 POWER QUALITY MANAGEMENT MONITORING Power quality events and customer complaints on power quality issues in TNB are monitored through PQMS Web. Refer to PSI Document PSI ENGR-750-31 “Prosedur Siasatan Aduan Kualiti Kuasa dan Mengurus Data PQMS” for the complete procedure of power quality management in TNB Distribution.

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CHAPTER

10 DATA MANAGEMENT

10.0 OBJECTIVE The objective of this chapter is to: i.

Indicate data that needs to be monitored and managed for LV distribution system development.

10.1 DATA CATEGORIES Data for LV planning can be categorised into three parts namely: i. Load and demand data. ii. System network data. iii. System performance data.

10.2 LOAD AND DEMAND DATA System demand data is usually considered in the form of a load profile. It includes the following: i.

Main intake substation demand, as substation peak and as system coincident peak . (Obtainable from TNBT Metering Webpage: http://txmeter.hq.tnb.com.my/tnbtMeter/ ) ii. Medium voltage feeder demand profile covering peak, and offpeak demand period. (Obtainable from SCADA system) iii. Local substation (11 /0.4 KV etc.) load profile and peak loads at substation peak and at system peak. (Obtainable from Integrated Load Management System: ILMAS)

Page | 54


DATA MANAGEMENT

iv. Low Voltage feeder load profile covering peak, and off-peak periods. (Obtainable from Integrated Load Management System: ILMAS) v. Local substation voltage profile. (Obtainable from Integrated Load Management System: ILMAS) vi. Feeder tail-end voltage profiles. (Obtainable from Integrated Load Management System: ILMAS)

10.3 SYSTEM NETWORK DATA A detailed diagram of low voltage system network is important for fast reference and prompt response when required. This diagram is stored in DNIM / CGIS network or centralized map intranet database in TNB Distribution. These diagrams must be updated regularly for real time network representation. The system details include those given below: i.

ii.

iii.

Substations Types and sizes of substations • Locations and capacities of local substation transformers and • their tap settings, Types and sizes of substation feeder pillars • Ratings of fuses at the distribution board and feeder pillar • outgoing units Types and sizes of outgoing cable feeders • Date of commissioning • Date of last maintenance work done • LV feeder Overhead lines and cables routes and section lengths • Types of poles and pole numbers • Types and sizes of fuses and their positions • Services Types and sizes of service cables • Types and sizes of service fuses • Number of customers served • Types of customers served •

Most of the above data is entered into ERMS PM Module as well.

10.4 SYSTEM PERFORMANCE DATA The performance of LV system must be continuously monitored to ensure that it meets the desired reliability and quality standard. General system Page | 55


DATA MANAGEMENT

performance data that is monitored by TNB through TOMS (TNB Outage Management System) includes: i. ii. iii. iv. v.

Number of faults according to the type of equipment involved. Types of faults on the system. Causes of faults according to the equipment involved. Durations of supply restoration and fault repair. Number of customers affected by faults.

The analysis of data recorded is used to determine appropriate response to repair the faults, and minimise the likelihood of such fault recurrence. The data also allows evaluation of common reliability performance factors, e.g. SAIFI and CAIDI, which permits benchmaking against other utilities performance, as well as indicating the need to plan system development and modifications to meet growing demand. The system performance data also facilitates performance reporting to Energy Commission (Suruhanjaya Tenaga). Table 10.1 lists an example of the system performance data analysis. Table 10.1: Example of System Performance Data Analysis Disturbances

Causes Feeder over-load

Fuse failures Inappropriate feeder fusing

Mitigation Through adequate system planning and development to avoid overloads, e.g. installing additional feeders or load balancing Fuse sizing base on load & distance as per ABC Manual

10.5 DATA MANAGEMENT MONITORING Diligent and professional management of system data, and appropriate responses to the deductions derived, contribute to continuous improvement in system capacity and performance. Consequently, customers gain through improved reliability and quality of supply. Management supervisory activities must include the following: i.

Monitor the system performance to detect, and overcome, common causes of faults. ii. Confirm that the system development ensures adequate capacity to meet system demand.

Page | 56


DATA MANAGEMENT

iii. Monitor and manage, load demand and system configuration for the most reliable system aperation. iv. Anticipate credible demand growth, and develop the system to cater for it without violating TNB’s quality and reliability standards. v. Constantly analyze system performance data details to minimize, or even eliminate, root causes of supply failures, in a cost effective manner.

10.6 INTERACTION BETWEEN VARIOUS UNITS IN AN AREA Figure 10.1 shows the interaction between various units required in ensuring a system with high security and reliability.

Figure 10.1 : Interaction between Various Units in an Area (kawasan)

Page | 57

APPENDICES

Page | 58


APPENDIX 1

APPENDIX 1: TYPES OF LOADS AND THEIR CHARACTERISTICS Table A1.1: Type of Loads and Their Characteristics No

Types Of Loads

Load Devices

Incandescent lamps Fluorescent lamps and Neon lights 1.

Lighting Mercury Vapour and Sodium Vapour, Metal Halide lights.

2.

Electronic Gear

Radio, television, X-ray, ;laser equipment, computers, digital time pieces and timing devices, rectifiers, oscillators for high frequency current production. Residential (small) cooking, water heaters, irons, toasters, clothes’ dryers, house heaters

3.

Heating Industrial (large) space heaters, ovens, furnaces, welders, and high frequency heating Direct current shunt, series and compound type

4.

Motor

A/C single phase and three phase induction and synchronous type

Universal for both AC and DC operation

Load Characteristics

Operate at essentially power factor (p.f.). Operate at p.f. of 0.5 and need capacitors to improve load p.f.. Operate at p.f. of 0.7 to 0.8 and need capacitors to improve load p.f.. Introduce harmonics to the system. Essentially operate at unity p.f

Welding, and some type of heaters (arc furnace & induction type), create severe harmonics into the system if not adequately filtered Single phase fractional horsepower motors operate at p.f. of 0.5 to 0.7 Larger motors without suitable starters cause voltage flicker disturbance to other customers on the system Induction motors operate at p.f. of 0.5 to 0.95. At less than full load operation the p.f. may drop to 0.5-0.6 Synchronous motors can be used for p.f. correction for the installation

Page | 59


APPENDIX 2

APPENDIX 2: TRANSFORMER SIZING COMPUTATION Table A2.1: Transformer Sizing and Computation for group domestic development Domestic Yr

Estimated Average Growth Rate

% Load Uptake vs Declared MD with GCF

% Utilisation of I nstalled Transformer Capacity

17% 34% 51% 68% 77% 81% 85% 88% 90% 93% 94% 96% 98% 99% 100%

1 2 3 4 5 6 7 8 9 10 11 12 13 14

100% 50% 33% 13% 5% 5% 3% 3% 3% 2% 2% 2% 1%

20% 40% 60% 80% 90% 95% 100% 103% 106% 109% 111% 113% 115% 116%

15

1%

117%

Page | 60


APPENDIX 2

Table A2.2: Transformer Sizing and Computation for Group Commercial Development Commercial % Load Uptake vs Declared MD with GCF

% Utilisation of Installed Transformer Capacity

4

40% 29% 10%

50% 70% 90% 100%

30% 42% 54% 60%

5 6

8% 8%

108% 116%

65% 70%

7

8% 7% 7% 6% 6% 5% 5% 4% 3%

124% 131% 138% 144% 150% 155% 160% 164% 167%

74% 79% 83% 86% 90% 93% 96% 98% 100%

Yr

1 2 3

8 9 10 11 12 13 14 15

Estimated Average Growth Rate

Page | 61


APPENDIX 3

APPENDIX 3: STANDARD MULTI-TENANTED BUILDINGS DESIGN

3A

Multi-Tenanted Buildings (< 5 storey) without Substation

Landlord Account1 bill = M(landlord1) Landlord Account2 bill = M(landlord2) – summation (m) TNB FEEDER PILLAR

M(landlord1)

1. CT (landlord) installed at TNB feeder pillar 2. Meter (landlord) installed at TNB Outdoor Meter Panel M(landlord2)

TNB

Water pump load

Tenant & water p ump MSB

LANDLORD MSB

Supply to Landlord

Landlord is recommended M1 to install M1 for land lord to check with indi vidual m tenant bills for any m irregularity m

m

m

m

m

m

m

Tenant Vertical Risers To tenant units

Figure A3.1: Standard Design for Multi-Tenanted Buildings (< 5 storey) without Substation

Page | 62


3B

APPENDIX 3

Multi-Tenanted Buildings (< 5 storey) with Substation

Owner bill = M(landlord) – Summation (m) TNB SUBSTATION

1. CT (landlord) installed at TNB transformer tail 2. Meter (landlord) installed at Meter Room in PE TNB

TNB FEEDER PILLAR

M(landlord ) TN B

LANDLORD MSB

TENANT MSB

M1

Landlord is recommended to install M1 for landlord to m Supply to Landlord check with i ndividual m tenant bills for any irregularity m

Water pu mp load m

m

m

m

m

m

Tenant meter at centralized meter room at ground floor

Tenant Vertical Risers

To tenant units

Figure A3.2: Standard Design for Multi-Tenanted Buildings (< 5 storey) with Substation

Page | 63


3C

APPENDIX 3

Multi-Tenanted Buildings (> 5 storey) without Substation

Landlord Account1 bill = M(landlord1) Landlord Account2 bill = M(landlord2) – summation (m) TNB FEEDER PILLAR

1. CT (landlord) installed at TNB feeder pillar 2. Meter (landlord) installed at TNB Outdoor Meter Panel M(landlord1)

M(landlord2)

TNB

Water pump load

M4

Tenant & water pump MSB

LANDLORD MSB

Supply to Landlord

Tenant meter at

Tenant Lateral Riser to individual tenant at each level

centralized meter room at each level

M1

m

m

m

M2

m

m

m

M3

m

m

m

To tenant units

Tenant Landlord is recommended to in stall M1, Vertical Riser M2, Mn.. for landl ord to check with individual tenant bills for any irregularity

Figure A3.3: Standard Design for Multi-Tenanted Buildings > 5 storey without Substation

Page | 64


APPENDIX 3

3E Multi-Tenanted Buildings (> 5 storey) with Substation (Landlord & Tenant takes MV supply)

1. CT & PT installed at TNB VCB 2. Meter installed at Meter Room in PE TNB

TNB SUBSTATION

VCB (B2) With slot for metering CT

M(Landlord)

M(Tenant)

TNB

LANDLORD MV PANEL TENANT MV PANEL

TO LANDLORD

TO TENANT

Figure A3.5: Standard Design for Multi-Tenanted Buildings > 5 storey with Substation (Landlord & Tenant takes MV supply)

Page | 66


APPENDIX 3

3F Multi-Tenanted buildings (> 5 storey) with Substation (Development takes MV supply with Landlord load >1600A)

Figure A3.6: Standard Design for Multi-tenanted Buildings > 5 storey with Substation (Development takes MV supply with Landlord load >1600A)

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APPENDIX 3

3G Multi-Tenanted Buildings (> 5 storey) with Substation (Development takes MV supply with Landlord load <1600A)

Figure A3.7: Standard Design for Multi-tenanted Buildings > 5 storey with Substation (Development takes MV supply with Landlord load <1600A)

Page | 68


APPENDIX 4

APPENDIX 4: FEEDER PILLAR

Figure A4.1: 1600A Feeder Pillar


Page | 69



Page | 70

APPENDIX 4


APPENDIX 5

APPENDIX 5: STREETLIGHT TYPICAL CONFIGURATION

TNB OUTDOOR METERING / SUIS BOARD

F E E D E R P I L L AR

OWNER : TNB MAINTAIN : TNB

O W N E R : P B T , J K R , .. . E T C MAINT AIN : PBT, JKR, ...ETC

MAIN ROAD

MAIN ROAD

U N D E R G R OU N D S T R E E T L I GH T I N G CABLE LAID AND MAINTAIN BY CONSUMER (PBT, JKR,...ETC)

UNDERGROUND SERVICE CABLE LAID AND MAINTAIN BY T NB

DECORAT IVE, SINGLE / DOUBLE ARM S T R E E T L IG H T C U S T O M E R : P B T , J K R , .. .E T C O W N E R : P B T , J K R , .. . E T C M A I N T A I N : P B T , J K R , . .. E T C

Figure A5.1: Streetlight Typical Configuration - PBT, JKR etc

Page | 71


APPENDIX 5

MAIN ROAD

STREET LIGHT ATTACH TO TNB POLE WITH METER PANEL CUSTOMER : PBT, JKR, ...ETC OWNER : TNB MAINTAIN : TNB

STREET LIGHT ATTACH TO TNB POLE WITH METER PANEL CUSTOMER : PBT, JKR, ...ETC OWNER : TNB MAINTAIN : TNB

Figure A5.2: Streetlight Typical Configuration - TNB

Page | 72


APPENDIX 5

S T R E E T L IG H T A T T A C H T O T N B P O L E W IT H O U T M E T E R P A N E L C U S T O M E R : IN D I V ID U A L ( D O S M E S T IC ) OWNER : TNB MAINTAIN : T NB

Figure A5.3: Streetlight Typical Configuration – Individual

Page | 73


APPENDIX 6

APPENDIX 6: O/H DOM A (SAVR with Five Foot Way Mains)

K V T 2 4 0 1 0 0 m

500 kVA

K V T 2 4 0 1 0 0 m

PE KLIA NO.2

PE DEPOH E R L (4700m) F/P 1600A 135 kW

UNTUK PEMBANGUNAN SEKITAR AKAN DATANG

46 UNIT RT 2TGKT 135kW

100m

CDGN. BA N 18 15

Figure A6.1: SAVR with Five Foot Mains for O/H Dom A

Page | 74


APPENDIX 7

APPENDIX 7: O/H DOM B (1 X 16mmp ABC as Service Cable or 7/083 PVC/PVC, Metered at Pole)

Figure A7.1: Single Phase Pole Meter Panel for Overhead Dom B

Page | 75


APPENDIX 7

RO A D 2 B

RO AD 1

RO A D 5

6 D A O R

6 L L A W E R

R OAD 6

Figure A7.2: Site Plan of Single Phase Pole Meter Panel for Overhead Dom B

Page | 76


APPENDIX 7

Figure A7.3: Schematic Diagram of Single Phase Pole Meter Panel for Overhead Dom B

Page | 77


APPENDIX 8

APPENDIX 8: O/H DOM C (25mmp 4C Underground Cable, Metered at Gate Pillar, Pipings are Required and Provided by Developers)

Figure A8.1: Three Phase Gated Meter Panel for Overhead Dom C

Page | 78


APPENDIX 8

Figure A8.2: Site Plan of Three Phase Gated Meter Panel for Overhead Dom C

Page | 79


Figure A8.3: Schematic Diagram of Three Phase Gated Meter Panel for Overhead Dom C

Page | 80

APPENDIX 8


APPENDIX 9

APPENDIX 9: U/G DOM A (Fully U/G domestic: PE ke FP, FP ke Mini FP, Mini FP service cables loop 2 houses)

Figure A9.1: Site Plan of U/G DOM A

Page | 81


APPENDIX 9

B

B

Figure A9.2: Site Plan of U/G DOM A

Page | 82


APPENDIX 9

Figure A9.3: Schematic Plan of U/G DOM A

Page | 83


APPENDIX 10

APPENDIX 10: O/H COM A (Meter at Individual Lots)

Figure A10.1: Site Plan of O/H COM A

Page | 84


APPENDIX 11

APPENDIX 11: U/G COM A (Meter at Individual Lots) PROPOSED PEDESTRIAN BRIDGE

20'

21

22

23

24

25 26

27

28

20'

29

30 3 1

32

33

34

35

37 3 8

36

39

40 41

42

43

44

20'

45

46 47

48

49 5 0

51

52

53

54

55

56 57

58

59

60 61

62

63

64 65

66

FL.57.85

FL.57.75

FL.58.10

57.80 57.90

58.00

FL.58.25

FL.58.40

FL.58.55

58.10 58.25

58.40

58.55

Figure A11.1: Site Plan of U/G COM A Page | 85


APPENDIX 11

Figure A11.2: Schematic Plan of U/G COM A

Page | 86


APPENDIX 12

APPENDIX 12: U/G IND A (Meter Pillar Located At Customers Front Gate)

Figure A12.1: Site Plan of U/G IND A

Page | 87


APPENDIX 12

Figure A12.2: Schematic Plan of U/G IND A

Page | 88


APPENDIX 14

APPENDIX 13: U/G RING (Use 800A F/P to distribute to MFP, LV l ooping at MFP)

Figure A13.1: Site Plan U/G Ring – LV U/G Mains

Page | 89


APPENDIX 13

Figure A13.2: Site Plan U/G Ring – LV U/G Service

Page | 90

334155066-TNB-Planning-Guide-LV.pdf

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