Tanesco Tanzania - Specification S23A Metal Clad Type Load Break Switches (2003)

TANZANIA ELECTRIC SUPPLY COMPANY LIMITED

SPECIFICATION SPECIFICATION S23A S2 3A

METAL CLAD TYPE LOAD BREAK SWITCHES

MAY 2003.

TANZANIA ELECTRIC SUPPLY COMPANY LIMITED Samora Avenue, P.O. Box 9024, Dar es Salaam, Tanzania. Telephone: +255-22-2111041/4 or 2114045/6 Facsimile: +255-22-2113836 or 2110844 or 2114981or 2110825

Specification S23A - Load Break Switches

TABLE OF CONTENTS PART 1: GENERAL

1.

SCOPE .............................................................................................S23A-1

2.

STANDARDS .................................................................................S23A-1

3.

SERVICE

CONDITIONS......................... CONDITIONS.............. ................... .................. .................... ................... ..........S23A-3 .S23A-3

4.

SYSTEM

CONDITIONS....................... CONDITIONS.............. ................... ................... .................. .................... .............S23A-4 ..S23A-4

5.

INSPECTION, TESTING AND QUALITY ASSURANCE........S23A-5

5.1 5.2 5.3

Inspection .........................................................................................S23A-5 Testing ................................ ........................................ ..................... .......................... ..................... .................. ....................S23A-5 ..........S23A-5 Quality Assurance........ Assurance......................... .................................. .................................. ................................. .................S23A-6 .S23A-6

6.

SPARE PARTS................................................................................S23A-7

7.

PACKING AND SHIPPING ..........................................................S23A-7

7.1 7.2 7.3

Packing ......................... ..................................... .................... ...................... .......................... ...................... .................... ............ ..S23A-7 S23A-7 Shipping ...........................................................................................S23A-8 Hazardous Substances .....................................................................S23A-9

8.

Submittals....................... Submittals ................................. ...................... ......................... ..................... ..................... .......................S23A-9 ..........S23A-9

8.1 8.2

Submittals required with the Bid.....................................................S23A-9 Submittals required after Contract Award ....................................S23A....................................S23A-10 10

PART 2: TECHNICAL 9.

GENERAL ......................... ...................................... .................... .................... ........................ ........................ ................S ...S23A-12 23A-12

10.

INSULATION LEVELS .................... ............................... ....................... ........................ ....................S23A-13 ........S23A-13

11.

CURRENT RATING ....................................................................S23A-13

12.

TEMPERATURE RATING .........................................................S23A-13


TABLE OF CONTENTS PART 1: GENERAL

1.

SCOPE .............................................................................................S23A-1

2.

STANDARDS .................................................................................S23A-1

3.

SERVICE

CONDITIONS......................... CONDITIONS.............. ................... .................. .................... ................... ..........S23A-3 .S23A-3

4.

SYSTEM

CONDITIONS....................... CONDITIONS.............. ................... ................... .................. .................... .............S23A-4 ..S23A-4

5.

INSPECTION, TESTING AND QUALITY ASSURANCE........S23A-5

5.1 5.2 5.3

Inspection .........................................................................................S23A-5 Testing ................................ ........................................ ..................... .......................... ..................... .................. ....................S23A-5 ..........S23A-5 Quality Assurance........ Assurance......................... .................................. .................................. ................................. .................S23A-6 .S23A-6

6.

SPARE PARTS................................................................................S23A-7

7.

PACKING AND SHIPPING ..........................................................S23A-7

7.1 7.2 7.3

Packing ......................... ..................................... .................... ...................... .......................... ...................... .................... ............ ..S23A-7 S23A-7 Shipping ...........................................................................................S23A-8 Hazardous Substances .....................................................................S23A-9

8.

Submittals....................... Submittals ................................. ...................... ......................... ..................... ..................... .......................S23A-9 ..........S23A-9

8.1 8.2

Submittals required with the Bid.....................................................S23A-9 Submittals required after Contract Award ....................................S23A....................................S23A-10 10

PART 2: TECHNICAL 9.

GENERAL ......................... ...................................... .................... .................... ........................ ........................ ................S ...S23A-12 23A-12

10.

INSULATION LEVELS .................... ............................... ....................... ........................ ....................S23A-13 ........S23A-13

11.

CURRENT RATING ....................................................................S23A-13

12.

TEMPERATURE RATING .........................................................S23A-13


13.

BUSHINGS....................................................................................S23A-14

14.

RADIO INFLUENCE VOLTAGE...............................................S23AVOLTAGE...............................................S23A-14 14

15.

CLEARANCES .............................................................................S23A-15

16.

INTERRUPTING MEDIUM ........................... ................................... ..................... .....................S23A-15 ........S23A-15

17.

MAIN ASSEMBLY ......................................................................S23A-15

18.

OPERATING MECHANISM ......................................................S23A-16

19.

OPERATION SPEED ...................................................................S23A-16

20.

TERMINALS AND CONNECTIONS ........................................S23A-16

21.

EARTHING TERMINALS ..........................................................S23A-17

22.

SURFACE TREATMENT............................................................S23A-17

23.

GUARANTEE ...............................................................................S23A-19

24.

TESTS ............................................................................................S23A-20

24.1 24.2 24.3 24.4

Routine Tests..................................................................................S23A-20 Type Tests ......................................................................................S23A-20 Corrosion Tests ..............................................................................S23A-20 Galvanising Tests...........................................................................S23A-21

25.

SCHEDULES ................................................................................S23A-23

25.1 25.2 25.3

Technical Data Schedule ...............................................................S23A-23 Non Compli Compliance ance Schedul Schedulee ...... .......... ....... ...... ....... ....... ....... ....... ...... ....... ....... ...... ....... ....... ...... ....... ....... ...S23 S23A-26 A-26 Test Certificates Schedule .............................................................S23A-27

PART 3: INSTALLATION 26.

INSTALLATION ..........................................................................S23A-28

TABLES


Table 1: Minimum Galvanising Requirements ..........................S23A-18


PART 1: GENERAL 1.

SCOPE

This specification covers the design, manufacture, testing, supply, delivery and performance requirements of Metal Clad Type, Totally enclosed, Load Break Switches for use in the networks of the Tanzania Electric Supply Company Limited ( TANESCO). Any departure from the provisions of this specification shall be disclosed at the time of tendering in the Non compliance schedule, in part 2 of this document.

2.

STANDARDS

The equipment shall comply with the latest editions of, and amendments to, the international standards listed below. Where any provision of this specification differs from those of the standards listed below, the provisions of this specification shall apply: BSI

British Standards Institution:

o

BSI 729: Specification for hot dip galvanized coatings on iron and steel articles.

European Union Commission:

o

SI 426: European Communities (dangerous substances) (classification, packaging, labelling and notification) regulation, 1992

IEC International Electrotechnical Commission:

o

IEC 60: High-voltage test techniques.

o

IEC 60-2: High-voltage test techniques. Part 2: Measuring systems.

o

IEC 129: Alternating earthing switches.

current

S23A-1

disconnectors

(isolators)

and


o

IEC 383-1: Insulators for overhead lines with a nominal voltage above 1 000 V. Part 1: Ceramic or glass insulator units for a.c. systems - Definitions, test methods and acceptance criteria.

o

IEC 437: Radio interference test on high-voltage insulators.

o

IEC 507: Artificial pollution tests on high-voltage insulators to be used on a.c. systems.

o

IEC 694: Common clauses for high-voltage switchgear and controlgear standards.

o

IEC 1109: Composite insulators for a.c. overhead lines with a nominal voltage greater than 1 000 V - Definitions, test methods and acceptance criteria.

ISO

International Organization for Standardization:

o

ISO 752: Zinc ingots.

o

ISO 1460: Metallic coatings - Hot dip galvanised coatings on ferrous materials. Gravimetric determination of the mass per unit area.

o

ISO 2178: Non magnetic coatings on magnetic substrates Measurement of coating thickness - Magnetic method.

o

ISO 9000: Quality management and quality assurance standards Guidelines for selection and use.

The bidder may propose alternative standards, provided it is demonstrated that they give a degree of quality and performance equivalent to that of the referenced standards. Acceptability of any alternative standard is at the discretion of TANESCO.

S23A-2


3.

SERVICE CONDITIONS

The service conditions shall be as follows: o

altitude (above sea level)

1,600m

o

maximum outdoor temperature

40°C

o

minimum outdoor temperature

10°C

o

maximum monthly mean temperature

35°C

o

annual mean temperature

22°C

o

maximum relative humidity

o

isokeraunic level

tropical

o

maximum wind velocity

58km/h

o

prevailing wind direction

o

type of atmosphere

60% to 96%

SE and NW coastal

Environmentally, the region where the work will take place is a coastal area, subject to an overall medium relative humidity, which can give rise to condensation. Onshore winds are frequently salt laden. On occasions, the combination of salt and condensation may create pollution conditions for outdoor insulators. Therefore, outdoor material and equipment shall be designed and protected for use in exposed, polluted, salty, corrosive and humid coastal atmosphere. Indoor material and equipment shall be designed and protected for use in buildings, which occasionally may be wet and damp.

S23A-3

Specification S23A - Load Break Switches 4.

SYSTEM CONDITIONS

The equipment shall be suitable for installation in supply systems of the following characteristics: o

frequency

50Hz

o

nominal system voltages

o

maximum system voltages: 33kV 11kV

o

maximum LV voltage

440/253V

o

minimum LV voltage

374/215V

o

nominal short circuit levels: 33kV 11kV

o

insulation levels:

33kV 11kV 400/230V

1.2/50µs impulse (positive and negative polarity):33kV 11kV power frequency (one minute withstand, wet): 33kV 11kV LV o

o

neutral earthing arrangements: 33kV 11kV LV creepage distance

36kV 12kV

16.5kA 25kA

170kV 75kV

70kV 28kV 3kV

effectively earthed effectively earthed effectively earthed

30mm/kV (of maximum system voltage)

S23A-4


INSPECTION, TESTING AND QUALITY ASSURANCE

5.1

Inspection

The manufacturer/supplier shall submit a detailed programme covering the design, manufacture and testing of the equipment within one month of receipt of the contract award. Reports shall subsequently be submitted at intervals, outlining progress and, if necessary, explaining deviations from the programme. The TANESCO representatives shall have free entry at all times, while work on the contract is being performed, to all parts of the manufacturer's works which concern the processing of the equipment ordered. The manufacturer shall afford the TANESCO representatives, without charge, all reasonable facilities to satisfy themselves that the equipment being furnished is in accordance with this specification. 5.2

Testing

The equipment shall successfully pass all the type tests and routine tests referred to in part 2 and those listed in the most recent edition of the standards given in clause 2 of this specification. The TANESCO representatives reserves the right to reject an item of equipment if the test results do not comply with the values specified or with the data given in the technical data schedule. Type tests shall be carried out at an independent testing laboratory or be witnessed by a representative of such laboratory or some other representative acceptable to TANESCO. Routine tests shall be carried out at the manufacturer's works. Type tests may be dispensed with at the TANESCO's discretion if the manufacturer/supplier furnishes evidence to TANESCO's satisfaction that the relevant tests have already been performed on identical equipment. In this case test certificates shall be submitted with the bid for evaluation. TANESCO shall have the tests witnessed by a representative. In order to facilitate this, the manufacturer/supplier shall give TANESCO a minimum of four weeks notice that the material is ready for testing. S23A-5


If TANESCO does not indicate her intention to participate in the testing, the manufacturer shall carry out the tests and the supplier shall furnish the results thereof to TANESCO. Full details of the proposed methods of testing, including connection diagrams, shall be submitted to TANESCO by the manufacturer/supplier for approval, at least one month before testing. All costs in connection with the testing shall be borne by the manufacturer/supplier who shall provide the TANESCO representatives with all the test facilities, which the latter may require, free of charge. The TANESCO representatives shall have the right to select the samples if he or she so desires and shall also have the right to satisfy themselves that the testing apparatus is correct. The manufacturer/supplier shall submit to TANESCO five signed copies of the test certificates, giving the results of the tests as required. No materials shall be dispatched until the test certificates have been received by the TANESCO and the manufacturer/supplier has been informed that they are acceptable. The test certificates must show the actual values obtained from the tests, in the units used in this specification, and not merely confirm that the requirements have been met. TANESCO shall have the equipment inspected after reception and the TANESCO representatives shall have the right to select the samples if desired. The supplier shall co-operate with this inspection and shall provide the TANESCO representatives, free of charge, all the facilities, which the latter may require. In the case of components for which specific type tests or routine tests are not called for in part 2 or in the quoted standards in clause 2 of this specification, the manufacturer shall include a list of all tests he or she proposes to carry out. 5.3

Quality Assurance

The manufacturer/supplier shall provide current certification showing the manufacturer's compliance with ISO 9000 or equivalent national standard.

S23A-6


6.

SPARE PARTS

The bid shall include, a comprehensive list of all consumable and nonconsumable spare parts and accessories, if any necessary for five years of normal operation as specified by the manufacturer. In addition, the bid shall include, in price schedule of these Bidding documents, a price list of recommended non-consumable spare parts for all major items of equipment. The bidder shall give an assurance that spare parts will continue to be available through the life of the equipment. The spare parts shall be clearly identified and related to the specific equipment item. Spare parts shall be delivered suitably packed and treated for long periods in storage. Each pack shall be clearly and indelibly marked with its contents, including a designation number corresponding to the spare parts list in the operation and maintenance instructions. All spare parts shall be stored in the TANESCO central store at kurasini.

7.

PACKING AND SHIPPING

7.1

Packing

All equipment, including accessories, shall be packed and securely clamped against movement in robust, wooden, non returnable packing cases to ensure safe transit from the manufacturer's works to the work sites. The packing shall provide suitable protection against all climatic conditions prevailing during transport and on site. Equipment or material liable to deterioration by sea water, moisture, or ingress of foreign matter shall be totally sealed in strong polythene bags. S23A-7


All accessories shall be carefully packed so that they are fully protected during transport and handling operations and in storage. Internal surfaces of loose accessories shall be sealed off by means of gaskets and blanking off plates. Equipment and surfaces liable to deterioration due to condensation shall be protected by packs of silica gel or other approved desiccant. Each packing case shall be indelibly marked, in two adjacent sides and on the top, with the following: o o o o o o o o o o

individual serial number; client's name, that is: Tanzania Electric Supply Company Ltd .; contract number; name and address of manufacturer's agent in Tanzania; manufacturer's name; description of contents; country of origin; case measurements; gross and net weights in kilogrammes; and all necessary slinging and stacking instructions.

Each case shall contain a fully detailed packing list in a sealed waterproof envelope. Five copies of each packing list shall be sent to TANESCO prior to dispatching the equipment. 7.2

Shipping

The manufacturer/supplier shall be responsible for the shipping of all plant and equipment supplied from abroad to the ports of entry and for the transport of all goods to the Tanesco Central Stores and for all the costs and expenses resulting from it, including customs clearance, offloading, warehousing and insurance. All transport accessories, such as riding lugs, jacking pads, blanking off plates, etc. shall become the property of TANESCO. All items of equipment shall be securely clamped against movement to ensure safe transit from the manufacturer's facilities to the work sites. S23A-8


All accessories shall be carefully packed so that they are fully protected during transport and handling operations and while in storage.

The manufacturer/supplier shall advise, if requested, the storage required for any plant and equipment that may be delivered to the TANESCO's stores. The manufacturer/supplier shall be required to accept responsibility for the advice given, in so far as these arrangements may have a bearing on the behaviour of the equipment in subsequent service. 7.3

Hazardous Substances

The manufacturer/supplier shall submit safety data sheets for all substances used with the equipment. These substances shall be classified in accordance with the European Union SI 426: European Communities (dangerous substances) (classification, packaging, labelling and notification) regulation, 1992, or any subsequent amendment. The manufacturer/supplier shall give an assurance that there are no other substances classified as hazardous in the equipment supplied. The manufacturer/supplier shall accept responsibility for the disposal of such hazardous substances, should any be found. The manufacturer/supplier shall also be responsible for any injury resulting from hazardous substances.

8.

SUBMITTALS

In addition to the documentation set out in General tender requirements, some technical documentation is required as set out in clauses 8.1 and 8.2 below 8.1

Submittals required with the Bid

The following shall be required: o

completed technical data schedule;

o

descriptive literature giving full technical details of equipment S23A-9


offered including ORIGINAL brochure;

8.2

o

outline dimension drawing for each major component and general arrangement drawing showing component layout;

o

general drawing showing the mounting arrangements in a single pole and a double pole support;

o

size and characteristics of the initial and follow through pulling force on the load break switch rope and on the minimum speed or the minimum time of operation required for the complete opening of the contacts in order to interrupt the current, at any time during the life of the switch;

o

Confirmation that the current carrying contacts shall meet the temperature rise requirements after approximately 20 years and that other metal parts shall retain their mechanical strength;

o

safety data sheets for all substances used with the equipment;

o

type test certificates, where available, and sample routine test reports;

o

detailed reference list of customers already using equipment offered with particular emphasis on units of similar design and rating; The list shall include the full name, address, phone and fax number of the purchasers, quantities supplied and delivery time;

o

details of manufacturer's quality assurance standards and programme and national or international quality assurance certificate; and

o

deviations from this specification. Only deviations approved in writing before award of contract shall be accepted.

Submittals required by TANESCO after Contract Award

The following shall be required: o

programme for production and testing;

S23A-10


o

a training video or compact disk illustrating installation, operation and maintenance, if any, of the plant item; and

o

five bound folders with records of the technical particulars relating to the equipment. Each folder shall contain the following information:

*

general description of the equipment and all components, including brochures;

*

technical data schedule, with approved revisions;

*

detailed dimension drawing for all components and general arrangement drawing showing detailed component layout;

*

detailed drawing of the mounting arrangements in a single and a double pole support;

*

statement drawing attention to all exposed points in the equipment at which aluminium or aluminium alloy parts are in contact with or in close proximity to other metals and stating clearly what protection is employed at each point to exclude air and moisture;

*

inspection and test reports carried out in the manufacturer's works;

*

detailed installation and commissioning instructions;

*

guarantee of the equipment in writing; and

*

operation and maintenance instructions, as well as trouble shooting charts.

S23A-11


PART 2: TECHNICAL

9.

GENERAL

This specification covers the design, manufacture, testing, supply, delivery and performance requirements of 33kV and 11kV pole mounted, triple pole, Metal Clad type, Totally enclosed , Load Break Switches (LBS) for use in the lines of 33kV and 11kV of TANESCO. In general, the load break switches will be installed in trunk lines at suitable intervals. The load break switches described in this specification are intended to correspond to typical outdoor, pole mounted, manual operated by polyethylene rope, easily installed, maintenance free, compact, light weight, air interrupting media, metal clad type, totally enclosed load break devices, similar to those already used in TANESCO's networks in order to take advantage of the familiarity of TANESCO's staff with this kind of equipment. However, the bidder is free to propose alternative equipment provided there is no reduction in the operating characteristics required and would be of additional advantage to TANESCO at no extra cost. However acceptability of any alternative is at the discretion of TANESCO. The bidder shall describe fully the unit offered, including the type of interrupting manner in which circuit making and breaking is accomplished, the energy required to operate the switch, and the operating duty of the load break switch , covering the switch capability and the maintenance requirements, if any. A small number of load break isolators may be installed in locations at an altitude between 1,000m and 1,600m. The bidder shall take this into account when considering the basic impulse level and the rated maximum voltage required. A de-rating of the continuous current rating of the load break isolators due to altitude will be acceptable but the derating factor shall be given in the technical data schedule.

S23A-12


INSULATION LEVEL

The insulation level of the 33kV Load Break Switches shall be: o

1.2/50µs impulse wave: 170kV; and

o

50Hz, one minute, withstand voltage level (wet and dry): 70kV.

The insulation level of the 11kV Load Break Switches shall be:

11.

o

1.2/50µs impulse wave: 75kV; and

o

50Hz, one minute, withstand voltage level (wet and dry): 28kV.

CURRENT RATING

The current ratings of the 33kV Load Break Switches shall be: o

continuous current rating: 630A

The bid shall indicate the switches' capability to close on a fault .

The current ratings of the 11kV Load Break Switches shall be: o

continuous current rating: 630A or above; and

The bid shall indicate the switches' capability to close on a fault .

12.

TEMPERATURE RATING

The complete assemblies shall be rated 105°C for normal circuit conditions as per IEC 129.

S23A-13


BUSHINGS

The bushings shall be of the solid glazed porcelain insulator type and shall be bird proof. They shall meet the electrical and mechanical characteristics required in IEC 383. Insulators shall be appropriate for the switch's rated voltage of 33kV or 11kV, as the case may be. The bushings shall be protected from mechanical damages while lifting up the unit by providing holding grips around the bushings. The bidder may offer bushing insulators manufactured from insulating materials other than porcelain such as silicone materials, complying with IEC 1109 but, in that case, full particulars of such materials shall be given, including long term weathering and tensile tests, and evidence of experience under practical conditions. The bushing insulators for the 33kV load break switches shall withstand for one minute, dry and wet 50Hz test voltages of not less than: o o

70kV to earth and between poles; and 80kV across the isolating distances, in accordance with IEC 60-2.

The bushing insulators for the 11kV load break switches shall withstand for one minute, dry and wet 50Hz test voltages of not less than: o o

28kV to earth and between poles; and 32kV across the isolating distances, in accordance with IEC 60-2.

The bidder shall also give the following information in the technical data schedule: o o o

14.

the minimum dry flashover voltage value; the minimum wet flashover voltage value; and the 50Hz puncture voltage of bushing insulators.

RADIO INFLUENCE VOLTAGE

The maximum radio influence voltage for both 33kV and 11kV load break switches shall be 250µV, measured in accordance with IEC 437.

S23A-14


CLEARANCES

The bidder shall give the following information in the technical data schedule for both, 33kV and 11kV load break switches: o o

16.

minimum phase to phase clearance; and minimum phase to earth clearance.

INTERRUPTING MEDIUM

The interrupting medium shall be air although the load break switch is totally enclosed. This shall be achieved by use of arc chute also known as elephant ears to quench the arc; similar to the load break switches current in use on TANESCO distribution network

17.

MAIN ASSEMBLY

The enclosure shall be of high weather-proof, 316 marine grade stainless steel. The enclosure shall be painted grey, colour RAL 7035 to a minimum thickness of 30 µm. The RAL colour code system is that of the DNA (German Standards Board, Frankfurt, Germany). The required load break switches shall be manually operated by polyethylene rope. The ropes and the grips shall have different colour for “ON” and “OFF” preferably red for “ON” and green for “OFF”. The mounting brackets shall be provided at the top of the switch and shall be applicable to accommodate 60mm x 60mm to 100mm x 100mm crossarms. Lifting hooks shall also be provided at the top of the switch. These shall be provided on all Load Break Switches and be so disposed as to allow the entire switch to be lifted without damage, particularly to bushings

The Load Break Switches shall be of the outdoor, triple pole, preferably hinged blade type, arc chute also known as elephant ears to quench the arc and front connected. PVC covered flexes shall connect the moving blades to the rear contacts. A mechanism for the simultaneous isolation of all three phases shall be provided

S23A-15


The fixed contact at which the circuit is broken should have a split head contact, shaped to take the switch's blade parallel to the direction of motion. The contact area of current carrying components shall be made of silver plated, high conductivity copper.

18.

OPERATING MECHANISM Necessary springs shall be included to assist with operation of the load break switch. All joints in the operating mechanism shall be capable of withstanding the vibration arising from wind and from the operation of the equipment so that no slackening can occur.

Each unit shall be provided with the necessary linkage rope to allow the load break switch to be operated from ground level after the ropes are connected to the operating handle mounted on the switch. Indications for operation state, that is ON or OFF shall be provided. Markings of ON/OFF indications shall be of painted illumines or reflecting colours and they shall be readable from the ground level. Colours of preference are GREEN for OFF and RED for ON positions. The length of the operating ropes shall be suitable for installation on 12m poles which have a maximum overground height of 10.2m.

19.

OPERATION SPEED

The bidder shall provide information on the size and characteristics of the initial and follow through pulling force on the load break switch handle and on the minimum speed or the minimum time of operation required for the complete opening of the contacts in order to interrupt the current, at any time during the life of the switch, assuming that the recommended operating conditions are observed.

20.

TERMINALS AND CONNECTIONS

The lead wires from the bushings on the load break switch units for connecting to the line conductors shall be insulated annealed copper 2 conductors 125mm of minimum length 2 meters. Also each end of the lead wires shall be ferrule ready for connecting to the line conductor. S23A-16


21.

EARTHING TERMINALS

Each unit shall be provided with earthing screws and lugs in an accessible position for earthing the operating handle and the switch frame. The earthing screw shall have a diameter not less than 6.5mm.

22.

SURFACE TREATMENT

All iron and steel parts shall be protected against corrosion by hot dip galvanising to the standards of BS 729 or equivalent in so far as they meet the requirements that follow. The supplier shall ensure that internal stresses in the material brought about by such treatments as extensive cold working, bending, welding etc., are relieved as necessary before submission for hot dipping as these stresses could lead to embrittlement and/or intercrystalline cracking after galvanising. Surface contaminants which cannot be removed by pickling, for example, oil, fat, tar, paint, welding slag and similar impurities, shall be removed prior to pickling. Crevices and pin holes shall be avoided in welds as they trap pickling acid and lead to premature corrosion of the zinc coating. Articles shall not be galvanised if their design and shapes are such that the pickling solution cannot be removed with certainty or if adequate venting or drainage is not possible to ensure a safe and effective galvanising dip. If it is necessary to bore drainage or vent holes in articles, the galvaniser or supplier may do so only after the consent of TANESCO representative has been obtained. The zinc of the hot dip galvanising bath shall contain not less than 98.5% by mass of zinc according to ISO 752. No zinc impurities or additives which could have a deleterious effect on the durability of the zinc coating shall be acceptable. The galvanising coating shall be smooth, continuous, uniform and free from anything that is detrimental to the stated use of the coated article. It shall be free from acid spots and flux stains and shall not scale or blister, S23A-17


or be removable by normal handling or packing. Shiny, dull grey or spangled surface appearance shall be generally acceptable. Extensive wet storage stain (white rust) shall be unacceptable. The thickness of the galvanising coating shall comply with the minimum average values given in Table 1 overleaf when tested in accordance with the requirements of this specification. The uniformity of the galvanising coating shall be such that the minimum individual thickness measurement on any test sample shall not be more than 7µm below the minimum average figure specified in Table 1 for that article. The mass of the galvanising coating per square metre of the surface area shall comply with the minimum values given in Table 1 overleaf when tested in accordance with the requirements of this specification. Item Description

Minimum Zinc Mass Deposited (g/sq.mm)

Min. Ave. Coating Thickness (µm)*

Steel items, 5mm thick and over

610

85

Steel items between 2mm and 5mm thick

460

65

Steel items under 2mm thick

335

47

Threaded Steel Items

305

43

Iron Castings

610

85

Table 1: Minimum Galvanising Requirements

* The minimum average thickness figures given in Table 1 can be defined as the lowest of the individual average values for the number of samples under test.

S23A-18


23.

GUARANTEE:

Each Load Break Switches shall be guaranteed in writing, against all defects arising from faults in design, material and workmanship. The guarantee period shall not be less than twelve (12) months from commissioning date or eighteen (18) months from the delivery date. This period shall be extended to five (5) years to cover all defects attributed to inadequate corrosion protection. Should any design fault become apparent to TANESCO after the expire of the above guarantee periods, the manufacturer in collaboration with his local agent shall deliver components necessary to correct the faults, together with any necessary instructions and specialist assistance, FREE OF CHARGE.

S23A-19


TESTS

24.1

Routine Tests

Routine tests for load break switches shall be carried out in accordance with IEC 129. In addition galvanising tests shall be carried out, as detailed below. 24.2

Type Tests

The following type tests shall be carried out in conformity with IEC 60, IEC 129, IEC 437 and and IEC 507: o

dielectric test;

o

radio interference test;

o

short time current test;

o

temperature rise test;

o

operating and mechanical endurance tests;

o

operation at the temperature limits in conformity to IEC 129; and

o

corrosion performance tests;

Where load break or making current tests have been performed on the model being offered, these test results shall also be supplied with the bid. 24.3

Corrosion Performance Tests

Performance shall be tested after the load break switch has been subjected to 1,000 hours of salt spray corrosion, in conformity with IEC 507. An equivalent field experience in coastal sites shall be acceptable. The bidder shall confirm that the current carrying contacts shall meet the temperature rise requirements after approximately 20 years of coastal exposure and that other metal parts shall retain their mechanical strength.

S23A-20

Specification S23A - Load Break Switches 24.4

Galvanising Tests

The following tests, measurements or inspections shall be carried out on each of the load break switch: o o o

visual inspection; thickness of galvanising coat; and uniformity of galvanising coat.

In the event of disagreement or dispute over the results of the above tests a coating mass test shall be carried out, as set out below. The result of this test shall be definite and binding. The visual inspection shall include the following aspects: o

smoothness: there shall be no exposed spots, spikes or anything detrimental to the stated use of the articles or to the personnel handling them;

o

stains: there shall be no acid spots, flux or dross stains;

o

adhesion: there shall be no blisters, peeling or flaking. Normal handling shall not give rise to deterioration;

o

wet storage: storage and stacking conditions shall be appropriate. Excessive white rust will cause the consignment to be rejected; and

o

threaded items: oiled nuts with uncoated female threads, cut oversize to allow for the galvanising coating on the standard bolt threads, shall have free travel.

Thickness measurements shall be determined by a magnetic instrument method as set down in ISO 2178. The instrument used shall have the necessary degree of accuracy, range of probes and probe adapters to enable reliable readings to be obtained consistently. Otherwise, the TANESCO representative shall nominate a suitable instrument for the purpose of obtaining the measurements.

S23A-21


Before taking measurements, the instrument shall be calibrated, preferably on an ungalvanised sample of the articles under test. The steel surface used for the calibration shall be cleaned, if possible, by machine process or abrasive. Between five and ten measurements shall be taken per sample, depending on size, shape, etc. The average thickness shall be taken to be the average of all the readings for that sample. The minimum average coating thickness shall be defined as the lowest of the individual average thickness values for the number of samples under test. The minimum individual value of the readings taken on each sample shall be used to determine the coating uniformity. The coating mass shall be determined by a coat stripping procedure as set down in ISO 1460. This test, when required, shall normally be carried out on two samples. The two samples chosen shall be the ones that have given the lowest readings when tested by the magnetic measurement method. For shaped items, details of the method of calculating the surface area shall be agreed between the contractor and the project manager. A consignment that has been rejected may be regalvanised and again offered for test, provided that it is according to specification in all other respects.

S23A-22


SCHEDULES

25.1

Technical Data Schedule Description

Unit

Type of Load Break Switch Original catalogue enclosed? Catalogue Number Manufacturer Country of origin International standard it complies with Type of Mounting Maximum 50Hz Operating Voltage

kV

Basic Impulse Level (1.2/50us)

kV

50Hz, 1 min., Withstand Voltage Level: Wet

Dry

kV kV

Continuous current carrying capacity:

A

De-rating factor at altitude of 1,600m

%

Short Time Current Rating:

1s 3s

kA kA

Active load breaking current

A

Fault make rated current, if can be closed on fault.

kA

Temperature rise at rated current

°C

Radio influence voltage

uV

Minimum Clearance:

Phase to Phase Phase to Earth S23A-23

mm mm

Bid


Description

Unit

Mechanical Endurance

Times

Type of Bushing – Insulators Creepage distance Material Type and Grade Minimum wet flashover voltage

kV

50Hz puncture voltage

kV

Are bushing-insulators bird proofs? (y/n) Are all assemblies potted into the porcelain? (y/n) Is shed incorporated into the upper contact assembly? (y/n) Method of attachment to frame Insulator Colour Material and grade of main contacts Length of lead wires from the bushings of LBS for connecting to the line conductor (each)

Are the ends of the lead wires ferrule ready for connection to the line conductor? (y/n) Contact weathering protection Type of main bearings Type of earth terminal Diameter of earth terminal S23A-24

m

Bid


Description

Unit

Material and form of insulator in operating mechanism Type of protection of ferrous components Range of pole height suitability Dimensions of Load Break Switch: Heigth Width Others

mm mm mm

Degree of Protection Colour of rope & grips for “ON” position Colour of rope & grips for “OFF” position Material and grade of enclosure Weight of Switch in Service

Kg

Expected life time of the switch

Years

Guarantee period

Months

NOTE: please, fill one schedule for EACH TYPE of Load Break Switch

S23A-25

Bid


Non Compliance Schedule

On this schedule the bidder shall provide a list of non compliances with this specification, documenting the effects that such non compliance is likely to have on the equipment's life and operating characteristics. Each non compliance shall be referred to the relevant specification clause. Clause No.

Non Compliance

S23A-26


Test Certificates Schedule

On this schedule a list of the test certificates included with the bid shall be provided. This list shall include type test certificates and sample routine test reports. Each certificate listed shall be referred to the relevant specification clause. Clause No.

Type Test Certificate or Routine Test Report

S23A-27

Tanesco Tanzania - Specification S23A Metal Clad Type Load Break Switches (2003)

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