WELCOMES ALL OF YOU
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Bus Switching Scheme& Substation Layout
K K Sarkar (E_mail:
[email protected]) Chief Design Engineer (Engg-s/s)
Power Grid Corporation of India 2
Bus Switching Scheme& Substation Layout
K K Sarkar (E_mail:
[email protected]) Chief Design Engineer (Engg-s/s)
Power Grid Corporation of India 2
Important considerations in layout..
Reliability and Security -
Selection of Bus Scheme Ease of Maintenance Operational Flexibility
Short Circuit Level Shape of the land Altitude of the land above mean sea level Feeder orientation Safety of Equipment and personnel Possibility of future expansion Cost 3
Bus Switching Schemes
…
Single Main Scheme Double Main Scheme Single Main & Transfer Scheme Double Main with by-pass isolator scheme Double Main & Transfer Scheme One & Half Breaker Scheme Double breaker Scheme Ring Bus Scheme
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SINGLE BUS SCHEME
Simplest and cheapest bus bar scheme Maintenance and extensions of busbars are not possible without shutdown of the substation. Operation & maintenance of bus bar is easy.
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SINGLE MAIN AND TRANSFER SCHEME
Individual CB can be taken out for maintenance on-load at a time.
The transfer bus coupler acts as the breaker for the circuit under by pass.
Individual circuits have a bypass isolator to connect to the transfer bus and this isolator will be closed during bypass operation of that particular circuit. 6
DOUBLE BUS SCHEME
Load will be distributed on both the buses and the bus coupler shall be normally closed.
For maintenance & extension of any one of the buses the entire load will be transferred to the other bus.
On load transfer of a circuit from one bus to the other bus is possible through bus isolators provided the bus coupler is closed and thereby two buses are at the same potential.
On load bypassing of any circuit for breaker maintenance is not possible . 7
DOUBLE BUS WITH BY-PASS SCHEME
This bus arrangement provides the facilities of a double bus arrangement & a main and transfer bus arrangement.
The bus to which the transfer bus isolator is connected can be used as a transfer bus also.
During the time a circuit is under bypass, the bus coupler will act as the breaker for the bypassed circuit.
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DOUBLE MAIN AND TRANSFER SCHEME
In this bus scheme, in addition to the two main buses there will be a separate transfer bus also.
Since separate transfer bus is available there will be no need of transferring the load from one bus to the other bus unlike in a double main cum transfer bus arrangement.
Other features are similar to the one described in double bus with by pass arrangement. 9
ONE AND HALF BREAKER SCHEME
In this scheme, two circuit have three breakers, the middle breaker ties the two circuits and hence is called the tie breaker.
Breaker or bus maintenance is possible without any shut down of the feeder
Even if both the buses are out of service, power can be transferred from one feeder to another feeder through tie breaker
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DOUBLE BUS TWO BREAKER SCHEME
Each feeder is controlled by two breakers.
This arrangement is comparatively costlier than other scheme and hence followed in very important circuit only.
In this arrangement breaker maintenance for any feeder circuit is easily possible without any shutdown. 11
RING BUS SCHEME
As long as the ring is closed load has two sources of supply and any circuit breaker can be taken out of service without affecting the supply.
Extension of ring scheme is difficult.
No bus bar protection required.
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Selection of Switching Schemes
…
No reliability in Single Main, Double Main, Single Main & Transfer Scheme w.r.t bus fault, feeder fault & breaker maintenance Double Main & Transfer Scheme, One & Half Breaker Scheme & Double breaker Scheme are characterized by reliable and interruption free supply. One & half breaker scheme can be selected for EHV substations due high reliability, operational flexibility, ease of maintenance, ease of expansion, due consideration of cost 13
Important considerations in layout..
Reliability and Security -
Selection of Bus Scheme Ease of Maintenance Operational Flexibility
Short Circuit Level Shape of the land Altitude of the land above mean sea level Feeder orientation Safety of Equipment and personnel Possibility of future expansion Cost 14
Bus Bar Design, Selection of conductor levels & Bay width calculation..
Selection of conductor (AAC, ACSR, Tube) Current Carrying capacity with temperature rise of 35 deg.C over ambient of 50deg.C ambient (IEEE-738) Temperature Rise during short circuit Stresses in tubular bus Cantilever Strength of post insulator Deflection of the tube Natural frequency of tubular bus bar Aeolian Vibration 15
Bus Bar Design & Selection of conductor levels..
Electrical Clearances (IEC-60071) Corona Electric Field (10kV/m)& Magnetic Field (500 μT) Short Circuit Forces (IEC-60865) Sag-Tension Calculation Normal Tension (Factor of safety 2.0) and Short Circuit Tension (Factor of Safety 1.5) Height of conductor levels Bay width & Phase to Phase spacing 16
Minimum Clearances for Layout (at altitude <1000m above mean sea level)… Voltage Level (Rated)
Ph-Ph (m)
Ph-E (m)
Sectional Clearance (m)
BIL (kVp)
SIL (kVp)
765 kV
7.6 (cond-cond) 9.4 (rod-str)
4.9 (cond-str) 6.4 (rod-str)
10.3
2100
1550
400 kV
4
3.5
6.5
220 kV
2.1
2.1
5
1550 1050
1050 650 17
Minimum Clearances for Layout (at altitude <1000m above mean sea level)… Voltage Level (Rated)
Ph-Ph (mm)
Ph-E (mm)
Sectional Clearance (mm)
132 kV
1300
1300
4000
110 kV
1100
1100
3800
66 kV
630
630
3500
33 kV
320
320
2800
Altitude corrections w.r.t clearances, insulation levels, creepage and oil temperature rise of the equipment shall be considered for altitudes more than 1000 m above mean sea level. 18
Bay widths & levels… Voltage Level
Bay width
First Level
Second Level
Third level
BIL
SIL
400 kV
24m
8m
15m
22m
1550
1050
220 kV
16m
5.9m
11.7m
16.2m
1050
650
132 kV
12m
4.6m
8m
12m
650
NA
66 kV
7.6m
4m
6m
9.5m
325
NA 19
Type of Isolator & Structure in Layout
Type of Isolator
Horizontal Centre Break Isolator (HCB) Horizontal Double Break Isolator (HDB) Pantograph Isolator (Panto) Vertical Break Isolator (VB) Staggered
Type of Structure
Pie ( ╥) structure Enclosed (Π) structure 20
Height of shield wire, Height & Location of LM & Location of Fence..
DSLP Calculation to decide the height of shield wire and/or Height & location of LM
Rolling Sphere Method (IEEE-998) Razevig Method
Earthmat Design (IEEE-80/CBI&P Report No. 302) Location of switchyard fence –
Touch Potential Step Potential Grid Resistance Earth Potential Rise (EPR) 21
Location of other buildings, auxiliaries..
Control Room Fire fighting pump house (FFPH) DG set LT station placement Roads & rail tracks Switchyard Panel Room Open Store Colony and other infrastructures 22
SLD & LAYOUT (PLAN) -400kV D type layout
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LAYOUT (SECTIONS) -400kV D type layout
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SINGLE LINE DIAGRAM -220kV DMT layout
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LAYOUT (PLAN) - 220kV DMT layout
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LAYOUT (SECTIONS) - 220kV DMT layout Transformer Bay
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LAYOUT (SECTIONS) - 220kV DMT layout 220kV Line Bay
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LAYOUT (SECTIONS) - 220kV DMT layout 220kV TBC Bay
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LAYOUT (SECTIONS) - 220kV DMT layout 220kV Bus Coupler Bay
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LAYOUT (PLAN) -400kV I-type layout
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LAYOUT (SECTIONS) - 400kV I-type layout
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GA Drawing of 400/132kV Substation 0 . 5 7 3 5
0 . 0 5 3 5
0 . 5 2 3 5
0 . 0 0 3 5
0 . 5 7 2 5
0 . 0 5 2 5
0 . 5 2 2 5
0 . 0 0 2 5
0 . 5 7 1 5
0 . 0 5 1 5
0 . 5 2 1 5
0 . 0 0 1 5
0 . 5 7 0 5
0 . 0 5 0 5
0 . 5 2 0 5
0 . 0 0 0 5
0 . 5 7 9 4
0 . 0 5 9 4
0 . 5 2 9 4
0 . 0 0 9 4
0 . 5 7 8 4
0 . 0 5 8 4
0 . 5 2 8 4
0 . 0 0 8 4
0 . 5 7 7 4
0 . 0 5 7 4
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
0 3 5400.0 E
5375.0 E
5350.0 E
5325.0 E
5300.0 E
5275.0 E
5250.0 E
5225.0 E
4 0 0 k V
M A I N B U S I I
5200.0 E
4 0 0 k V
5175.0 E
M A I N B U S I
5150.0 E
5125.0 E
5100.0 E
5075.0 E
5050.0 E
PRESENT SCOPE FUTURE
5025.0 E
FOR TENDER PURPOSE ONLY 5000.0 E
4975.0 E
1. ALL DIMENSIONS ARE IN METRE UNLESS SPECIFIED. 2. LOCATION OF ALL BUILDINGS ARE INDICATIVE. 3. ROUTE OF APPROACH ROAD IS INDICATIVE ONLY. THE SAME SHALL BE DECIDED BY SITE.
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A.
DSLP by Lightning Mast
0.2h h 2h/3 hx 0.75h 1.5h
rx 0.75h 1.5h
rx
Fig. 2 (a) : Zone of Protection for single lightning mast
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Zone protected by two lightning mast around themselves R a
c b
0.2h h hox
a
rx hx 0.75h 1.5h
rx Box rx
Fig. 2.(b): Zone of protection for two lightning masts 35
DSLP Calculation Calculation of overlappings (Bx) :
Bx=1.5.hox.px( 1-(hx/0.8hox)) Bx=0.75.hox.px.( 1-(hx/hox))
if hx<2/3rd of hox if hx>2/3rd of hox
where, h is the height of the lightning mast/tower including peak hox is the maximum hight protected is given by, hox=h-(a/7p) a is the distance Lightning Masts / Tower Peaks hx is the maximum height of the objects to be protected from side strokes px= 5.5/sqrt(hox) if hox>30.0 m px= 1.0 if hox<30.0 m
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PROTECTION ZONE OF THREE LIGHTNING MAST
LM1
Bx
a1 D a3 LM2 a2
LM3 rx
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DSLP Calculation Zone protected by three(3) lightning masts : The condition that the area among the three (3) lightning masts at a level 'hx' will be protected is given as :
D <= 8(h-hx)p w ere, D is the circumdiameter of the triangle formed by the three lightning masts. 2
2
2
D=a1 /sin{arccos((a2 +a3 -a1 )/2a2a3)}
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LIGHTNING PROTECTION BY OVERHEAD SHIELD WIRES:
0.2h h 2h/3 hx
0.6h 1.2h
bx
0.6h 1.2h
2bx
Fig : Protective Zone of a ground/ shield wire
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DSLP Calculation The breadth of the protective zone offered by a single shield wire on the ground level in a plane perpendicular to the shield of wire is equal to 1.2 h , where h is the height suspension of the shield wire. Half the breadth of the protective zone "bx" at level hx is given by:
bx=1.2 h ( 1-(hx/0.8h)) bx=0.6 h ( 1-(hx/h))
if hx<2/3rd of h if hx>2/3rd of h
where, h is the height of the tower including peak hx is the height of the objects to be protected from side strokes
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DSLP Calculation The radius of protective zone offered by a lightning mast at height "hx" from ground level is given by: rx=1.5hp( 1-(hx/0.8h)) if hx<2/3rd of h rx=0.75hp( 1-(hx/h)) if hx>2/3rd of h where, h is the height of the lightning mast/tower including peak hx is the height of the objects to be protected from side strokes p= 5.5/sqrt(h) if h>30.0 m p= 1.0 if h<30.0 m
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POWERGRID 400 kV STANDARD LAYOUT Bus Scheme adopted : One & Half Breaker Scheme Layout : I-Type First (Equipment Level)- 8m Second Level (Main Bus) - 15m Third Level (Jack Bus) – 22m Bay Width – 24m Main Bus : Quad ACSR Bersimis/Quad AAC BULL Main Bus Span: 48m Equipment Interconnection: 4” or 4.5” IPS Al tube Normal Tension for gantry Structure: 4T/phase Normal Tension for O/H shield wire: 0.8T, 10.98mm dia GS wire (7m peak) Fault Level: 40kA/50kA/63kA (1 sec) Cantilever Strength of Post Insulator : 800 kg 42
POWERGRID 220 kV STANDARD LAYOUT Bus Scheme adopted : Double Main & Transfer Scheme Scheme First (Equipment Level)- 5.9m Second Level (Main Bus) – 11.7m Third Level (Jack Bus) – 17.2m Bay Width – 16m Main Bus : Quad ACSR Moose Main Bus Span: 48m Equipment Interconnection: 4” IPS Al tube Normal Tension for gantry Structure: 4T/phase or 2T/Phase Normal Tension for O/H shield wire: 0.8T, 10.98mm dia GS wire (5m peak) Fault Level: 40kA/50kA (1 sec) Cantilever Strength of Post Insulator : 800 kg 43
