This document discusses various busbar arrangements used in substations including: - Single busbar system - Single bus with sectionaliser system - Double busbar system - One and half breaker system It provides diagrams and explanations of how each system works, their advantages and disadvantages. It also discusses the different busbar configurations adopted by the Andhra Pradesh Transmission Corporation (APTRANSCO) at various voltage levels.

1. PREPARED BY
GOPALA KRISHNA PALEPU
ADE/MRT(PROTECTION)

2. BUSBAR ARRANGEMENTS
SINGLE BUSBAR SYSTEM.
SINGLE BUS WITH SECTIONALISER SYSTEM.
SINGLE BUS & TRANSFER BUS SYSTEM.
DOUBLE BUSBAR SYSTEM.
DOUBLE BUS WITH SECTIONALISER SYSTEM.
DOUBLE BUS & TRANSFER BUS SYSTEM.
DOUBLE BUS & TRANSFER BUS WITH
SECTIONALISER SYSTEM.
ONE & HALF BREAKER SYSTEM
1. 3CTs METHOD
2. 4CTs METHOD
3. 5CTs METHOD
4. 6CTs METHOD
ONE & HALF BREAKER WITH SECTIONALISER
SYSTEM

3. SINGLE BUS SYSTEM
FEEDER1
MAIN BUSBAR
FEEDER2
T/F-1 T/F-2
FEEDER3 FEEDER4
BAY1
BAY2
BAY3 BAY4
BAY5
BAY6

4. SINGLE BUS SYSTEM
MAIN BUSBAR
3
1-89
1-52 CB
1-CT
1-89 L
LINE-1
3
2-89
2-52 CB
2-CT
2-89 T
T/F-1
3
4-89
4-52 CB
4-CT
4-89 T
T/F-2
3
3-89
3-52 CB
3-CT
3-89 L
LINE-2

5. SINGLE BUS SYSTEM
1. In case of bus fault or bus bar
isolator fault or maintenance
Total Substation is out of
service.
2. In case of maintenance of
transformer circuit breaker the
associated transformer has also
to be shut-down. Similarly for
Line also.
1. Simple in Design
2. Easy Maintenance
3. Less Expenditure
4. Good Appearance
DISADVANTAGESADVANTAGES

6. SINGLE BUS WITH CB SECTIONALISER SYSTEM
FEEDER1
MAIN BUSBAR
FEEDER2
T/F-1 T/F-2
FEEDER3 FEEDER4
BAY1
BAY2
BAY3 BAY4
BAY5
BAY6
CB SECTIONALISER

7. SINGLE BUS WITH CB SECTIONALISER SYSTEM
BUS-1
3
1-89
1-52 CB
1-CT
1-89 L
LINE-1
3
2-89
2-52 CB
2-CT
2-89 T
T/F-1
3
5-89
5-52 CB
5-CT
5-89 T
T/F-2
3
4-89
4-52 CB
4-CT
4-89 L
LINE-2
BUS-2
3
3
3-89 A 3-52 CB
3A-CT
3-89 B
3B-CT
BUS SECTIONALISER

8. In this, Main Bus is divided into two sections with
a Circuit Breaker and isolators in between the
adjoining sections. One complete section can be
taken out for Maintenance without disturbing the
continuity of other section. Even if a fault occurs
on one section of the Bus, that faulty section
along will be isolated while the other section
continues to be in service.
SINGLE BUS WITH CB SECTIONALISER SYSTEM

9. SINGLE BUS & TRANSFER BUS SYSTEM
FEEDER1
BUS-1
TRANSFER BUS
FEEDER2
TRANSFERBUSCOUPLER
T/F-1 T/F-2
FEEDER3 FEEDER4
BAY1 BAY2 BAY3 BAY4 BAY5 BAY6 BAY7

10. SINGLE BUS & TRANSFER BUS SYSTEM
1-89A
1-52 CB
1-CT
1-89 L
LINE-1
3 3 3 3
3
1-89 B
2-89A
2-52 CB
2-CT
2-89 T
2-89 B
T/F-1
3-89A
3-52 CB
3-CT
3-89 B
4-89A
4-52 CB
4-CT
4-89 L
4-89 B
LINE-2
5-89A
5-52 CB
5-CT
5-89 T
5-89 B
T/F-2
MAIN BUSBAR
AUX BUS
TRANSFERBUSCOUPLER

11. SINGLE BUS & TRANSFER BUS SYSTEM
With this arrangement, all the feeders are normally
on the Main Bus Bar. If at any time, a Line Circuit
Breaker Maintenance is required, that particular
feeder, can be transferred on to the Transfer Bus.
The feeder protection thus gets transferred to trip
Transfer Bus Coupler Breaker. On fault occurrence
or maintenance, entire bus becomes de-energised.
Salient features:-
Only one Circuit at a time can be transferred on the
Transfer Bus.
For Maintenance or on fault occurrence, total Bus
becomes dead.

12. DOUBLE MAIN BUS SYSTEM
FEEDER1
BUS-2
BUS-1
FEEDER2
T/F-1 T/F-2
BUSCOUPLER
FEEDER3 FEEDER4
BAY1 BAY2 BAY3 BAY4 BAY5 BAY7 BAY8

13. DOUBLE MAIN BUS SYSTEM
1-89 A
1-89 B
3
1-52 CB
1-CT
1-89 L
LINE-1
2-89 A
2-89 B
3
2-52 CB
2-89 T
T/F-1
3
T/F-2
3
LINE-2
3
32-CT
5-89 A
5-89 B
5-52 CB
5-89 T
5-CT
4-89 A
4-89 B
4-52 CB
4-89 L
4-CT
3-89 A
3-89 B
3A-CT
3B-CT
3-52 CB
BUS -1
BUS -2
BUSCOUPLER

14. DOUBLE BUS SYSTEM
Salient features:-
This has got flexibility of transferring any Circuit to
any of the Bus.
For Maintenance or on fault occurrence on one Bus,
then only that Bus becomes dead, while the other
Bus remains in service.
For Maintenance of a Circuit Breaker, that particular
Circuit has to be taken out of service.
To overcome this, an additional bypass isolator is
provided as indicated in figure below.

15. DOUBLE MAIN BUS & CB BYPASS ISO SYSTEM
FEEDER1
BUS-2
BUS-1
T/F-1
BUSCOUPLER
FEEDER2
T/F-2
FEEDER3 FEEDER4
BAY1 BAY2
BAY3
BAY4
BAY5
BAY6 BAY7
WHEN ANY CB PROBLEM OR FOR
PREVENTIVE MAINTANENCE THEN ALL
OTHER FEEDERS SHIFTED TO
ANOTHER BUS OF FAULTED CB BUS
AND CLOSE THE BYPASS ISOLATOR,
THEN PROTECTION IS SHIFTED TO BUS
COUPLER AND OPEN THE FAULTY CB.

16. DOUBLE MAIN BUS & TRANSFER BUS SYSTEM
FEEDER1
BUS-2
BUS-1
FEEDER2
TRANSFERBUS
COUPLER
T/F-1 T/F-2
BUSCOUPLER
TRANSFER BUS
FEEDER3 FEEDER4
BAY1 BAY2
BAY3 BAY4 BAY5
BAY6 BAY7 BAY8

17. DOUBLE MAIN BUS & TRANSFER BUS SYSTEM
1-89 A
1-89 B
1-52 CB
1-CT
1-89 L
LINE-1
5-89 C1-89 C 2-89 C
T/F-1
3
3
3-89 A
3-89 B
3A-CT
3B-CT
3-52 CB
BUS -1
BUS -2
BUSCOUPLER
3
2-89 A
2-89 B
2-52 CB
2-CT
2-89 T
3
4-89 A
4-89 B
4-52 CB
4-CT
4-89 C
3
5-89 A
5-89 B
5-52 CB
5-CT
5-89 L
LINE-2
3
6-89 A
6-89 B
6-52 CB
1-CT
6-89 T
T/F-2
3
6-89 C
AUX BUS TRANSFER
BUS COUPLER

18. This is combination of Main and Transfer Bus and
Double Bus Arrangement.
Salient features:-
This has got flexibility of transferring any Circuit
to any of the Main Buses.
For Maintenance or any fault occurrence on a
Bus, Particular Bus only becomes dead, while the
other Bus continues to be in service.
Any Circuit Breaker can be taken out for
Maintenance by transferring that circuit to
Transfer Bus, and transferring its Protection to
Transfer Bus Coupler Circuit Breaker.
DOUBLE MAIN BUS & TRANSFER BUS SYSTEM

19. DOUBLE BUS WITH SECTIONALISER SYSTEM
FEEDER1
BUS-2
BUS-1
T/F-1 T/F-2
FEEDER2
BAY1 BAY3 BAY6 BAY8
BUSCOUPLER
BAY2
BUSCOUPLER
BAY7
BAY4
BAY5
BUS
SECTIONALISER
This is an improvement over the double bus
bar arrangement. For maintenance or an
occurrence of a fault, only one section of the
faulty bus only becomes dead while the rest
continues to be in service.

20. DOUBLE BUS WITH SECTIONALISER SYSTEM
1-89 A
1-89 B
3
1-52 CB
1-CT
1-89 L
LINE-1
3-89 A
3-89 B
3
3-52 CB
3-89 T
T/F-1
2-89 A
2-89 B
2-52 CB
2A-CT 3
32B-CT
5-89 A
5-89 B
3
5-52 CB
5-CT
5-89 L
LINE-2
7-89 A
7-89 B
3
7-52 CB
7-89 T
T/F-2
6-89 A
6-89 B
6-52 CB
6A-CT 3
36B-CT
3
3
4-89 B 4B-52 CB
4B-CT
4-89 D
4D-CT
BUS SECTIONALISER
3
3
4-89 A 4A-52 CB
4A-CT
4-89 C
4C-CT
3-CT 7-CT
BUS -1
BUS -2
BUS -3
BUS -4

21. ONE AND HALF CIRCUIT BREAKER SYSTEM
(I-CONFIGUARATION)
FEEDER2 FEEDER4 FEEDER6 FEEDER8 FEEDER10 FEEDER12
FEEDER1 FEEDER3 FEEDER5 FEEDER7 FEEDER9 FEEDER11
BUS-2
BUS-1
BAY1BAY2BAY3
BAY4BAY5BAY6
BAY7BAY8BAY9
BAY10BAY11BAY12
BAY13BAY14BAY15
BAY16BAY17BAY18
DIA1 DIA2 DIA3 DIA4 DIA5 DIA6

22. BUS-2
BUS-1
FEEDER3 FEEDER4 FEEDER7 FEEDER8 FEEDER11 FEEDER12
FEEDER1 FEEDER2 FEEDER5 FEEDER6 FEEDER9 FEEDER10
BAY1
BAY2
BAY3
BAY4
BAY5
BAY6
BAY7
BAY8
BAY9
BAY10
BAY11
BAY12
BAY13
BAY14
BAY15
BAY16
BAY17
BAY18
DIA1
DIA2
DIA3
DIA4
DIA5
DIA6
ONE AND HALF CIRCUIT BREAKER SYSTEM
(D-CONFIGUARATION)

23. DIFFERENT CT METHODS OF ONE & HALF BREAKER SYSTEM
3 CTs METHOD
4 CTs METHOD
6 CTs METHOD
6 CTs METHOD
LINE
LINE
LINE
LINE
CB CB CB
CB CB CB
CB CB CB
CB CB CB
AT/F
AT/F
AT/F
AT/F
5 CTs METHOD
LINE
CB CB CB
AT/F
6 CTs METHOD
LINE
CB CB CB
AT/F

24. Salient features:-
• It has 3 Circuit Breakers for Two Circuits.( One is
Line another is Transformer or Bus Reactor or both
are Lines)
• No changeover of Line from one Bus to the other is
required.
• For Circuit Breaker Maintenance of any Line, the
load gets transferred Automatically to the other bus.
• For Maintenance or an occurrence of a Bus fault, all
the interconnections will be on healthy bus and no
disturbance to the Circuits.
• Even if both Buses become dead, Circuits can still
be in service through the Tie Circuit Breaker.
• This has got many such advantages to maintain the
system stability.
ONE AND HALF CIRCUIT BREAKER SYSTEM

25. DOUBLE BUS & DOUBLE BREAKER SYSTEM
FEEDER1
BAY1
BAY2
BAY3
BAY4FEEDER2
FEEDER3
BAY5
BAY6
BAY7
BAY8
FEEDER4
FEEDER1
BUS-2
BUS-1
BAY1BAY2
BUS-2
BUS-1
FEEDER2
BAY3BAY4
FEEDER3
BAY5BAY6
BAY7BAY8
FEEDER4
FOR ECONOMICAL& RELIABULITY PURPOSE THIS SYSTEM ADOPTED IN 800KV SYSTEM

26. MESH / RING
LAYOUT
FEEDER 1 FEEDER 2
FEEDER 3
FEEDER 4FEEDER 5FEEDER 6
FEEDER 7
FEEDER 8
1-52 CB 2-52 CB
3-52 CB
4-52 CB
5-52 CB6-52 CB
8-52 CB
7-52 CB

27. BUSBAR SYSTEMS ADOPTED IN APTRANSCO
400KV BUS1. 400KV KALAPAKADOUBLE BUS WITH AUX
BUS & SECTIONALISER
400KV BUS (4 CTs)
400KV BUS (5 CTs)
1. 400KV MAMIDIPALLY & VEMAGIRI
2. 400KV KHAMMAM & NUNNA
(APTRANSCO BAYS IN PGCIL)
ONE & HALF BREAKER
SYSTEM
400KV BUS1. 400KV NELLOREONE & HALF BREAKER
SYSTEM WITH
SECTIONALISER
220KV BUS
220KV BUS
1. 400KV MAMIDIPALLY
2. 400KV KALAPAKA
DOUBLE BUS & AUX
BUS SYTEM
220KV BUS
220KV BUS
1. 220KV MALKARAM
2. 220KV TALLAPALLY
DOUBLE BUS WITH
SECTIONALISER
220KV BUS
220KV BUS
1. 220KV GACHIBOWLI
2. 220KV GHANAPUR
DOUBLE BUS SYTEM
132 KV BUS
132 KV BUS
1. 220KV YEDDUMAILARAM
2. 220KV GHANAPUR
SINGLE BUS & AUX BUS
SYSTEM
220KV BUS
220KV BUS
1. 220KV SHAPURNAGAR
2. 220KV CHANDRAYANA GUTTA
SINGLE BUS WITH
SECTIONALISER
220KV BUS
220KV BUS
1. 220KV SIVARAMPALLY
2. 220KV NARKETPALLY
SINGLE BUS SYSTEM
BAY VOLTAGE LEVELNAME OF THE SUBSTATIONBUSBAR CONFIGUARATION

28. What does a substation contains..
Substation
Main
Equipment
Engineered
items
Auxiliary
Equipment
Civil
Auxiliary
System
Structure
Main
Equipment
TRANSMISSION AND DISTRIBUTION SUBSTATIONS

29. TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Main Equipment
Circuit Breaker (CB)
Instrument Transformer (CT/CVT/EMVT/PT)
Surge Arrester (LA)
Isolator (ISO)
Transformer & Reactor
Bus Support Insulator (BPI)
Line Traps (WT/LT)
Control & Protection system (C&R)
Power Line Carrier Communication system (PLCC)

30. BUS
BUSISOLATOR
CIRCUITBREAKER
3CURRENTTRANSFORMER
89 52 CT 89
LINEISOLATOR
UUU
WAVE/LINETRAP
WT
UUU
3
CAPACITORVOLTAGETRANSFORMER
LIGHTENING/SURGEARRESTOR
CVT LA
TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Main Equipment

31. What does a substation contains..
TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Substation
Main
Equipment
Engineered
items
Auxiliary
Equipment
Civil
Auxiliary
System
Structure

32. TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Engineered items
1. Busbar Materials
A. Strung Bus Conductor (ACSR).
B. Rigid Bus Conductor (AL Tube).
C. Clamps & Connectors.
D. String Insulator & Hardware.
2. Earthing Materials
A. Main Earthing Materials (Rod or Flat).
B. Earth Pits.
3. Cables & accessories
A. LT Power & Control Cable
B. HT Power Cable
C. Cable terminations, gland, lugs, ties, marker etc.
D. Cable Supporting Materials.

33. What does a substation contains..
TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Substation
Main
Equipment
Engineered
items
Auxiliary
Equipment
Civil
Auxiliary
System
Structure

34. TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Auxiliary Equipment
LTAC Switchgear Panel
AC Distribution Board
Battery & Battery Charger
DC Distribution Board
Auxiliary LT Transformer
Lighting Transformer
Main Lighting Distribution Board
Emergency Lighting Distribution Board
Diesel Generator
UPS

35. What does a substation contains..
TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Substation
Main
Equipment
Engineered
items
Auxiliary
Equipment
Civil
Auxiliary
System
Structure

36. TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Auxiliary System
1. Illumination system
A. Indoor
I. Control Room Building
II. Diesel Generator Building
III.Fire Fighting Pump House Building.
IV.Store Room Building
V. Repair Bay
B. Outdoor Switchyard
2. Fire Fighting and Fire Detection System
3. Air Conditioning and Ventilation System

37. What does a substation contains..
TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Substation
Main
Equipment
Engineered
items
Auxiliary
Equipment
Civil
Auxiliary
System
Structure

38. TRANSMISSION AND DISTRIBUTION SUBSTATIONS
Substation Structures
Main Column and Beam structures
Equipment supporting structures
Substation Civil
Foundation for gantry column & Equipment
Foundation for Transformer / Reactor
Control Room Building / DG, FFPH Building
Outdoor Switchyard Cable Trench
Surface Drainage
Roads
Fencing and Gate

39. TRANSMISSION AND DISTRIBUTION SUBSTATIONS
A Typical Sub-Station content wise cost structure.
A > Transformer / Reactor----------------------------------------- 27%
B > EHV Circuit Breaker, CT, CVT, LA, Isolator, BPI------- 22%
C > Control, Protection & PLCC----------------------------------- 7%
D > Medium Voltage Switchgear---------------------------------- 5%
E > Cables, AC/DC Aux., Lighting, Busbar etc.--------------- 16%
F > Structures---------------------------------------------------------- 6%
G > Civil------------------------------------------------------------------ 13%
H > Erection------------------------------------------------------------- 4%
27
22%
7%
5%
16%
6% 13% 4%
A B C D E F G HA B C D E F G H
27%
22%
7%
5%
16%
6% 13% 4%

40. NORMS OF PROTECTION FOLLOWED BY UTILITIES
FOR TRANSMISIION LINES & DISTRIBUTION LINES ( FEEDER / LINE PROTECTION )
NUMERICAL DISTANCE SCHEME (21) OR LINE
DIFFERENTIAL SCHEME (87L) WITH 67N
NUMERICAL DISTANCE SCHEME (21P + 21N)
+ in BUILT DEF RELAY(67N)765 KV LINES7.
NUMERICAL DISTANCE SCHEME (21) OR LINE
DIFFERENTIAL SCHEME (87L) WITH 67N
NUMERICAL DISTANCE SCHEME (21P + 21N)
+ in BUILT DEF RELAY(67N)400 KV LINES6.
SWITCHED DISTANCE SCHEME OR
NUMERICAL DISTANCE SCHEME (21P+ 21N)
NON SWITCHED DISTANCE SCHEME OR
NUMERICAL DISTANCE SCHEME (21P + 21N)220 KV LINES5.
IF MAIN-1 & MAIN-2 ARE NUMERICAL RELAYS, BOTH SHOULD BE SEPARATE MEASURING PRINCIPLES (CHARECTERESTICS), MODELS
AND ALGORITHAMS (SHOULD NOT BE DUPLICATED) AND ALL FEATURES SHOULD BE AVAILABLE IN BOTH SCHEMES AND BOTH RELAYS
SHOULD BE 100% REDENDENCY IN ALL ASPECTS ( COMPLEMENTARY TO EACH OTHER ) . DISSIMILAR CARRIER SCHEMES ARE TO BE
SELECTED ( POTT & PUTT or BLOCK & UNBLOCK). OTHER WISE MAIN-2 MAY BE DIFFERENT MAKE OR PHASE COMPARISION
PROTECTION/LINE DIFFERENTIAL PROTECTION WITH BACKUP DISTANCE PROTECTION IS TO BE ADOPTED. BOTH M1 & M2 SHOULD
CONTAIN DIRECTIONAL EARTH FAULT PROTECTION (67N) WITH DIRECTIONAL COMPARISION PICKUP SCHEME AS INBUILT FUNCTION.
ZONE-1: 80% OF MAIN LINE
ZONE-2: 100% OF MAIN LINE + 50% OF SHORTEST LINE AT OTHER END
ZONE-3: 100% OF MAIN LINE + 100% OF SHORTEST LINE AT OTHER END
ZONE-4: 100% OF MAIN LINE + (100% OF SHORTEST LINE + 20% OF LONGEST LINE) AT OTHER END.
DIRECTIONAL O/L & E/F RELAYS WITH HIGH
SET ( 67 + 67N )
SWITCHED DISTANCE SCHEME OR
NUMERICAL DISTANCE SCHEME (21P+ 21N)132 KV LINES4.
66 KV LINES3.
-3 O/L + E/F ( 51 + 51N )33 KV LINES2.
-2 O/L + E/F ( 51 + 51N )11 KV LINES1.
MAIN-2 PROTECTION/ BACKUP PROTECTIONMAIN- 1 PROTECTIONVOLTAGESr.No

41. NORMS OF PROTECTION FOLLOWED BY UTILITIES
FOR POWER TRANSFORMERS & AUTO TRANSFORMERS
3 OL +
1 DIR EL
(51P + 67N)
400 / 132
100, 200 &
2507
HV & LV
REF 64
220 / 66
31.5, 50 &
1006
66 / 33
7.5 , 16 &
252
BUCHHOLZ
OVER FLUX
OLTC OSR
PRV/PRD
OIL TEMP
WDNG TEMP
132 / 33
16 , 31.5 50 &
804
765 / 400630, 750,
1000 & 150010
3 DIR OL
(HIGHSET)
+
1 DIR EL
(HIGHSET)
3 DIR OL
(HIGHSET)
+
1 DIR EL
(HIGHSET)
400 / 220
315, 500 &
6309
OVER LOAD
ALARM RELAY
+
NEUTRAL
CURRENT E/F
RELAY
87TH/64REF
ICT/AUTOTFR
220 / 132100 & 1608
2WINDINGTRANSFORMER(STAR/STAR)
T
Y
P
E
220 / 3331.5, 505
3OVERLOAD+1DIRECTIONAL
EARTHFAULTRELAY(51P+67N)
HVREF(64)
132 / 11
7.5 , 16 ,
25 & 31.53
64REFIS1-PHHIGHIMPEDANCE
DIFFERENTIALRELAY
87THIS3-PHHIGHIMPEDANCE
DIFFERENTIALRELAY
(PRINCPLE:CIRCULATINGCURRENT)
BUCHHOLZ,
OLTC OSR
OIL TEMP
WDNG TEMP
3OVERLOAD+1EARTHFAULT
RELAY(51)
3OL+1 EL
(51)
NIL
87TLDIFFERENTIALRELAY
(LOWIMPEDANCEPERCENTAGEBIASEDPHASESEGREGATED
DIFFERENTIALRELAYPRINCIPLE:MERZPRICE)
66 / 117.5 & 161
LVHVPROTECTION
SPECIAL
PROTECTION
ADDITIONAL
PROTECTION
BACK UP
PROTECTION
MAIN-2MAIN-1VOLTAGE
RATIO IN
KV
CAPACITY
IN
MVA
S.No