1. Sharon Shaji, Deefuljith Divakaran, and Janasudhan K attended an industrial training at the 66 kV substation in Alappuzha from September 19th-24th, 2022. 2. The Alappuzha 66kV substation receives normal power supply from the 220 kV Punnapra substation and backup supply from the 220kV Pallom substation. It has 7 bays and distributes power through 4 incoming 66kV feeders and 13 outgoing 11kV feeders. 3. The substation contains 3 transformers ranging from 10-16MVA with on-load tap changers, along with associated protection systems including

1. INDUSTRIAL TRAINING ON
19/09/2022- 24/09/2022
AT 66 kV substation, Alappuzha

2. TEAM MEMBERS
1. Sharon Shaji
2. Deefuljith Divakaran
3. Janasudhan K

3. Alappuzha 66kv Substation- In General
66 kV substation Alappuzha is a Substation under KSEB Itd in Alappuzha district.
The ALAPPUZHA 66kV substation is located within the municipal limit of
Alappuzha town at the Eastern side of NH 66 and the Northern side of V.C.N.B
road. This substation mainly feeds almost all the consumers of Alappuzha
Municipality through the 13 (thirteen) 11kV outgoing feeders. In addition to this,
the 66kV Substation at Pathirappally is also normally fed from this substation
through Alappuzha-Pathirappally 6ALPT 66 kV feeder.
Normal supply is taken from 220 kV Substation Punnapra through Punnapra-
Alappuzha 66kV Double Circuit (6PUAL NO. 1 & 2) 66kV feeders. As a standby
source, 66kV supply from 220kV substation, Pallom supply is kept available to
this station through Kuttanadu Substation via Kuttanadu-Alappuzha (6KTAL)
66kV single circuit feeder. The 66kV switch yard of this substation is having 7
(seven) Bays with parallel duplicate bus arrangements.

4. SINGLE LINE DIAGRAM OF 66 KV
SUBSTATION

5. 66KV FEEDERS
There are four 66Kv feeders in this substation.
 6ALPT 66kV feeder( ALPY-PATHIRAPPALLY 66 kV feeder)
 6 KTAL 66kV feeder (KUTTANAD-ALPY 66kV feeder)
 6 PUAL No.1 66kv feeder(PUNNAPRA-ALPY No.1 66Kvfeeder)
 6 PUAL No.2 66kv feeder(PUNNAPRA-ALPY No.2 66Kvfeeder)

6. FEEDER BAY - (GENERAL)
The 66 kV feeder bay consists of the following equipments.
 1. Lightening arrester
 2. Potential transformer
 3. Line isolator with Earth switch
 4. Current transformer
 5. SF6 Circuit Breaker

7. SUBSTATION YARD

8. POWER TRANSFORMER
 The substation has three nos of Power Transformers.
16 MVA 66/11kV, Transformer no 2 with OLTC (TOSHIBA MAKE)
10 MVA 66/11kV, Transformer no 3 with OLTC (TELK MAKE)
16 MVA, 66/ 11kV, Transformer no 1 with OLTC (TELK MAKE)
All the three transformers are controlled by 1500 MVA, SF6 circuit
breakers(CROMPTON GREAVES MAKE).
 The remote and manual control of the breakers are possible. Since we are having a
double bus system, there are 2 nos 66Kv bus isolators installed for each transformer bay.
 Each transformer bay consist of 2 bus isolators, SF6 circuit breaker (SF6 CB), current
transformer (CT) and lightning arresters (LA).

9. 16 MVA, 66/11kVTransformer with on load
tap changer

10. MAKE TELK
KVA HV 12500/16000
LV 12500/16000
VOLT HV 66000
LV 11000
AMPERE HV 109/140
LV 657/841
Type of connection Star/star
No of phases 3
Frequency 50 Hz
C&R panel make ALIND
Type of cooling ONAN/ONAF
Impedance voltage 10.19%
Vector group YNyn0
Year of manufacture 2015
No of tap positions 11
Normal tap positions 3

11. 10 MVA, 66/11kVTransformer with on load
tap changer

12. MAKE TELK
KVA HV 10000
LV 10000
VOLT HV 66000
LV 11000
AMPERE HV 87.6
LV 525
Type of connection Star/star
No of phases 3
Frequency 50 Hz
C&R panel make ALIND
Type of cooling ONAN
Impedance voltage 9.83%
Vector group YNyn0
Year of manufacture 2004
No of tap positions 11
Normal tap positions 3

13. TRANSFORMER PROTECTION
SCHEMES
1.Differential protection
 It employs differential relay(87).
 It mainly responds to those faults which occur in the differential protection zone of the
transformer, which includes the region between primary and secondary side CTs of the
transformer.
2. Restricted Earth Fault(REF) Protection
 It employs REF(64) relay. It protects the transformer from internal earth fault.
3. Over current and Earth fault Protection
 It employs the relays 51 (Over Current Relay) and 51N (Earth Fault Relay).
 They are used for protection of transformer from external short circuits and excessive
over load.

14. 4.Buccholz Protection Scheme
 It employs buccholz relay which is sensitive to the effects of dielectric failure inside the
transformer.
5.Winding temperature and Oil temperature Indicators
 They are precision instruments that monitor the temperature rise of oil and windings.
 They operate the alarm or the circuit breaker when the recorded temperature exceeds a pre-
set value.

15. IMPORTANT RELAYS IN TRANSFORMER
Name of relay T/F lll T/F ll T/F l
Differential
relay
87, Alind 87, Siemens 87, Alind
Buccholz relay 30A, Alind 30AABB 30AAlind
Master trip
relay
86, Alind 86,ABB 86, Alind
REF relay 64R, Alind 64, Alstom 64, Alstom
Over current
&
Earth fault
relay
50/51 N, 50/51
R,
50/51 B, Alind
-
50/51 N, 50/51
R,
50/51 B, Alind
PT selection
relay
30 B, Alind - 30 B, Alind
DC
supervision
relay
30 C, Alind 80 DC, ABB 30 C, Alind
Directional
numerical
O/C and E/F
relay
-
67/67 N
Siemens
-

16. OPERATION TO BE CARRIED OUT OF ON
OCCURENCE OF FOLLOWING ALARMS
1. Buccholz alarm
 When the Buccholz alarm rings, accept the alarm and note down the relay and
annunciator indications.
 Inform the matter to the station Engineer.
 Observe the transformer for any abnormal heating or sound.
 Observe if any abnormality is seen on the transformer.
 Switch off and Isolate the transformer after intimating the higher officials...

17. 2. Temperature alarm (oil and winding)
 The oil temperature and winding temperature alarm will be activated when
the temperature of oil or winding exceeds a pre-set value.
 This can be due to some faults inside the transformer such as inter turn
shorts, loose contacts etc. Or due to overload.
 If the cause is overload, make arrangements to reduce the load of the
transformer immediately.
 If the cause is not overload, immediately switch off and isolate the
transformer
 Inform the Station Engineer Inspect the temperature gauge.
 Charge the transformer only after the rectification of the fault.

18. SF6 CIRCUIT BREAKER

19. PERMIT TO WORK ON A
TRANSFORMER
1. Confirm that the total load of the Transformer which is under permit to work can be
safely transferred to remaining transformers in service.
2. Switch off 11 KV feeders under the transformer.
3. Switch off, confirm all three ammeter readings are zero & isolate the VCB of incomer
on which permit is to be issued and provide "CAUTION SUPPLY BACK FED" board4.
4. Rack in the VCB of Bus Coupler No I or II and charge its VCB.
5. Charge 11 kV feeders.
6. Switch off the SF6 breaker of transformer and isolate the same from the live buses
(open both bus 18:11 isolators and provide "CAUTION SUPPLY AVAILABLE" board).
7. Switch off AC and DC control supply (if necessary) and check for any supply in the
marshalling box. Provide "PERMIT TO WORK board on TF control panel.

20. 8. Switch off the SF6 breaker of 16MVA transformer 1 and isolate the same from the live
buses (open both bus 1811 isolators and provide CAUTION SUPPLY AVAILABLE"
board), Switch off AC and DC control supply (if necessary) and check for any supply in the
marshalling box. Provide "PERMIT TO WORK board or control panel.18/977.
9. Earth the HVLV&SF6 terminals of the transformer.
10. Fix caution board on every point of switching off and isolation made, encircle the
working area with a caution ribbon and keep the keys, if any in custody, and issue permit to
work and get it signed. Note the points earthed in the permit form along with the number of
earth rods.
11.Monitor the load on the Transformer in service and make arrangements with the
Distribution authorities to limit the load to the admissible maximum load.

21. SAFETY EQUIPMENT TO BE USED
1. Earth rods
2. Safety belts
3. Ropes and ladders
4. Caution ribbon
5. Safety helmets and safety shoes
6. Tool baskets
7. LV/ HV gloves
8. Chain block
9. Multimeter

22. RELAY CLASS