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Flashcards in 230KV Deck (52):
1

Describe the MPT cooling equipment arrangement.

7 transformers make up two Unit MPT's and one spare transformer. There are 4 HX's and 2 groups of fans per transformer, with 3 fans per group.

2

List the modes of operation for MPT fans.

Two fan group switches, each able to be positioned to MANUAL/OFF/AUTO. In MANUAL, the fans for that group will run regardless of temperature using manual operation control power. In OFF, those fans do not operate regardless of temperature or lead group selection. In AUTO, operation is thermostatically controlled in conjunction with the LEAD 1 - LEAD 2 switch using automatic operation control power. The selected group is assigned the 50C setpoint, and the other group is automatically assigned the 70C setpoint.

3

State the power supplies to the MPT fans.

Normal - 1(2)TC
Alternate - 1(2)TE

NOTE: On a loss of normal power supply, the alternate supply will automatically provide power to the fans.

4

Describe what conditions enable the MPT cooling system controls.

1. The associated Main Generator Exciter Field Breaker is CLOSED.

2. The unit is shutdown and in UAT Backfeed.

5

State MPT oil temperature limits and required actions.

100C - Log start time and ensure this limit is not exceeded for more than 8 hours. If unable to reduce temperature below 100C in 8 hours, then reduce load to maintain top oil temperature less than 90C.

110C - Remove all load from the transformer within 30 minutes.

6

State MPT winding temperature limits and required actions.

120C - Log start time and ensure this limit is not exceeded for more than 8 hours. If unable to reduce temperature below 120C in 8 hours, then reduce load to maintain winding temperature less than 110C.

130C - Remove all load from the transformer within 30 minutes.

7

Describe the response to loss of normal power supply to the MPT cooling system, MCC 1(2)TC.

Automatic transfer to the alternate supply, MCC 1(2)TE. Additionally, MAIN XFMR AUTO THROW OVER SWITCH annunciator is received.

8

Describe the SAT cooling equipment arrangement.

Two sets of cooling equipment in each SAT. Each set consists of an oil pump and cooling fans, which are controlled by winding temperature detectors.

9

State the power supplies to SAT cooling equipment.

Normal - MCC 1(2)TC [D1, BOP Bus D -> 1(2)E 480V]
Alternate - MCC 1(2)TE [D2, BOP Bus C -> 1(2)F 480V]

10

Describe the operation of SAT cooling equipment.

On rising SAT winding temperature, the cooling fans will start at 70C and oil pumps will start at 75C.

11

List the trips for the SAT Lockout.

1. SAT Differential Current, 87ST
2. SAT Fault Pressure, 63FP

12

List the Auto Actions for an SAT Lockout.

1. Trips and locks out Transformer Bus PCBs, 25(26)A and 25(26)B.
2. Starts all four EDGs
3. Trips and locks out all SAT output breakers - SAT Feeder to Common A(B), Bus 1(2)B, 1(2)C, and 1(2)D.
4. With MOD 89-ST1(2) and Circuit Switcher T-1(2) closed:
a. Trips OCB M-29(33)
b. Trips Circuit Switcher 89-T1(2)
5. Trips and locks out MOD 89-ST1(2) after no-load interlocks are met.

13

List the automatic actions from a trip of Generator/Transformer Primary (86GP), Backup (86GB), or Main Generator Differential (86G) Lockout Relays.

1. Main Generator output breakers trip and lock out.
2. Main Turbine trips.
3. Main Generator exciter field breaker trips and locks out.
4. UAT supply breakers to B,C, and D buses trip and lock out.
5. SAT supply breakers to BOP buses C and D auto close.
6. Four EDGs auto start for 86G and 86GP, but not for 86GB.

14

List the trip signals for Generator/Transformer Primary (86GP) Lockout Relay.

1. Unit/UAT differential overcurrent.
2. Main Generator reverse power (32 device).
3. Generator Impedance / Out-of-Step Protective relay on low grid impedance or loss of synchronism.
4. Generator loss of excitation.
5. Generator output breaker failure.

15

List the trip signals for Generator/Transformer Backup (86GB) Lockout Relay

1. TSV closure with generator online - Relay trips with TSV's and CIV's with the generator online.
2. UAT/MPT Fault Pressure.
3. Time Overcurrent - UAT, Gen Grnd, Neg phase, etc.
4. Generator output breaker failure.
5. Generator over-excitation.

16

List the trip signals for Main Generator Differential (86G) Lockout Relay.

Main Generator differential overcurrent.

17

List the automatic actions from a trip of the 89-TB Primary Transformer Bus Lockout.

1. Trips and locks out Transformer Bus PCBs, 25(26)A and 25(26)B.
2. Trips and locks out SAT output breakers to Buses 1(2)B, 1(2)C, 1(2)D, and Common A(B).
3. Trips and locks out 89-T1(2) circuit switcher.
4. IF 89-T1(2) circuit switcher was closed, then OCB M29(M33) is tripped and locked out.
5. Starts all 4 EDG's.

18

List the initiation signals for the 89-TB Primary Transformer Bus Lockout.

Phase differential overcurrent.

19

List the initiation signals for the 89-TBB Backup Transformer Bus Lockout.

Instantaneous/timed overcurrent relays 50/51/62BF for PCBs 25(26)A and/or 25(26)B.

20

List the automatic actions from a trip of the 89-TBB Backup Transformer Bus Lockout.

1. Trips and locks out Transformer Bus PCBs, 25(26)A and 25(26)B.
2. Trips and locks out SAT output breakers to Buses 1(2)B, 1(2)C, 1(2)D, Common A(B) and the cross tie to U2(U1) SAT.
3. Trips and locks out 89-T1(2) circuit switcher.
4. IF 89-T1(2) circuit switcher was closed, then OCB M29(M33) is tripped and locked out.

21

Describe the UAT cooling system.

Two sets of cooling fans controlled by internal winding temperature and winding current inputs.

22

List the power supplies to the UAT cooling system.

Normal - MCC 1(2)TC [D1, BOP Bus D -> 1(2)E 480V]
Alternate - MCC 1(2)TE [D2, BOP Bus C -> 1(2)F 480V]

23

Describe the operation of the UAT cooling system.

On rising winding temperature, the Stage 1 cooling fans start at 70C or at 70% rated load after 120 seconds. Stage 2 cooling fans start at 75C or at 90% of rated load after 120 seconds.

24

Describe the basic operation of ABB IPO Breakers, and which switchyard PCBs are of this type.

A hydraulic pump charges the storage springs, which provide the stored energy needed to use hydraulic oil to open and close the breaker. This hydraulic oil (under pressure from the storage springs) acts on the piston/pullrod of the mechanism, consuming energy from the springs. Once the spring pack has expanded to a certain point, the hydraulic pump will run to recharge the spring pack.

All Line PCBs are ABB IPO.

25

How many operations of an ABB IPO Breaker can be performed without recharging the storage springs?

A fully compressed disc spring assembly allows for two open operations: OPEN-CLOSE-OPEN.

26

Describe ABB IPO breaker response to decreasing SF6 gas pressure.

With "SLOW LEAK AUTO TRIP" enabled at the breaker panel:

Slow Leak - SF6 pressure drops from 74 to 72 PSIG in longer than 3 seconds => breaker TRIPS and LOCKS OUT (blocks close operation).

Rapid Leak - SF6 pressure drops from 74 to 72 PSIG is less than 3 seconds => breaker LOCKS OUT ONLY (blocks trip operation).

27

List ABB IPO Breaker Failure Modes.

1. Slow Leak
2. Rapid Leak
3. Low Spring Energy
4. Pole Disagreement

28

Describe the effect of Low Spring Energy on ABB IPO Breakers.

Indication of low spring energy first by "BLOCK CLOSE ON LOW SPRING ENERGY" and "LOW SPRING ENERGY" alarms at the local alarm panel. If not promptly opened, may then get "LOW SPRING ENERGY BLOCK TRIP" which will fail the breaker in the closed position.

29

Describe the effect of Pole Disagreement on ABB IPO Breakers.

Since the poles are operated independently, disagreement in pole position will result in a trip and lock out of that breaker. When closing, the poles must agree within 3 cycles to avoid pole disagreement.

30

List the locations from which PCBs may be operated.

1. Local (at the PCB housing)
2. Relay House
3. Control Room
4. Energy Control Center

31

Describe the operation of the Control Switch for PCBs locally at the breaker housing.

Control Switch - close or trip breaker, bypassing all remote interlocks. This bypass does not include local lockouts such as low SF6 pressure, low spring energy, pole disagreement, etc. NO SYNC PROTECTION.

32

List the available controls for PCBs at the Relay House.

Local/Remote Switch
Control Switch
Preferred Breaker Switch

33

Describe the operation and available controls for PCBs from the Control room.

Supervisory Switch
Sync Selector Switch
Control Switch
Auto Reclose Switch
Carrier Control Switch

34

Describe the operation of the Local/Remote Switch for PCBs at the Relay House.

Selects whether the Relay House control switch or a remote switch controls the breaker. Actuates PCB IN LOCAL CONTROL annunciator in LOCAL.

35

Describe the operation of the Control Switch for PCBs at the Relay House.

Active in LOCAL only. NO SYNC PROTECTION

36

Describe the operation of the Preferred Breaker Switch for PCBs at the Relay House.

Selects which of the 2 breakers on each transmission line is preferred for auto reclosure first. The second breaker in a pair closes after the first one has completed closing. NOT FOR SAT PCBs.

37

Describe the operation of the Supervisory Switch for PCBs from the Control room.

Selects whether the Control Room or ECC can operate the breaker. Control Room only active in LOCAL. NOT FOR SAT PCBs.

38

Describe the operation of the Sync Selector Switch for PCBs from the Control room.

Must be ON for CR to close the breaker. ECC and auto reclose use a sync check relay, but it is not wired into the Control Room switch.

39

Describe the operation of the Control Switch for PCBs from the Control room.

Close or trip breaker

40

Describe the operation of the Auto Reclose Switch for PCBs from the Control room.

Enables or disables breaker auto reclose feature. ECC also has this capability when Supervisory Switch is in REMOTE, but this switch will override. NOT FOR SAT PCBs.

41

Describe the operation of the Carrier Control Switch for PCBs from the Control room.

In OFF, terminate carrier signals in to the switchyard preventing tripping of PCBs, and prevents sending a BLOCK TRIP signal. This blocks bus overcurrent plus low line impedance (distance relay) and carrier ground directional and carrier overcurrent trips.

42

Describe the PCB Auto Reclosure Feature.

Requires Auto Reclosure to be enabled at XU-5 AND at the ECC.

Remote End - Has instantaneous and 15 second reclosure from trip to attempt to re-energize the line.

Preferred Breaker - The selected preferred breaker from the Relay House will close 20 seconds after INITIAL TRIP if the line re-energized from Remote End reclosure. If the line does not re-energize, the 20 second timer stalls, and the PCB will auto close whenever the line is re-energized. ECC will typically disable auto-reclosure at this point to prevent this.

Companion Breaker - Closes 35 seconds after preferred breaker closes.

43

Describe the basic operation of Mitsubishi PCBs, and which switchyard PCBs are of this type.

The phases of Mitsubishi PCBs are ganged to operate in tandem. They are spring to open and spring to close, utilizing a motor to charge the closing spring. Closing operation charges the trip spring for subsequent trip. Latches hold the breaker in each position until a signal causes close/trip mechanism to unlatch the breaker.

Generator PCBs 22A(B) and 29A(B), and Transformer Bus/SAT PCBs 25A(B) and 26A(B) use this type of PCB.

44

Describe the effect of lowering SF6 gas pressure in Generator PCBs 22A(B)/29A(B).

At 71 PSIG SF6 pressure, the Low Gas Pressure Lockout relays with ONLY lock out the PCB from opening or closing in auto or manual.;

45

Describe the effect of lowering SF6 gas pressure in Transformer Bus/SAT PCBs 25A(B)/26A(B).

Slow Gas Leak Trip selector switch must be ENABLED to receive the slow leak function. A slow leak is defined as pressure dropping from 78 PSIG to 71 PSIG in more than 3 seconds, and will result in the PCB tripping and locking out at 71 PSIG.

At 71 PSIG, Low Gas Pressure Lockout relays will lock out the PCB from opening or closing in auto or manual if the loss of gas is rapid. A rapid leak is defined as pressure dropping from 78 PSIG to 71 PSIG in less than 3 seconds.

46

Explain the Breaker Failure feature of PCBs.

After a protective signal, if higher than normal current is sensed the PCB has failed to trip. This will trip and lock out the companion PCB and initiate the associated bus primary and backup lockout.

For a turbine trip, if a generator PCB fails it will initiate a Generator Primary Lockout but will NOT lockout the 230KV bus.

47

Describe the basic operation of an MOD, and where it is used in the switchyard.

An MOD (89-ST1/ST2) is used to connect the high side of the SAT to 230KV via the Transformer Bus. It is to be operated under NO LOAD only, and interlocks prevent opening MODs by remote operations unless load connections are open.

A DC motor, with control power from 5A(6A), operates the ganged phase mechanisms to open and close the disconnect. It can also be manually operated via crank. Inserting the crank into the operator disconnects DC control power, preventing remote operation and defeating associated interlocks.

48

State the control power supply to MODs 89-ST1(ST2).

DC Panel 5A(6A).

49

Describe the basic operation of Circuit Switchers, and where they are used in distribution.

Circuit Switchers 89-T1(T2) are used for Caswell Beach, and function as both a breaker and disconnect in one device. For tripping, it acts as a breaker and can open under load. For closing, it acts the same as an MOD and must be closed under NO LOAD.

50

State the control power supply to Circuit Switchers 89-T1(T2)

DC Panel 5A(6A).

51

Describe the basic operation of OCBs, and where they are used in distribution.

OCBs M29(M33) are used for Caswell Beach, and are motor operated to close / spring to open.

52

State the power supplies to the OCBs.

Closing power (motor) from MCC 1TC(2TC). Tripping power from DC Panel 5A(6A).