SCADA Operation Engieer Test Part 3

1.

2 points

Consider a typical 2x20MVA Primary S/S in Oman with 11kV bus coupler in ON position and 33kV bus coupler in OFF position. The load in each transformer is 400A.
An incident happened with the following alarms:
- 11kV CB of Tx 1 tripped by O/C E/F Relay.
- 11kV CB of Tx 2 tripped by O/C E/F Relay.
- 11kV CB of Bus coupler tripped by O/C E/F Relay.
The fault in this case will be in _________________

11kV busbar

33kV feeder

11kV feeder

33kV busbar

2.

2 points

Consider a typical 2x20MVA Primary S/S in Oman with 11kV bus coupler in ON position and 33kV bus coupler in OFF position. The load in each transformer is 400A.
An incident happened with the following alarms:
- 11kV CB of Tx 1 tripped by Directional O/C & E/F Relay.
- 11kV CB of Tx 2 tripped by O/C E/F Relay.
- 11kV CB of Bus coupler tripped by O/C E/F Relay.
The fault in this case will be in _________________

Tx 1 11kV Side

Tx 2 11kV Side

Tx 2 33kV Side

Tx 1 33kV Side

3.

2 points

Consider a typical 2x20MVA Primary S/S in Oman with 11kV bus coupler in OFF position and 33kV bus coupler in OFF position. The load in Tx 1 is 550A and in Tx 2 is 400A.
One phase is missed in Tx 2
The correct first and second operation sequence would be:

(1) Close 11kV bus coupler . (2) Open 11kV incomer of Tx 2.

(1) Open 11kV incomer of Tx 2. (2) Close 11kV bus coupler.

(1) Open 11kV incomer of Tx 1. (2) Open 11kV incomer of Tx 2.

non of the above

4.

2 points

20MVA transformer tripped with winding temperature indication. The problem will be with

High load of the substation.

Transformer Cooling System is faulty.

Bucholz relay is faulty.

all of the above

5.

2 points

Normally the oil temperature in a transformer is higher than the winding temperature.

True

False

6.

2 points

A 20MVA transformer tripped by differential relay. What shall you do first.

Try to close the tripped breaker (1 trial) to test if the problem still exist.

Isolate the transformer and wait for inspection.

Visually check if the transformer is healthy and then try to close the tripped breaker (1 trial).

non of the above

7.

2 points

The 11kV side of a 20MVA transformer tripped by directional OC&EF relay. The problem should be in

The transformer itself

33kV side

11kV side

High Load

8.

2 points

The 33kV side of a 20MVA transformer tripped by neutral voltage relay. The problem should be in

Unbalanced Load

High Load

Open phase in 33kV side.

Open phase in 11kV side.

9.

2 points

A 33kV feeder is tripped by directional OC&EF relay. The problem should be in

The 33kV feeder

One of the 11kV feeders

The 33kV side of the transformer

The 11kV side of the transformer

10.

2 points

A 33kV cable feeder tripped by differential line relay. The correct sequence of operation should be.

(1) Try to close the tripped feeder (2) Decide based on the result of (1)

(1) Patrol the line visually. (2) Try to close the tripped feeder if nothing was found faulty in (1)

(1) Isolate the line (2) Investigate the fault.

non of the above

11.

2 points

Consider a typical 2x20MVA Primary S/S in Oman with 11kV bus coupler in ON position and 33kV bus coupler in ON position. The load in each transformer is 400A. Both 33kV feeders are OHL.
An incident happened with the following alarms:
- 33kV feeder 1 tripped by distance relay Zone 2 alarm
- 33kV feeder 2 tripped by distance relay Zone 1 alarm and the Auto Recloser Locked Out.
The problem should be in

Both 33kV feeders

33kV feeder 1

33kV feeder 2

non of the above

12.

2 points

If a 20MVA transformer is tripped by Standby Earth Fault relay. The possible cause of the tripping may be.

Main Earth Fault relay didn't operate.

Earth Fault relay is not installed.

Unbalanced Load

all of the above

13.

2 points

Both Earth Fault and Standby Earth Fault relays should be with the exact same connections scheme and settings.

True

False

14.

2 points

One of the main reasons for having DC supply in primary substations is to supply the tripping circuits of 11kV and 33kV circuit breakers.

True

False

15.

2 points

If we have 20MVA, 30/10kV transformer. The maximum line current in the 10kV side is

2000A

1160A

2500A

3000A

16.

2 points

It is not possible to parallel 2 transformers if their victor groups are DYn11 and DYn5

True

False

17.

2 points

The restricted earth fault relay is considered as mechanical relay.

True

False

18.

2 points

The main protection on any 33kV cable feeder is OC&EF relay.

True

False

19.

2 points

The normal practice is to have the auto recloser tripping before the transformer fuse blow.

True

False

20.

2 points

What is the angle (time) between input and output voltage of a transformer with vector group DYn11

0 Degree

150 Degree

180 Degree

330 Degree