PROTECTION & COMMISSIONING: CT Testing , CB Testing.

 PROTECTION & COMMISSIONING:

1. CT- IEC Standard?

Ans : IEC 60044-1

2. Difference between X class and PX class.

Ans: Both are the same. In old BS It is mentioned X class. In IEC std It is

mentioned in PX class.

Class PX is the definition in IEC 60044-1 for the quasi-transient current transformers formerly covered by class X of BS 3938, commonly used with unit protection schemes.

3. Explain the CT Testing?

3. CT testing procedure – What are all the test sequences?

1. Before starting C.T testing check the name plate details are matching with the drawing and customer requirements.

2. Confirm the polarity (P1, P2) as per drawing.

3. Check if the panel is earthed or not.

4. Verify the test blog number’s / ferrule No’s with drawing.

Start the test with following sequence:

1. IR Test

2. Polarity Test

3. Winding Resistance Test

4. Knee point voltage Test

5. Ratio Test

5. Explain CB Testing.

Ans:

1. Before starting the test check the name plate details are matching with drawing and customer requirements.

2. Visually inspect C.B for any mechanical damages.

3. Verify the SWGR is earthed.

Start the test with the following sequence:

1. IR value Test

2. Timing test

3. Contact resistance measurement test

4. Local operation, general checks and interlocks

5. Mechanical operational / Functional checks

6. Electrical operational / Functional checks

7. Coil resistance measurement checks

8. C.B penetration test.