Protection Relay Testing

 Protection Relay Testing

1. Simplified diagram

2. Protection Relay Testing – Typical Relay Test Set

3. Protection Relay Testing

a. Connect the current output from the Relay Test Set (RTS) to the current transformer terminal on the protection relay.

b. Connect the timer stop contact input on the Relay Test Set to the trip contact on the protection relay.

c. Turn on the current output of the RTS and adjust the current as required.

d. Turn on the current output of the RTS along with the timer. The current output and timer on the RTS will stop automatically when the relay trips.

e. The relay operating time will be displayed on the RTS LCD screen.

4. Protection Relay Testing –OCEF (MikroMK1000A)

5. Protection Relay Testing –OCEF (DELAB DP34)

6. Protection Relay Testing - ELR

7. Protection Relay Testing - OCEF: example of test report

8. Protection Relay Testing: ST Borang H (JPE)

Note refer from: Ir. Jamil Ahmad Radziyan (Warna RS Sdn Bhd) 

Current Transformer Introduction & Testing

 CURRENT TRANSFORMER

Function of a Current Transformer

1. Measurement

Transform the primary signal into a secondary signal which can be measured by secondary equipment.

> CT 1000/5A Ip = 1000 A → Is = 1 A

2. Isolation

Isolation of the secondary circuit and equipment from the high voltage of the primary circuit.

   

Relevant CT Standards and Field Testing Guides

1. IEC 60044-1 (old): Current transformers

2. IEC 60044-6 (old): Requirements for protective current transformers for transient performance

3. IEC 61869-2: new, replacing 60044-1 & 60044-6, Additional requirements for current transformers

Metering CT requirements

Protection CT requirements

IEC Knee Point Definition

Differences between Metering and Protection CT

Current Transformer Specification (IEC61869)

1. Protection CT

2. Example Protection CT: CT for OCEF, 600/5A, 10P20, 15VA

3. Metering CT

4. Current Transformer –Typical name plate

5. Current Transformer Testing typical site testing includes:

a. Resistance measurement

b. Polarity

c. Ratio

d. Excitation / Magnetizing Curve

e. Insulation resistance

Current Transformer Testing

1. Resistance Test

- Performed for assessing possible electrical damages in windings or contact problems.

- Shorted turns could change the winding resistance and endanger CT operation.

2. Polarity Test

- Verify the correct orientation of the primary and secondary windings of the CT as per name plate/drawing.

3. Ratio Test

- Compares measured ratio of CTs to nameplate specifications and factory measurement results

- Deviations from specifications may indicate internal faults (e.g. open circuits)

- Ratio deviations may cause malfunction of protection and false interpretation of the system current

4. Excitation / Magnetizing Curve Test

- Knee point voltage important for a proper operation of the protection device

- e.g. for Class X CT.

- Indication of: shorted turns & core faults

5. Insulation Test

- Ensure CT insulation is in good condition.

Current Transformer Testing: Typical test result

Note refer from: Ir. Jamil Ahmad Radziyan (Warna RS Sdn Bhd) 

Power System Protection

 Requirements of Power System Protection

1. Fast: Fast operation in order to clear the fault from the system and minimize system damage.

2. Reliable: Work when required, and only when required. Protective equipment should not fail to operate in the events of fault in the protected zone.

3. Stable: To leave all healthy circuits intact and ensure continuity of supply.

4. Selective: Disconnection of equipment is restricted to the minimum necessary to isolate the fault.

5. Sensitive: Sensitive enough to operate under minimum fault condition.

Type of Protection

A. Unit Protection

1. Operates on differential principle, Kirchhoff’s current law

2. Discrimination by a defined ‘zone protection’ determined by CT

3. Must be stable during external fault

4. Fast operating time, typical:20-50ms

5. Main protection system

6. Example: 

- Line/Transformer/Busbar differential, Restricted Earth Fault

- Defined by CT position

Non-Unit Protection: Overcurrent & Earth Fault protection

B. Non-Unit Protection

1. No defined area of coverage

2. Simple and cheaper

3. Slower operating time

4. Backup protection system

5. Discrimination by time factor

6. Requires time coordination between various stages

7. Example: 

a. OCEF

-Time-delayed/IDMT: Can range from a few hundred milliseconds to several seconds, 

-Depending on coordination with up/downstream devices.

b. SBEF (2000-5000ms)

Typical Protection Scheme for Cable

1. The cheapest protection relay compared to differential protection, REF etc.

2. Use standard characteristics:

a. Definite Time (DT)

b. Standard/ Normal Inverse (SI/NI)

c. Very Inverse (VI)

d. Extremely Inverse (EI)

e. Long Time Inverse (LTI)

Inverse Definite Minimum Time Characteristic (IDMT)

1. The relay operating time varies inversely with the magnitude of the fault current.

2. This means that the higher the fault current, the faster the relay will operate.

3. In contrast to definite-time relays, which have a fixed time delay, the operating time of inverse-time relays is dependent on the severity of the fault.

4. Normal Inverse characteristic

5. Normal Inverse calculation example

6. Calculation using website.

https://myelectrical.com/tools/idmt-tripping-time

7. IDMT Relay Operating Time

8. ANSI Device Function Numbers

Note refer from: Ir. Jamil Ahmad Radziyan (Warna RS Sdn Bhd) 

AutoCAD-Plot Setup & Publish (Lesson Learn)

 Harini nak share sikit berkenaan AutoCAD. cara nak buat plot setup & publish. step ni amat penting sekiranya kita perlu print menggunakan AutoCAD yang bilangan sheet yang banyak. Ambil masa yang lama kalau nak print satu persatu dalam model. 

Langkah ni, amat menjimatkan masa samada print terus ke printer ataupun print convert ke PDF. Selamat mencuba