The testing of protection relays is one of the most important activities in the power systems to guarantee the reliability and safety of the power systems.
There are many ways of testing these relays and all these techniques tend to test various aspects of the relays.
Abnormalities are detected of the protection relay with the help of the following general tests:
- Action Time Test
- Repeatability Test
- Stability Test
- Sensitivity Test
- Action Current Characteristic Test
- Voltage Drop Test
- Standalone Testing
- Real-Time Hardware-in-the-Loop (HIL) Testing
- Full Voltage and Current Simulation
- Functional Testing
Action Time Test
This basic test determines the time that the relay takes to respond when detecting these faults. It is energized with input signals from current and voltage transformers and the time it takes to actuate is measured to satisfy the requirements.
Repeatability Test
This test helps determine the variability of the relay’s performance through repeating the same test several times and comparing the results of differing variance. It guarantees the relay’s proper working without mis-operation or leakage.
Stability Test
Stability testing is done to know that the relay can withstand in any faulty conditions or not. It will help in ensuring that the relay will work as required any time there are actual system failures.
Sensitivity Test
Popularly referred to as the accuracy verification test, this measures the relay’s capacity in identifying faults. Thus, it is significant for guaranteeing that the relay has the ability to respond to system failures in time to avoid big problems.
Action Current Characteristic Test
This test checks the relay’s feasibility when various current levels are applied and ensures that it turns ‘ON’ and ‘OFF’ as needed, mostly at 0. 95 and 1. 05 times the rated current.
Voltage Drop Test
This test determines the relay’s capability to operate under low voltages to detect a fault in event of further lowering of voltage besides being crucial for stabilizing the system.
Standalone Testing
In this classical method, there are separate testers applied to protect the relays along with providing the voltage and current signals that are required for causing the selective faults.
This has been useful in affirming the performance of the relay under well-to-conditioned circumstances.
Real-Time Hardware-in-the-Loop (HIL) Testing
This superior technique entails connecting the relay to an actual time simulator designed for the power system. It permits the relay to be tested dynamically depending on the different faults enabling the assessment of the relay in a more real world atmosphere.
Full Voltage and Current Simulation
This method calls for feeding secondary voltage and current to the relay with a view of testing it under conditions that are real as possible. It confirms the relay threshold and tripping characteristics by determining how the relay responds to faults that are created during the test.
Functional Testing
This check unites all protection elements of the relay and it tested its functionalities correctly on different conditions such as special tests for different functionalities like the directional over current protection.
Conclusion
Every testing method helps in the confirmation of the performance of the protection relays in their respective ways. Through the use of such techniques, engineers are able to confirm that relays would be able to perform in the field conditions, hence protecting the power system from faults and failure. One only needs to ask why one should often service or test their computer to discover that some problem is likely to occur when left unresolved.