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Relay protection
Specific and advanced applications

Specific and advanced applications

Advanced relay testing refer to protection functions that isn’t straight forward parameters such as current, voltage or frequency. Even though that is exactly what is measured and calculated, the advanced protection category is either presented in another format, such as impedance for distance protection, or require complex test setup as transformer differential. Common is that they require rather advance mathematic calculations to the voltages, currents and phase angles to perform the tests. This is why software support is preferred.

Power swing detection/trip testing in IEDs using smart testing methodology

Power swing which is principally caused by an oscillation in active and reactive power of transmission line, consequent to an enormous disruption in power system, which if not blocked, could cause wrong operation to the distance relay which may lead to tripping the healthy part of the transmission line. In the absence of power swing function it may result in severe damage to the machines or cascading tripping in the grid resulting in blackouts. To prevent such scenarios, intelligent electronic devices (IEDs) have power swing block (PSB) detection and trip logics incorporated with distance schemes.

This logic provides severe challenges to T&C engineers, where the conventional methods of using several states and multiple configuration steps while testing the IEDs complicates the process of testing. Further, the variations in logics due to manufacturer specific algorithm add to the complications. To address such complications, a new testing philosophy has been developed in, where PSB, PSD and PST functionality testing methodology and detailed discussion on the oscillography file is explained. Read more about RTMS Relay Test & Management Software.

End-to-end testing for line differential protection

Line differential protection is one of the most popular forms of transmission line protection. This type of protection is based on Kirchoff’s current law, which states that the current flowing into a line must be equal to the current flowing out of the line. With line differential protection, the zone of protection is defined by the location of the current transformers (CTs) monitoring the currents at each end of the line. When a fault occurs, it is essential for the protective relays at the ends of the line to communicate with each other and issue a trip signal for in-zone faults.

This article (link to article) discusses line differential protection, the importance of end-to-end testing, and the procedure for testing alpha-plane characteristics using the end-to-end test method. Specifically, testing the 87L element is considered in relation to pick-up accuracy, time of operation, dependability (by simulating internal faults) and security (by simulating external faults).