Improved testing of relays under the aegis of IEC 60255-1XX and a comprehensive study on performance of protection functions

The capabilities of IEDs (Intelligent Electronic Device) have improved with modern technologies in hardware and processing. This improvement in IEDs needs standardized ways of evaluating the performance. The standards IEC 60255-151,127,149,121,181 and 187-1 have detailed the minimum functional requirements of the protection functions, which is a major milestone in TC95 standards. The tests are aimed at finding the steady state accuracy under various settings and the performance during dynamic conditions. These tests are mandatory as part of type tests. The accuracy claims and the performance of the protection are established and assessed based on these tests. The first part of this paper describes about the importance of performing these tests during the function development. It explains about considerations related to the setting ranges of the protection functions and the test procedures. It also describes an approach with which, high volume of tests could be performed. An automation using VBA script is implemented to derive the accuracy claims in an efficient manner. The second part focuses on the test results of various functions and the findings related to the test methods. It also puts forth the conclusions which could be used to test and compare the performance of IEDs.