A New Method for the End-To-End Testing of Differential Relays

The stability of power systems has always been an important issue of the electric power transmission industry. Protection systems are one of the significant factors guaranteeing the stability. A very big problem of such systems is that a system defect will be detected when there is a fault in the system. In this case, if the protection system does not operate correct, the power system may encounter instability. The instability of power systems can cause severe damage to power transmission companies and consumers. Protection systems require periodic tests in order to prevent such an incident. In this paper, a new method was introduced for the end-to-end test of the longitudinal differential protective relay. This method was implemented on the AMT-105 relay tester device made by Vebko Amirkabir Company. The proposed algorithm was tested both in a laboratory and in practical conditions (with real line relays). In the following, the test results are expressed in different fault types. The results obviously shows that the mentioned algorithm has the same performance against different faults and there are low changes in the results. This increases insure of the algorithm and its results that is very important in relay Testing.