Abstract: bstract:The distance protection of transmission line in the process of testing input many parameters, including impedance, angle of impedance,fault types,short circuit current,rated voltage, zerosequence compensation coefficient and so on. According to the request of parameters put into, relay protection testing device can be calculated automatically with the calculation program and the generation of voltage and current test required, but without corresponding calculation process. By through analysis of calculation in process of tester output voltage, current , enable testers to clear from the theoretical principle of distance protection test in various short circuit faults,the result of this paper provide refercece for operator relate to testing.

Key words: distance protection, shorted fault, positive sequence, negative sequence, null sequence, voltage, current