Protection relay test set is also called the relay protection tester, the main role is in the electrical equipment and electrical line fault automatically cut off the power, to avoid the expansion of the accident, and ensure the safety of the power grid and personal. Therefore, the role of the protection relay test set must be selective, rapid, sensitivity, reliability.

1, Selectivity, when the system failure, the protection device should choose the partial removal fault. Non-fault parts continue to work.

2, When the short circuit short circuit, rapid troubleshooting can reduce the fault range. Reduce the damage caused by short circuit current, reduce the impact on users, improve the stability of the system.

3,Sensitivity refers to the sensitivity of the protection relay test set to the possible failure and normal operation of the protection device. The sensitivity of the protective device is expressed by the sensitivity coefficient KL.

The sensitivity coefficient of the protective device reflecting the increase in the number of parameters in the case of failure is as follows:

KL= minimum calculated value of short-circuit parameter of terminal gold property of protection area/action value of protection device

The sensitivity coefficient of the protective device whose parameters are reduced to reflect the fault is as follows:

KL= action value of protection device/maximum calculated value of short-circuit parameter of terminal gold property of protection area

4, Reliability. Protection relay test set need to maintain a complete and flexible working state at all times. In the event of failure, the protection device should be timely and reliable action, should not have its own defects, to prevent failure. Therefore, it is required that the construction is urgent, simple and accurate, the construction quality is good, the debugging is correct and the operation and maintenance are proper.