On-line evaluation and verification of protection relay settings — Design and field experience

This paper presents a system developed for on-line evaluation and verification of protection relay settings based on the advanced information and computer technology. The inputs to the system are real-time topology and operation data of electricity networks from the EMS, and protection settings obtained from relays. The relay settings are evaluated by simulating various faults on the real-time topology of the networks. It can check the sensitivity and selectivity of the main and backup protection settings. The evaluation results are then displayed in a visualization window on a workstation. If a setting value is found incorrect or inadequate, an alarm is raised and a new setting is recommended. The operator can then change the setting or adjust the network operating mode to minimize the risk of protection mal-operations. This system has realized the online checking for the reliable operation of protection relays, and early warning of any inadequate protection settings. The system has been installed in a distribution network in China Southern Power Grid. Since it is in operation in Dec 2013, its performance is satisfactory.