Abstract: Among the variety of relay protection maintenance operations, the maintenance activities concerning the secondary circuit current test and relay calibration are considered time-consuming and laborious,and bring about heavy workload for teams with inadequate personnel and heavy maintenance tasks, which is unbenef itial to perform other routine maintenance activities. In view of this, a portable relay calibration bench and a portable AC circuit current passing device are developed, with standardized operation instructions compiled. The application of calibration bench, f low passage device and instruction manuals signif icantly shortens maintenance time and improves the maintenance eff iciency of relay protection.