103, NERC PRC-005, and recommendations from manufacturers like SEL suggest that relays should be tested at least annually, and more frequently (e., every 6 months) for high-impact or automated systems. These devices spend years in standby mode, waiting to isolate faults in milliseconds when called upon. A general rule of thumb would be to visually inspect every one to two years, secondary injection testing every one to three years, and primary injection every three to five years or on major. This is why protection relays must undergo thorough tests throughout their entire lifecycle – from development and manufacturing to commissioning and regular maintenance during operation. Protective relays are extensively utilized throughout the power system to promptly remove any element from service experiencing a short circuit, operating abnormally, or posing a risk to system operation. Instrument transformers support the relaying equipment in this task by sensing. Such tests are conducted on every new installations only. The protection circuits, CTs, VTs are also checked. Minor repairs done. Relay protection is essential to ensure the stability, reliability, and safety of electrical power systems.
