The sole purpose of protective relays is to rid power systems of the elements that lead to short circuits. However, before protective relays are used, it is crucial that they are acceptance tested. Additionally, in order to ensure that protective relays continue to safely and efficiently fulfill their purpose, NFPA 70B 2016 states that they must undergo periodic testing every two years. Not sure what protecting relay tests or why they are important for your power systems? Here are four different tests—from the engineering experts at North Central Electric—that should be done during the installation and maintenance of protective relays.
Inspect to Protect
Before testing or maintenance can start, the protective relays must first undergo a thorough visual and mechanical inspection. For circuits that are currently being serviced, each individual relay will be tested at a time—this will prevent protection features from being disrupted.
Verify to Fortify
After protective relays are inspected, the next step is to make sure that the settings match up with its latest coordination and arc-flash studies. By doing this, you will have confirmation that the protective relays settings satisfy the latest studies and sheets that the owner has provided.
After relay settings have been confirmed, it is time for acceptance testing. At a minimum, this should include the following:
- Inject a known current and voltage and verify correct meter readings
- Test all enabled protection element pickups and timer delays
- Verify correct characteristics according to the manufacturer’s literature
Unite to Validate
Once the testing of every individual component and the checking of the function of each element has been completed, it is now time to test the unit as a whole. By doing a system functional test, you will know if all of the sensing, processing and action devices are interacting with one another as they should be. A system functional test should include the following:
- Testing lock-out relays
- Testing breaker block close circuits
- Testing breaker trip circuits
- Verify all current and potential transformer circuits
- Verify all relay inputs/outputs to/from equipment and SCADA systems
Whether you are placing new protective relays into a power system or you want to know if your current ones are operating as they should be, the team at NCE can help! To schedule your protective relay test, contact us today!