Primary / Secondary Injection Testing

Primary injection testing is essential in commissioning and verifying a protection scheme since the secondary injection test does not check all the components in the system and the condition of the overall protection installation; unlike the primary injection testing, the secondary injection tests do not simulate the real operating conditions, it would not reveal a defective CT, whether that CT is the correct ratio or polarity, or whether the secondary wiring is correct and serviceable. The primary injection testing is the only way to prove correct installation and operation of the whole protection chain, as involves testing the entire circuit; current transformer primary and secondary windings, relays, trip and alarm circuits, circuit breakers and all wiring are checked. Primary injection testing is often the last test performed in the commissioning and maintenance process, or after any modification, as a functional test of the whole system, not excluding the also needed secondary injection tests that must be performed first. Primary injection testing is also a big help in troubleshooting and corrective maintenance..