Secondary injection tests are performed by injecting currents into the relay terminals to determine that the relay is operating correctly and in accordance with its settings. Such tests are usually carried out in the substations on the existing panels provided for the purpose.
These tests include injecting currents of various magnitudes from minimum operations all the way up to 6 or 10 times current setting and measuring the relay operating time. Both Over current and Earth fault schemes are tested on the protection relays. Some relays have additional settings which need to be taken into consideration, such as instantaneous over current, earth fault or Sensitive earth fault settings.
If the protection relay being off characteristic during the secondary injection test it might have an effect on the co-ordination with other schemes in the network causing unnecessary nuisance tripping of the supply.
Having performed these tests you have done all that is reasonable to prove the correct operation of the protection scheme.
AMP is capable of performing secondary injection testing on most, if not all Protection relays according to the OEM’s specification. AMP is in possession of a 3–phase and Single phase injection test set to perform secondary injection tests. AMP is also in possession of dedicated instruments to perform secondary injection on LV Switchgear protection. Normally with the Secondary injection testing we also perform service and testing of the MV Switchgear as well as testing and service the Battery Tripping Unit (BTU). By doing it this way only one outage is required and reduces your downtime.