Primary Injection is done to prove a CTs (current transformer), current-circuit, and protective devices are all properly connected.
Three common tests are:
Power Transformers – A three-phase source is connected to a short-circuited transformer, to supply current through the windings. The CT circuits are then checked to verify that all test-switches and protective relays receive the proper current at the proper angle.
Bus-work, Switchgear, and HV Breakers – Sufficiently high current is applied to the primary conductors. The CT circuits are then checked to verify that all test-switches and protective relays receive the proper current at the proper angle.
Low Voltage Breakers – Very high current is applied to the breaker for short duration, to measure how the Trip-Unit reacts. The trip-unit’s time delay is measured at various current magnitudes to verify compliance with manufacturer’s published time-current curves.
For primary injection testing of current transformers, VTs or primary relays, the Omicron CMC 356 Universal Relay Test Set and Commissioning Tool is ideal. The high current amplitudes in parallel allow for checking current transformer polarities. The portably rugged case allows the set to be used in the field without worry of damage by weather or dirt conditions.
Omicron CMC 356 features:
– Very powerful current sources for testing high-burden electromechanical relays
– High current amplitudes for 5 A relay testing
– High accuracy and versatility for testing static and numerical relays of all types
– Integrated network for testing IEC 61850 IEDs
– Continuous synchronized outputs with CMIRIG-B (e.g. for PMU or MU testing)
– Primary injection capabilities for commissioning tasks
– Test Universe software with unrivaled manual and automated testing functionality
With multiple locations to better serve your needs, Protec offers electrical testing equipment rental options that work for you.
Editor’s Note: This post was originally published August 2014 and has been updated freshness, accuracy and comprehensiveness.