Primary Injection Test

Primary Injection Test (Step by step)

  1. Isolate the breaker
    • Rack out or ensure it’s in test position
  2. Connect the test set
    • Connect output leads to line and load terminals
    • For 3-phase: test phase-by-phase
  3. Connect measurement devices
    • Ammeter / CT secondary if needed
  4. Check all connections
    • Tight, clean, secure.

      Visual & Mechanical Check

      • Inspect contacts, insulation, and mechanism
      • Perform manual open/close operation

        Test Procedure (Step-by-Step)

        1. Visual & Mechanical Check

        • Inspect contacts, insulation, and mechanism
        • Perform manual open/close operation
        • Use micro-ohmmeter
        • Confirms good contact condition

        3. Primary Injection Test

        a. Close the breaker

        • Ensure breaker is in closed position

        b. Inject current gradually

        • Start from low current
        • Increase to required test value (e.g., 100%, 200%, or pickup level)

        c. Monitor readings

        • Verify current matches expected values
        • Check CT secondary output if applicable

        4. Trip Test

        • Increase current until:
          • Protection relay trips, or
          • Breaker trips at setpoint
        • Record:
          • Pickup current
          • Trip time

        5. Time-Current Verification

        • Compare measured trip time vs protection curve
        • Ensure coordination is correct

        6. Repeat for All Phases

        • Test Phase A, B, C individually.

          Typical Values to Verify

          • Pickup current (e.g., 1x, 2x, 5x In)
          • Trip time (instantaneous / short-time / long-time)
          • CT ratio accuracy
          • Breaker trip consistency