Fault Finding and Repair
Domain 10: Fault Finding and Repair
This domain tests systematic diagnosis of common meter and connection faults.
Core rules
- Complaint categories include no display, no registration, fast or slow running, reverse running, burnt terminal and communication failure.
- First isolate and prove dead; check supply voltage, neutral, load current and terminal tightness.
- No registration with load present: check meter connections, programming, display register and load current.
- Fast meter: check CT ratio, PT ratio, wiring, calibration and any bypass.
- Reverse running: check CT polarity, phase sequence and import/export configuration.
Worked example
A consumer says the meter advances with all loads switched off. Isolate, confirm no current in the load circuit and observe. If registration continues, suspect creep, a wiring bypass or a live neutral return. Test with a known load and compare pulses; if the meter is faulty, replace it and record the evidence. Reasoning: separate load-present conditions from meter defect before condemning the meter.
Traps that cost marks
- Replacing a meter without testing the load circuit.
- Ignoring a neutral bypass.
- Resetting a meter without authorization.
- Failing to record the seal and final reading.
- Treating a communication fault as an energy-measurement fault.