Scope
- Unexplained tripping: finding the cause of residual current device, fuse and circuit breaker trips.
- Insulation faults: insulation resistance of cables, motors and boards (test voltages up to 1,000 V).
- Protective conductors and earthing: continuity, high-resistance faults between phase and protective conductor, equipotential bonding.
- Grid-related problems: voltage dips, harmonics, resonance and neutral overcurrent (event recording).
- Hot spots: loose connections, overload and unbalance (thermal camera).
- Portable appliances (PAT): protective conductor continuity and insulation resistance checks.
Method and instruments
First the timing and conditions of the fault are established (time of day, load, weather, machines starting). For intermittent faults the Kyoritsu KEW 6315 is left on site for several days to record voltage and current changes at the moment of tripping.
Circuits are divided into sections and insulation resistance and continuity are measured with the KEW 6516BT, narrowing down the faulty section systematically.
Thermal imaging is carried out with the board under load; temperature differences are compared between connections of the same type and between phases.
Regulations and standards
- TS HD 60364-6Verification: insulation resistance, continuity, automatic disconnection
- TS HD 60364-4-41Protection against electric shock
- TS EN 61557Equipment for testing protective measures
- IEC 61000-4-30Measurement and recording of power quality events
- Regulation on Internal Electrical InstallationsRules for low-voltage installations in buildings
Deliverables
- Fault investigation report: symptoms, measurement plan, results (value and limit), source of the fault
- Thermal images with temperature values
- Prioritised corrective recommendations; verification measurement after correction
- Record archived under a report number (for comparison with future faults)
Frequently asked questions
Why does our residual current device keep tripping?
The most common causes are a circuit or appliance with deteriorated insulation, connections in damp areas, neutral and protective conductors joined somewhere downstream of the device, and the combined leakage current of many electronic devices on the same device. The source is found by measuring circuits one by one.
How is an intermittent fault found?
A power analyser stays on site for several days to record voltage and current changes at the moment of tripping, and the timing of the fault is compared with other events (machines starting, rain, grid events).
When should a thermal camera check be done?
With the board at normal load. Hot spots may not show at low load, so we schedule the measurement for the facility's busiest hours.