Power quality describes the characteristics of the electrical supply experienced by equipment. Disturbances can affect operation, but a trip or failure is not proof of a supply problem. Investigate with recorded evidence.
A problem can have more than one cause
A drive trip might coincide with a voltage disturbance. It might also be caused by a process overload, cooling problem, wiring fault or equipment setting. Starting with a conclusion can lead to the wrong repair.
Record what stopped, the exact time, the alarm or trip message and what else was happening. Those details let an electrical specialist compare the event with supply measurements and process records.
Four useful distinctions
| Condition | Possible effect | What to investigate |
|---|---|---|
| Voltage dips or interruptions | Resets, trips or loss of control power. | Timing, duration, affected phases and coincident operations. |
| Harmonic distortion | Additional heating or interaction with equipment. | Voltage and current distortion, load mix and network impedance. |
| Voltage unbalance | Uneven motor currents and thermal stress. | Measurements and the distribution of connected loads. |
| Low power factor | Higher current for a given real-power demand. | Load behaviour, tariff terms and any correction equipment. |
The effect depends on magnitude, duration, equipment tolerance and the system. Generic percentages cannot diagnose the loss of life of a particular motor.
Why the cost is wider than the electricity bill
A short disturbance can interrupt a process that takes much longer to restart. Repeated trips also consume maintenance time and may lead to unnecessary component changes. Conversely, normal-looking energy totals can hide a brief event.
Low power factor may affect capacity and charges, depending on the supply agreement. Check the actual tariff rather than assuming every New Zealand customer has the same penalty threshold. A correction scheme also needs assessment of harmonic interactions.
Turn observations into a measurement brief
- List the affected equipment and observed events.
- Collect timestamps, alarms and relevant process changes.
- Identify the supply arrangement and recent load additions.
- Agree the measurement locations, recording capability and duration.
- Compare electrical events with the process log before selecting a remedy.
For questions about supply obligations, use the current connection agreement and applicable network and regulatory requirements. A measurement result needs to be interpreted against the right basis for the site.
The power quality monitoring guide explains how to specify the instruments and data. CWS can discuss metering and monitoring interfaces as part of a switchboard or control-panel scope.