How to check the generator electrical system: What details should be looked at in ATS, distribution cabinet and load testing

The fact that the generator can start does not mean that the electricity has been stably delivered to the critical load. ATS automatic switching, low-voltage distribution cabinets, grounding, cables, circuit breakers, parallel control and load testing all need to be inspected regularly and recorded.

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01 ATS automatic switching View content 02 Low voltage distribution cabinet View content 03 Load testing View content 04 Parallel system View content

Applicable scene

Suitable for mining sites with ATS automatic switching, parallel systems, complex low-voltage power distribution, drainage to ensure power, or frequent trips.

Many sites understand maintenance as engine maintenance, but ignore the power transmission and distribution links after the generator output. Low-voltage power distribution cabinets, circuit breakers, cables, grounding, ATS automatic switching, parallel cabinets and controllers. If any link is unstable, critical loads may not be able to receive power.

For electrical maintenance, it is not recommended for non-professionals on site to dismantle and modify the equipment at will. What we can do on a daily basis is to observe, record, clean, confirm that the power is off and lock out and tag out before tightening, and clearly hand over any abnormal phenomena to the electrical personnel or engineers for judgment.

Terminals, grounds and cables

Check the control cabinet, output cabinet and cable terminals for signs of looseness, blackening, odor, overheating or moisture.
Check whether the ground connection is complete and whether the ground wire has been affected by construction, transportation or corrosion.
Observe whether the cable path has been run over by vehicles, soaked in water, worn on sharp edges, or has too many temporary joints.

ATS automatic switching and backup circuit

Confirm that the ATS is in the correct mode and that the automatic/manual status meets the operating requirements for the day.
Regularly record switching test results, including main power loss, generator starting, load transfer and switchback processes.
Check whether the critical load is really connected to the backup circuit. Don’t just look at the presence of a backup unit on site.

Parallel operation and load testing

When multiple units are paralleled, record the load distribution, frequency, voltage and alarm status of each unit.
Regularly conduct actual load or staged load tests to avoid long-term startup of the standby unit with no load.
Pay attention to voltage drops, frequency fluctuations and protection actions when starting large motors.

Execution steps

On-site personnel follow fixed steps so that engineers can make judgments based on the same set of facts.

Maintenance actions must be performed repeatedly and evidence must be left. The following steps are suitable as the basic process before team handover and repair report.

Confirm the security requirements first

Before entering the electrical cabinet, terminals and ATS for inspection, qualified personnel should perform power outage, power inspection and lockout and tagout. Routine inspection personnel are mainly responsible for appearance, sound, temperature rise and records.

Verify switching logic with fixed tests

Backup power cannot wait for an actual power outage to be verified. ATS and critical load switching should be tested as planned, and start-up time, switching time, switchback status and abnormal alarms should be recorded.

Look at tripping and load changes together

If the trip occurs when the crusher, water pump or air compressor is started, you should not just look at the circuit breaker itself, but also review the starting method, cables, protection settings and unit capacity.

Exception signal

In these cases, do not just reset and continue running.

The electrical cabinet smells burnt, generates heat, terminals are discolored, or cable insulation is damaged.
The generator was able to start during the ATS test, but the critical load was not transferred.
The backup unit has only been started without load for a long time and has never carried actual critical loads.
The load of a certain unit in the parallel system was obviously too high or too low, and the alarm was reported but there was no review.

Record list

It is recommended to keep these data for each inspection and repair report

ATS test date, mode, startup time, switchover time, switchback time and results.
List of critical loads, actual load test load rate and voltage frequency changes.
Photos of terminals, grounds, cables, control cabinets and circuit breakers.
The load, alarm code, protection action and recovery method before and after each trip.

How engineers can assist

The more complete the information, the faster the remote judgment, and the more efficient the door-to-door judgment.

If alarms, trips, starting difficulties, abnormal voltage, abnormal fuel consumption, or unstable loads have occurred on site, please give priority to retaining controller photos, fault videos, operating hours, recent maintenance records, oil status, load lists, and ATS/power distribution photos.

When it comes to ATS, parallel machines, low-voltage distribution cabinets and protection settings, single-line diagrams, cabinet photos, controller alarms and test videos should be provided.
If critical load switching fails, the main power supply, backup power supply, ATS model, load circuit and on-site operating procedures should be described.
If frequent trips occur, equipment starting methods, cable distances, circuit breaker specifications and load change records should also be provided.

Continue reading: How to send repair information Contact engineer service

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