Generator tripping: causes and remedies

Understanding generator tripping

Generator tripping is a safety mechanism designed to protect both the generator and connected equipment. When abnormal conditions occur, the generator automatically shuts down, preventing serious issues such as electrical faults, engine damage, or fire hazards.

Like your home’s electrical system, a generator is protected by circuit breakers and overload protection systems. These devices detect unsafe conditions and “trip,” immediately stopping the generator to prevent minor problems from becoming major failures.

Common causes of generator tripping

1. Electrical/internal generator faults

• Overloading: asking the generator to supply more than its rated capacity can cause overheating of the windings. Overload protection trips the generator to prevent damage.
• Short circuits: sudden current surges from short circuits can harm the generator and connected equipment. Circuit breakers trip to stop the flow of electricity.
• Rotor/stator failures: faults in rotor or stator windings cause abnormal currents or vibrations, triggering trips.
• Over-fluxing: excessive magnetic flux overheats the core and windings, prompting a trip.
• Differential protection trips: detects unusual current differences between terminals caused by internal faults, isolating the generator.

2. System disturbances/external causes

• External short circuits: faults in the grid or connected circuits produce high currents, triggering trips to protect the system.
• Loss of synchronism: falling out of phase with the grid leads to instability; protection systems trip the generator.
• Over/under frequency: deviations from the safe frequency range due to load changes or grid issues trigger trips.
• Over/under voltage: unsafe voltage levels can damage equipment, causing protective relays to trip.

3. Mechanical and prime mover failures

• Overheating: high engine temperature can damage the generator; temperature sensors initiate a trip.
• Low oil or coolant pressure: insufficient lubrication or cooling triggers trips to prevent engine damage.
• Overspeed: exceeding safe rotational speed activates overspeed protection.
• Vibration or bearing issues: excessive vibration or worn bearings are detected by protection systems, causing trips.

4. Environmental causes

• Humidity: high moisture can lead to insulation failure and short circuits.
• Dust/debris: accumulation of dust or foreign objects may cause overheating or electrical faults.
• Poor fuel quality: contaminated or low-quality fuel can lead to combustion issues and engine malfunctions.

Troubleshooting generator tripping

Initial safety measures

Turn off the generator: ensure the generator is completely shut down to prevent injury or further damage.

Inspect for visible damage: check for obvious faults such as burnt wires, oil leaks, loose connections, or corrosion.

Step-by-step troubleshooting

Step 1: Check the load

Ensure the generator is not overloaded. Reduce or disconnect non-essential loads and try restarting the generator.

Step 2: Check the GFCI receptacle

Turn off the generator and disconnect all appliances.

Press the “reset” button on the GFCI outlet and restart the generator.

If the button does not stay depressed, the GFCI outlet may be faulty and should be replaced.

Keep the gfci clean and dry, as dust, water, or electrical faults can damage it and cause trips.

Step 3: Inspect electrical connections and breakers

Check all wiring, terminals, and circuit breakers for loose connections, corrosion, or damage.

Reset any tripped breakers and replace cords or breakers that are faulty.

Look out for issues like burning smells or automatic air switch trips, which may indicate a bad contact or insufficient spring pressure in the switch.

Step 4: Check capacitors (if applicable)

Some circuit breakers have built-in indicators for overloads, but they are not always reliable.

Use a multimeter to measure resistance at lead wire connections.

A reading of ‘ol’ (overload) or infinity indicates a faulty breaker that must be replaced.

Step 5: Examine engine systems

Oil level and pressure: low oil or faulty sensors can trigger trips—refill or service as needed.

Coolant level and temperature: check coolant levels and ensure the engine is not overheating.

Fuel system: verify fuel supply, quality, and filters to prevent combustion problems.

Step 6: Read error codes (if available)

Modern generators often display error codes or warnings. Consult the user manual to interpret codes and address the indicated faults.

Analyze generator logs, relays, and sensor data to identify the root cause.

When to call a professional

• The generator trips repeatedly despite troubleshooting.
• Complex electrical or mechanical faults are suspected.
• Safety hazards exist that require specialized tools or expertise.