Identifying Common Electrical Faults During PAT Testing

Luke Johnson
Nov 26, 2025
3 min read

Updated: Dec 8, 2025

Portable Appliance Testing (PAT) plays a crucial role in maintaining electrical safety in workplaces and homes. It helps detect faults that could lead to electric shocks, fires, or equipment failure. Understanding the common electrical faults found during PAT testing can help users and technicians take timely action to prevent accidents and ensure compliance with safety standards.

What is PAT Testing?

PAT testing involves examining electrical appliances and equipment to ensure they are safe to use. The process includes a visual inspection and a series of electrical tests using specialized equipment. The goal is to identify any defects or damage that could pose a risk.

Common Electrical Faults Found During PAT Testing

1. Damaged or Frayed Cables

One of the most frequent faults is damaged or frayed cables. Over time, cables can suffer wear and tear from bending, twisting, or exposure to heat and chemicals. This damage exposes live wires, increasing the risk of electric shock or short circuits.

Signs to look for:

Visible cuts or abrasions on the cable sheath
Exposed copper wires
Stiff or brittle cables indicating internal damage

Replacing or repairing damaged cables is essential to maintain safety.

2. Faulty Plugs and Sockets

Plugs and sockets often show signs of damage due to frequent use. Loose connections inside plugs can cause overheating, while cracked or broken plugs increase the risk of electric shock.

Common issues include:

Loose or missing screws inside the plug
Burn marks or discoloration around pins
Cracks or breaks in the plug casing

Technicians should replace faulty plugs or sockets immediately to avoid hazards.

3. Earth Continuity Failures

The earth wire provides a path for electrical faults to safely discharge, preventing electric shocks. During PAT testing, earth continuity is checked to ensure this path is intact.

Earth continuity failures occur when:

The earth wire is broken or disconnected
Corrosion or damage interrupts the earth path
Incorrect wiring in the plug or appliance

An earth continuity failure is a serious fault that requires immediate repair.

4. Insulation Resistance Problems

Insulation resistance testing measures how well the appliance’s internal wiring is insulated. Low insulation resistance indicates that electricity could leak, potentially causing shocks or fires.

Causes of low insulation resistance include:

Moisture ingress inside the appliance
Age-related deterioration of insulation materials
Damage from impact or heat

If insulation resistance falls below safe levels, the appliance should be repaired or taken out of service.

5. Polarity Issues

Polarity faults happen when the live and neutral wires are reversed. This can cause appliances to operate unsafely or damage sensitive electronics.

Indicators of polarity faults:

Incorrect wiring in plugs or extension leads
Appliances behaving unusually or not powering correctly
Failed polarity tests during PAT

Correct wiring is critical for safe appliance operation.

6. Overheating Components

Overheating can result from loose connections, overloaded circuits, or internal faults. Signs include discoloration, melting, or a burnt smell near plugs or cables.

Overheating risks:

Fire hazards
Damage to appliance components
Increased risk of electric shock

Regular PAT testing helps catch overheating issues early.

How PAT Testing Helps Prevent Electrical Accidents

By identifying these common faults, PAT testing reduces the risk of electrical accidents. It ensures that appliances meet safety standards and remain reliable. Regular testing also helps organizations comply with legal requirements and insurance policies.