What happens when electrical insulation fails?

Electrical insulation is not just the plastic polymer material that wraps the wire, it is a complete system of cable insulation, bushing insulators, space inside the conduit, motors and general equipment. Mechanical stress, contamination, and temperature changes can cause these components to deteriorate over time, allowing current to leak. Current leakage can cause the following problems:

1. When the current passes through the insulating layer, heat is generated, which will deteriorate the insulating layer until the insulation fails and cause a fire hazard.

2. The leakage current must return to the source, it will flow back to the source through any available conductor, conduit, pipe, water or earth. This unfavorable current can generate dangerous voltages.

3. The leakage current is inefficient. The current that leaks through the insulation doesn't drive motors, light or heat, but it still consumes.

4. The leakage current will cause the overcurrent protection device to trip and overheat the motor and transformer. The result is poor electrical insulation causing equipment failures and production line shutdowns. Now, no factory can survive an unplanned shutdown. “Customers need to diagnose faults quickly. No one wants to lose production time, and many are eager to know if they need to fix their equipment or simply replace it.”

The role of insulation resistance tester:

By testing the insulation resistance of different components in the system (transformers, switchgear, wires, motors), technicians can isolate and repair failed components. Technicians use tests to verify high insulation resistance between conductors and ground or adjacent conductors. Two common examples are testing the insulation between the motor windings and the motor base, and checking the resistance between the phase conductors and the ground wire/cage. Using insulation testing to verify that a system is healthy before powering it up can improve system performance; insulation testing can uncover manufacturing process issues and equipment defects that would not normally be discovered until the equipment fails. In the EU, the test is mandatory, even for civilian systems.