Insulation begins to age as soon as it is made. With the passage of time, its insulation performance declines. Any harsh installation environment, especially one with extreme temperature and/or chemical contamination, will accelerate the process. Stress caused by different factors, such as:

• electrical stress: mainly related to overvoltage and undervoltage.

• mechanical stress: frequent start and close sequences may cause mechanical stress.

• in general, the balancing of rotating machines and any direct stresses on cables and equipment.

• chemical stress: proximity of chemicals, oil, corrosive vapors and dust will generally affect the insulation properties of the material.

• stresses related to temperature changes: when used in combination with mechanical stresses caused by the start and close sequence, expansion and contraction stresses affect the properties of the insulation. Operating at extreme temperatures can also lead to material aging.

• environmental pollution can lead to accelerated aging of insulation.

This wear reduces the electrical resistivity of the insulation, increasing the leakage current, which can lead to accidents, which can be serious in terms of safety (personnel and property) and downtime costs. It is therefore important to identify this deterioration quickly so that corrective action can be taken. In addition to measuring new and refurbished equipment during commissioning, regular insulation testing of equipment and equipment can help prevent such incidents through preventive maintenance. These tests detect aging and premature deterioration of insulation performance before the insulation performance reaches a level that could lead to the above events.

This test is usually used as a customer acceptance test, and the customer usually specifies a minimum insulation resistance per unit length. Results obtained from IR tests are not as helpful in finding localized defects in insulators as they are in real HIPOT tests, but only provide information about the quality of bulk materials used as insulators.

Wire and cable manufacturers use insulation resistance tests to track their insulation manufacturing process and detect problems before process variables exceed the allowable limit.