The insulation resistance can be described as the resistance offered by the insulation which covers a conducting wire that carries electrical current. The resistance that is offered by the insulation of the cable in the leakage current path is called the insulation resistance of the cable. Certain factors would affect the insulation resistance test such as the installation of the device, operating conditions, and the type of usage.
When an electric current is sent through a conducting wire it would reach the destination but due to certain reasons, some of the electric current would be lost along the way. So we need to do the insulation testing to check if there is any leakage of current and this current leakage could be harmful. Insulation resistance testing is really important to prevent damage and injury. This test must be conducted to ensure the reliability of the electrical systems and also the equipment. The electrical resistance of insulating material is to direct a voltage, and it can be detected by measuring the leakage of current which flows through the insulation. By doing an insulation resistance test we can determine if the equipment is in proper condition, and we can almost detect the service life of the insulation by this test.
The insulation testing must be done when installing new electrical machinery, so while testing this equipment we can make sure that the insulation is in proper condition for the operation and it would also be useful as a reference for future testing. An insulation resistance test usually has four phases: charge, dwell, measure, and discharge. During the charge phase, the voltage is ramped from zero to the selected voltage, which provides stabilization time and limits the inrush current to the DUT. Once the voltage reaches the selected value, the voltage can then be allowed to dwell or hold at this voltage before measurements begin. When the voltage is applied, some current immediately starts to flow through the insulation. The instrument measures and displays the measured resistance.