Electrical Insulation Resistance Testing

When installing new electrical machinery or equipment testing insulation resistance is important for two reasons.

Electrical insulation resistance testing.

An infinite resistance would be the perfect result but no insulator is perfect so the higher the reading the better. Basically you re applying a voltage specifically a highly regulated stabilized dc voltage across a dielectric measuring the amount of current flowing through that dielectric and then calculating using ohm s law a resistance measurement. The measured resistance indicates the condition of the insulation between two conductive parts. The measured value is then compared with minimum values stated in the standard in order to verify that there is not a breakdown of insulation caused by damage to cables and other component parts of a circuit.

The insulation resistance test is an electrical test which uses a certain type and level of voltage 500v d c. Before performing this test the position of the main switch fuses switches etc. It tests the resistance of the insulation of all live parts in electrical circuits. Insulation resistance test between wiring conductors to ensure that the insulation of the cables or wires is not damaged and there is no leakage between them this test is performed.

Let s clarify our use of the term current. This type of initial test is usually referred to as a proof test. The insulation resistance test consists in measuring the insulation resistance of a device under test while phase and neutral are short circuited together. First it ensures that the insulation is in adequate condition to begin operation.

The megger insulation tester is a small portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. The results obtained from ir test are not intended to be useful in finding localized defects in the insulation as in a true hipot test but rather give information on the quality of the bulk material used as the. Insulation resistance testing or megger testing as it is more commonly known does what it says on the tin. Main switch in off position.

What is insulation resistance testing. The insulation resistance test is the second test required by the electrical safety testing standards. For low voltage installations i e. The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables.

Its objective is to measure the ohmmic value of the insulation under a direct voltage of great stability generally 50 100 250 500 or 1000 vdc. 230v to measure insulation resistance in ohm s. Recommended test voltages for routine maintenance insulation resistance tests of equipment rated to 4 160v and above. The ohmmic value of the insulation resistance is expressed in megohms mω.

Should be as under. As a production test this test is often used as a customer acceptance test with minimum insulation resistance per unit length often specified by the customer. Second it provides a baseline reading to use as a reference for future testing. The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables.