All Rights Reserved. © 2020 Southwire Company, LLC. Cables shall be tested for insulation resistance with an insulation tester (i.e. Any reading above 1.25 is considered excellent. 1000 Volts for 1 minute. Residue inside the sealing cap can be conductive and lead to false readings. IR Value for Electric motor: For electric motor, we used a insulation tester to measure the resistance … The voltages are high, but the currents are small enough to be safe. The test measures the insulation resistance between the phases and/or between phase and ground. Insulation Resistance Testing – Megger Testing, Withstand Testing - for low voltage cables, Medium Voltage Switchgear and Substation Cable, Strand-Fill in Medium Voltage Tape Shield Cable, Terminating Variable Frequency Drive (VFD) Cables, Begin with the End in Mind - Proper VFD Cable Termination, Insulation Resistance Testing – Megger Testing. It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. • NOTE: It is important to remove sealing caps from both ends of the cable to be tested. • For other cable on a reel, insulation resistance testing can be performed provided the sealing caps are removed. For electric motor, we used a insulation tester to measure the resistance … It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. Figure 2 – Typical Megger test instrument hook-up to measure insulation resistance. The generator can be hand-cranked or line-operated to develop a high DC voltage which causes a small current through and over surfaces of the insulation being tested (Fig. If the megger reads a resistance between 1-1.25 on your meter, then the cable passes. Insulation Resistance Testing Cable Type Test to Perform Notes Medium Voltage Shielded ϕ to Shield Conductor shield Medium Voltage Non-Shielded ϕ to ϕ ϕ to Ground Earth ground or the cable’s metallic conduit Low Voltage Multi-Conductor ϕ to ϕ ϕ to Ground ϕ to Neutral Neutral to Ground Earth ground or the cable’s metallic conduit Example Insulation resistance testing is a non-destructive test procedure. General Testing Information • For single conductor non-shielded cable on a reel, insulation resistance testing cannot be performed due to the fact that low voltage single conductors do not have a grounding conductor, shield or ground plane. The procedure to test these cables is outlined below. The minimum insulation resistance to earth or between phases shall be 100 meg-ohms. Written by Steve Wetzel, Mark Dulik on April 24, 2019 in Megger Testing. 2).This current (usually at an applied voltage of 500 volts or more) is measured by the ohmmeter, which has an indicating scale. IR Value for Electric motor. A megger is also known simply as an insulation tester. If the megger reads a resistance under 1 (1,000 ohms) on your meter after the initial 60-second interval, the cable has failed and the cable should be removed. The test measures the insulation resistance between the phases and/or between phase and ground. Megger) at. Equipment AC Rating dC Test Voltage up to 100 volts 100 and 250 volts 440 to 550 volts 500 and 1,000 volts 2,400 volts 1,000 to 2,500 volts or higher 4,160 volts and above 1,000 to 5,000 volts, or higher Test voltages used for proof testing of equipment are considerably higher than … It's basically an ohmmeter, but it's one that generates its own electricity under high DC voltages, such as 500 and 1,000 volts, and transmits it in small currents through the cable to be tested. Insulation resistance testing is a non-destructive test procedure. The instrument used for this measurement shall have a minimum resolution of 10 megohms on the 0 to 500 meg-ohm range.