How to check IR value of LT cable by megger. LT cable Megger value

The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables. 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. 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. Even when not required by the end customer, many wire and cable manufacturers use the insulation resistance test to track their insulation manufacturing processes, and spot developing problems before process variables drift outside of allowed limits.  Selection of IR Testers (Megger):- Insulation testers with test voltage of 500, 1000, 2500 and 5000 V are available. The recommended ratings of the insulation testers are given below: Voltage LevelIR Tester650V500V DC1.1KV1KV DC3.3KV2.5KV DC6.6Kv and Above5KV DC  Test Voltage for Meggering:- When AC Voltage is used, The Rule of Thumb is Test Voltage (A.C) = (2X Name Plate Voltage) +1000. When DC Voltage is used (Most used in All Megger), Test Voltage (D.C) = (2X Name Plate Voltage).