5.2.3.Measuring insulation resistance.Measure the insulation resistance of each cable core to the ground or to the metal shielding layer and between the cores. Test with a 2500V megohmmeter. 6/6kV and above cables can also be used as a 5000V megohm meter,Before and after the withstand voltage test, there should be no significant change in the insulation resistance value.The insulation resistance of the outer sheath and inner lining of rubber and plastic cables shall not be lower than that of the cable 0.5MΩ/km.Record the ambient temperature and relative humidity during the test.