Eaton SEFELEC 5 Series User Manual

User manual SEFELEC 5x Series 190 v1.06100 Mohm.km x 10 = 1,000 Mohm.kmC) The insulation resistance value of a cable being a function following a time exponential law, itis important to make sense to the measured value, to indicate the duration of the measure-ment. The units of the SEFELEC 5x range allow complying with this requirement with thebuilt-in timer, able to measure times going from 1 second up to 3 hours.19.4.4. MEASUREMENT VOLTAGE SELECTIONThe insulation resistance measurements intending to verify that materials or equipments complywith standard requirements, it is important to refer to these standards to select the voltage. Thestandard voltages are generally: 50, 100, 250, 500 VDC.In case of no standard, select a 100 VDC value.When measuring on capacitive specimens and when studying the voltage influence on the insu-lation resistance values, it is important to start always with the lowest voltage and then to followthe measurements in increasing the voltage. A procedure in the reverse way could give incoher-ent results.DIELECTRIC STRENGTH TESTSThe dielectric strength test is intended to stress components and sub-assemblies of electricalequipments and to check that the leakage lines either between points or between points andground are correctly designed according to the used technology.The principle of a dielectric strength test is to apply a voltage (DC or AC) between defined pointsand after voltage stabilization, to check that the leakage current, created by breakdown phe-nomena or breakdown discharges (in the air or in the insulating materials), is not greater thanthe nominal acceptable value.The default sanction is determined by the analyse of the shape, the amplitude and the holdingtime of the current supplied by the generator to the specimen under test and by comparison witha preset limit.