Ultra-Low Frequency Dielectric Loss Tester is capable of testing medium-voltage cables in accordance with the relevant standards of the European Committee for Electrotechnical Standardization (CENELEC) harmonization documents HD 620 S1:1996 and HD 621 S1:1996. 
A 0.1Hz sine wave voltage of up to 24kV RMS. With this type of cable testing, faults in the insulation, especially water tree damage, can be reliably detected in both polyethylene (PE)/cross-linked polyethylene (XLPE) cables as well as paper-insulated cables, causing flashover. The testing procedure will not damage fault-free insulation. Cables can also be tested for dielectric breakdown strength using both positive and negative DC voltages, as well as trapezoidal AC voltage (rectangular wave voltage). The slew rate of the rectangular wave voltage depends on the cable capacitance and is automatically adjusted. Additional leakage current measurement in DC mode allows for evaluating the relative quality of the cable insulation. The sine wave shape of the system's test voltage can also be used to directly measure the cable's dielectric loss factor, thereby determining the degree of deterioration in the cable's loss factor. For a detailed description of this application, please refer to the relevant manuals.