The HVA line of VLF/DC test instruments, unlike many other VLF units on the market, also measure the resistance as well as the capacitance of the load.
Note the resistance value displayed is not the impedance of the load but it is the actual real component of the overall current. The real component IR of the total current IT is then divided into the applied AC RMS voltage to give the resultant insulation resistance.
The capacitance of loads like cables play a very small role when measuring steady state resistive leakage currents under DC, but play a major role under AC (including VLF) conditions.
Therefore the real resistance value of the load under AC applied voltages may not be the same as the resistance of the load under applied DC voltages. Most cables are naturally under AC applied voltages when in normal operation.
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