Tan Delta Measuring
Prevention of “Capacitive Rise Effect”
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The Reason for Voltage Rise Indication Under 10kV - Introduction on Voltage Self-correction Technology in Prevention of “Capacitive Rise Effect”


During voltage rise measurement with HCL2840 dielectric loss tester, especially when measuring test object with large capacity (>1000P, for instance transformer test object), operators sometimes come across indication of voltage rise under 10kV (for instance 9.8kV, 9.5kV), whereas printed test voltage reach 10kV after measurement, this happens when voltage self-correction is activated in prevention of “Capacitive Rise”.

Internal voltage rise transformer(L) and test object capacitance(C) compose a LC circuit, voltage rises within the circuit, namely the “Capacitive Rise Effect”. Due to voltage rise caused by “Capacitive Rise Effect”, test object and instrument working voltage is above 10kV, which may well lead to insulation breakdown or parameter change, causing instrument damage or error in test outcome. The instrument will automatically track output voltage and circuit voltage, conduct précised voltage rise control, effectively protect test object and instrument.

“Capacitive Rise Effect” appears more evident during dielectric loss test with CVT self-excitation method, in result of large capacitance of CVT lower segment coupling (>40000P), secondary side voltage rise by volts will cause primary side voltage rise by thousands volt. Make sure to monitor strictly that primary side (point A) voltage below 3kV, secondary side current below 6A. Thus type HCL2840-C and HCL2840-D are equipped with protection control for high voltage, high voltage current, low voltage and low voltage current for CVT measurement, HCL2840 adjust voltage with accuracy according to these four protection control to ensure safety of test instrument and device.