A high-voltage high-precision self-balancing capacitance and dissipation factor-measuring bridge

A fully automatic measuring bridge to determine the capacitance and dielectric losses of liquid and solid insulating materials, cables, capacitors, line transformers, voltage transformer, etc., has been developed. The bridge uses a current comparator which, when balanced, allows a direct reading of the capacitance, dissipation factor (tan δ), and test voltage. The unit has been especially designed for stringent industrial applications, which necessitate special precautions in order to protect the bridge against a breakdown of the test specimen, as well as against stray magnetic fields which may affect the measurement accuracy. By using current comparators, an accuracy of 1×10^-8 can be attained; however, because of the incorporated protective circuits, a compromise was reached at the cost of accuracy. Regardless of this, an accuracy of 1-2×10^-5 for tan δ and better than 1×10^-4 for capacitance measurements can be achieved.