A microcomputer-controlled loss angle meter

Measurements of the loss angle or loss tangent of high voltage insulation are widely used throughout the electricity industry to assess the quality of insulation. Attempts are presently being made to extend the useful life of equipment by monitoring its properties and not replacing it until its properties have either deteriorated or are noticeably inferior to other similar equipment. It follows that a self-balancing instrument would be of great value for field measurements. While it is undoubtedly possible to design a self-balancing bridge with digital data output, it was felt that such an instrument would be more complex than the application warranted. The simpler technique of zero-crossing detection was examined, to see whether it could be made sufficiently accurate. It was thought that a loss angle accuracy of ±2% of reading ±10^-3 radians in the range 10^-3 to 10^-1 (0.001 to 0.1) radians would be more than adequate for field use, and acceptable for most laboratory measurements