Measurement and communication techniques for remote condition monitoring of high voltage transformer bushings

The insulation used in high voltage transformer bushings experiences an aging process, which reduces its effectiveness and ultimately may lead to catastrophic breakdown. The progress of aging can be estimated by measuring various parameters of the insulator material. The most easily obtainable parameters are electrical, and this fact has led to the introduction of commercial automated measurement systems suitable for condition monitoring of various types of high voltage bushings. This paper describes the development phase of a system using fibre optic communications to construct a network based on standard PCs serving as the instrumentation at the point of measurement. The system is designed to measure tan δ, partial discharge and harmonics. It is expected that the system can measure relative phase angle to within 0.1 m radians. All nodes across the network are synchronised using a dedicated fibre carrying timing pulses. The software design uses a modular approach to maintain flexibility. A supervisory system comprises a graphical user interface communicating with network software using windows dynamic data exchange (DDE). The remote nodes communicate with this system using remote procedure calls (RPC), which is a multiplatform protocol, enabling other operating systems to be integrated if desired.