Abstract: To study fault detection and diagnostics problem of hydraulic power system in machinery engineering, the mathematic model and experimental set about the study, as well as the experimental results are introduced, and four kinds of standard of detecting fault type about hydraulic power equipment based on current signal is given, which uses grey association degree to the spectrum of current signal. The method can detects reliably machinery fault, motor fault, pump fault of the system. The method can detect running condition of hydraulic power system on line because the arithmetic is simple and reliable.

Key words: Condition detection, Current signal, Grey association degree, Hydraulic power system