Application of PCI DeviceNet card and short-window Morlet complex wavelet in protective relays measuring and control-system

By using PCI DeviceNet card and short-window Morlet complex wavelet algorithm and combining protective relays technology, field bus technology and measuring and control technology, a new full-distributed protective relays measuring and control system is developed. The design method of PCI DeviceNet card's hardware and the developing process of its driver and monitoring program are described. A difference filter adding short-window Morlet complex wavelet measurement algorithm is adopted to calculate the amplitudes of the fundamental and harmonics components of current and voltage signals. Its calculating results can hardly be affected by frequency fluctuation. As all protective measuring and control units adopt a uniform hardware platform and system design, the complexity is reduced and the maintainability is improved for the system. The results of the network test, dynamic simulation and field test indicate that this system is characterized by accurate response to various faults of the transformer, line, capacitor and motor, higher measuring accuracy and favorable controlling capability.