Research And Development Of The Microcomputer Distance Protection Based On Digital Signal Processor

Protective relaying is one of device to respond the fault and abnormal operating conditions of electric power system, and trip the circuit breakers or send signals. In the modern power network, along with the extra-high voltage, high-capacity and long-distance transmitting line increasing unceasingly, it is proposed stricter request to the security and stability during power system's operating. The traditional protection devices are based on microprocessor as the SCM which has low digit capacity. When these devices are used in HV transmission line protective relaying, there may be some disadvantages, such as slow computing speed, small memory capacitance and low reliability. It is very difficult to satisfy the demand of the modern electric power system's development.On the base of generalizing the development history and the existing condition of microprocessor-based relays of the transmitting lines, this topic analyzes the existing conditions about the hardware of microprocessor-based protection in domestic. The topic compares several of processor chips, and considers the demand of the modern transmitting line, and chooses the core processor, finally gives a scheme of relays based on DSP and ARM processors. This design uses SEED-DPS2812M industrial control board made by SEED company as the protective CPU, which mainly answers for A/D sampling, switching values inputting, digital filtering, relay protection measuring element, logic function implementation, setting values management, signals outputting, tripping and closing of breakers. On the other hand, the design uses M2020-N20 embedded industrial control board as the management CPU, which mainly answers for system monitoring, starting element, touch screen controlling, LCD displaying, RS232 serial communication, Ethernet communication. At the same time, in order to realize equal interval sampling, this topic designs the frequency tracking circuit, which can adjust the sampling intervals according to frequency change in real-time. The hardware uses the module design. The topic describes the data sampling system and I/O switching mode in detail. As the protection algorithm and measurement algorithm have different emphasis points on precision and response speed, this topic chooses different sampling points for different algorithms. By comparing several of protection algorithms, the topic adopts the Fourier algorithm with the first cut linter difference, which can reduce the effect of the damping DC component efficiently. The recursive Fourier algorithm is used to calculate real-time parameters in real-time, which can satisfy the requirement of performance.The software uses typical up to down and modular designing methods. The software includes main program, interrupt service routine and fault processing program, which are explained in detail. According to the characteristics of the HV transmission line protection and the hardware design, the topic explains the protection functions of the fault processing program mainly. The phase-to-phase distance protection adopts the impedance relay which has the quasi quadrilateral characteristic. The impedance relay possesses well standing resistance ability and avoiding load ability. Zero sequence current protection is used for the grounding faults, which is simple, fast and reliable.This design not only can be used in high voltage line protection, but also can be improved as a testing device for protective relaying. The testing device can be used for experiment teaching and software debugging.