Research And Development Of A Hardware Platform Of Microprocessor-Based Bus-Bar Protection Equipment

The bus-bar is an important component of power transmission system, and its security and reliability have great influence on the security and stability of all power system.The failure to operate and undesired tripping of bus-bar protection will jeopardize all system badly.Firstly, analysis the characteristic and disfigurement of the existing bus-bar protection, this paper presents an integrated scheme for the new developed device of digital bus-bar protection on the base of General Specification for Microprocessor-based Bus-bar protection Equipment.Secondly, testing the performance-price ratio for existing high capability hardware, a scheme is singled out, which not only satisfy the requirement, but also can reduceinvestment, ensure precision and simplify software structure. The scheme makes use of three relatively unattached CPU as the main computation system. The circuit diagrams of house, differential-lockout and unit are designed on the foundation of the unitary. The one-main-two-assistant SPI transmission plan is introduced to ensure the speed and precision of the transmission of information among the three relatively unattached CPU, and the communication protocol among modules are programmed. The transmission scheme used in the paper not only assures the transmission speed, but also improves the precision.Lastly, when the short circuit occurs out of the area of power system bus-bar protection, the instantaneous current, which is arisen by the saturation of current transformer, will make the difference bus-bar protection act. This is an important problem in the bus-bar protection. According to principle of wavelet and principle of traveling wave, the paper presents a new method to judge the fault out of protection area, without the verdict to the saturation of current transformer. The analysis of simulation results indicates that the batter characteristics of wavelet transformation make the protection equipment identify the traveling wave of current and the polarity of voltage accurately, judge the fault of out of protective region reliably without the influence of the failure type and the initial phase angle of fault. The method has the characteristics of rapid act, simplification, reliability and nicety, and turns away the difficulty of estimating the occurring time of the saturation of current transformer.The test to the new device proves that the new developed hardware platform of bus-bar protection device has the higher precision, more reliable performance, advanced technique, prominent macrocosm capability, logical system structure, better expandability and flexible configuration. It resolves the problem, which is the undesired tripping of bus-bar protection arose by the saturation of current transformer.