Study And Development Of Digital Busbar Protection Device

With continuous enlargement of the scale of power network, the damage of bus-bar fault to electrical equipment and steady operation of power network is increasingly severe. The requirement of power system to bus-bar protection becomes stricter and stricter. It is of great significance to develop a set of new style digital bus-bar protection device based on high performance hardware platform.Firstly, the paper analysis several digital bus-bar protection which serving now, and on the basis of that,a set of new protection scheme is presented. According to characters of all kinds of bus-bar protection principles, the paper selects the best one which can be applied to this device, that is current difference protection principle which relies mainly on ratio difference component.And then, Traditional digital busbar protection device, which is widely used in the power networks, is based on the introduced auxiliary contacts of switch for realization of busbar protection adaptive to operation. Though it is direct and efficient, this method still has many limitations. In order to enhance reliability, this paper presents a new realization scheme. The scheme using current instantaneous value to detect the branch circuit which is serving, and the branch circuit permuted and combinated with recursion algorithm till the difference of each busbar balances. Then, the balance of the current difference is continuously verified. The scheme can reduce dependence of busbar protection device on auxiliary contacts of switch and increase the reliability of operation.Further more, on the base of new hardware platform,several algorithms for filter the waves that adapt to bus-bar protection are carried out to experiment in this paper, take precision, response speed and amount of calculation into account ,and with reference to comparison result of performance, the best scheme of algorithm isdetermined.At last, software of CPU and HOST is designed in this paper, and interrupt service programme and the failure calculation programme are also presented in the paper. In addition, the mode of communication between CPU and HOST is also introduced.The new style digital bus-bar protection device that designed in this paper is applicable to all kinds of voltage step and connection mode of bus-bar in our country. Some resolutions are presented for several problems such as sensitivity reliability and rapidity which exist in bus-bar protection, and they are practical and efficient. In a word, it's a set of device which possess of good performance.