The Research Of SoftWare Arithmetic In The Single Line-to-earth Fault Location Of Non-direct-grounded System

The choosing of the type of the ground of power system is a question of technology and economy. It depends on many factors.In our country, middle and low voltage distribute net system uses non-direct-grounded system including no-grounded system and anti-arc system. Because the fault current is very small, the fault defection is difficult.This paper researches the non-direct-grounded system fault detection from software arithmetic view, whose main content is as follows:The paper analyses the system running characters before and after fault. And the paper analyses the fault transient signal and fault steady signal and all parts in fault steady signal after the single line-to-earth fault occurs, and discovers the fault laws and appearance of fault signal. The analyzing of the fault laws and fault phenomenon of non-direct-grounded system all above is the base of analyzing arithmetic.On the base of mastery of fault laws and fault phenomenon, all arithmetic is sorted from the view of using what fault signal, and compared. The signal source of all arithmetic and the area of every arithmetic applying are compared, so the capability of arithmetic is evaluated, which is the basing of choosing the arithmetic.After the comparing of all arithmetic, the paper points out the now all arithmetic is limited when the system is anti-arc system, which makes it difficult for fault to defect. For this reason, the paper gives two new arithmetic, current break arithmetic and net arithmetic, which solve the problem of fault detection in anti-arc system effectively. The current break arithmetic and net arithmetic use fault steady signal as defection gist which is steady and easily identified, and the two arithmetic inherits the excellence of the tradition breadth comparing and phase comparing, which overcomes the effect of the changing of the system parameters which brings the difficult for fault defection.The two pointed out arithmetic are tested in 1:1 high voltage physics simulation lab. The test indicates that the two arithmetic is fit to anti-arcsystem, whose fit is strong and fault defection is good.