Views:171 Author:Site Editor Publish Time: 2021-06-24 Origin:Site
The development history of accurate electric wire fault indicators can be divided into two stages. The first-generation product is the short circuit fault indicator designed before the 1990s and the second-generation product is based on the current mutation method in the 1990s. Although the earthing and short-circuiting device has appeared in recent years, the detection technology of these products is still the second-generation design technology.
The short-circuit fault detection principle of the second-generation automated electric wire fault indicator breaks through the limitation of the over-current method to a certain extent. The core of this principle is to judge the current sudden change in the transmission and distribution lines as the line short-circuit fault, which is a constant or a constant in a certain range. This short-circuit fault detection method solves the limitation of false alarm and leakage alarm of the first-generation products, but it is not completely solved. Different lines with different structures, different geographical environments, and even different operation times will lead to a different sudden change of short-circuit fault current. Therefore, it is obvious that there are limitations to take a constant current sudden change as the basis for short-circuit fault diagnosis and it is inevitable to misjudge or miss judgment.
On the other hand, because the current value or current mutation increment value needs to be set separately according to different lines or different positions of the same line, the second-generation reliable electric wire fault indicators are not easy to scale production. Now the common way is to determine an empirical value or to produce according to the special requirements of customers, which will seriously affect the reliability of fault detection.
The so-called two in one digital electric wire fault indicator is based on the second generation of short-circuit fault indicator, which means that it has the function of short circuit and earth fault detection at the same time.
As the fault detection technology of the first-generation and the second-generation of accurate overhead line fault indicator cannot adapt to the development trend of the power grid, a new generation of fault indicator which is not affected by line structure, management mode, geographical environment, load change, and operation time has become the urgent demand of the majority of power consumers. It is the third-generation advanced electric wire fault indicator ——intelligent fault indicator.
In the aspect of short-circuit fault detection, the intelligent fault indicator introduces the principle of microcomputer protection into the design technology and uses the method of detecting the sudden change value of current variation ratio If / I0 (the ratio of fault current to load current) to detect the short-circuit fault. This variable ratio mutation value is adjusted automatically and dynamically according to the curve algorithm and the load current built in the automated overhead line fault indicator. Therefore, the third-generation digital overhead line fault indicator fundamentally overcomes the defects of the design principle based on the over-current method or the current sudden change method and makes the short-circuit fault detection accurate and reliable.