Short Circuit And Earth Fault Indicator Used To Detect Power Systems
Short circuit and ground fault indicator is used to detect the power system short circuit and ground fault device, run on the branch of the feeder, if a short circuit or ground fault occurs, the device through the four letter equipment to send the information back to the main station, Alarm information, so that duty officers immediately notify the relevant maintenance personnel arrived at the scene. The master station will be real-time to obtain the data from the station, and to determine whether there is an exception, so that we can achieve real-time monitoring effect.
Fault indicator mainly refers to the cable line fault indicator, generally have three phase sensors (respectively installed in the A, B, C phase), a zero sequence sensor (wrapped in three-phase cable) and a host (also known as the display unit ). When the distribution network short circuit failure occurs, the power side to the point of failure of the indicators are fault alarm, and the fault point after the indicator does not alarm,Short Circuit And Earth Fault Indicator which can determine the location of the fault point interval to help people find the point of failure. According to the basis of fault diagnosis, the fault indicator can be divided into two kinds: fault indicator with overcurrent principle and fault indicator with current mutation principle. As for the use of other principles such as the first half of the wave method, the fifth harmonic method, injection method, fault current direction method to determine the basis of the fault indicator, due to the existence of a variety of problems, the application of less.
1. Fault indicator with overcurrent principle
Line short circuit and ground fault, the fault current in the line will increase, when the current increases more than a certain set value, the use of over-current fault indicator will alarm display. Such indicators need to set a short circuit and ground fault alarm threshold in advance,Short Circuit And Earth Fault Indicator short circuit in general 400A-1200A, ground generally in the 5-60A, adjustable range. At present, the use of this principle indicators of the mainstream market position, such as Germany EMG, HHH, the British NORTECH and some domestic manufacturers of products.
2. Fault indicator with current mutation principle
When the line short circuit and ground fault, the line will occur more significant instantaneous current changes, when the protection device action trip, the line steady current current will be zero. Detection of the current value of this mutation, but also to determine the short circuit and ground fault. Because this type of indicator does not need to set the alarm threshold in advance,Short Circuit And Earth Fault Indicator its scope of application is more extensive. But because of the need for real-time monitoring of line current, product power consumption, shorter service life. There are currently Schneider FLAIR series and some domestic manufacturers of products using such principles.