Line Fault Indicator Is How To Detect?
Detection principle of single-phase earth fault indicator is still in use of single-phase grounding line selection in small current grounding system principle, the detection principle of single-phase grounding fault include the following categories:
1.5 harmonic law. On line 5 of the current harmonic sampling, when the 5 harmonic mutations increases, and an abrupt voltage drop, then what happens to Earth.
2. the current mutation method. The method is based on single-phase grounding fault occurred in phase voltage close maximum value moments this a assumed, in occurred single phase to of moments, line on to capacitor in short time within discharge, while due to line resistance and distribution inductance of exists, in line Shang formed a larger of attenuation oscillation current, fault indicator detection to the current Hou, while detection to on to voltage declined, is judge for grounding.
3. first-half wave method. Sample grounding capacitive current of the moment the first half wave with the first half-wave voltage at impact, comparing the phase when the grounding capacitive current mutations of the moment of sampling and greater than a certain value, and ground instantaneous voltage half wave phase, and wire for voltage drop, judge circuit grounding.
4. method of zero-sequence current. When the zero-sequence current value exceeds the set value judgments as earth fault.
Above all is the passive detection, is dependent on the single-phase grounding fault of distribution parameters before and after the change.