Short Circuit And Earth Fault Indicator Safety Protection Measures
For small current grounding system, how to quickly find single-phase ground fault, I give you some simple and feasible way.
1, manual search method
If there is no installation in the substation grounding line device, the line is not installed grounding Short Circuit And Earth Fault Indicator or short-circuit ground two-in-one Short Circuit And Earth Fault Indicator, there is no good ground fault detector, it had to use artificial search Benban method. Look for the following steps:
(1) by manual (or scheduling, the same below) in turn open, you can know which substation substation ground, through the scheduling that know which ground.
(2) Then there are two ways to find the point of failure: First, the line step by step, or often the failure of the line opened, with 2.5kV shaking table measured ground insulation, insulation resistance of the small For the fault section, in order to narrow the scope of the search (of course, in the substation outlet side must be done to mount the ground and other security measures); Second, the line as much as possible segment, and then step-by-step power transmission, and scheduling interaction , There is zero sequence voltage alarm when the section for the fault section.
Manual search method operation is very troublesome, if the line is long, more branches, switch segment and less, it is not good operation, coupled with the weather and bad weather, it is more difficult to deal with the. It is recommended to use some of the equipment to invest less scientific and technological means to meet the manual search, can achieve a multiplier effect, both to provide power supply reliability and social benefits, but also to create economic benefits.
2, the use of ground line selection device and Short Circuit And Earth Fault Indicator to find
Substation stations are generally equipped with a grounding line selection device, although sometimes not allowed, but can provide technical reference for manual discharge. And then install some ground Short Circuit And Earth Fault Indicator (or short-circuit ground two-in-one Short Circuit And Earth Fault Indicator) on the line to indicate the ground fault path. At present, the more reliable ground fault detection method is to use the signal source method, the more sensitive ground fault detection method is the first half wave method or DC transient analysis method. It is suggested to use two kinds of grounding Short Circuit And Earth Fault Indicator to find the ground fault is better, mainly to the source method, supplemented by the first half wave method or DC transient analysis method.
3, the use of feeder automation methods to find
If the user is rich, it is recommended to use the feeder automation method to find the ground fault. This method replaces the traditional manual search method with the logic function of intelligent switch (electric load switch, splitter, circuit breaker, recloser + FTU), and can automatically realize fault isolation, recovery and transfer power supply. Assuming a dual power hand-hand line is divided into six sections, that is, there are five intelligent switches (bilateral with three-phase five-column signal PT or capacitive PT), the middle of that station to do contact, and to ground fault point in the first and The second smart switch between the example, the specific steps are as follows:
(1) substation will be ground outlet power outage, the line on the sub-intelligent switch automatically open.
(2) substation closing power transmission, power station zero sequence voltage does not alarm, the section to resume power transmission success; the first intelligent switch FTU detected line voltage, but did not detect the zero sequence voltage, the delay after a period of time automatically Closing, due to the ground fault to detect the zero sequence voltage, then immediately open and "lock"; the second intelligent switch also detects the zero sequence voltage, the switch does not move and "lock" to cancel the " Automatic closing "function.