We have different schemes for the compensation of fault resistance because it affects performance of conventional ground and phase distance relays.
But which are the cases in which the high resistance faults occur? And how many percentages of these faults occur as compared to dead short circuit faults (means the faults with negligible fault resistance or fault impedance)?
Could be L-G(arc ing ground, as 3ph. 3wire), yet using all three available voltage and current, find the +,- & zero seq. voltage, current and impedance offered, would gave you the answer, could refer my paper Microprocessor based load balance control and fault type detection using symmetrical components...
L-G fault happens when conductor is broken and falls on dry wood or wood fence.
The most commonly happened fault is single line to ground fault that may occurred due to breaking conductors or damaging the structure. Line to line fault is happened for example in case that two wires are touched because of wind or some crashes etc.
One of the most popular earth-fault for overhead lines is flashover of polluted insulators and the beginning of rain fall.
Thera are several cases for high resistance faults in transmission network. High resistance faults always happened only for phase to ground. In my professional praxis I do not have made any analyses for high resistance fault between phases (phase to phase). We can have broken conductor, which fall on tree, and those cases are usually high resistance fault. In addition, you can have faults that some tree fall on lines. It is the same case. We can have faults on specific ground and when the resistance of transmission lines grounding is are not so good. Those cases can be very dry soil; it can be gravel or pebble (small stones) in ground. Also when you have lines across the area where are the ground from only from rock. You can have high resistance faults when some tracks or another special vehicle “touch” the line phase wire. Those cases can be very dangerous for people inside the truck and this fault are also very challenge for line protection. In most cases those faults can be effectively remove only with directional earth faults current protection or with line differential protection and distance protection are not so efficient. In general, those kind of faults are very rear. In my opinion, only few percentages but you must remove them effectively in very short period of time.
About high resistant fault.
This kind of fault is very difficult to measure for distance protection relay. The fault resistance is the source of the problem and in other hand, the fault current is not very high. Physically, it can be an intermittent tree branch touch, partial arcs on insulators and bushing,...
The second dangerous fault type is the evolution from 1 phase-earth fault to 2 or 3 earth fault. This kind of faults are very difficult to predict because they occurs on fault transient state.
The most dominant type of short-circuit (SC) faults is the LG fault (60% to 70%) of all fault types. In addition, the high resistance faults are also LG SC faults. Please note that it is popular for LG faults to transform to other SC faults (such as LLLG) faults during the fault stages.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Condensed Matter Physics
- Soft Matter
- Liquids