by Alex Apostolov, Editor-in-Chief

Fault Location

The reliable operation of the electric power grid is one of the main goals of our industry. One of the key requirements is the reduction of the duration of outages. There are many different ways that we can achieve this goal, with fault location being one of them.

Like everything else, finding the location of a fault has changed over time with the changes in technology. In the world of electromechanical and solid state relays we did not have any accurate indication about where the fault might be.
The closest we can get is based on the knowledge of which protection element operated. For example, if we have operation of the Zone 1 distance at one end of the line in substation A and Zone 2 operation from the other end of the line in substation B, we have reasons to believe that the fault is somewhere in the first 10 to 15 percent of the line from substation A. We need to send a crew to patrol the line and find where it is and what the cause is. If this is a long transmission line that is in a mountain and it is winter, it may take some time before the location of the fault is found and the problem fixed in order to put the line back in service.

With the development of microprocessor based protection technology in the last third of the last century it became possible to use the available data to estimate more accurately the location of the fault. Dedicated fault locator devices or fault location functions in hybrid (solid state and microprocessor based) devices were available on the market in the 1980s.
This function became one of the most common in digital multifunctional protection IEDs. Starting with simple single ended algorithms, the industry developed many different innovative methods to determine the location of the fault by the protection devices that detected it and sent the trip command to clear it, or to use the recorded waveforms in double or multi-ended off-line applications to more accurately estimate the location.

The combination of these methods allows utilities to dispatch immediately a crew based on the IED fault location information,  and then while the crew gets on its way to run the more accurate fault location software to send more precise information to reduce the time for finding the faulted element.

The challenges of more complex line configurations such as double and multi-circuit lines with mutual coupling or series compensated lines became the subject of research and development of universities and suppliers, all with the same goal - to improve the accuracy of the fault location calculation.
Advanced fault location technology based on the travelling wave principle is becoming more accessible and can further help utilities by giving them another tool based on a different operating principle.

Locating faults on the distribution system’s feeders represents a different group of challenges, due to the multiple single or three phase branches that might be available on the feeder. The developments of different forms of communications, distribution automation and more recently smart grid applications introduces a new range of tools that can significantly help utilities in reducing the time to find a fault and the overall duration of an outage.
Thus, understanding the methods and tools that are available today on the market to help us find the location of a fault is an important requirement for their successful application and the improvement of the efficiency of our work. That is why we focus this issue of the magazine on fault location - because knowledge will gives us the power to make a decision of what to do and take action.  

“Action is the proper fruit of knowledge.”

American proverb

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