Electricity substations contain complex protection systems designed to detect problems and prevent equipment damage or power outages.
But some electrical faults can develop quietly, making them difficult to identify before they become serious.
Researchers have now developed a diagnostic method that could help substations spot hidden insulation problems much earlier.
The approach combines three different electrical signals to provide a clearer picture of what is happening inside relay-protection circuits.
The research, published in the International Journal of Energy Technology and Policy, focuses on insulation faults.
Electrical insulation is essential for keeping current flowing along its intended path.
As insulation deteriorates, however, small amounts of current may begin flowing where they should not. If the problem goes unnoticed, it can eventually interfere with protection equipment or contribute to larger electrical failures.
Instead of relying on a single measurement, the new system examines three signals at the same time.
The first is known as zero-sequence current, which can indicate that electricity is flowing along an unintended path. The second measures waveform similarity, comparing current patterns recorded by the system with patterns expected during normal operation. The third examines third-harmonic content, a particular component of an electrical waveform that can provide clues about abnormal or nonlinear grounding conditions.
By combining these three pieces of information, the researchers found that their system could identify faults with high accuracy.
In testing, the method detected 98.6% of insulation faults. It was also 94.3% accurate in identifying the locations of multiple grounding points. Importantly for power systems, the diagnosis was fast, taking less than 45 milliseconds on average. During normal operation, the false-positive rate was 1.5%.
The system could also recognize early insulation deterioration when electrical resistance dropped to between 50 and 100 kilohms. This could give maintenance teams an opportunity to investigate and repair deteriorating equipment before the problem develops into a more serious failure.
The researchers also tested the technology for six months at a 500-kilovolt substation in Nanjing, China. The pilot system was connected with inspection robots, allowing information about potential problems to be communicated rapidly between devices.
The results suggest that the technology could have practical benefits beyond simply detecting faults. During the pilot, average fault-resolution time fell from more than four hours to just over one hour. The need for manual inspections was also reduced by 76%.
For electricity networks containing large amounts of equipment that must operate reliably around the clock, finding small problems before they become major ones can make a significant difference. By combining several electrical clues rather than waiting for an obvious failure, the new approach could help substations move toward faster, more automated and preventive maintenance.
