Extremely Accurate Fault Detection

How does the world's most accurate fault indicator work in practice? Can it really help detect overcurrent and earth faults faster, more efficiently, and more economically?

Overcurrent detection is a common way to locate faults in medium voltage electricity distribution networks. A new addition to the Ensto family, Ensto Protrol, has tackled the problem of earth fault detection, which has so far been a challenge, and launched its fault indicator, which detects earth faults only by measuring phase currents. The device has a patented, highly accurate algorithm.

Testing proves it

The electricity distribution company KSS Verkko Oy was the first company in Finland to pilot Ensto Protrol's fault indicator, which detects overcurrent and earth faults of overhead line and underground cable networks with unprecedented accuracy and correctness. The product has already been tested in Sweden, but now it was time to test it also in Finland. The earth fault tests ordered by KSS Verkko were carried out with LOFA current sensors intended for overhead lines and they were carried out by Jesse Lehtonen from the electricity distribution service company, Maviko Oy.

Delightful results

Harri Tuononen, Sales Manager of Ensto's network automation products, says, "Finland's first Protrol fault indicator was installed at KSS Verkko's Kouvola site. The goal of the earth fault tests was to be able to prove that the device really works as promised."

The sensitivity of the device to detect an earth fault was tested with several resistors simulating faults of different sizes. The indicator measured up to 0.6A fault current accurately and Protrol's algorithm also correctly deduced the direction of the failure. The indicator detected a fault of 16,000 ohms in the network, which is even more accurate than the faults detected at the substation.

"The test results were in line with expectations and very promising,” says Tuononen. “They proved that the device may well be the most accurate on the market! We left the settings of the fault indicator such that they are close in time and current to the settings of the substation protection. In this way, the current sensor only indicates those faults that are detected at the substation."

Shorter interruptions expected

Kai Kuvaja, Technical Service Director at KSS Verkko Oy, thanks Ensto’s Tuononen for introducing a new kind of fault indicator and confirms the good news: "The test results were impressive, and it is great to have new good products on the market! The more information we get from the field, the faster faults can be repaired, and the supply interruptions experienced by customers become even shorter. This will be emphasized when there are more fault sensors in the network than at present."

Kuvaja says that he was immediately excited when Tuononen described the accuracy of the new product in detecting earth faults. "We visited Ensto to familiarize ourselves with the device in more detail and, after the visit, decided to pilot the fault indicator in Finland. Now we know that it really delivers on all promises. The great thing is that fault locating in Ensto's product is clearly more accurate than with other products we have tested. This gives us immediate access to the right area to fix the fault, which naturally shortens the duration of the distribution outage."

Continuation of cooperation

The fault indicator cooperation between Ensto and KSS Verkko Oy will continue, and the products are planned to be installed elsewhere in the overhead line network. According to Kuvaja, the long-term cooperation between the companies is strongly linked to trust capital: when there is trust, it is easier to try new solutions. An effective fault indicator is planned to be installed in the underground cable network in late summer, this time to a secondary substation in a new construction. There, Protrol’s solution is used not only for fault indication but also to control motor-controlled disconnectors.

Suitable for Finland and other markets

Distribution system owners have a constant need to detect faults causing distribution outages and restore the power as quickly and efficiently as possible. The extremely accurate fault indicator brings much-needed efficiency, speed and cost-effectiveness, and the best part of course, satisfied customers – electricity users. Ensto Protrol's products are well known in the Swedish market for 20 years already and are now increasingly attracting international interest.

Read more about fault passage indicators