In-Focus: dLab and proactive fault management

On the beautiful west coast of Sweden, Västra Orust’s Energitjänst distributes electricity in a highly demanding environment with the archipelago and the salty Skagerrak nearby. Västra Orust’s Energitjänst is one of the early adopters of dLab’s platform and has utilized the disturbance analysis application dAnalyzer since 2016. Below is a scenario that occurred during the summer of 2022 that describes how dLab’s analysis early detected two incipient faults on the same feeder, as well as why a proactive approach is important.

Proactive fault management is driven from a continual improvement perspective and aims to trigger on identified risks before a failure happens. By acting upon the early warnings from the dLab platform, and avoiding power outages provides several tangible benefits including:

• Increased customer satisfaction

• Reduced costs

• Increased workplace safety

“Thanks to dLab, we could act on the early signs of incipient problems, identify, and fix them before a power outage occurred for our customers. Another important aspect for us is that these early warnings give us the opportunity to be able to prioritize and plan patrolling and other actions during daytime in a controlled manner, under good conditions and with reduced stress, important issues that affect the safety of our staff,” says Per Hedlund power grid technician.

The summer months is a time with many temporary residents in the area, and thus a period of high load on the local power grid. This means that an outage on the faulty line followed by re-sectionalizing during troubleshooting may lead to consequential disturbances and extending the outage to affect additional residents.

How did Västra Orust’s Energitjänst use the dLab system

During the month of June, Västra Orust’s Energitjänstnoted an increased activity of high-ohmic earth faults via indications in dLab’s system. The disturbances that originated from a single feeder in one of the primary substations, and were of a similar nature, justified a patrol of the overhead line sections of the feeder. During the inspection, overhanging tree branches were discovered and the assessment was made that they most likely struck the overhead line due to strong winds during the relevant period. The tree branches were quickly fixed, and the disturbances disappeared.

However, it just so happened that, during the following month, there was a second wave of recurrent high-ohmic earth faults on the same feeder, this time of a slightly different nature. Over several weeks, the frequency of the disturbances increased, where the fault resistance gradually dropped from the initial 26 kΩ down to just over 10 kΩ. In dLab’s portal, Västra Orust’s Energitjänst could easily track the development.

“Repeated warnings from the same feeder and the same phase, in addition with decreasing fault resistance, usually mean that it is the same fault that gives rise to the warnings”, says Victor Bagge, power system engineer at dLab.

Since it was the same substation and feeder that was affected as in June, Västra Orust’s Energitjänst this time focused on inspecting the high-voltage cabinets and secondary substations with the help of a thermal-imaging camera. The inspection resulted in the discovery of local heat build-up in an isolator, something which would likely have led to an arc flash at a later stage if not replaced.

dLab’s upcoming Grid Health Score – another dimension

If you take a look at dLab’s upcoming function for Grid Health Scoring, you can clearly see the accelerated problem. The score indicates how the health gradually declines from the end of May to the middle of June when the first measure was implemented. After that, the health score recovers slightly until the beginning of July, when the problems due to the local heat build-up started. The dashed line is a trend curve and at the beginning of August an accelerating deterioration is obvious, which would most likely have led to a severe fault if Västra Orust’s Energitjänst had not acted so exemplary!