Overdue Maintenance

30th September 2024

EME Power Systems was recently tasked with carrying out an assessment on a single transformer site which had not been maintained for a considerable time following a change of ownership.

With the outdoor substation being heavily overgrown we first had to clear the compound to enable access and upon sight of the transformer it was evident the lack of attention it had been shown.

On discovering no oil was visible in the sight glass and numerous spots with well-established rust we were very sceptical of actual oil levels and, although there was nothing visible indicating any leaks, it was fortunate that neither the rust nor dense undergrowth had managed to penetrate the transformer at this point.

Testing for any partial discharge indicated none present. Usually at this point we would obtain an oil sample to send for analysis, with the oil analysis indicating both the condition of the oil and the internal elements of the transformer. However, not being able to verify the amount of oil in the transformer along with the visual and physical findings, we recommended that we liaise immediately with the DNO for an emergency isolation to enable a thorough intrusive inspection.

We ran through all the permutations regarding costs for various scenarios with our customer who decided that, whilst we engaged the DNO for an isolation, they would also like an oil change to be carried out. With our in-house stocks and industry experience we were able to organise this for later the same day enabling the downtime to be out of 'business working'

Once the transformer was isolated and earthed and safety documents issued we proceeded to remove the lid, finding the oil just below the sight glass which gave a little further confidence that the rust or undergrowth hadn't penetrated the unit. The transformer was drained of oil, the internal elements inspected, connections checked, and insulation resistance measurements of the cores taken. Following a sample from the existing oil being taken for analysis the transformer was thoroughly flushed through, replacing the oil with new. The insides of both the Hv and Lv air cable boxes were checked and all the rust spots were repaired and repainted. With all the necessary safety signage having been fitted the transformer and compound had received a thorough maintenance and was re-energised.

The analysis reports indicated elevated moisture levels, reducing di-electric strength and so proved that the decision to change the oil had been beneficial. The reports also indicated <2ppm of PCB so we returned to site to remove the oil and issue a waste transfer note.

General Manager Steve Myson commented:

PPM helps to both preserve an asset's condition, extending its lifespan, and to prevent faults from occurring that would result in costly and inconvenient power outages. When considering costs from unexpected failures of such valuable assets, along with various legislative requirements stating that a system must be in place to look after such assets, an EME Power Systems maintenance package certainly outweighs these costs and gives peace of mind that compliance is observed.

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