Power Network Disturbances

Throughout my time in the power transmission and distribution industry I have probably had experiences that many others may never have. In a previous post, I talked about the current and voltage unbalances and how a large factory in the Western Cape in South Africa was severely affected by negative phase sequencing. In this post I want to touch on another incident we have had around that same time.
Without being directly involved, I learnt about a 500kW electric water-pump motor that was ripped out of its foundation, breaking the water pump, and causing major havoc in the pump station leaving a large urban area without water.

The question that should be asked: are those responsible for looking after the factory or mine aware of the influences of voltage / current harmonics and phase unbalances among several other similar negative effect on their plant? Most probably not since many think that if the lights are burning, everything is hunky-dory, and they should not worry about anything. Fact is, it is not and it is worthwhile to read the other blogs.

If you think that this only applies to South Africa, think again. It is happening in Ireland and the USA or wherever you are from: those reading my blogs.

A second topic I want to discuss is how something unexplained is later contributed to something someone think is “fact”. Many years ago, the loss of power transformers connected to overhead power lines were all contributed to lightning damage. When I worked at Eskom Western Cape in the eighties, I used to receive a daily incident report for the entire region. One day, I noticed that twelve 22kV/380V transformers were lost due to lightning in the Calvinia and Williston areas. I would not except what was stated in the reports and instructed the depot to dispatch all those transformers back to the main workshop in Brackenfell. I also instructed the head of the transformer workshop to cut those transformers open as soon as they arrived and let me when it is done. After the top lid of the transformers were cut open, we found that the core of the transformers was “standing” in water that penetrated over time. We would have spent vast amounts of money on additional lightning protection for something that had nothing to do with lightning.

Then, a few years later, I asked one of my subordinates why there was such a large maintenance backlog. His explanation was that the maintenance crews are not maintaining the 22kV/380V transformers. I immediately instructed him and the person reporting to me to remove all those transformers from the maintenance schedule. I then had to explain that one of the maintenance strategies that should be employed is run-to-failure. It cost less to replace those transformers than to maintain them on a regular basis. Obviously, the cost includes all the associated costs.

Now, I am an independent consultant and working for myself, I can do these types of investigations. That means proper Power Quality Investigations and many more similar types of analytical work.