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What happens at solar power plants (SPP)?

Beontop company has been producing instrument voltage transformers (VT) for eight years. Currently, about 10 thousand transformers of our production are in operation. From time to time, we receive messages about the failure of the VT. Each such case is recorded and analyzed in detail. The results of the analysis turned out to be quite interesting.

We divide all cases into two different groups.

  1. Failures during the commissioning of facilities. Such cases are predictable and the reason is very simple, in most cases it is installation errors. The consumer can avoid such failures by fulfilling the requirements of the operational documentation for the VT and the requirements of the electrical installation rules.
  2. Failures during operation. It is quite difficult to identify the causes of such failures and it is not always possible to determine them unambiguously.

But the purpose of this article is somewhat different. If we trace at which objects the cases of failure of the second group of VT take place, we can identify a rather strange pattern. Up to 65% of failure cases occur at solar power plants (SPP), despite the fact that the percentage of VTs operated at SPP does not exceed 5-10% of the total. Numerous attempts to determine the reasons when communicating with SPP workers did not lead to any unambiguous conclusions.

From a technical point of view, it is obvious that the probable cause of most VT failures at SPP is a significant excess of the rated voltage on the VT. For the failure of grounded VTs, which, according to the current standard DSTU EN 61869-3, have a voltage excess factor Fv = 1.9 (8 hours), the rated voltage on the VT must be exceeded by more than 2 times, which most likely happens at SPP. Such an assumption is quite realistic, given the fact that only a solar power plant uses a large number of inverters to convert energy and transfer it to the grid.

We are concerned about this situation with our products at SPP, but we have no way to influence it. Therefore, we offer a real way to improve the reliability of the measuring VT at SPP, which we can implement. For operation in solar power plants, it is necessary to use a voltage transformer with an overvoltage factor Fv significantly higher than according to the requirements of the standard, for example, increase the Fv value from 1.9 to 2.5. Beontop has the ability to manufacture measuring VTs with Fv=2.5 and offer them for supply to solar power plants.

We will be very grateful to everyone for any comments regarding the problem of VTs failures at SPP, for expressing opinions on possible causes and ways to solve the problem. Comments can be sent to e-mail emc@beontop.com.ua

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