Capacitor bank energisations have the potential to draw high magnitude inrush currents from the grid, which in turn can lead to POC voltage disturbances. Capacitor bank energisations require special attention and modelling to ensure capacitor ratings and voltage disturbance limits are maintained.
ENA Engineering Recommendation P28 (ER P28) Issue 2 defines planning limits in terms of voltage fluctuations caused by customer connected equipment such as power transformers, large motors, shunt reactors and capacitor banks. ENA ER P28 Issue 1 1989 was replaced by ENA ER P28 Issue 2 2018. P28 Issue 2 clearly points out that voltage increases caused by capacitor bank energisations must comply with the voltage disturbance limits specified by Issue 2.
The aim of this paper is to investigate and outline these voltage disturbances at the POC. The investigations have been conducted based upon the energisation of capacitor banks connected directly to the POC. We do this by modelling various capacitor bank sizes at different fault levels in PSCAD. We then find the worst case energisation point across a cycle and use this to simulate the POC voltage increase. Finally we assess this against the P28 issue 2 envelopes to compare for compliance.
It was clear to see from the paper result that energising capacitor banks directly at the POC poses a difficult challenge for P28 compliance.
The full paper is available to download from the link below.
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Capacitor bank switching against P28 Issue 2
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