This study aims to quantify the transformer tap changer operations on distribution networks with large penetration of photovoltaic systems. The influence of solar generation variability on transformer tap changer is investigated by using five different solar variability day types collected in Malaysia with 1 min resolution. The case studies have been performed on a Malaysian representative distribution network. Results show that high solar variability day could increase the transformer's tap changes by 600% as compared to the clear sky day. The transformer's time delay setting plays a vital role in limiting the tap operations.

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The introduction of Feed-in Tariff (FiT) scheme has prompted an increasing number of grid-connected Photovoltaic (PV) systems installations in Malaysia. As a consequence, the network issues related to the PV systems integration need to be properly addressed. This includes the effect of solar irradiance intermittency which is caused by the passing-clouds. In this regard, this paper investigates the effect of passing-cloud on a standard IEEE 4 node test feeder, focusing on short term voltage drop analysis. Actual five-minute interval PV generation data in Melaka, Malaysia was used in the analysis. The network was analyzed by using the well-knownOpenDSStool. The network voltage impact of different PV penetration levels were investigated on both sunny and cloudy days. The results show that temporal voltage drop could occur on the network when there is a sudden drop of PV generation driven by passing-cloud. The percentage of voltage drop recorded was observed to be proportionate to the increment of PV penetration levels.