Impact of Operating Voltage Variations on Transformer Overcurrent Protection in Central Java

Adjusting the secondary side operating voltage of power distribution transformer helps minimize voltage drop and maintain quality at the distribution line's endpoint. However, this adjustment alters the transformer ratio, especially in transformers with an on-load tap changer, causing an increase in high-voltage side current that could exceed the nominal current when the medium-voltage side is fully loaded. Analyzing protection parameters, operational schemes, and historical voltage trends helps identify transformers at risk of malfunction due to voltage variations. To address this, adjusting overcurrent protection parameters on either the high-voltage or medium-voltage side is recommended. For medium-voltage adjustments, an adaptive scheme based on tap changer conditions or operating voltage can further enhance protection. This approach prevents malfunctions while ensuring reliable operation with minimal load limitations.