Voltage calculation
After determining short circuit power the voltage is evaluated. Let us estimate minimum loading conditions (all distribution network loads will consume 0% of their nominal power). When the solar power plant is working at full power, the voltage level at medium voltage Section 2 bus is equal to 10.503 kV (105.033%). Due to generation loss from the solar power plant, the voltage would go down to 10.502 kV (105.023%). As a result, the voltage difference is only 0.01%, therefore, the autotransformer will not change tap position.
Not only does the no-load operation mode must be determined but also the maximum loading conditions have to be evaluated (all distribution network loads will consume 100% from their nominal power). When the solar power plant is working at full power, the voltage at medium voltage Section 2 bus is equal to 10.548 kV (105.478%). Due to generation loss from the solar power plant, the voltage would go down to 10.547 kV (105.466%). As a result, the voltage difference is only 0.012%, therefore, the autotransformer will not change tap position.
In conclusion, power losses from the solar power plant’s effect on voltage levels in the distribution network are negligible.