What is the voltage across the delta winding of a transformer connected to a power system with 199 kV L-G high side voltage?

In a three-phase transformer connected in a delta configuration, the phase voltage is related to the line-to-ground (L-G) voltage on the high side. Given a line-to-ground voltage of 199 kV, it is important to first understand the relationship between line voltages and phase voltages in a delta configuration.

In a delta connection, the line voltage is equal to the phase voltage, but when converting from line-to-ground voltage to line-to-line voltage for a three-phase system, you need to consider that the line-to-line voltage is √3 times the line-to-ground voltage. The calculation is as follows:

1. Convert line-to-ground voltage to line-to-line voltage:

Line-to-Line Voltage = Line-to-Ground Voltage × √3

Line-to-Line Voltage = 199 kV × √3 ≈ 199 kV × 1.732 = 345 kV

Therefore, the voltage across the delta winding is equal to 345 kV, which is the calculated line-to-line voltage in this case. This confirms that the choice indicating 345 kV is indeed the correct and valid answer based on the electrical principles governing transformers and their configurations.