How To Calculate 3-Phase Line-To-Ground Voltage

Three-phase systems are prevalent in many power distribution systems. This is because 3-phase systems have built in efficiencies for high power transmission systems. The word 3-phase means the system has three separate lines, spaced 120 degrees apart, where each line carries the identical voltage. This identical voltage is the line to ground voltage.

Step 1

Find the kilovolt-amperes or "KVA" rating associated with the three-phase power distribution system. This is a standard rating associated with power distribution systems. Refer to system specification and/or circuit diagram. As an example, assume it's 20 KVA

Step 2

Find the current rating, or "A", in units of amperes or amps. Refer to system specifications and/or circuit diagram. As an example, assume it's 30 amps.

Step 3

Calculate the line to ground voltage using the formula: V (line to ground) = (KVA x 1000)/(I x 1.73). Continuing with the example:

V (line to ground) = (20 x 1000)/(30 x 1.73) = 20000/51.9 = 385.4 volts.