380V voltage relative to zero and ground
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Why does 380V electricity read 220V when measured against the neutral wire, and 380V when measured against the ground wire?
Under normal circumstances, it shouldn’t be like that; normally, the line voltage should be 220V with respect to both the neutral and ground. Is the ground wire connected incorrectly?
This post was last edited by cmjzy on 2016-6-12 at 22:18. The three-phase live wires are L1, L2, and L3; the neutral wire is also known as the center wire, denoted as N. The protective ground wire is PE. Under normal conditions, the line voltage (between live wires) L1-L2, L2-L3, L3-L1 is 380V, while the phase voltage (between a live wire and the neutral wire) L1-N, L2-N, L3-N is 220V. In China, a system with the center wire grounded is commonly used; therefore, if the voltage between a live wire and the ground is measured, it will also be 220V, which is the phase voltage. However, if the center wire becomes disconnected from the ground for some reason, the voltage between a live wire and the neutral wire at the consumer end becomes uncertain, and it depends on the size of the three-phase load – it could be over 300V or around 100V. This is why in older power distribution systems, when the neutral wire of the transformer was broken, some devices would suffer from overvoltage and get damaged, while others would not.
Transformer outputs are available in three-phase four-wire and three-phase five-wire configurations. The three-phase four-wire system involves grounding the neutral point, with the neutral wire being the output; such a system requires multiple repeated groundings. When the three phases are unbalanced, the voltage on the neutral wire experiences drift. Three-phase five-wire system with an ungrounded neutral point. The situation described by the poster is likely due to incorrect wiring
It’s obvious that there’s a problem with the wiring; the ground wire has been connected to the phase wire, which is why there is 380V between the phase and ground wires. It can also be determined that the ground wire is not connected to the external ground system – it’s disconnected
Neutral point drift, or phase line to ground