A severe electrical fault in a multi-phase or split-phase system where the neutral conductor breaks or disconnects. Without the neutral to balance the return currents, the system voltage floats. Loads on the less heavily loaded phase experience severe overvoltage, while loads on the heavier phase see undervoltage. This condition rapidly destroys sensitive electronics, blows lamps, and poses a severe fire risk.
We've a lost neutral at the pole, the customer is seeing 300 volts on their lighting circuits and blowing appliances.
A classic sign of a lost neutral in a residential split-phase system is lights getting brighter in one room when a heavy appliance turns on in another.
Also heard as
- broken neutral
- open neutral
- floating neutral
Related terms
Neutral conductor
The wire in an alternating current system that provides the return path for load current.
Single-phasing
A destructive fault condition where a three-phase motor loses one of its supply phases.
Overvoltage category
Class from I to IV ranking equipment by its position in an installation and the surges it must survive.