Source: http://electrical101.com/open-neutral.html
Timestamp: 2019-04-18 18:45:11+00:00

Document:
In an electrical system, ground and neutral are connected together in one location only, at the neutral point. This connection is either at the power company transformer or in the main electrical panel of the dwelling (see Electrical Circuits).
The voltage on a neutral wire is normally 0 volts (V) on a live circuit. However, if a neutral wire is open, the voltage on the line side of this open neutral is 120 V.
Sometimes electricians forget about this while working on a live circuit and get a shock from an open neutral wire.
In the diagram above, the neutral is opened. The neutral wire on the left side of the open (comes from the panel) is 0 V. The wire on the right side of the open (goes to the load) is 120 V.
In the diagram above, the A phase circuit breaker is turned off. The neutral wire on the left side of the open (comes from the panel) is 0 V. The wire on the right side of the open (goes to the load) is 120 V.
Even though the A phase circuit breaker is turned off, there is still 120 V on the load side of the open because the B phase circuit breaker is turned on.
If both circuit breakers are closed in the right side diagram, there would be 240 V present at the open neutral instead of 120 V.
See Multi-Wire Branch Circuits for more information.
In the diagram above, the A phase and B phase circuit breakers are turned off. The neutral wire on the left side of the open (goes to the panel) is 0 V. The wire on the right side of the open (goes to the load) is also 0 V.
Since the A and B phase circuit breakers are turned off, there is now 0 V on the load side of the open.
See Multi-Wire Branch Circuits and Open Neutral Multi-Wire Circuit for more information.
* 0 V or a very low voltage.
In the diagram above, the A phase and B phase circuit breakers are turned on. The neutral wire on the left side of the open (goes to the panel) is 0 V. The wire on the right side of the open (goes to the load) is also 0 V or a very low voltage.

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