Voltage between the neutral and ground connection can be as a result of various things within a power system, and thus knowledge of these causes is very essential for safe and efficient operation.
Why Neutral to Ground Voltage is Occurring?
Improper Bonding
The neutral and ground should only be connected once in the entire electrical installation which is at the main service panel.
Further, if there are more than one bond in sub-panels, this tends to give rise to the voltage difference between neutral and ground.
Voltage Drop
When current is passing through the neutral conductor, the voltage drops because of the resistance in the conductor.
These drops can lead to a variably measurable voltage between the neutral and ground, specifically in conditions with load.
Faulty Equipment
Equipment including surge protectors may develop a fault and put voltage to the ground.
If any of these devices are not functioning properly, then they can generate undesired voltages.
Poor Earthing
Some of the ground faults like loosened connections and corrosion may result to improper earthing and hence the potential difference between the neutral and ground.
Unbalanced Loads
In three-phase systems it is possible to have excessive neutral currents because of unbalanced loads, and then higher neutral to ground voltages will be respectively.
This is very much the case especially in the industrial setting.
Cable Insulation Damage
This can be caused by failure in the insulation of cables, which may also cause leakage currents to be present in the wiring system as well as different voltage levels for neutral and ground.
Acceptable Voltage Levels
Basically the voltage between neutral point and zero reference should ideally be zero. Still, in practical applications, voltages up to 1 volt as the maximum are indicated as allowable.
Values above this range suggest that there could be a severe problem that a professional electrician needs to address immediately.
In case, you obtain a reading that indicates a voltage level between neutral and ground, then it is wise to look for the root cause.
This may include improper bonding check, observation of grounding system status, checking of loads balance and etc. Fixing these problems as soon as possible will help to avoid possible threats, which can arise in operation of the equipment.
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