Yes, Neutral to Earth Voltage is also called common mode voltage. Sources for common mode voltages in power line systems vary and they can occur at power line frequency and at higher frequencies (with switch mode power supplies and the nonlinear electronic loads of today's equipment. The 50/60 HZ part is the simple one occurring due to voltage drop of 50/60Hz current in the neutral conductor. The in-ballance in 3 -phase loads increases this as the neutral is usually downsized because one neutral is commonly used for the 3-phases and ideally this current is 0 (for balanced loads) because phase currents cancel each others. But with balancing disturbed more currents flow causing the drop especially that this neutral is downsized. Other sources at high frequency are the common mode voltages due to switching electronics and induced noise from external sources. Thanks. @AlDmour.

lot off different is there with we are going to increasing voltage level

Neutral wire carries the current back to the transformer neutral point that is grounded at the supplying transformer secondary side, Hence, a voltage drop on the neutral wire exists. This means that the voltage at the neutral point at the customer premises shall be at a higher voltage than the neutral point at the transformer which is usually earthed. Therefore the voltage at the neutral point of user premise is higher than the earthed neutral at the transformer. The earth point at the user's premises is usually just a point connected to earth rode with no current flowing in. Ideally it is at 0 V. Again neutral point at user's premises shall be higher in voltage than this one as well. I would advise you to measure the voltage between the Neutral and Earth of the socket outlet (take care) and you will find some voltage difference that depends on the wire gauges used, how far you are away from the transformer, and the load current. You may also remember at times when you found that the tester bulb lights up in both L and N (Neutral) indicating a voltage higher than ground.

Of course, above situation is only under normal conditions whereby no current is flowing into it to ground. Under abnormal condition, e.g. a live wire touches the grounded chassis of your equipment a large current flows into ground and depending on how good earthing you have (deeper into earth and humid soil to give low earth resistance). This large current causes the voltage to rise up on the earth point typically higher than the neutral and possibly dangerous. Electric codes ensures that this voltage rise shall not exceed certain value and some breaker breaks the current supply to protect against live chassis. Hope this helps. Thanks.@AlDmour.

thanks all,

Practically i connect a LED in between neutral and earth wire then it glows with out a live wire so it indicates both will have some voltage difference another result we find the continuity or proper earthing in our system.It also signifies that we can check the neutral or earth is proper working or not.

This is not an approved method for checking proper working of the neutral or earth conductor . If you want to check your installation you have to use proper instruments, like this: http://www.sonel.pl/en/katalog-produktow/electrical-safety-measurements/mpi-525.html

According to my point of it is called the common mode voltage it exist between the neutral and ground. This is due to current available in the neutral point due to the unbalanced load condition. The current will find a path to flow through whenever it is connecting with ground potential with LED automatically light will glow

Dear Raghu,

i am not indicating the unbalance condition. in this case no live wire (Phase) in the system.

Yes, Neutral to Earth Voltage is also called common mode voltage. Sources for common mode voltages in power line systems vary and they can occur at power line frequency and at higher frequencies (with switch mode power supplies and the nonlinear electronic loads of today's equipment. The 50/60 HZ part is the simple one occurring due to voltage drop of 50/60Hz current in the neutral conductor. The in-ballance in 3 -phase loads increases this as the neutral is usually downsized because one neutral is commonly used for the 3-phases and ideally this current is 0 (for balanced loads) because phase currents cancel each others. But with balancing disturbed more currents flow causing the drop especially that this neutral is downsized. Other sources at high frequency are the common mode voltages due to switching electronics and induced noise from external sources. Thanks. @AlDmour.

If the Three Phase System is Balanced,then the Potential of the Neutral will be Zero Volts.Generally the system will be Unbalanced and hence there will be a small Potential Difference between the Neutral and Earth Points even if the earthing in the consumer premises is provided.This Potential Difference can be measured with a Digital Multimeter.

In the case of Computer Centers this difference has to be less than one Volt for the systems to work well..This can be achieved by having a number of earth pits located at intervals and running copper earth strips.

Earth Leakage Relay is used to protect a person coming in contact with a Live Terminal.

P.S.

The neutral wire is typically tied to earth ground near the fuse box at the line entry (e.g., in buildings). Ideally, there would be no voltage difference because ideally the wires connecting them would have zero resistance. In reality, the wires have a low resistance and therefore there can be a voltage difference between the neutral and earth ground, especially with longer wires. Current (I) is flowing through the neutral wires and there is resistance (R) in the wire, and thus there is voltage (V = IR)

Question is replied in two answer of mine, yet I will clear "in balance load condition neutral point(starpoint) atzero potential as ground point" no current will flow from neutral to ground. If neutral point is isolated from ground and load is unbalance neutral point consider as floating neutral and the havely load phase voltage will reduce and lightly load phase voltage will rise which will damage the appliances.

Yes definitely

Most if not all distribution transformers are delta / star. It is common practise to earth the star point of the secondary winding as well as form the connection point for the neutral wire.

As others above have indicated in ideal conditions and under perfect balanced loads no current will flow in either the earth or neutral wire and no voltage will or can therefore exist.

However in practise the loads are almost never balanced and thus a neutral current is mostly found to exist and hence a neutral and earth voltage; if the neutral is removed to do this. This is made worse as most loads (say households or businesses) also use a local earth at the residence or business. This causes a loop to exist between the earth point at the distribution transformer and the local earth point at the residence or business and the same will apply for each residence or business supplied by the distribution transformer leading to multiple earth point returns and loops.

Hence it is highly likely that a voltage (generally small) will always exist between earth and neutral and sufficient to light up an LED . Most earth leakage systems only require 20 mA to operate so an LED should be no problem.

In South Africa we commonly have cable theft in which the earth wire at the substation is removed as well as the neutral connection from the transformer star point. This leaves the system with no neutral or earth point such that it causes all 240V equipment to be damaged as without the earth point and neutral at the transformer 400V is applied to the appliances and equipment, as Bhupendra highlights, causing it to become damaged despite the local earths and neutrals remaining connected.