Circulating Current.

Perhaps you mean alternating current. All electricity is circulating other than static. Alternating current goes back and forth 60 times per second in North Amentrica, 50 times in Europe. They do this because the voltage can be easily be reduced using a transformer with AC. Direct current is what you get from a battery and is not used in houses or buildings outside of electronics.

Your electrical panel arranges the incoming current (think flow) into parallel streams, each one protected by a breaker that is going to another part of the house. Too much current and the breaker opens. That is one reason for the parallel circuit, the other is to keep the voltage the same for each circuit. Sometimes its 115 volt, sometimes its 230 volts depending on what the use is.

Thanks for the explanation.

In one of my inspection project, the electrical inspector was telling the contractor that in the sub-panels the neutral bar and the ground bar shall be isolated and not be connected. And he cited about avoiding the current from circulating from main panel to sub-panel and this is what I am not clear about.

If the neutral is not grounded at the sub-panel, the current flowing through the Hot wire to the load returns through the neutral in the opposite direction. The magnetic flux produced by the Hot wire current is cancelled out by the flux produced by the neutral current.

If the neutral is grounded at the sub-panel, some of the neutral current can return via a different path. The steel conduit acts like the core of a transformer. The magnetic flux in the conduit, by transformer action, induces a current in the ground wire (also inside the conduit) which can generate a voltage at a high resistance connection. The ground should not be carrying current except in a fault condition.

the subpanel is electrically "dropped down" from the main panel. You should know that the neutral wire allows the sub panels to return to the main panel. In the main panel the neutral then goes to ground, because as you know electricity goes through the load to find ground. Now, if the sub panel neutral is grounded, then the main panel electricity will find ground at the subpanel and will likely change the flow direction of the circuit. By having a ground in the subpanel and in the main, then depending on the load characteristics the flow will be crazy as the circuit tries to chase the path of least resistance. This will create a crazy circulating current as the resistance swings between the main panel and the sub panel.

In power systems engineering, it is the current that flows and circulate within the windings of transformers that are connected in parallel or delta due to unequal transformer impedances and unbalance voltages in the winding (delta connected). It introduces additional copper losses and heating of the transformers.

"Can anyone who has a good knowledge of electricity explain about circulating current?"

Circulating currents: The warnings are out

Are you talking about completing a circuit via the earth. That is dangerous but detected by the Earth Leakage unit.

The following is not intended for educational purposes!

I always thought that circulating current is when you take an extension cable and plug it into a socket. if you wait for the cable to fill up and quickly remove it from the socket and plug into the other end. the power should continue to flow in opposite directions(in 2 loops). The power is saved as DC.

For you that intend to tell me it wont work, my reply would be that it is a matter of perfect timing. The phase must be caught when at a maximum.

I have never succeeded in using the power stored in the cable. It seems to spill on the floor.

If you connect the neutral bar and the ground bar, there are 2 possibilities:

1. in case of unbalanced load, current flowing in the neutral bar will also flows into ground bar. This is dangerous for people if he touches the grounded-part of devices.

2. in case of phase-to earth fault, current will also flow in the neutral bar (connected to earth by ground bar) this will weaken to current under the nominate value of relay protection, so the fault is not detected and the current keep flowing in the device and grounded part.

The thoi nhi.