incomer reding

Are your ammeter properly calibrated before you close the bus coupler. What is the ammeter 1 and ammeter 2 reading?.

it is properly work when bus coupler is off condition..its incomer-1 reading 300 A and incomer-2 reading 67A.both meter are digital and it is ok..

When the coupler is open, each individual incomer runs the load connected to the incomer's bus side. If the coupler is closed, the load is shared between the two incomers. The load sharing depends on the factors like upstream impedance, voltage, capacity of the incoming circuits and the load shared by the each incomer may not be the same of the loads connected to each side (the load in one side may be shared by the incomer on the other side). So, definitely the ammeters show different reading, there is nothing abnormal with this.

- MS

dear MS but it saws a same value in start up of plant.

If both meter working properly I don't see that is a problem. What about your CT Setting of both meters?. Are they having the same setting in your digital meter. As far as I can see is that, those digital meters can set the CT ratio independently even you have the same CT installed in the incoming lines. So you have to check your meter CT Setting and I presume that both incoming having the same CT installed otherwise you will not get the same current when you couple both incoming.

both CT setting are same.at the time of plant it saws same load sharing..so wats the reason

Well, the final test to solve this problem is to interchange both meter. Meter 1 goes to incoming nos;2 and meter 2 goes to incoming nos: 1. Just to compare if the meter is faulty.

I think you will get some results from there since all the setting are the same and no changes have been made.