HT Panel Issue

Did you ask Siemens for help? They would know their VCB best

Assuming you have done that, and haven't got help..... what is the trip mode? Overload, short-circuit, earth-fault, undervoltage.... ? Also, what is the protection device, a separate relay. SCADA, VCB's own microprocessor relay ?

This information may help in narrowing down the search for the root cause....

What loads does this system feed, and what do the "normal" currents add up to? Is there any particular load that, when cut in, is followed by the tripping? Is the total load put on all at once, or sequentially?

We came across similar problem in LT ACB. The siemens 7SJ600 protection relay was tripping at load occasionally.The problem was in third CT. Its S1 was momentarily getting grounded, due to this 7SJ600 manipulated wrong amps in other two phases and tripped on over current. Similarly there are lot of possibilities. It is better if you try by your own.

plz explain how this S1 current transformer was getting grounded temporarily?

we are facing same issue with out LT ACB.

does the breaker trip frequently some time after being loaded?

or does the breaker trip frequently as soon as load is switched on?

does some load have a very large inrush current when switched?

Dear All,

Thanx for paying heed to my discussion. Actually we are using Siemens Protection relay 7sj602. We are still trying to solve this problem internally but we definitely are in contact with siemens representative. The main problem is that the time we put on the load on HT breaker it trips suddenly. We put the whole load on it at once and no sequential steps or procedures are adopted.

Best Regards,

is it a single load?

is it possible to load it in steps?

i repeat part of what i wrote in Post#1....

..... what is the trip mode? Overload, short-circuit, earth-fault, undervoltage.... ?

The 7sj602 relay has the feature to show why it tripped, right ?

The nature of the load current and the relay setting needs to be considered.

RElay setting should be such that it will not trip for the normal load current - including the current during start up. it should trip only under over load or short circuit conditions.

You can check the 50,51 settings of this relay with respect to above parameters.

If you have a number of heavy inductive loads (i.e., electric motors), your initial inrush current could be several times the rated operating current. If you are switching the entire load at once, this could well exceed the breaker capabilities. Sequential loading would help...

To add if u have number of distribution tranformers also the inrush current can trip the breaker.

Is this a new install or existing equipment?

Has this problem just started or have you always had it?

If a new install, then get the installers and/or Siemens back to fix it

If existing equipment and the fault has just started, what are you doing differently now, that is, how has the load changed, any additional load put on the system etc?

Dear All,

Thanx for needful collaboration. I would like to discuss here one more thing and that is We have one incoming HT Panel and 4 outgoing HT Panels. This incoming Panel is feed through the Power House 41 MW of capacity and having its own outgoing Panel of 11KV for this incoming Panel to feed. We are using 7sj602 Numerical Relay to monitor. It was giving IE>> fault when the problem rose.We checked the parameter 64 which gave the measuring details. here we found the earth leakage current was being measured by the relay. We checked the earth monitoring loops where there was loosing. fixed it and now ok. We are just waiting that in the future it might not happen.

Best Regards,

good to see that you have found your problem and solved it . . .