22KV Seamless Switching

Even if you only have only single phase power, this is 4.4 Megawatts of power that you are asking for "seamless switching". This seems to me to be a little more than just a blog conversation. You should be considering this as an engineering project with a budget and licensed engineers. I do not think that you will be able to find an already designed system that will exactly meet these specifications. You will have to consider how brief of a power outage you can tolerate before your backup will be on line (less than a cycle of your power grid frequency or ten minute start up of a diesel generator). You will also have to consider how long your backup will have to provide power (long enough for a safe shutdown after an hour or running power for a few months). This is not a simple task. This is not a new task that has never been done either.

22kV is also used in Railways and giving quick backup for change over between two power source is a design problem to match the delay and purpose. Battery or capacitor bank can deliver power for very limited period. These devices also degrade in time and require replacement at set interval or on detection of failure.

All critical systems employ their own backup for switch over time. Centralized switchover time need to to be seamless power changeover needed only when it is very critical and is a must.

Detection of failure itself may take time. Rarely phase correction system employ backup from stored energy in battery system as energy may run out in no time. Perhaps Capacitor bank can help for a short period and is to be employed in same manner as phase correction or power factor but employed for many cycles that are lost and are regenerated by the backup system.

I think it is still a very good engineering problem. It is worth discussing some new possibilities that were not explored. 22kV is not very straight forward, and most of the parts are custom design with limitations.

Dear Shyam,

Thank you very much of your information.

redfred,

Thank you very much of your explaination.

Can you please give a SLD of the power supply system you are handling. Gathering from what you have said in your question, you probably mean Autochangeover scheme to be incorporated into your system so that tripping of any of the incomer breakers on fault should switch on the bus coupler so that uninterrupted power supply to the plant is ensured.

"Parallel supply first then switch off the problem cable" is rather a crude way saying that supply has to be maintained as the faulty cable is isolated (but still in the system). You will agree with me that in Electrical Engineering a faulty cable/ equipment/system must be isolated as soon as possible lest it leads to cascade trippings and other unsafe and dangerous operating conditions.

So our approach has to be to isolate the faulty cable immediately and at the same time bring in alternative supply source automatically using an elaborate interlock schem with proper time delays. Yours being 3 incomers switchgear, interlock scheme may be a bit complicated, but is doable.

BB Raina

Hi BB Raina,

Thank you for replied, in my case is manual change over by power company,they are switching over very frequent to carry out some 'endless' repair works at whole electrical system and this is very old 22kv PLISTA cable , at least 30yrs old. with the distance of 8km from main step down transformer 132/22KV 60MVA. Our factory is here for 47years with progressive growth until today the consumption at 4.5Mw/hr, we are manufacturing glass container so there are many equipment are in operation such compressors,cooling blower,electric booster system etc therefore if any power dip or power failure due to any reasons. there is big problems for us.

If there is 'seamless switching method or devices' in the system and when In the schedule shut down we are not suffer from factory total stoppage due to power supply break. Because we can supply in parallel with 2nd power source before shut of the 1st power source.

All the change over switch gear are with the momentary power lost . Right now if there is 'seamless' change over switch then we are not been effect by power company supply change over.

Regards