DC to DC Step Up voltage convertor for protection relay 1

[dfdt]

In our system few old Substations run with 32 V DC power supply. We would like to standardise on 125 V DC rated relays which are used in majority of the substations. In that context do you see any issue if we power 125 V rated relay by an external 32/125 volt step up convertor?
Regards,

 

[Overvoltage]

Increased amperage on the 32V system would be the first thing I would be concerned about. May not be an issue versus old EM relay draws, but something to consider.

 

[Edelma_1]

the only problem you would probably face is the current supply ,which is a function of the Power availability, remember

Power = Voltage x Current ; increasing the voltage would make the current fall. so you have to make sure that the load you want to feed through the converter is capable for the converter to handle.

 

[cranky108]

I was going to say purchase a relay with a voltage input range to cover from 32 to 125. But I don't know of any. I do know the SEL can be speced. for 48 to 125. But even for that, what voltage would you use for the inputs.

We presently do use a relay with the range 48 to 125 power, and we spec one input board with 48 V and the second with 125, so we can use the relay in most substations that we have.

Maybe that helps.

 

[stevenal]

Your relays (and their internal power supplies) are built to meet the standards applying to substation equipment. Do your convertors meet these standards?
It is also another failure point you need to consider in your redundancy planning.

 

[dpc]

As stevenal said, the main concern would be a decrease in reliability by adding a converter - probably would become the least reliable component in the dc system. I would install at least two in parallel, a switching scheme to allow removal of a failed unit without an outage and a third on the shelf. It might make more sense to bite the bullet and convert to a higher dc voltage.

 

[dfdt]

Thanking all the contributors. I agree with dpc and Stevenal regarding degradation of reliability by add third party external DC/DC convertor. As part of my research, I did find that Siemens compact relay type 7SX800 does have truly universal DC range i.e. DC 24 V through DC 125 V