bus transfer scheme

[seinfinn]

Can any one give me any sort of information or consulting on how to set up a GE D25 multifunction IED to use in a bus transfer setup. My partner and I intend it to monitor two step down transformers and three breakers. This is to ensure there is nol oad loss in the event of a fault or power failure on one of the transformers. We want to monitor and control the system using the D25 instead of several protective relays.
Shane.

 

[peterb]

I wasn't able to find any info on the GE D25 IED on the GE website, other than a generic mention in a brochure on substation automation - this shows the D25 interconnecting individual feeder relays and other IEDs with a LAN.

Does the D25 have the logic and measurement capability to perform the functions required? If it does, then it should be a straightforward exercise to program it to sense breaker status and/or bus voltage loss and to initiate a bus transfer. Even if it needs the inputs for the individual bus relays to do the measurement functions, the logic could reside in the device to do the actual switching. More data needed to properly evaluate the scheme.

 

[dpc]

If you are talking about a medium-voltage system, you will need to decide how fast a transfer you really want. If there are large motors on this system, you should consider monitoring the bus voltage to delay transfer until residual voltage has decayed to a safe value. If you really need a fast transfer, you will have to do a synch-check so you can momentarily parallel the sources (for a normal transfer)if they are generally in phase.

You also need to implement logic for re-transfer depending on how you want it to work, and a way to designate preferred source versus alternate source if you are going to operate single-ended.

Be careful with the residual voltage. If you transfer too quickly you can damage your motors and/or trip on overcurrent from out-of-synch operation.

The D25 probably can be programmed to do this, but it might be easier in a PLC.