Thank you very much 521AB for your valuable inputs. I agree with your points regarding backup protection in non carrier aided distance relays.
Now a days, most of the line differential relays have distance back up as well, which get enabled when the communication link fails - such as MiCOM...
Smallgreek, I agree with the point that in some cases budget might be a constraint and in some cases it might be impractical (for various reasons), but good things always come at a price.
I have no doubt that current differential is more suitable for line protection. OPGW would be a good option...
Distance relays are fast being replaced by line differential relays in most parts of the world, and hence the inaccuracies and under/over reach shall no longer be an issue. Until then, a distance relay accurate at reach point at line angle, is good enough.
My Personal View: I have seen that...
Its hard to find standard values of CT secondary resistances as they differ from manufacturer to manufacturer. Generally they vary between 2.5 to 4 milli ohms per turn. hence 2000/5 CT could have a resistance between 1 to 1.6 ohms. This is just a guideline and depending on the design many CTs...
I doubt that the processor would be incapable of handling multiple functions. There are many other MiCOM models, which use the same processor and perform much more complex algorithms. I believe it could be something to do with the PSL. If you back trace the output relay which is picking up, you...
Answer to ScottyUK - Yes MiCOM P432 does exist and its a Fast Distance Protection and Bay Control Unit and it comes from Alstom's (now Areva) German unit (erstwhile AEG).
I also feel MiCOM P343 would be an ideal choice for 2MVA genset.
Cheers
always remember, the best way to protect a generator winding is by use of high impedance differential protection and not by biased differential, as the setting keeps on increasing with fault current.
cheers
