Multiratio CT disadvantages?
Multiratio CT disadvantages?
(OP)
Are there any disadvantages of using multiratio CT's for substation protection? The possibility of selecting different ratios adds ofcourse flexibiliy, but is there a negative side? Any protections that do not work well with multiratio (high impedance?)?






RE: Multiratio CT disadvantages?
The CT's accuracy will always be worse at the lower tapped values.
RE: Multiratio CT disadvantages?
RE: Multiratio CT disadvantages?
RE: Multiratio CT disadvantages?
Most of the time, the lower ratios are used to match up to other CTs for differential protection. Of course, most of the 'C' ratings for modern substation applications are over-kill for newer electronic relays, which bails many a protection engineer out of mis-applications.
Advice to users from a vendor of IT's, always specify that your multi-ratio CT windings are equally distributed.
You would be surprised at how many people think you can apply the full-winding performance to any tap arrangement and get the same performance. Some even try to use them for revenue meterings.
RE: Multiratio CT disadvantages?
Many times they are specified because it seems to provide much greater flexibility and adapatbility. This is often done so the local analog ammeter will read up in a reasonable part of the scale for each feeder.
But there's definitely a price to pay for this flexibility.
RE: Multiratio CT disadvantages?