Understanding CTs and PTs in SLD

[khanpk]

Hi friends,

i have quires that i can't count the CTs and PTs in the SLD. how many CTs for Protection and how many for Measuring or Metering and what is P2 means ?

.

 

[Windadct]

No idea on the P1 and P2 -- Point 1/Point 2 - for Polarity of the CTs is my only guess - since the polarity is "into" the HV side of the transfomer.

The CT notation is #/ CTs and # / wires - you can wire three CTs in a Delta ( 3 wires out ) or a Wye (4 wires out).

The measurement CTs (3) have a different spec than the protection CTs - because for measurement the accuracy in the nominal current range is most important - for the protection CTs they may need to provide accurate output at higher then nominal current ( 3 or more x) so the Protection CTs are typically heavier - larger core to prevent saturation at higher currents. I would consider the differential CTs part of the protection - but you do want them dedicated to the differential circuit to prevent errors.

 

[khanpk]

No idea on the P1 and P2 -- Point 1/Point 2 - for Polarity of the CTs is my only guess - since the polarity is "into" the HV side of the transfomer.

The CT notation is #/ CTs and # / wires - you can wire three CTs in a Delta ( 3 wires out ) or a Wye (4 wires out).

The measurement CTs (3) have a different spec than the protection CTs - because for measurement the accuracy in the nominal current range is most important - for the protection CTs they may need to provide accurate output at higher then nominal current ( 3 or more x) so the Protection CTs are typically heavier - larger core to prevent saturation at higher currents. I would consider the differential CTs part of the protection - but you do want them dedicated to the differential circuit to prevent errors.

Thanks a lot,

if i have 02 CTs

one is 1600:800:400/1
0.2FS5/5P20/5P20/5P20
15(10)(5)VA/30VA/30VA/30VA2nd is

0.2FS5
15(10)VA 800:400:200/1A

then what is the difference , one is 04 cores and 2nd is 01 core ? right ?