Help needed interpreting current transformer description 3

[amylase]

I got a description of current transformer that asks for

3000/2500/2200/1000-5-5-5-5

Is this asking for four kinds of current transformers or is
this one current transformer with four wire coils?

Thanks!

 

[tem1234]

Probably for a multi-ratio CT. It is one CT with multiple tap on the secondary that allow you to have different ratio. For a multi ratio 3000:5 CT, the standard ratio with secondary tap are:


300:5 X3 - X4
500:5 X4 - X5
800:5 X3 - X5
1000:5 X1 - X2
1200:5 X2 - X3
1500:5 X2 - X4
2000:5 X2 - X5
2200:5 X1 - X3
2500:5 X1 - X4
3000:5 X1 - X5


See IEEE std C57.13 1993

 

[tem1234]

A little important thing to add:

If it's a class C200 3000:5 multi ratio, the class C200 only applied on the 3000:5 ratio. On the 1500:5 tap, it will be like a C100.

 

[randyman]

-5-5-5-5 defines it as four (4) separate CT cores each with its own separate Multi-Ratio winding arrangement. This can either be all stacked in a single housing or separate CTs stacked or assembled together on the same conductor or bushing.

You did not post the accuracy class but do not assume each core to have the same accuracy.

 

[waross]

Unused secondaries should be shorted.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[randyman]

I would like to expand on waross' post - shorting of unused cores!!! Usually they would be marked X1-X5, Y1-Y5, Z1-Z5 and W1-W5 in the ANSI/IEEE world or 1S1-1S5, 2S1-2S5, 3S1-3S5 and 4S1-4S5 in the IEC world. If you are using intermediate taps of any given core, like 2-4, leave the other unused taps of that same core alone - do not short them. But for any core not being used, short across its entire winding (1-5).

 

[scottf]

tem1234-

Exactly correct, accept a ratio written as 3000/2500/2200/1000:5A is multi-ratio per CSA and not IEEE (splitting hairs of course).

The tap configurations in this case are the same as the IEEE 3000:5A MR designation. In some other cases, there are minor deviations between CSA and IEEE.

Randyman-

By the letter of the law (standard) something rated as 3000/2500/2200/1000:5:5:5:5A would only mean 4 cores/windings in a single unit.