Multi Ratio Current Transformer - CT 3

[dmapower]

Hi;
What would be the standard ratios for a CT Multi Ratio CT-4000/5

Thanks,

DMA

 

[stevenal]

500, 1500, 1000, and 1000:5 from X1 to 2, and 2 to 3 and so on. Other ratios are derivable from those. ANSI/NEMA/IEEE assumed, don't know if IEC is the same.

 

[scottf]

500/1000/1500/2000/2500/3000/3500/4000:5A

I don't remember the tap combinations off the top of my head

 

[JensenDrive]

Interesting. I never looked at how turns ratios add up on CTs. I went to a document I found in my old files and found the datat below. With this info, you can figure the turns ratio between any two terminals. e.g., on a 600:5, the ratio for tapping beween X2 and X4 is (50+250):5 or 300:5.

600:5
X1:X2 20 turns x 5 = 100:5
X2:X3 10 turns x 5 = 50:5
X3:X4 50 turns x 5 = 250:5
X4:X5 40 turns x 5 = 200:5

1200:5
X1:X2 40 turns x 5 = 200:5
X2:X3 20 turns x 5 = 100:5
X3:X4 100 turns x 5 = 500:5
X4:X5 80 turns x 5 = 400:5

2000:5
X1:X2 80 turns x 5 = 400:5
X2:X3 160 turns x 5 = 800:5
X3:X4 60 turns x 5 = 300:5
X4:X5 100 turns x 5 = 500:5

3000:5
X1:X2 200 turns x 5 = 1000:5
X2:X3 240 turns x 5 = 1200:5
X3:X4 60 turns x 5 = 300:5
X4:X5 100 turns x 5 = 500:5

4000:5
X1:X2 100 turns x 5 = 500:5
X2:X3 300 turns x 5 = 1500:5
X3:X4 200 turns x 5 = 1000:5
X4:X5 200 turns x 5 = 1000:5

5000:
X1:X2 300 turns x 5 = 1500:5
X2:X3 100 turns x 5 = 500:5
X3:X4 400 turns x 5 = 2000:5
X4:X5 200 turns x 5 = 1000:5

 

[isquaredr]

Just as a side issue, what is the standard with regards to P1 & P2
ie is it the standard to have P1 nearest to the source ?

 

[stevenal]

In the case of BCTs on devices, the primary polarity is toward the device.

 

[jghrist]

I'll have to disagree with stevenal. On circuit breakers and transformers I've seen in the USA, the polarity marks of bushing CTs have been away from the device. I don't know if there is a standard for this.

 

[davidbeach]

In switchgear with CTs on the bushings of drawout breakers, primary polarity is toward the breaker.

 

[stevenal]

jghrist is correct, away from the device is what I should have said. NEMA SG-4 details this for outdoor breakers.

 

[rbyrne15]

Sorry to barge in on this one, but is there a specific IEEE standard that lists standard CT ratios?

Thanks,

Richard Byrne.

Richard Byrne, E.E.T.

 

[jghrist]

ANSI/IEEE C57.13

 

[scottf]

Confirm for the BCTs and other CTs we make for apparatus, the polarity is normally away from the device, i.e. on the top for a BCT.