What is c.t (current transformer)ratio.how to calculate.?
Answer:
Utilities use CTs because all the power can't be delivered through the electric meter. CTs measure a known fraction of the actual usage.
Common revenue CT sizes include 300, 600, 1200, 1600, and 2000 amps. This is the primary winding rating. When loaded to the nameplate amperage, the secondary current is 5 amps.
The CT ratio is a ratio the primary amps to the secondary amps.
300:5 = 60:1
600:5 = 120:1
1200:5 = 240:1
2000:5 = 400:1
This ratio becomes a multiplier on the customer's electric bill.
current rating of cable x 1.25/5= CT Ratio
Example 200x1.25=250/5= 250:5 CT Ratio
...hope this helps
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