CT data meaning and interpretation
- Thread starter alexi
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greenspark1
Senior Member
- Location
- New England
Not sure what you're asking, or what the chart means, sorry.
ATSman
ATSman
- Location
- San Francisco Bay Area
- Occupation
- Electrical Engineer/ Electrical Testing & Controls
Like the other post indicated, not sure what you question is. The chart shows ratios with 1amp secondary current. The standard in the USA is 5 amp secondary current. And it shows KW ratings. CT ratio has nothing to do with KW rating of equipment.
It is a current device and is selected to match the current rating of the supplied load. For instance, if the load is rated for a maximum of 400A then a 400:5 ratio is selected to feed a 400A full scale ammeter (0 to 5A) and would be installed on each phase of the 500MCM cable and wired thru a shorting block and an ammeter switch.
You need to google current transformers and learn the basics before you can specify these devices.
It is a current device and is selected to match the current rating of the supplied load. For instance, if the load is rated for a maximum of 400A then a 400:5 ratio is selected to feed a 400A full scale ammeter (0 to 5A) and would be installed on each phase of the 500MCM cable and wired thru a shorting block and an ammeter switch.
You need to google current transformers and learn the basics before you can specify these devices.
rcwilson
Senior Member
- Location
- Redmond, WA
Table looks like IEC CT sizing information for various sizes of transformers or services. The CT specification, ratios and 1 A secondaries look like IEC.
Top row lists the transformer/load size in kVA. Right Column lists the CT type- metering or protection (X or P), the size (10VA) and the accuracy.
Rows A-C list various ratios of CT's. Row A looks like dual ratio metering CT's, 600:1 or 400:1. Class X is usually a higher accuracy for metering pruposes.
Row B look like dual ratio protection CT's, 100:1 or 50:1. The 5P20 rating means a protection CT capable of delivering 20 times rated current (20A) with a 5% accuracy. (If I recall the specs correctly).
Row C are single ratio protection CT's. The ratios look like they might be for 400V secondary CT's for the given size of the transformer in the top row.
Could be a chart for sizing CT's for transformers. A is for HV metering, B for HV protection and C for LV protection. (Wild guess).
Top row lists the transformer/load size in kVA. Right Column lists the CT type- metering or protection (X or P), the size (10VA) and the accuracy.
Rows A-C list various ratios of CT's. Row A looks like dual ratio metering CT's, 600:1 or 400:1. Class X is usually a higher accuracy for metering pruposes.
Row B look like dual ratio protection CT's, 100:1 or 50:1. The 5P20 rating means a protection CT capable of delivering 20 times rated current (20A) with a 5% accuracy. (If I recall the specs correctly).
Row C are single ratio protection CT's. The ratios look like they might be for 400V secondary CT's for the given size of the transformer in the top row.
Could be a chart for sizing CT's for transformers. A is for HV metering, B for HV protection and C for LV protection. (Wild guess).
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