Technical Information Required for an Enquiry

In order that your enquiry may be dealt with promptly, it will be useful to have the following information to hand at the outset:

GENERAL

a) FULL TRANSFORMATION RATIO
eg. 1000/5 AMP not 200/1 or 660/110 VOLT not 6/1

b) BURDEN
c) ACCURACY
d) FREQUENCY

RING TYPE CURRENT TRANSFORMERS

e) LIMITING DIMENSIONS
The minimum necessary is the internal diameter required.

f) TYPE OF MOUNTING
eg. plain ring, foot mounted, busbar mounting bracket, clamp mounted. If busbar mounting is required the size of the busbar should be provided. Special mounting arrangements will need to be considered if the transformer is large or the mounting location onerous.

g) SURROUNDING MEDIUM IF NOT AIR
eg. Compound, insulating oil, silicone fluid.

PROTECTION CURRENT TRANSFORMERS

h) If the accuracy class required is not known, the RELAY TYPE and LEAD RUN from CT to relay may enable us to recommend a rating and class.

"CLASS PX" CURRENT TRANSFORMERS

i) If the knee point voltage and secondary winding resistance at 75 C is not known, the RELAY TYPE, LEAD RUN from CT to relay and STABILITY LEVEL will be required.

NOTE: The stability level is the fault current expected to flow through the zone protected by the CTs and not the maximum fault level on the protected equipment, with which it is often confused. For restricted earth fault schemes on power transformers it is normally a factor of 20 times the CT rated current and on generators a factor of 10 times the CT rated current.

SUMMATION CURRENT TRANSFORMERS

j) The individual LINE CT RATIOS feeding the summation transformer (especially if unequal) and the OVERALL RATIO of the line CTs and summation transformer will be required.

CERTIFIED TEST RESULTS

Certificates of conformity will be supplied free of charge on request. Where specified at the time of ordering, recorded test results on metering transformers or magnetization curve data on protection transformers can be supplied for an additional charge.