Using a low voltage current transformer in high side ( 13200 V ) power
Using a low voltage current transformer in high side ( 13200 V ) power
(OP)
A friend of mine is using a low voltage current transformer to measure the current is passing through a 15 KV insulated cable in the high side of a power transformer. He states that it is working ok and he is saving a lot of money in the instalation because instead of using the right 13200 Volts current transformer,he is using the cheap low voltage current transformer , which by the way has not blown out yet.
Do you guys agree with that ?






RE: Using a low voltage current transformer in high side ( 13200 V ) power
Is the cable shielded or otherwise?
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
Usually, 95kV is preferred and 110kV is the luxury BIL required by some Utilities.
RE: Using a low voltage current transformer in high side ( 13200 V ) power
For shielded MV cables, use of 600V window CTs is generally acceptable where the CTs are placed “downstream” of the termination where voltage stress is low. {Note the shield-grounding lead should be routed ‘back through’ the CT opening.} In IEEE C37.20.2 MV metalclad equipment, often 600V CTs are positioned over extended insulation located at the ‘throats’ of primary disconnects for ndrawout MV circuit breakers, being integral to the fixed cradle portion on the switchgear.
Related discussion at “PTB #85” www.powellelectric.com/pdf/ptb/booklet%201-91.pdf page 138. Supporting ‘bare-air clearance’ info at energy.tycoelectronics.com/rrg/raychem_rrg/98.pdf
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
Greg May
Two Sockets - Two Meters, Inc.
WEB: socket-two-me.com
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
You are correct. Unfortunately, several of the higher voltage installations that I have seen have the concentric neutral passing through the window of the 600 volt CT in only one direction. Apparently some forget that it (concentric neutral) can, and many times does, carry current!
My comments were only to emphasize the point.
A similar situation occurs when the metering potential connection is made after the metering CTs, especially in pad mount transformers. For convenience, the termination is often done on the load side of the CTs, but, the conductor must be passed backwards through the CT to cancel out the metering potential current needed to power the metering equipment. Failing to do so renders the installation technically illegal in most U.S. jurisdictions. I am aware of one large energy theft case that was thrown out of court because of this condition! The judge ruled that the installation was technically illegal.
Greg May
Two Sockets - Two Meters, Inc.
WEB: socket-two-me.com
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
RE: Using a low voltage current transformer in high side ( 13200 V ) power
Reference:
James Clerk Maxwell "A Treatise on Electricity and Magnetism", Volume One, Dover Publications, Inc., 1954 (Slightly modified reprint of 1891 publication).
Fig. II Art. 119
RE: Using a low voltage current transformer in high side ( 13200 V ) power
Now, if the phase conductors are without shield, there will be some deformation of the electrical equipotentials; however, the insulation will withstand it. There will not be short. The shield is added to conductors as an additional measure to make the electrical equipotential concentric to avoid electrical stresses and displacement of equipotential circles. The insulation is rated between the inner insulation diameter and outer insulation diameter, i.e. insulation thickness. E.g. Inslulation level 100% may be compared to insulation level 133% by insulation thickness, not by any extra shields.
RE: Using a low voltage current transformer in high side ( 13200 V ) power