6.6KV AC Current Measurement

Wrong question. Its fitting is one thing. What is wanted is some indication whether it would survive the experience once energised. On the basis of the information stated, it sounds a highly risky thing to do, so it would be best to select the correct equipment in the first place rather than install the wrong thing and regret it later.

Equipment and facility damage is one thing. Killing someone is something else.

As any further remarks would be superfluous, the invitation is declined.

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What is "right" is for you is to not attempt this work, or worse, direct anyone else to do it for you. Your question indicates a total lack of understanding of the dangers to property and life that you are facing, therefore no one here should attempt to assist you and this thread should be closed.

For the most part the posters here have enough ethics to not put you in danger, so your best bet is to find another forum where no one cares if you kill yourself. Better a thousand times cautious than one time dead.

"can a low voltage CT(current transformer) be used for a medium voltage current measurement ?" NO.

What is the diffence between an LV and a MV CT. ?. LV is less than 600V. MV is 600-13.8KV. This is a critical insulation safety rating on electrical equipment.

The CT voltage rating must comply with/match the voltage present in the circuit.

If you install a CT that is not rated for the application the CT will fail causing equipment damage, personnel injury and/or death.

Never install any device into an electrical circuit that is operating at a voltage level higher than the device rating.

Thank you and sorry for my initial outburst. I technically agree with you now 100%. My lack of experience is the factor(s) which will affect the LV CT inserted in a MV circuit(intending 6.6'KV). Let me know if MV current measuring devices are rated as the LV CTs I'm so used to(ie 400/5. 800/1 etc). Let me know what the MV instruments manufacturer(s) alter in LV designs to make them work in MVs. I don't intend to bore you with my askings but your kind response in sharing your experience is all I look up to. I intend to witness a 6.6KV motor spin test conducted with a temporal current measuring device indicating its no load starting and running Amperes. And I intend to improvise this measurement safely

The CT voltage rating is determined by the type of coating utilized for insulating the wire used for CT winding(s) and the critical physical spacing/size of the CT components.

If you are going to be executing 6.6KV motor testing I strongly suggest you use a clamp-on current measuring device to ensure personnel safety and prevent equipment damage.

These can be rented from various suppliers from/through internet websites.

Use of an exposed in-line CT anywhere near personnel traffic is a recipe for disaster.

CT's are not usually modified after being manufactured due to high cost and high risk of CT failure.

If you do decide to use an in-line CT please make sure the area is barricaded and well labeled to prevent anyone and everyone from being within 10 feet of the CT when energized.

CAUTION! DO NOT EVER OPEN-CIRCUIT THE CT SECONDARY CIRCUIT.

Doing so will cause the voltage level at the CT terminals to exceed safe operable limits and there will be arcing and/or catastrophic failure which in turn can result in an arc flash incident. These arc flash incidents are deadly.

Good luck and stay safe.

Thanks for your true kind response "SHOCKHISCAN" I was able to capture "insulation" and "spacing" from you. Thanks again for warning me about opening the secondary CT circuit. I will heed your warning. I shall intend to measure the current by an "O.E.M" CT inserted in the load conductor(without any physical touch), I shall also ensure the secondary terminals are closed(and perhaps earthed too?) - shall then attach a fluke(376) clamp on meter to the secondary closed conductor and check the current as the circuit is energized. My pending issues now will be the OEM CT calibration(s) and the ability of the handheld fluke meter to pick-up the transformed secondary current. The area I'm using is remote and restricted from human traffic. As of the clamp-on measuring device you suggested, I will be happy to lay my hands on any but I doubt availability of such "logistic" favouring my time/location.I don't know what an OEM MV CT will physically look like, but I shall enter the electrical scrap market and search. What do you advice master SHOKHISCAN ?

Thank you SHOCKHISCAN, the ct is rated for 12/28/75 kv, there is an issued warning same as yours regarding secondary open circuit fatal high volts. The unit is as heavy as a block. I shall take the rest from here. God bless you

I am not a politician anymore than you are an electrical engineer, but I have personally witnessed the result of "improvisation" when it comes to electrical equipment, its operation, and its measurement. I also don't care where you come from or what your position is, I am just trying to protect you and your coworkers from your naivete.

Electricity is an equal opportunity killer, it provides no warnings, strikes at will, and rarely affords a second chance. If you have the stomach for it then you should view these very graphic images of what happens when you fail to heed the advice of those who deal with it on a daily basis.

Many of these are low voltage burns, as evidenced by the lack of charring; medium and high voltage burns involve instant charring due to the enormous energy involved. One more point of reference, the voltage of the execution device known as the "electric chair" is 2,000Volts, and you want to play with 6,600??? Best of luck to you, you are going to need it.

Thank you "RAMConsult" for attempting to make me beg for your experience and intellectual mercy. You are sitting on the throne of electrical engineering consultancy today because thousands before you toiled and died to bring you the information you refuse to freely share. I'm not "naivete" of paying your consultancy if you can fly into my location and executute common MV current measurement for a junior fellow in the year 2015. This is not stone age. We are thinking about the closest star to our solar system, we are thinking about machines that can effectively replace the physical works of men and you are there trying to type fear disguised as warning to someone who is trying to redo what has been already done a billion times. If you can't share, you stay off empty words. Thanks for telling me 2000volts kills. Is that a new information? -f I need it, I go to google. I don't understand why some people don't want to move with time

You are correct, I refuse to share knowledge that will potentially harm you, especially since you have demonstrated that you readily accept the information that will.

There are none so deaf as those that refuse to hear, nor as blind as those who refuse to see. <unsubscribes>

I'm not an electrical engineer, so for my education - how does a CT know the voltage of the line it's installed on? I assume it has a coil surrounding the cable being measured, but without any electrical connection to the cable. If high voltage is an issue, can't the CT be installed on the neutral side? As far as I'm aware, the voltage induced in the CT depends only on the (AC) current in the measured cable.

Thank you "Codemaster" this is exactly my assumption until I noticed that the LV CTs in my posession are apart from current ratios RATED in volts too. I juat learnt here too that INSULATION and SPACING of its internal windings plays a crucial safety and pragmatic role. So, we may assume that LV CTs will not work in MV circuits, berhaps they will arc-off.

You should hire a COMPETENT engineer before you or, sadly, some poor fool who has to work for you experiences this:

Quite funny I can say. I don't intend anybody's harm. And if I may ask, who is a "competent engineer" ? And what makes a "poor fool"...I bet you may not want to answer

My answer is that you defiantly belong in one or the other of these categories, and we all already know that you are not a competent engineer, just by reading your question.

Good Luck.

Thank you for your foolish judgment, and who exactly are you refering to as "we", perhaps you don't know how loney your judgment sounds to me. You can brag all you like but I'm certain you don't have answer(s) but a big sense of self importance. Good luck as you massage your sense of self importance

I always carry a mouse in my pocket so the "we" is valid.

We also never argue with fools.

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All your comments are not valid. I wonder what your perspective definition of foolishness is. People like you are exactly the reason certain good things cannot be done because you wish only you could. But the obvious is that everyone expires from life and the world of men never expires with anyone. So, comfort your meaningless wisdom.

He has already left the discussion.

Don't suppose you could answer my #10 when you get a minute? I'm still curious.

Also I would assume the CT is designed for the current it's measuring, to give a voltage high enough to read accurately but not dangerous. Is this correct?

Just stop being so pig-headed. The advice you've received is valid. No-one cares if you don't like it.