P1 P2 in a Current Transformer

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Current Transformers Installation Guide

FAQ | Autometers Ltd, Manchester, UKwww.autometers.co.uk/help/faq

In certain metering applications & in some protection applications, the polarity of the CT is very critical. Hence, the primary polarity (P1 & P2) and the secondary polarity (S1 & S2) are to be properly identified & wired fort proper functioning of such meters & relays.

Hi Mukultyaqi,

The answer by ElectricalExpert65 should answer your question, however I would like to add from my experience.

It is good practice to always install CT's with the correct polarity both on the primary and secondary sides. Having been caught a couple of times by incorrectly connected CT's I always double check my connections and carry out a 'flick test' just to confirm that the connection is correct.

Incorrectly connected CT's will cause problems when used as part of the protection circuit by outputting an 'unbalanced' signal and causing a protection trip. When incorrectly connected CT's are connected to an energy meter the result will be that the meter incorrectly records the power being used (can be a major problem when used with summation CT metering).

The links provided by Joshi should help you to understand more about CT's and are very informational. (Thanks Joshi!)

Hope this helps!

if there are equipments on both sides , p1 and p2 like ct pt etc , so to which side this ct can be used for providing protection

Is it an exiting plant or a new one? A properly laid out plant would have taken care of every thing. What you see at your site, we don't see. Post your plant lay out drawings. Are you in a position to relocate major equipments? You have many questions to answer. Are you in a position to do so?

MR. Joshi you do not provide any solution to any question ,

this forum is about technical knowledge i guess and instead of giving any input which can clarify technical stuff you ask questions which are off the topic , I am learning about these things so I need to know how it works , if i am not in a position to change the position if the equipment does it stops me ffrom knowing about the technical stuff , your answers are of no help ?? I expect to learn the fundamentals and that can be done by asking questions which come up in mind

Please see my post in reply, on this linked thread:

• #13 "Re: How to Determine the Number of Cores and Core Ratio of CT's to be Used?" by Joshi on 12/29/2012 10:19 AM