Posts Tagged ‘current transformer’

Impact of Current Transformers errors on protective relays

January 23rd, 2019 | Make a comment | Posted in Electrical Safety
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Picture 1. Bus through-fault currents

Picture 1. Bus through-fault currents


Current transformers are the interconnection element between the power system and all measurement devices like protective relays. CTs actually lower the value of the primary current to a nominal secondary level in order to be used by meters, protective relays, meters, and monitoring devices.

Here’s a list of the impacts of current Transformers errors on protective relays written by Electrical Engineer Mile.


Current Transformers

August 2nd, 2013 | 1 Comment | Posted in Electrical distribution
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Hi there, here’s the last but one part of Nasir’s tutorial on transformers. The last one will be about “3 Phase Transformers”. Hope you’ll enjoy it and find it helpful.


Current transformers can be defined as the type of instrumental transformers which are used to convert very high currents which can burn or cause damage to measuring instruments like ammeters or other small devices like relays, into lower current values, which are in direct proportion to their higher, primary current values.

In this way, current can be easily measured through the device, and as it is directly proportional to the original high current, the true and precise values of current can also be found without damaging the instrument.

The secondary current differs in the phase angle from the primary current in a very small value which can almost be approximated to zero if the direction of the connections are appropriate.

On the basis of the output supply, the current transformers can be classified into two categories:

  1. Measuring Type Current Transformers
  2. Protection Type Current Transformers


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