Answer / sekhar_anama

i think you know why we are connecting ammeter inseries in
the circuit.now,as we know the current will be flown in a
line thats why ammeter is connected in series.as we know
C.T is used to measure the currents in higher ratings.the
primary of the C.T has less number of turns with thick
conductor therefore the resistance of primary is very low
(R=rho*L/A),if CT is connected in parallel the CT acts as a
short circuit(low resistance of primary of CT).thats y it
will definetly burns out.if any answer is there plz mail me.

Answer / syamdas

Current transformers are connected in parallel in the
restricted earth fault relay of transformers to nullify the
current, it doesn't burn out the ct's only nullify the
current output.The unbalance current will flow thru the
relay coil and the relay operates.

Answer / maheswaran

we know that area of cross section of the conductor is
proportional to current flow.. so that we are using thin
conductors.. but the resistance of the conductor is low.
if CT is connected as parallel,it s like a short circuit..

Answer / martin vester

As can be seen in the different answers this is not a
simple Yes of No question.

It is possible to use CT's directly parallel, but you need
to determine beforehand exactly what kind of CT's you must
use and for what purpose.
Kneepoint voltages must be equal etc.
For protection purposes this principle has been used in
high impedance (earth)differential protection schemes
including possible overvoltage protection (varistor)
In modern differential protection schemes we always use low
impedance inputs and all seperate CT's are connected to
seperate inputs and never set in parallel connection.
The protection will add seperate CT's for one Side if set
properly automatically.

Therefore I would strongly advise caution to just connect
them in parallel without further calculations and demand of
protection and measuring purposes are met.

See manuals on protection schemes for Siemens on:
www.siprotec.com

Answer / mark fisher

Current transformers should be connected in series to
provide accurate signals for relaying or metering.

A CT has a very low resistance in the secondary winding.
Therefore, connecting two CT's in series does not
significantly alter the resistance of the circuit (i.e.
.0001 ohm + .0001 ohm = .0002 ohm). The voltage drop caused
by the addition of a second CT to the circuit is negligible.
Connecting two independent CT's in series to obtain a "Net
Current" value in a Breaker-and-a-Half configuration is
quite common.

However, connecting two CT's in parallel will result in the
effective resistance of the circuit being significantly
lower than the resistance of either individual CT (i.e.
.0001 ohm // .0001 ohm = .00005 ohm) and will cause the
voltage to be significantly higher (4X) than with a single
CT.

Answer / vineshkumar

Ct connected in series. It has low resistance .so it can measure current properly.if we connect ct is parallel high resistance so current is nulified.

Answer / gunasekaran

we can do the parallel connection also but current will be
boosted up. Connection of the ct in series 400/1 ratio same
ct if ur connected in parallel we can get 800/1A ratio.refer
TNEB manual.

Answer / guest

CURRENT TRANSFORMER NOT CONNECTED IN PARALLEL DUE TO CURRINT
SAME IN SERIES AND DIFFERENT IN PARALLEL ALSO WINDING HAS
BURNED DUE TO SHORT CKT

Answer / sennapparajan

who told this???

for relay and energy meters , CT's are connecting in
parellel only.

Answer / kanime.m

CT have got a zero resistance, hence if connected in
parallel, then a short circuit will be created

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