CT. Current Transformer (CT) CT is. used to measure or monitor the current in transmission lines and to isolate the metering equipment and relay connected to. One of the major difference between them is that the current transformer convert the high value of current into low value whereas the potential or voltage. The Current Transformer (C.T.), is a type of “instrument transformer” that is There are a variety of metering applications and uses for current transformers such.


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By use of oil insulation and porcelain bushings, such transformers can be applied at the highest transmission voltages.

Instrument transformer

Ring-type current transformers ct and pt transformers installed over a bus bar or an insulated cable and have only a low level of insulation on the secondary coil. To obtain non-standard ratios or for other special purposes, more than one turn of the primary cable may be passed through the ring. Where a metal shield is present in the cable jacket, it must be terminated so no net sheath current passes through the ring, to ensure accuracy.

Current transformers used to sense ground fault zero sequence currents, such as in a three-phase installation, may have three primary conductors passed through the ring.

Only the net ct and pt transformers current produces a secondary current ct and pt transformers this can be used to detect a fault from an energized conductor to ground. Ring-type transformers usually use dry insulation systems, with a hard rubber or plastic case over the secondary windings.

For temporary connections, a split ring-type current transformer can be slipped over a cable without disconnecting it. This type has a laminated iron core, with a hinged section that allows it to be installed over the cable; the core links the magnetic flux produced by the single turn primary winding to a wound secondary with many turns.

Because the gaps in the hinged segment introduce inaccuracy, such devices are not normally used for revenue metering.

Current transformer - Wikipedia

Current transformers, especially those intended for high voltage substation service, may have multiple taps on their secondary windings, providing several ratios in ct and pt transformers same device.

This can be done to allow for reduced inventory of spare units, or to allow for load growth in an installation.

The original magnitude can be determined ct and pt transformers just multiplying the result with the transformation ratio. Such specially constructed transformers with accurate turns ratio are called as Instrument transformers.

Current Transformers CT Current transformers are generally used to measure currents of high magnitude. These transformers step down the current to be measured, so that it can be measured with a normal range ammeter. A Current transformer has only one or very few number of primary turns.

The secondary of the current transformer is connected to the ammeter or meter which measured the line value regarding fractions. The primary terminal of the potential transformer is connected to the line for measuring the line voltage.

Ct and pt transformers potential transformer reduced the high value of voltage into ct and pt transformers small value which can easily be measured by the voltmeter or meter. Key Differences between Current and Potential Transformer The current transformer transforms the high value of current into the low value so that it can conveniently measure by the instrument whereas the potential transformer converts the high value of voltage into low value.

The core of the current transformer is built up with the laminations of the stainless steel.

Instrument transformer - Wikipedia

The core of the potential transformer is made up with high operating core operating at low flux densities. Current transformers used in metering equipment for three-phase ampere electricity supply SF6 kV current transformer TGFM series, Russia Current transformers CT are a series connected type of instrument transformer.


They are designed to present negligible load to the supply being measured and have an accurate ct and pt transformers ratio and phase relationship to enable accurate secondary connected metering. Current transformers are often constructed by passing a single primary turn either an insulated cable or an uninsulated bus bar through a well-insulated toroidal core wrapped with many turns of wire.

This affords easy implementation on high voltage bushings of grid transformers and other devices by installing the secondary turn core inside high-voltage bushing insulators ct and pt transformers using the pass-through conductor as a single turn primary.

Clampmeter utilizing a split core A current clamp uses a current transformer with a split core that can be easily wrapped around a conductor in a circuit.

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