Difference between ct and pt

Difference between CT and PT

Current transformer (CT) and potential transformer (PT) are the types of instrument transformer. As there are similarities in both the transformer (CT & PT). So, there are some differences between CT and PT as well.

An instrument transformer is used to connect electrical instruments to measuring instruments. They are connected for measuring and controlling purposes. The measurement of high powered line with the conventional instruments is not possible as it owns the danger of harming the equipment as well as the operator. That’s where the instrument transformer comes into use. It steps down the voltage or current within the permissible range of the instruments.

Now let’s see a brief introduction of two types of instrument transformers. The first one is the current transformer and the other is a potential transformer.

Current transformer

A current transformer is the instrument transformer that transforms the current from high value to low value. The primary winding of the transformer is connected to the power line and the secondary winding is connected to the measuring instruments.

Potential transformer

A potential transformer is a device that steps down the high voltage level to the low voltage level. The primary winding is connected to the high voltage line and the secondary winding is connected to the measuring instruments.

Difference between CT and PT

Current Transformer (CT)Potential transformer (PT)
The current transformer steps down the current (from higher value to lower value)The potential transformer steps down the voltage (from a higher value to a lower value)
The core of CT is made up of siliconThe core of PT is made up of high-quality steel
The primary winding has fewer turns.The primary winding has a large no. of turns.
The secondary winding has a large no. of turns.The secondary winding has less no. of turns.
The secondary winding of the energized current transformer should never be open-circuited.The secondary winding of the energized potential transformer can be used safely as open-circuited.
The primary winding of CT is connected in series with the main lineThe primary winding of PT has connected across (in parallel with) the main line
The primary winding  of CT carries the measuring current and secondary winding is connected to the current winding of the instrumentThe primary winding of PT carries the measuring voltage and the secondary winding is connected to the metering instrument.
CT doesn’t depend upon the secondary burdenPT depends on the secondary burden

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