Current Transformer (CT)

CT is employed to live or monitor this in transmission lines and to isolate the metering instrumentation and relay connected to the secondary facet.

Voltage Transformer or Potential Transformer (PT)

PT is employed to live or monitor the voltage on transmission lines and to isolate the metering instrumentality from the lines.

CT Precaution

  • Ammeter resistance is extremely low, this electrical device ordinarily works short-circuited.
  • If for any reason the meter is taken out of coil then the coil should be short-circuited with the assistance of tangency switch
  • If this is often not done, then thanks to high m.m.f. can create high flux within the core and it’ll manufacture excessive core loss that produces heat and also the high voltage across the secondary terminals.

CT Vs PT Transformer

CT Transformer

  • A CT can usually have a solid core and equally distributed secondary windings thus on minimize leak electrical phenomenon. the first is often the most cable conductor, that passes directly through the solid core.
  • This type of electrical device is specifically for the aim of measurement current values, and also the secondary windings cannot be left open-circuited, or an outsized voltage is going to be made, leading to material failure(and typically Associate in Nursing explosion).
  • If a tool isn’t connected to the CT, its secondary should be short-circuited.

PT Transformer

  • A noble metal is connected between the most conductor and ground and may be either wound within the traditional approach,

  • the voltage is often taken from a section of a string of capacitors (this is named a CapacitiveVoltage electrical device or CVT, and is typically cheaper than the wound sort, however, is usually not as accurate).

  • This type of electrical device measures voltage values and also the coil cannot be short-circuited, as this may manufacture too high currents, leading to the failure of the noble metal or the wires it’s connected to.

  • A noble metal is often left open-circuited.

Current transformer (CT) and potential transformer (PT) grounding

There is many documents say that for three-phase instrument transformers (CT, PT), there ought to be only 1 grounding purpose. With this argument, am I able to short the secondary sides of this electrical device and voltage electrical device along on a bus-bar and so ground this bus-bar to make one grounding point?

In fact, these CT and atomic number 78 have already been put in at the station and that they are grounded, simply not at an equivalent purpose. My company can install a meter that uses their outputs. This meter has its CT and atomic number 78 neutral wires connected on the printed circuit and as mentioned, these neutral wires are grounded at their own points. therefore technically, the grounds of the aforementioned CT have connected along. I am asking if there’s any potential danger to the present.

Note that these CT and atomic number 78 are employed in the measure of High Voltage station (110 kV).

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