Answer / a.ramachandran

current transformer : transformation of high current into
required current rating of measuring instruments and
protection relays.

Potential transformer: step down the high voltage into low
voltage for the purpose of measuring instruments and
protection relays.

Answer / pragati kumar

Current Transformer(ct) is used to measure current in high
voltage ac circuit because it is not possible to measure
high voltage ac current with ammeter alone.Potential
Transformer(pt) is used to measure high ac voltage.

Answer / wasif arshad

Basically both CT and PT steps down the voltage but the difference is that in CT primary is not winded on the core and both the terminals of secondary are connected to ampere meter of appropriate transformation ratio while in pt both primary and secondary are wounded on the core like a simple step down transformer and both terminals of primary are connected to the high voltage and secondary to the voltmeter to give deflection according to scale of voltmeter having the same transformation ratio shown on PT.

Answer / mrudang

ct and pt both we are using for protection

Answer / sanjay kumar

current transformer(ct)works to reduce the current for
measuring equipment or protection relay bcoz ct works as a
step up transformer.
potential transformer(pt)works to the voltage for measuring
equipment or protection relay bcoz pt works as astep down
transformer.

I have a question, I visit 01 site and face a problem, there is 2.5 ton Air Con working, when air con compressor is running at that time rectifier voltages are increasing upto 290-295 v and rectifier is giving main high alarm (rectifier is APC single phase, before starting compressor rectifier voltages was 230v. when air con is going off rectifier voltages are decreasing smoothly at its actual voltages 230v. Load on Genset phases is this: Red-13.5 amp AC (Air Con load), Yellow-1.7 amp AC (BTS lights etc.) and Blew-4 amp AC (telecom system load), Genset phase to phase and neutral to phase voltages are also ok. These are 10 sites having same system and same rectifier APC brand at every site 02 genset are working but the problem is same at all these 10 sites. What will be the reason behind???

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