PT and CT
PT and CT
(OP)
What is the difference between a potential transformer and a control transformer?Can CT be used instead of a PT?
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RE: PT and CT
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RE: PT and CT
'CT' typically stands for 'Current Transformer'
'PT' typically stands for 'Potential Transformer' (A.K.A. 'Voltage Transformer', 'VT')
'CPT' typically stands for 'Control Power Transformer'
RE: PT and CT
Conversely, a PT does not make for a good CPT because it it not designed to provide the same current inrush capabilities of a CPT when it may be supplying inductive loads.
RE: PT and CT
And just to add a little more obsfuscation, the term Potential Transformer and hence "PT" is deprecated by IEEE. They now prefer the term "Voltage Transformer", which seems to create more confusion rather than less.
RE: PT and CT
Control power transformers are generally designed for power output only.
Depending on the power rating and voltage class, CPT's are generally cheaper than VTs, especially when rated 2-3kVA and below. VTs are often used for power applications as they do have a thermal burden rating, which is how much power they can output without overheating, if you don't need the accuracy class performance.
We sell a lot of VTs for power reclosers, automated switches, etc... at distribution level voltages. Mainly because most VTs at this level are dry-type and control power transformers are typically oil-filled.
RE: PT and CT
When you say, "but it will lack the ability to withstand a fault on the high voltage side as a PT is designed to do" I guess you are meaning over voltage withstand capability of PT windings that is defined in IEC 60044 (the voltage in unfaulted phases, in case of earth fault in HV system, can technically go up to 1.8 times the rated).