VT Class Clarification

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mohgamal201365 Active Contributor Join Date: Mar 2015 Posts: 17	VT Class Clarification 06/02/2015 5:26 AM
	Dear All I hope you are well now i want to ask you ,, what is the meaning of this VT class 0.2 (3P) ??!! what I know is that secondary is measuring or protecion but in this class as you see it can be measuring or protection Kindly revise I do appreciate your reply BR Mohamed Gamal
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nikolay Power-User Join Date: Dec 2007 Location: Brasov, Romania Posts: 255 Good Answers: 7	#1 Re: VT Class Clarification 06/02/2015 7:54 AM
	So, the documentation for the VT is missing... Ok, the 0.2 means the error class (0.2%) and the 3P reffers to a protection secondary, with a saturation factor of 3. Anyone has anything to add? __________________ The time is ......now
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raghun Power-User Join Date: Jan 2010 Location: Hyderabad Posts: 343 Good Answers: 22	#2 Re: VT Class Clarification 06/05/2015 3:32 AM
	Unlike CTs, VTs can be rated for dual accuracy - measurement as well as protection. 0.2 class means when used for metering purpose, the error doesn't exceed 0.2% and 3P means when used for protection purposes, the error doesn't exceed 3%. The difference here is we are interested in accuracy around rated secondary voltage in case of measurement circuits and that near zero volts when it comes to protection circuits. In case of CTs, a 5P CT will have only 1% error in the operating load range and 5% at the ALF. Yet, the protection CTs are not widely used for metering (unlike the VTs) for the simple reason that the protection CTs cannot meet Instrument Security Factor (ISF or Fs) requirements of analog meters. __________________ Raghunath
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