Insulation Level

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electricalexpert65 Guru Join Date: Oct 2009 Posts: 2061 Good Answers: 169	Insulation Level 08/11/2013 1:14 PM
	What is the calculation for fixing the Power Frequency Withstand Voltage and the Lightning Impulse Voltage Withstand levels for electrical equipment at various voltage levels? For example, for a 12kV System, the power frequency withstand voltage is 28kV (rms). How & why is this 28kV? Why not 15kV or 35kV? Similarly, the Lightning Impulse Withstand Voltage Requirement for a 12kV system is 75kV (peak). Why & How is this arrived at? Why not 65kV or 100kV? Pl. don't advise to go through Standards (IS/IEC/IEEE/ANSI, etc.) or Local Regulations. I have already gone thro all, but am unable to find a scientific explanation for these values. Experts, pl. help.
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redfred Guru Join Date: Dec 2008 Location: Long Island NY Posts: 15602 Good Answers: 982	#1 Re: Insulation Level 08/11/2013 3:22 PM
	Probably this is a legacy issue. When the standards were first attempted the maximum reliably produced voltages in the laboratory for insulation testing were these voltages. __________________ "Don't disturb my circles." translation of Archimedes last words
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RAMConsult Guru Join Date: May 2007 Location: NYC metropolitan area. Posts: 3230 Good Answers: 444	#2 Re: Insulation Level 08/11/2013 7:06 PM
	It is not a legacy issue, it is an insulation coordination issue. These values are not calculated numbers, they're empirically derived based upon statistical evidence from many experiments and actual recorded data. Factors such as location in a power system, ambient conditions, surrounding equipment, etc., also play a part. It's too broad a topic to cover here, your best bet is to Google on "insulation coordination", "BIL (Basic Impulse/Insulation Level", "Power Frequency Withstand Voltage", and "Lightning Impulse Voltage Withstand levels" to find many well written papers on the subject. __________________ “Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
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1capybara Power-User Join Date: Mar 2012 Location: the sandbox Posts: 341 Good Answers: 6	#3 Re: Insulation Level 08/12/2013 2:18 AM
	BIL levels as a function of nominal voltages are listed in NEC Table 490.24. i found this interesting: www.energy.siemens.com/us/pool/us/power-distribution/ansi-standard-products/techtopics/techtopics47.pdf __________________ BSEE but always learning
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Ronak Agrotech Participant Join Date: Aug 2013 Posts: 2	#4 Re: Insulation Level 08/12/2013 2:43 AM
	It is too wide a topic to protect here, your best bet is to Search engines on "insulation coordination", "BIL asic Impulse/Insulation Level", "Power Regularity Hold up against Voltage", and "Lightning Reaction Volts Hold up against levels" to discover many well crafted documents on the topic. ___________________ Briquetting Machines
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