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CT Knee point voltage calculation

Created by: jeet2907 at: 5/13/2014 11:05 AM (10 Replies)

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5/13/2014 11:05 AM
jeet2907 Posts: 235 Rating: (52)	Dear All, Waht is knee point voltage of PS class CT,when i am order for 4000/1A PS class CT ,vendor ask me for the knee point voltage of the same. Please help me how to calculate the same its very argent. Thanks in advanced.
jeet2907 Posts: 235 Rating: (52)
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5/13/2014 11:31 AM	Rate (1)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 12/31/2023 Posts: 8092 Rating: (878)	jeet2907 Dear All, Waht is knee point voltage of PS class CT,when i am order for 4000/1A PS class CT ,vendor ask me for the knee point voltage of the same. Please help me how to calculate the same its very argent. Thanks in advanced. Hello, Knee point voltage is the voltage generated across CT terminals above or atthis valueCT goes in saturation mode. You need to provide maximum system voltage, short circuit level/value of the system. Please search in google for more techincal detail information. HTH.

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5/13/2014 12:01 PM	Rate (0)
Madhava Silver Member Joined: 11/26/2011 Last visit: 6/29/2023 Posts: 508 Rating: (23)	In Simple words, 10 % increase in voltage gives you 50 % increase in excitation current iscalled knee point voltage. ForCalculation link 2you can find more links on internet.

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This contribution was helpful to 1 thankful Users @nkur

5/13/2014 12:42 PM	Rate (0)
PISCEAN 2010 Diamond Member Joined: 4/23/2010 Last visit: 12/31/2023 Posts: 8092 Rating: (878)	Madhava In Simple words, 10 % increase in voltage gives you 50 % increase in excitation current iscalled knee point voltage. No sorry. Knee point voltage i.e. saturation of CT means even if current in primary circuit increases, CT secondary current will not increase proportionately. It is the maximum, fixed. HTH

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5/13/2014 1:25 PM	Rate (0)
Madhava Silver Member Joined: 11/26/2011 Last visit: 6/29/2023 Posts: 508 Rating: (23)	You are correct. It s the saturation point of CT.

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5/13/2014 2:14 PM
jeet2907 Posts: 235 Rating: (52)	Madhava In Simple words, 10 % increase in voltage gives you 50 % increase in excitation current iscalled knee point voltage. ForCalculation link 2you can find more links on internet. Dear Madhava, Thanx for your reply but i cant found any calculation on your mentioned link pls help for calculation its very argent for me.
jeet2907 Posts: 235 Rating: (52)
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5/13/2014 2:33 PM	Rate (0)
Madhava Silver Member Joined: 11/26/2011 Last visit: 6/29/2023 Posts: 508 Rating: (23)	Normally Knee point voltage mentioned on the name plate of CT. I found it on net how to check the knee point voltage. 1.Isolate the CT from all external connections. 2. Apply 10% of knee point voltage (provided on name plate details) to the secondary circuit by using auto transformer. 3. measure secondary current by using leakage current tester. 4.increase the voltage by 10% step by step and measure current as said above. 5.Repeatthe steps up 100% of knee point voltage. 6. After knee point voltage , current will not increase as starting (proportionally). 7.Repeatthe same procedure for differenttapping.. I hope this will help you a bit.

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This contribution was helpful to 1 thankful Users @nkur

5/14/2014 10:36 AM
jeet2907 Posts: 235 Rating: (52)	Dear all, Thanking you for your valuable feedback. Finaly i got how to calculate Ct knee point voltage here is the attched file for calculation Attachment CT Knee point voltage calculation.pdf (2011 Downloads)
jeet2907 Posts: 235 Rating: (52)
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5/16/2014 6:52 AM
Er.digu Posts: 17 Rating: (4)	jeet2907 Dear all, Thanking you for your valuable feedback. Finaly i got how to calculate Ct knee point voltage here is the attched file for calculation Dear Jeet2907, Thanx for your reply but i cant understand some value hoe to find for your attach,ent can you provide excel shhet for the same so i can easily understand its helps to me. Thanx in advance. waiting for your reply
Er.digu Posts: 17 Rating: (4)
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5/26/2014 5:59 PM
@nkur Posts: 202 Rating: (16)	PISCEAN 2010 jeet2907 Dear All, Waht is knee point voltage of PS class CT,when i am order for 4000/1A PS class CT ,vendor ask me for the knee point voltage of the same. Please help me how to calculate the same its very argent. Thanks in advanced. Hello, Knee point voltage is the voltage generated across CT terminals above or atthis valueCT goes in saturation mode. You need to provide maximum system voltage, short circuit level/value of the system. Please search in google for more techincal detail information. HTH. Hi there You are refering to the short circuit condition & maximum voltage at the same time as both the current & the voltage are inversely proportional to each other shouldnt we be checking it at overvoltage condition if i am worong please advice
@nkur Posts: 202 Rating: (16)
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