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krishi 62
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Join Date: Jun 2008
Posts: 5

Star Point Grounding of Neutral -220kV Primary Side

06/12/2008 4:37 AM

Would like to know, what shall be the neutral insulator (voltage) rating for transformer primary side of 25/31.5 MVA - 220/22kv system in vector group YNyn 0 (d).

ANY OF THE FOLLOWING:

a.Insulation of neutral on HV Side - 220KV. Or

b.Insulation of neutral on HV Side - 36KV.
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Anonymous Poster
#1

Re: star point gounding of neutral -220kV primary side

06/12/2008 6:05 AM

Hi,

The neutral for the 220 kV Side will be 36 kV Only.

N.Suresh
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krishi 62
Member

Join Date: Jun 2008
Posts: 5
#2
In reply to #1

Re: star point gounding of neutral -220kV primary side

06/13/2008 12:57 AM

IS THERE ANY GUIDELINES FROM IEEE OR IS OR BS, ETC, IF SO PL LET US KNOW.
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krishi 62
Member

Join Date: Jun 2008
Posts: 5
#3
In reply to #1

Re: star point gounding of neutral -220kV primary side

06/13/2008 1:01 AM

IS THERE ANY STANDARDS, IN IEEE,IS,BS, ETC, IF SO WHERE CAN WE REFER
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Anonymous Poster
#4
In reply to #1

Re: star point gounding of neutral -220kV primary side

06/13/2008 10:31 AM

The insulation will be 36 KV if you are contemplating a continuous solid grounding of the star point if you may intend to install a neutral earth switch and operate with it open , you will habe to rate for 220KV , but that is just the working voltage.

What impulse voltage rating ( BIL) are you contemplating?

This is usually a function of expected lightening activity in the geographic area where the transformer is operated.
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krishi 62
Member

Join Date: Jun 2008
Posts: 5
#5
In reply to #4

Re: star point gounding of neutral -220kV primary side

06/16/2008 1:10 AM
  • Scenario: 1.Common NGR for two trafo of 25/31.5 MVA -220/23 KV with Vector group YNyn0 (d) Clarification needs, as we have standard practice to go with individual NGR for individual trafo, where as we working with German concern they are proposing to go with common NGR. Reason behind it ....
  • Scenario: 2. (25/31.5MVA transformer 220/22) 220kV solidly grounded YNyn0(d) With equalizing winding. the HV phase bushings are 460kV/1050kVp while the neutral is 36kV 630A, 70kV/170kVp. Neutral with solidly grounded configurations, as is as per standards or not. Star point of brought out Neutral ( 220kv side ) bushing rating and type -- shall be of 220kv or 36 kv .......

The above installation would like to pune - india.(geographic area) Thanks in advance.
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