What are the protections for SUT?

What are the protections for SUT? 
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1 Answer

Answer :

a) Over current protection for phase and earth fault

b) Differential protection

c) HV and LV restricted earthfault protection 

d) HV side directional back up over current protection for phase and earth fault.

e) LV back up over current and earth fault protection

f) Over fluxing protection

g) Buchholz and high oil, winding temperature protection. 
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Related questions

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Last Answer : To facilitate momentary paralleling of SUT with UT on 6.6kV buses.  

Why UT, SUT secondary is rated for 6.9kV where as bus voltage is 6.6kV?

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Last Answer : The no load secondary 6.9kV voltage level adequately takes into account voltage drop during loaded condition to cater station buses at 6.6kV level. 

Why twin secondary SUT?

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Last Answer : As per is, the rating single secondary power transformer is limited to 25MVA (6.6 kV) or 40 MVA (11 kV), in order to limit the 3 phase symmetrical fault level with in 26-40 kA (contribution from grid and local machines) 

Why REF is provided in the LV side of SUT and UT?

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Last Answer : The LV sides of the two transformers are earthed through the resistance. This will limit the flow of current in case of LV earth fault. Hence the differential protection may not act for a LV earth fault. Hence ref protection is provided. 

Why the neutral is earthed through earthing resistance in case of UT and SUT?

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