Question { Jacobs, 15706 }

how set earth fault over current in relay

Answer

In any relay Set earth fault to minimum That means If Earth
fault range is 20 to 80 % of secondary current then set it
to 20% . In case of over current calculate rated current
and add 5%for relay & ct error and 5% to over load that
means set it to 110% to full load capacity.
If for 200/1 CT If full load current is 160 that mens 80%
to secondary current of Ct+10% relay CT error and Over load
that means relay ia seted to 180A interms of secondary at
0.9 a that means 90%

Question { Essar, 109097 }

check list of maintenance of transformer?

Answer

Daily check up
1)Oil level in conservator tank (Main and OLTC)
2)Oil leakages if any
3)Counter rteading of OLTC
4)Sound of Transformer
5)Hourly reading

Querterly Maint.
1)Cleaning of Transformer
2)Note down of Maximum temp of HV LV Wdg. & LV Wdg.
3)Checking of OLTC mechanisum Step by step
4)Tighting of HV & LV connection
5)Checking of gas collection in Bucholz relay, cleaning of
glass cover
6)Operation of cooling fan in manually,remote and auto mode


Yearly Maint: All above quarterly maint point plus
1)DGA Of transformer oil
2)BDV of oil
3)Insulation resistance test
4)Earth resistance test of earth pits of neutral and body
earthing
5)Protection check up