Question { 24194 }

why we oltc on hv side of tranformer only

Answer

for a transformer, ratio of primary voltage to secondary voltage is equal to ratio of primary turns to secondary turns ie ... v1/v2=n1/n2 ,then v2=v1n2/n1
v1 is incoming or system voltage on which we depend upon & we can not change.now the variables are either n1 or n2 to get required secondary voltage. comparably primary turns are less and it requires less insulation level to change the primary turns,so providing tap changer on primary is better option.

similarly v1/v2 = i2/i1, ie v2 = v1i1/i2, here also vi is system voltage,i1 and i2 are variables. comparably i2 is always higher side and changing primary current with available insulation level is easy,and providing tap changer in primary is the option.