S
surya
> We have on load tap changer for transformer. When generator MVARS are high (lagging side) due to grid demand,
> then we will increase our tap position i.e from 13->14 to reduce Generator MVAR to keep excitation and stator parameters
> within limits. however system voltage are further reduced due to increase in tap position. Can u explain please what happen in reality?
when generator MVARS are high already due to grid demand, actually we should decrease our tap position but not to increase as you said 13-14...no never..you should decrease it from 13 to 12. in this condition the system voltage and generator voltage(primary side or low voltage side) both reduced. so that our var capability window will be more. then we can supply more var as required by the system. if you start increasing your var without reducing your transformer tap position from 13 to 12. then the v/Hz will trigger and active. if volts/hertz reach 1.18 and standing at that value then with in 45 sec m/c will trip
so you should reset by reducing var
if v/h limit further increases >1.18 then with in 2 sec m/c will trip.
Even when the var limits are high for the given MW allow you to go high var (say 100 mvar) but "excessive Volts/hertz limit" doesn't allow you to give more excitation in order to protect stator winding from over temperature
so, what we do.....
generally when u increase var, your terminal voltage of generator and results in further increase in voltage on SUT secondary.
But if you see the V/Hz limit is not active here
so, by reducing the tap position of SUT on secondary , the system voltage will drop slightly reducing generator terminal voltage
so, then volts/hertz limit will not act even if you increase the var.....until the limit again reaches
correct me if i am wrong
> then we will increase our tap position i.e from 13->14 to reduce Generator MVAR to keep excitation and stator parameters
> within limits. however system voltage are further reduced due to increase in tap position. Can u explain please what happen in reality?
when generator MVARS are high already due to grid demand, actually we should decrease our tap position but not to increase as you said 13-14...no never..you should decrease it from 13 to 12. in this condition the system voltage and generator voltage(primary side or low voltage side) both reduced. so that our var capability window will be more. then we can supply more var as required by the system. if you start increasing your var without reducing your transformer tap position from 13 to 12. then the v/Hz will trigger and active. if volts/hertz reach 1.18 and standing at that value then with in 45 sec m/c will trip
so you should reset by reducing var
if v/h limit further increases >1.18 then with in 2 sec m/c will trip.
Even when the var limits are high for the given MW allow you to go high var (say 100 mvar) but "excessive Volts/hertz limit" doesn't allow you to give more excitation in order to protect stator winding from over temperature
so, what we do.....
generally when u increase var, your terminal voltage of generator and results in further increase in voltage on SUT secondary.
But if you see the V/Hz limit is not active here
so, by reducing the tap position of SUT on secondary , the system voltage will drop slightly reducing generator terminal voltage
so, then volts/hertz limit will not act even if you increase the var.....until the limit again reaches
correct me if i am wrong
