Reverse Power Protection Theory & Settings


#1

Reverse Power Protection

1- Protection against overspend 32G (# 1).

In case of Turbine Failure, the Turbine is tripped and then the Generator is tripped by operation of reverse power relay to prevent overspending of the Turbine generator unit.

2- Protection against generator motoring 32G (#2).

Generator motoring protection is designed for the prime mover or the system, rather than for the generator.

With steam turbines, Turbines will overheat on low steam flow, motoring results from a low input To the Ac Generator,

When This I/P can’t meet all the losses, the deficiency is supplied by absorbing real power from the system.

since field excitation should remain the same , the same reactive power would flow as before motoring , thus, on motoring the real power will be into the generator, while the reactive power may be either flowing out or into the generator

Reverse%20Power%20Protection%20Theory%20%26%20Settings

Setting of Reverse Power Relays

Data for setting calculations
-Rated Capacity of Generator -------- 440,000 KVA
-No Load Loss of Generator --------- 1,785 KW
-No Load Loss of Turbine ---------- 1,350 KW
-No Load Loss of TG unit ---------- 3,135 KW
-Permissible Motoring Time ------- 60 Sec.
-Relay Constant ------------------- 1 P.U. = Generator KVA

Setting Of Reveres Power Relay 32G ( #1 )

1- Reverse Power Trip Level

Trip Level < No load loss of TG unit * 0.3
= 3,135 * 0.3
= 940.5 KW
Pick up = Trip level / relay constant
= 941 / 440,000
= 0.0021 P.U.
Setting = - 0.002 P.U. ( 880KW )

2- Reverse Power Trip Delay

Trip Delay < Perm. Motoring time (60 Sec.)
Setting = 50 Cycles (1 Sec.)

Setting Of Reveres Power Relay 32G ( #2 )

1- Reverse Power Trip Level

Trip Level < No load loss of TG unit * 0.5
= 3,135 * 0.5
= 1,568 KW
Pick up = Trip level / relay constant
= 1,568 / 440,000
= 0.004 P.U.
Setting = - 0.004 P.U. ( 1,760KW )

2- Reverse Power Trip Delay

Trip Delay < Perm. Motoring time (60 Sec.)
Setting = 750 Cycles (15 Sec.)