2.12 Reverse Power Protection (ANSI 32R)
87
7UM61 Manual
C53000-G1176-C127-3
The pickup value 3102 P> REVERSE is set in percent of the secondary apparent
power rating SNsec = √3
· U
Nsec
· I
Nsec
. If the primary motoring energy is known, it must
be converted to secondary quantities using the following formula:
with
Psec Secondary power corresponding to setting value
S
Nsec
Secondary rated power = √3 · U
Nsec
· I
Nsec
P
Mach
Machine power corresponding to setting value
S
N, Mach
Nominal apparent power of the machine
U
N, Mach
Nominal Voltage of the Machine
I
N Mach
Nominal Current of the Machine
U
N prim
Primary Nominal Voltage of the voltage transformers
I
N prim
Nominal primary CT current
Pickup Seal-In Time The 3105 T-HOLD pickup seal-in time serves to extend pulsed pickups to the param-
eterized minimum duration.
Delay Times If reverse power without emergency tripping is used, a corresponding time delay must
be implemented to bridge any short reverse power states after synchronization or
power swings subsequent to system faults (e.g. 3-pole short circuit). Usually, a delay
time 3103 T-SV-OPEN = approx. 10 s is set.
Under emergency tripping conditions, the reverse power protection performs a short-
time delayed trip subsequent to the emergency tripping via an oil-pressure switch or a
position switch at the emergency trip valve. Before tripping, it must be ensured that the
reverse power is only caused by the missing drive power at the turbine side. A time
delay is necessary to bridge the active power swing in case of sudden valve closing,
until a steady state active power value is achieved. A 3104 T-SV-CLOSED time delay
of about 1 to 3 s is sufficient for this purpose, whereas a time delay of about 0.5 s is
recommended for gas turbine sets. The set times are additional time delays not includ-
ing the operating times (measuring time, drop-out time) of the protective function.
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