Directional Underpower Protection Guppdup (37); Identification; Application - ABB REB670 Applications Manual

Section 7
Current protection
7.8
7.8.1
7.8.2
222
breaker. The time delay for back-up trip is bypassed when the 52FAIL is active.
Typical setting is 2.0 seconds.
tPulse: Trip pulse duration. This setting must be larger than the critical impulse time of
circuit breakers to be tripped from the breaker failure protection. Typical setting is 200
ms.

Directional underpower protection GUPPDUP (37)

Identification

Function description
Directional underpower protection

Application

The task of a generator in a power plant is to convert mechanical energy available as a
torque on a rotating shaft to electric energy.
Sometimes, the mechanical power from a prime mover may decrease so much that it
does not cover bearing losses and ventilation losses. Then, the synchronous generator
becomes a synchronous motor and starts to take electric power from the rest of the
power system. This operating state, where individual synchronous machines operate as
motors, implies no risk for the machine itself. If the generator under consideration is
very large and if it consumes lots of electric power, it may be desirable to disconnect it
to ease the task for the rest of the power system.
Often, the motoring condition may imply that the turbine is in a very dangerous state.
The task of the reverse power protection is to protect the turbine and not to protect the
generator itself.
Steam turbines easily become overheated if the steam flow becomes too low or if the
steam ceases to flow through the turbine. Therefore, turbo-generators should have
reverse power protection. There are several contingencies that may cause reverse
power: break of a main steam pipe, damage to one or more blades in the steam turbine
or inadvertent closing of the main stop valves. In the last case, it is highly desirable to
IEC 61850 IEC 60617
identification identification
GUPPDUP
P <
2
SYMBOL-LL V2 EN-US
Busbar protection REB670 2.2 ANSI
1MRK 505 370-UUS A
SEMOD156693-1 v4
SEMOD158941-2 v4
ANSI/IEEE C37.2
device number
37
SEMOD151283-4 v5
Application manual