Directional Overpower Protection Goppdop; Introduction - ABB Relion 670 Series Technical Reference Manual

1MRK 505 208-UEN B
6.7
6.7.1
Technical reference manual

Directional overpower protection GOPPDOP

Function description
Directional overpower protection

Introduction

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.
Figure 91 illustrates the low forward power and reverse power protection with
underpower and overpower functions respectively. The underpower IED gives a
higher margin and should provide better dependability. On the other hand, the risk
for unwanted operation immediately after synchronization may be higher. One
should set the underpower IED to trip if the active power from the generator is less
than about 2%. One should set the overpower IED to trip if the power flow from
the network to the generator is higher than 1%.
When IED with a metering class input CTs is used pickup can be set to more
sensitive value (e.g.0,5% or even to 0,2%).
Current protection
IEC 61850 IEC 60617
identification identification
GOPPDOP
P >
DOCUMENT172362-IMG158942
V1 EN
Section 6
ANSI/IEEE C37.2
device number
32
193