ABB RELION RET670, Applications Manual

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8.17 Out-of-step protection OOSPPAM (78)
GUID-8321AC72-187C-4E43-A0FC-AAC7829397C3 v1
8.17.1 Identification
GUID-BF2F1533-BA39-48F0-A55C-0B13A393F780 v2
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Out-of-step protection OOSPPAM
<
78
8.17.2 Application
GUID-11643CF1-4EF5-47F0-B0D4-6715ACEEC8EC v6
Under balanced and stable conditions, a generator operates with a constant rotor
(power) angle, delivering an active electrical power to the power system, which is
equal to the mechanical input power on the generator axis, minus the small losses in
the generator. In the case of a three-phase fault electrically close to the generator, no
active power can be delivered. Almost all mechanical power from the turbine is under
this condition used to accelerate the moving parts, that is, the rotor and the turbine. If
the fault is not cleared quickly, the generator may not remain in synchronism after the
fault has been cleared. If the generator loses synchronism (Out-of-step) with the rest of
the system, pole slipping occurs. This is characterized by a wild flow of synchronizing
power, which reverses in direction twice for every slip cycle.
The out-of-step phenomenon occurs when a phase opposition occurs periodically
between different parts of a power system. This is often shown in a simplified way as
two equivalent generators connected to each other via an equivalent transmission line
and the phase difference between the equivalent generators is 180 electrical degrees.
1MRK 504 163-UUS A
Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI 481
Application manual