8.17 Out-of-step protection OOSPPAM (78)
8.17.1 Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Out-of-step protection OOSPPAM
78
8.17.2 Application
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 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 467
Application manual
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