en06000313.vsd
IEC06000313 V1 EN-US
Figure 246: Relative generator phase angle at a fault and pole slip relative to the external
power system
The relative angle of the generator is shown for different fault duration at a three-phase short
circuit close to the generator. As the fault duration increases the angle swing amplitude
increases. When the critical fault clearance time is reached the stability cannot be maintained.
Un-damped oscillations occur in the power system, where generator groups at different
locations, oscillate against each other. If the connection between the generators is too weak
the amplitude of the oscillations will increase until the angular stability is lost. At the moment
of pole slip there will be a centre of this pole slip, which is equivalent with distance protection
impedance measurement of a three-phase. If this point is situated in the generator itself, the
generator should be tripped as fast as possible. If the locus of the out of step centre is located
in the power system outside the generators the power system should, if possible, be split into
two parts, and the generators should be kept in service. This split can be made at predefined
locations (trip of predefined lines) after function from pole slip protection (PSPPPAM) in the
line protection IED.
1MRK 505 343-UEN B
Section 7
Impedance protection
379
Application manual
Summary of Contents for Relion 670 series
Page 1: ...RELION 670 SERIES Line differential protection RED670 Version 2 1 IEC Application manual...
Page 2: ......
Page 40: ...34...
Page 64: ...58...
Page 150: ...144...
Page 406: ...400...
Page 472: ...466...
Page 494: ...488...
Page 512: ...506...
Page 524: ...518...
Page 604: ...598...
Page 686: ...680...
Page 718: ...712...
Page 722: ...716...
Page 758: ...752...
Page 759: ...753...