GE UR Series Instruction Manual page 160

5.5 GROUPED ELEMENTS 5 SETTINGS
c) SETTINGS
POWER SWING FUNCTION:
This setting enables/disables the entire POWER SWING DETECT protection element. The setting applies to both power
swing blocking and out-of-step tripping functions.
POWER SWING SOURCE:
The source setting identifies the Signal Source for both blocking and tripping functions.
POWER SWING MODE:
This setting selects between the 2-step and 3-step operating modes and applies to both power swing blocking and out-of-
step tripping functions.
The 3-step mode applies if there is enough space between the maximum load impedances and distance characteristics of
the relay that all three (outer, middle, and inner) characteristics can be placed between the load and the distance character-
istics. Whether the spans between the outer and middle as well as the middle and inner characteristics are sufficient should
be determined by analysis of the fastest power swings expected in correlation with settings of the power swing timers.
The 2-step mode uses only the outer and inner characteristics for both blocking and tripping functions. This leaves more
space in heavily loaded systems to place two power swing characteristics between the distance characteristics and the
maximum load, but allows for only one determination of the impedance trajectory.
POWER SWING SUPV:
A common overcurrent pickup level supervises all three power swing characteristics. The supervision responds to the pos-
itive sequence current.
POWER SWING FWD REACH:
5
This setting specifies the forward reach of all three characteristics. For a simple system consisting of a line and two equiva-
lent sources, this reach should be higher than the sum of the line and remote source positive-sequence impedances.
Detailed transient stability studies may be needed for complex systems in order to determine this setting.
POWER SWING FWD RCA:
This setting specifies the angle of the forward reach impedance. The angle is measured as shown in the POWER SWING
DETECT ELEMENT OPERATING CHARACTERISTICS diagram.
POWER SWING REV REACH:
This setting specifies the reverse reach of all three power detect characteristics. For a simple system consisting of a line
and two equivalent sources, this reach should be higher than the positive-sequence impedance of the local source.
Detailed transient stability studies may be needed for complex systems in order to determine this setting.
POWER SWING REV RCA:
This setting specifies the angle of the reverse reach impedance. The angle is measured as shown in the POWER SWING
DETECT ELEMENT OPERATING CHARACTERISTICS diagram.
POWER SWING OUTER LIMIT ANGLE:
This setting defines the outer power swing detect characteristic. The convention depicted in the POWER SWING DETECT
ELEMENT OPERATING CHARACTERISTICS diagram should be observed: values greater than 90° result in an "apple"
shaped characteristic, values lower than 90° result in a lens shaped characteristic. This angle must be selected in consider-
ation of to the maximum expected load. If the "maximum load angle" is known, the outer limit angle should be coordinated
with some 20° security margin. Detailed studies may be needed for complex systems in order to determine this setting.
POWER SWING MIDDLE LIMIT ANGLE:
This setting defines the middle power swing detect characteristic. This setting is relevant only if the 3-step mode is
selected. A typical value would be close to the average of the outer and inner limit angles.
POWER SWING INNER LIMIT ANGLE:
This setting defines the inner power swing detect characteristic.
The inner characteristic is used by the out-of-step tripping function: beyond the inner characteristic out-of-step trip action is
definite (the actual trip may be delayed as per the setting). Therefore, this angle must be selected in consider-
TRIP MODE
ation to the power swing angle beyond which the system becomes unstable and cannot recover.
5-76 L90 Line Differential Relay GE Power Management