GE 845 Instruction Manual page 272

PROTECTION
FASTPATH:
4–168
Path:
Setpoints > Protection > Group1(6) > Current > Phase Dir OC
FUNCTION
Range: Disabled, Enabled
Default: Disabled
ECA
Range: 0° to 359° in steps of 1°
Default: 30°
The setting is used to select the element characteristic angle, i.e. the angle by which the
polarizing voltage is shifted in the leading direction to achieve dependable operation.
POLAR VOLT THRESH
Range: 0.050 to 3.000 x VT in steps of 0.001 x VT
Default: 0.700 x VT
The setting is used to establish the minimum level of voltage for which the phase angle
measurement is reliable. The setting is based on VT accuracy.
REV WHEN V MEM EXP
Range: No, Yes
Default: No
The setting is used to select the required operation upon expiration of voltage memory.
When set to "Yes" the directional element output value is forced to 'Reverse' when
voltage memory expires; when set to "No" the directional element is 'Forward' when
voltage memory expires.
BLOCK
Range: Off, Any operand from the list of FlexLogic operands
Default: Off
EVENTS
Range: Enabled, Disabled
Default: Enabled
TARGETS
Range: Self-reset, Latched, Disabled
Default: Self-reset
The Phase Directional element responds to the forward load current. In the case of a
following reverse fault, the element needs some time – in the order of 8 ms – to change the
directional signal. Some protection elements such as Instantaneous Overcurrent may
respond to reverse faults before the directional signal has changed. A coordination time of
at least 10 ms must therefore be added to all the instantaneous protection elements under
the supervision of the Phase Directional element. If current reversal is a concern, a longer
delay – in the order of 20 ms – is needed.
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS