GE UR Series Instruction Manual page 179

5 SETTINGS
The positive-sequence restraint must be considered when testing for pickup accuracy and response time (multiple of
pickup). The operating quantity depends on the way the test currents are injected into the relay (single-phase injection:
= 0.9375 × I
I ; three-phase pure zero-sequence injection: I
op injected
The directional unit uses the zero-sequence current (I_0) or ground current (IG) for fault direction discrimination and may
be programmed to use either zero-sequence voltage ("Calculated V0" or "Measured VX"), ground current (IG), or both for
polarizing. The following tables define the Neutral Directional Overcurrent element.
Table 5–23: QUANTITIES FOR "CALCULATED 3I0" CONFIGURATION
POLARIZING MODE DIRECTION
Voltage
Current
Dual
Table 5–24: QUANTITIES FOR "MEASURED IG" CONFIGURATION
POLARIZING MODE DIRECTION
Voltage
1
(
where: V_0 -- - VAG
= +
3
1 1
(
I_0 -- - IN -- - IA
= =
3 3
ECA = element characteristic angle
IG = ground current
When
NEUTRAL DIR OC1 POL VOLT
The following figure explains the usage of the voltage polarized directional unit of the element.
GE Power Management
DIRECTIONAL UNIT
COMPARED PHASORS
–V_0 + Z_offset × I_0
Forward
–V_0 + Z_offset × I_0
Reverse
Forward IG
Reverse IG
–V_0 + Z_offset × I_0
Forward
IG
–V_0 + Z_offset × I_0
Reverse
IG
DIRECTIONAL UNIT
COMPARED PHASORS
–V_0 + Z_offset × IG/3
Forward
–V_0 + Z_offset × IG/3
Reverse
)
VBG VCG zero sequence voltage
+ =
)
IB IC zero sequence current
+ + =
is set to "Measured VX", one-third of this voltage is used in place of V_0.
L90 Line Differential Relay
5.5 GROUPED ELEMENTS
= 3 × I
).
op injected
I_0 × 1∠ECA
–I_0 × 1∠ECA
I_0
–I_0
I_0 × 1∠ECA
I
or
I_0
–I_0 × 1∠ECA
or
–I_0
IG × 1∠ECA
–IG × 1∠ECA
OVERCURRENT UNIT
= 3 × (|I_0| – K × |I_1|)
op
OVERCURRENT UNIT
I = |IG|
op
5-95
5