GE D60 Instruction Manual page 408

5.7 CONTROL ELEMENTS
To distinguish between single-phase disappearance and system disturbance in all three phases (such as load change,
switching, etc.), the broken conductor element monitors the change in all three phase currents at the present instance and
at four cycles previous. It also monitors changes in the I_2 / I_1 ratio, I_1 minimum, and I_1 maximum.
The broken conductor function should not be used to respond to fault transients and single-pole tripping/reclosing condi-
tions. Therefore, the time delay should be programmed to a sufficient length to ensure coordination with the breaker dead
time of the recloser function.
• BROKEN CONDUCTOR 1 FUNCTION: This setting enables and disables the broken conductor function.
• BROKEN CONDUCTOR 1 SOURCE: This setting selects a signal source used to provide three-phase current inputs
to this function.
• BROKEN CONDUCTOR 1 I2/I1 RATIO: This setting specifies the ratio of negative-sequence current to positive-
sequence current. When one phase conductor is broken, the I_2 / I_1 ratio with a balanced remaining two phases is
50%. So normally this setting should be set below 50% (for example, to 30%).
• BROKEN CONDUCTOR 1 I1 MIN: This setting specifies the minimum positive-sequence current supervision level.
Ensure this setting is programmed to a sufficient level to prevent I_2 / I_1 from erratic pickup due to a low I_1 signal.
However, this setting should not be set too high, since the broken conductor condition cannot be detected under light
load conditions when I_1 is less than the value specified by this setting.
• BROKEN CONDUCTOR 1 I1 MAX: This setting specifies the maximum I_1 level allowed for the broken conductor
function to operate. When I_1 exceeds this setting, this it is considered a fault. This broken conductor function should
not respond to any fault conditions, so normally this setting is programmed to less than the maximum load current.
• BROKEN CONDUCTOR 1 PKP DELAY: This setting specifies the pickup time delay for this function to operate after
assertion of the broken conductor pickup FlexLogic operand.
5
SETTINGS
BROKEN CONDUCTOR 1
FUNCTION:
Enabled = 1
BROKEN CONDCT 1 BLK:
Off = 0
SETTINGS
BROKEN CONDUCTOR 1
SOURCE:
I2
I1
Ia
Ib
Ic
5-286
SETTING
BROKEN CONDUCTOR 1
I1 MIN :
RUN
| I1 | > I1 MIN
| Ia | < I1 MIN
| Ib | < I1 MIN
| Ic | < I1 MIN
| Ia' | - | Ia | > 0.05pu
| Ib' | - | Ib | > 0.05pu
| Ic' | - | Ic | > 0.05pu
Where I' is 4 cycles old
One phase current loss
detection
Figure 5–159: BROKEN CONDUCTOR DETECTION LOGIC
D60 Line Distance Protection System
SETTING
BROKEN CONDUCTOR 1
I1 MAX :
BROKEN CONDUCTOR 1
I2/I1 RATIO :
RUN
| I1 | < I1 MAX
BROKEN CONDUCTOR 1
| I2 | / | I1 |> RATIO
I1 MAX :
t
PKP
2 cyc
0
5 SETTINGS
SETTING
FLEXLOGIC OPERAND
BROKEN CONDUCT 1 OP
0
FLEXLOGIC OPERAND
PKP
BROKEN CONDUCT 1
GE Multilin