GE C70 Instruction Manual page 352

5.7 CONTROL ELEMENTS
SETTING
BREAKER RESTRIKE 1
FUNCTION
= Enabled
SETTING
BKR RSTR 1 BLK
= Off
SETTING
BREAKER RESTRIKE 1
SOURCE
= IA
= IB
= IC
SETTING
BKR RSTR 1 BKR OPEN
= Off
SETTING
BKR RSTR 1 OPEN CMD
= Off
SETTING
BKR RSTR 1 CLS CMD
= Off
d) VT FUSE FAILURE

PATH: SETTINGS CONTROL ELEMENTS
5
 VT FUSE FAILURE 1

Every signal source includes a fuse failure scheme.
The VT fuse failure detector can be used to raise an alarm and/or block elements that may operate incorrectly for a full or
partial loss of AC potential caused by one or more blown fuses. Some elements that might be blocked (via the
are distance, voltage restrained overcurrent, and directional current.
There are two classes of fuse failure that occur:
• Class A: loss of one or two phases.
• Class B: loss of all three phases.
Different means of detection are required for each class. An indication of class A failures is a significant level of negative-
sequence voltage, whereas an indication of class B failures is when positive sequence current is present and there is an
insignificant amount of positive sequence voltage. Also rapid decrease in the phase voltages magnitude from a healthy
voltage level without disturbance in current can indicate a VT fuse fail conditions. These noted indications of fuse failure
can also be present when faults are present on the system, so a means of detecting faults and inhibiting fuse failure decla-
rations during these events is provided.
Once the fuse failure condition is declared, it is sealed-in until the cause that generated it disappears.
An additional condition is introduced to inhibit a fuse failure declaration when the monitored circuit is de-energized; positive-
sequence voltage and current are both below threshold levels.
The
VT FUSE FAILURE 1 FUNCTION
The
VT NEU WIRE OPEN 1 FUNCTION
VT is connected in Delta, do not enabled this function because there is no neutral wire for Delta connected VT.
5-228
AND
RUN
ARMED
Current interruption
detection logic
I < 0.05 pu
mag
for > ¼ cycle t
OR
AND
Figure 5–108: BREAKER RESTRIKE SCHEME LOGIC

MONITORING ELEMENTS
VT FUSE FAILURE 1
FUNCTION: Disabled
 NEUTRAL WIRE OPEN 1
MESSAGE
 DETECTION: Disabled
 NEUTRAL WIRE OPEN 1
MESSAGE
 3 HARM PKP: 0.100
setting enables and disables the fuse failure feature for each source.
setting enables and disables the VT neutral wire open detection function. When the
C70 Capacitor Bank Protection and Control System
SETTING
SETTING
BREAKER RESTRIKE 1
BREAKER RESTRIKE 1 PICKUP
RESET DELAY
RUN
0
Restrike detection logic
0
0
RESET

VT FUSE FAILURE 1(6)
Range: Disabled, Enabled
Range: Disabled, Enabled
0.000 to 3.000 pu in steps of 0.001
5 SETTINGS
T
RST
FLEXLOGIC OPERANDS
T
BKR RESTRIKE 1 OP A
RST
BKR RESTRIKE 1 OP B
BKR RESTRIKE 1 OP C
T
RST
FLEXLOGIC OPERAND
BKR RESTRIKE 1 OP
OR
834012A1.CDR
input)
BLOCK
GE Multilin