GE c60 Instruction Manual page 370

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
5.8.8.5 VT fuse failure
SETTINGS  CONTROL ELEMENTS  MONITORING ELEMENTS  VT FUSE FAILURE 1(4)
5  VT FUSE FAILURE 1

Every signal source includes a fuse failure scheme.
The VT fuse failure detector is used to raise an alarm and/or block elements that operate incorrectly for a full or partial loss
of AC potential caused by one or more blown fuses. Some elements that can be blocked (via the BLOCK input) 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, a rapid decrease in the phase voltages magnitude from a healthy
voltage level without disturbance in current can indicate 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
declarations 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.
VT FUSE FAILURE 1 FUNCTION
NEUTRAL WIRE OPEN 1 DETECTION
connected in Delta, do not enable this function because there is no neutral wire for Delta connected VT.
5-244
Figure 5-128: Breaker restrike logic
AND
RUN
ARMED
Current interruption
detection logic
I < 0.05 pu
mag
for > ¼ cycle t
OR
AND
VT FUSE FAILURE 1

FUNCTION: Disabled
VT FUSE FAILURE 1

ALARM DELAY: 1.000 s
NEUTRAL WIRE OPEN 1

DETECTION: Disabled
NEUTRAL WIRE OPEN 1

3 HARM PKP: 0.100 pu
— Enables and disables the fuse failure feature for each source.
— Enables and disables the VT neutral wire open detection function. When the VT is
SETTING
SETTING
BREAKER RESTRIKE 1
BREAKER RESTRIKE 1 PICKUP
RESET DELAY
RUN
0
Restrike detection logic
0
0
RESET
Range: Disabled, Enabled
Range: 0.000 to 65.535 s in steps of 0.001
Range: Disabled, Enabled
Range: 0.000 to 3.000 pu in steps of 0.001
C60 BREAKER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 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