GE L30 Instruction Manual page 510

CONTROL ELEMENTS
INCIPNT FLT 1 MODE
"Number of counts" mode, a trip is initiated only after the selected number of faults is detected. In the "Counts per window"
mode, a trip is initiated only after the selected number of faults is detected within the time specified by the
setting.
DETECT WINDOW
INCIPIENT FLT 1 TRIP COUNTS NUMBER
INCIPNT FLT 1 DETECT WINDOW
INCIPIENT FAULT 1 RESET DELAY
5
5.8.11.5 VT fuse failure
SETTINGS  CONTROL ELEMENTS  MONITORING ELEMENTS  VT FUSE FAILURE 1(2)
 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
5-296
— There are two modes of operation available for the incipient cable fault detector element. In the
— Selects the number of faults required to initiate a trip.
— Specifies a time window for "Counts per window" mode of operation.
— Specifies a reset time for the output after the trip is initiated.
Figure 5-158: Incipient cable fault detector logic
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
Range: Disabled, Enabled
Range: 0.000 to 65.535 s in steps of 0.001
Range: Disabled, Enabled
Range: 0.004 to 3.000 pu in steps of 0.001
L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
INCIPNT FLT 1