Vt Fuse Failure Unit (Vtff); Vt Fuse Failure Unit Setpoints; Fuse Failure Algorithm - GE Multilin F650 Instruction Manual

5 SETPOINTS
Note: The Switchgear element used in the VT Fuse Failure unit is the one configured in the Number of Switchgear
setpoint, inside Breaker setpoints at Setpoint > Protection Elements > Breaker > Breaker setpoints. This switchgear
must have previously been configured at Setpoint > Relay Configuration > Switchgear
Fuse failure detector is used to block protection units that can operate incorrectly due to a partial or total voltage loss. This
loss can be caused by the voltage transformers secondary circuit protection fuse failure.
Setpoint > Control Elements > VT Fuse Failure
Table 5–80: VT FUSE FAILURE UNIT SETPOINTS
SETPOINT > CONTROL ELEMENTS > VT FUSE FAILURE
SETPOINT DESCRIPTION
Function permission
Snapshot event generation
The fuse failure unit has only two setpoints, one to enable or disable the unit and the other to enable or disable the
snapshot event generation.
The fuse failure signal provided by the unit (VT FUSE FAILURE) can be monitored at Actual> Status > Control Elements
>VT Fuse Failure

5.5.7.1 FUSE FAILURE ALGORITHM

To detect the different types of fuse failure that can occur, it is necessary to use different detection methods. A fuse failure
indication with loss of one or two voltage phases provides a significant level of negative sequence voltage, while a failure
caused by loss of the three phases is present with a noticeable positive sequence current level, being the positive
sequence voltage level very low.
F650 units detect fuse failure under three possible situations:
(1)Breaker closed and positive sequence voltage (V1) under an established value (V1<0.5 p.u.).
(2)Positive sequence voltage lower than 0.5 p.u (V1<0.5 p.u.) and positive sequence current higher than 0.075 p.u.
(I1>0.075 p.u.).
(3)Ratio between the negative and positive voltage components (V2/V1) higher than 0.25.
With the activation of any of the three previous signals during a period longer than 80 ms, the fuse failure signal (VT FUSE
FAILURE) is activated. Once this signal is activated, it is latched until the cause that produced it disappears; for this
purpose the following condition must be met:
(4)Positive sequence voltage higher than 0.75 p.u and positive sequence current lower than 0.05 p.u.
The fuse failure signal can be used to issue an alarm and/or to block elements that may operate incorrectly due to a partial
or total loss of voltage. Protection elements that are usually blocked by the fuse failure signal are voltage restraint
overcurrent units, and directional units. To configure the block of these elements it is necessary to enter the Setpoint >
Relay Configuration > Protection Elements" menu and select as block input for protection units, the fuse failure
operation signal.
GE Multilin
NAME DEFAULT VALUE
Function DISABLED
Snapshot Events ENABLED
F650 Digital Bay Controller
5.5 CONTROL ELEMENTS

5.5.7 VT FUSE FAILURE UNIT (VTFF)

STEP RANGE
N/A [DISABLED – ENABLED]
N/A [DISABLED – ENABLED]
5
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