Vt Fuse Failure Element (Vtff) - GE F650 Instruction Manual

5 SETTINGS
Note: The Switchgear element used in the VT Fuse Failure element is the one configured in the Number of Switchgear
setting, inside Breaker settings at Setpoint > Protection Elements > Breaker > Breaker settings. This switchgear must
have previously been configured at Setpoint > Relay Configuration > Switchgear
The fuse failure detector is used to block protection elements 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 5–85: VT FUSE FAILURE ELEMENT SETTINGS
SETPOINT > CONTROL ELEMENTS > VT FUSE FAILURE
SETTING DESCRIPTION
Function permission
Snapshot event generation
The fuse failure element has only two settings, one to enable or disable the element and the other to enable or disable the
snapshot event generation.
The fuse failure signal provided by the element (VT FUSE FAILURE) can be monitored at Actual> Status > Control
Elements >VT Fuse Failure
5.5.7.1 FUSE FAILURE ALGORITHM
To detect different types of fuses failures, it is necessary to use different detection methods. In example, a fuse failure
indication with loss of one or two voltage phases provides a significant level of negative sequence voltage, instead of a loss
of all voltage phases which will cause a very low positive sequence voltage, but any negative sequence voltage.
F650 elements 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 whatever caused 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 elements, and directional elements. 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 elements, the fuse
failure operation signal.
GEK-106310AB
NAME DEFAULT VALUE
Function DISABLED
Snapshot Events ENABLED
F650 Digital Bay Controller
5.5 CONTROL ELEMENTS

5.5.7 VT FUSE FAILURE ELEMENT (VTFF)

STEP RANGE
N/A [DISABLED – ENABLED]
N/A [DISABLED – ENABLED]
5
5-107