FUNCTION CHARACTERISTICS
86
NA30 - Manual - 04 - 2022
• OFF: no action are issued by 74VT.
• Block: all the four thresholds are blocked when the 74VT external signal is active.
• Not directional: all the four thresholds are switched from directional to not directional criteria
when the 74VT external signal is active.
Malfunctioning of the directional overcurrent elements can be avoided when VTs secondary fault
will arise (fuse or MCB tripping) by switching the overcurrent directional to non directional overcur-
rent protection
The
74VText67N
parameter may be set as
OFF, Block, Not directional
inside the
Set \ Profile
A(or B) \ Directional earth fault overcurrent-67N \
Common configuration
menu, while the
74VText
function must be assigned to the selected binary inputs inside the
Set \ Inputs \ Binary input IN1(...x)
menus (IN1 or ...INx matching).
For all the four thresholds (common for all thresholds) an insensibility zone may be enabled in the
voltage-current plane.
If enabled, the insensibility zone is user adjustable by means the M multiplier (common for all thresh-
olds); the rectangle defined by the current and voltage thresholds and the same multiplied by M
becomes a No trip zone.
Such insensibility zone may be useful to avoid unwanted trip in the presence of some fixed residual
current and/or voltage (e.g. CT and or VT errors in the residual measurements).
The
Insens-Zone
(
OFF, ON
) and
M
parameters may be adjusted inside the
Set \ Profile A(or B)\Di-
rectional earth fault overcurrent-67N \
Common configuration
menu
.
Module
If the
module
principle and the operation mode is not switched to “not directional” (by the 74VT
function), the start of any 67N threshold becomes active when the following A) and B) conditions
are contemporaneously active:
A) in the “Insens-Zone=OFF” operating mode:
- The residual current (
I
E
) fundamental component overcomes the threshold (
I
ED>
,
I
ED>>
,
I
ED>>>
,
I
ED>>>>
)
AND
- The residual voltage (
U
E
or
U
EC
) fundamental component overcomes the threshold (
U
ED>
,
U
ED>>
,
U
ED>>>
,
U
ED>>>>
),
while in the “Insens-Zone=ON” operating mode:
- The residual current (
I
E
) fundamental component overcomes the threshold (
I
ED>
,
I
ED>>
,
I
ED>>>
,
I
ED>>>>
)
AND
- The residual current (
I
E
) fundamental component overcomes the threshold (M∙
U
ED>
, M∙
U
ED>>
,
M∙
U
ED>>>
, M∙
U
ED>>>>
)
OR
- The residual current (
I
E
) fundamental component overcomes the threshold (M∙
I
ED>
, M∙
I
ED>>
,
M∙
I
ED>>>
,
M∙
I
ED>>>>
)
char-F67N-IeUe.ai
Voltage/current characteristic concerning the earth fault overcurrent element - 67N
with insensibility zone disabled
Voltage/current characteristic concerning the ground directional overcurrent - 67N
with insensibility zone enabled
I
E
I
ED
>,
I
ED
>>,
I
ED
>>>,
I
ED
>>>>
M∙
I
ED
>, M∙
I
ED
>>, M∙
I
ED
>>>, M∙
I
ED
>>>>
M∙
U
ED
>, M∙
U
ED
>>, M∙
U
ED
>>>, M∙
U
ED
>>>>
TRIP
U
E
U
EC
I
E
I
ED
>,
I
ED
>>,
I
ED
>>>,
I
ED
>>>>
TRIP
U
E
U
EC
U
ED
>,
U
ED
>>,
U
ED
>>>,
U
ED
>>>>
U
ED
>,
U
ED
>>,
U
ED
>>>,
U
ED
>>>>
