12
SME70-O-Manual-04-2020
Operating characteristic voltage-residual current
for directional earth fault element (67N)
Operating characteristic time to voltage-residual current
for directional earth fault element (67N)
Fig.1
67NS1 (INV=OFF)
67NS2 (INV=OFF)
I
0
>
I
0
>,
V
0
>,
V
i
>
TRIP
TRIP
I
0
V
0
V
0
>,
V
i
>
I
0,
V
0,
V
i
t
120°
60°
V
0
,
V
i
&
I
0
255°
60°
V
0,
V
i
V
0
,
V
i
&
I
0
Fig.2
67NS1 (INV=ON)
67NS2 (INV=ON)
300°
240
V
0
,
V
i
&
I
0
240°
75°
V
0
,
V
i
&
I
0
TRIP
TRIP
TRIP
TRIP
NO TRIP
NO TRIP
NO TRIP
NO TRIP
t
ED
>,
t
ED
>>
V
0,
V
i
V
0,
V
i
V
0,
V
i
• V
0
Operation
The start of any 67N element becomes active when the following conditions are contemporaneously
active:
• The residual current fundamental component (
I
0
) overcomes the threshold
• The residual voltage fundamental component (
V
0
) or the negative sequence voltage (
V
i
) over-
comes the threshold
• The residual current phasor (
I
0
) is located inside the trip angular sector.
Each directional earth fault overcurrent elements can be enabled or disabled by setting ON or OFF
the
67NS1 Enable
,
67NS2 Enable
parameters inside the
Set \ 67
menu.
The setting in which both thresholds are disabled is indicated by a flashing LED 67N.
Depending on the type of fault the relays 51 and 67N and the LED 67N are driven.
• The trip of the 67NS1 threshold (60 ... 255°), with the 67NS2 threshold disabled, drives the relay 67N
and 67N LED
• The trip of the 67NS2 threshold (60 ... 120°), with the 67NS1 threshold disabled, drives the 51 and
67N relays and 67N LED
• A fault inside the 120...255° sector with the 67NS1 and 67NS2 threshold enabled, drives the 67N
relay and 67N LED
• A fault inside the 60...120° sector with the 67NS1 and 67NS2 threshold enabled, drives the 51 and
67N relays and 67N LED
