Functions
2.12 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
237
Direction Determination for cos-
ϕ
/ sin-
ϕ
Addresses
3115
to
3126
are important for direction determination.
Address
3115
67Ns-2 DIRECT
determines the direction of the definite high-set current element 50Ns-2 and
can be set to either
Forward
or
Reverse
or
Non-Directional
, i.e. to both directions. The direction of the
current element 50Ns-1 or or 51Ns can be set to
Forward
or
Reverse
or
Non-Directional
, i.e. to both
directions, at address
3122
67Ns-1 DIRECT.
.
Current value
RELEASE DIRECT.
(address
3123
) is the release threshold for directional determination. It is
based on the current components which are perpendicular to the directional limit lines. The position of the di-
rectional limit lines themselves are based on the settings entered at addresses
3124
and
3125
.
The following applies to the determination of direction during ground faults: The pickup current 3I0 DIR.
(=
RELEASE DIRECT.
address
3123
) must be set as high as possible to avoid false pickup of the device pro-
voked by asymmetrical currents in the system and by current transformers (especially in the Holmgreen-con-
nection).
If direction determination is used in conjunction with one of the current elements discussed above (
50Ns-1
PICKUP
, addresses
3117
ff, or
51Ns PICKUP
, addresses
3119
ff), it is sensible to select a value for address
RELEASE DIRECT.
that is lower than or equal to the above pickup value.
A corresponding message (reverse, forward, or undefined) is issued upon direction determination. To avoid
chatter for this message resulting from extremely varying ground connection currents, a dropout delay
RESET
DELAY
, entered at address
3126
, is initiated when directional determination drops out, and the message is held
for this period of time.
When address
3124
PHI CORRECTION
is set to 0.0°, in address
3125
the following signifies
•
MEAS. METHOD
=
COS
ϕ
the resistive component of the ground current with respect to the displacement voltage is most relevant for
the current value
RELEASE DIRECT.
(3I0 DIR.),
MEAS. METHOD
=
SIN
ϕ
the reactive (capacitive) component of the ground current with respect to the displacement voltage is most
relevant for the current value
RELEASE DIRECT.
(3I0 DIR.) (Figure 2-92).
Figure 2-92
Directional characteristic for sin–
ϕ
–measurement
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