Functions
2.3 Directional Overcurrent Protection 67, 67N
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
113
67-1 Directional Overcurrent Element (phases)
The pickup value of the 67-1 element (
67-1 PICKUP
) address
1504
should be set above the maximum antic-
ipated load current. Pickup due to overload should never occur since in this mode the device operates as fault
protection with correspondingly short tripping times and not as overload protection. For this reason, lines are
set to approx. 20% above the maximum expected (over)load and transformers and motors to approx. 40%.
If the relay is used to protect transformers or motors with large inrush currents, the inrush restraint feature of
7SJ62/64 may be used for the
67-1
relay element (for more information see margin heading "Inrush Restraint").
The delay for directional elements (address
1505
67-1 DELAY
) is usually set shorter than the delay for non-
directional elements (address
1205
) since the non-directional elements overlap the directional elements as
backup protection. It should be based on the system coordination requirements for directional tripping.
For parallel transformers supplied from a single source (see "Applications"), the delay of elements
67-1
DELAY
located on the load side of the transformers may be set to 0 without provoking negative impacts on se-
lectivity.
The selected time is only an additional time delay and does not include the operating time (measuring time,
dropout time). The delay can be set to
∞
. After pickup the element will then not trip. Pickup, however, will be
signaled. If the 67-1 element is not required at all, the pickup value
67-1 PICKUP
should be set to
∞
. This
setting prevents from tripping and the generation of a pickup message.
67N-1 Directional Relay Element (ground)
The pickup value of the
67N-1
relay element should be set below the minimum anticipated ground fault current.
If the relay is used to protect transformers or motors with large inrush currents, the inrush restraint feature of
7SJ62/64 may be used for the
67N-1
relay element (for more information see margin heading "Inrush Re-
straint").
The delay is set at address
1605
67N-1 DELAY
and should be based on system coordination requirements
for directional tripping. For ground currents in a grounded system a separate coordination chart with short time
delays is often used.
The selected time is only an additional time delay and does not include the operating time (measuring time,
dropout time). The delay can be set to
∞
. After pickup the element will then not trip. Pickup, however, will be
signaled. If the 67N-1 element is not required at all, the pickup value
67N-1 PICKUP
should be set to
∞
. This
setting prevents from tripping and the generation of a pickup message.
Pickup Stabilization (67/67N Directional)
The pickups can also be stabilized via parameterizable dropout times under address
1518
67 T DROP-OUT
or
1618
67N T DROP-OUT
.
67-TOC Directional Element with IEC or ANSI Curves (phases)
Having set address
115
67/67-TOC
=
TOC IEC
or
TOC ANSI
when configuring the protective functions (Sec-
tion 2.1.1), the parameters for the inverse characteristics will also be available.
If the relay is used to protect transformers or motors with large inrush currents, the inrush restraint feature of
7SJ62/64 may be used for the
67-TOC
relay element (for more information see margin heading "Inrush Re-
straint").
If the inverse time trip characteristic is selected, it must be noted that a safety factor of about 1.1 has already
been included between the pickup value and the setting value. This means that a pickup will only occur if a
current of about 1.1 times the setting value is present.
The current value is set in address
1507
67-TOC PICKUP
. The setting is mainly determined by the maximum
operating current. Pickup due to overload should never occur, since the device in this operating mode operates
as fault protection with correspondingly short tripping times and not as overload protection.
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