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At address 131 Earth Fault O/C you can set the characteristic group which the earth fault protection uses
for operation. In addition to the definite time overcurrent protection, which covers up to three phases, an
inverse-time earth fault protection function may be configured depending on the version ordered that operates
either according to an IEC characteristic (TOC IEC) or an ANSI characteristic (TOC ANSI) or according to a
logarithmic-inverse characteristic (TOC Logarithm.). If an inverse-time characteristic is not required, the
stage usually designated „inverse time" can be used as the fourth definite-time stage (Definite Time). Al-
ternatively, you can select an earth fault protection with inverse-time characteristic U0 inverse or a zero se-
quence power protection Sr inverse. The different characteristics are depicted in the Technical Data. You
can also disable the earth fault protection (Disabled).
When using the earth fault protection, it can be complemented by teleprotection schemes. Select the desired
scheme at address 132 Teleprot. E/F. You can select the direction comparison scheme
Dir.Comp.Pickup, the unblocking scheme UNBLOCKING and the blocking scheme BLOCKING. The proce-
dures are described in detail in Section 2.9. If you do not want to use teleprotection in conjunction with earth
fault protection set Disabled.
If the device features an automatic reclosing function, address 133 and 134 are of importance. Automatic re-
closure is only permitted for overhead lines. It must not be used in any other case. If the protected object con-
sists of a combination of overhead lines and other equipment (e.g. overhead line in unit with a transformer or
overhead line/cable), reclosure is only permissible if it can be ensured that it can only take place in the event
of a fault on the overhead line. If no automatic reclosing function is desired for the feeder at which 7SD5 oper-
ates, or if an external device is used for reclosure, set address 133 Auto Reclose to Disabled.
Otherwise set the number of desired reclosing attempts there. You can select 1 AR-cycle to 8 AR-cycles.
You can also set ADT (adaptive dead times); in this case the behaviour of the automatic reclosure function is
determined by the cycles of the remote end. The number of cycles must however be configured at least in one
of the line ends which must have a reliable infeed. The other end — or other ends, if there are more than two
line ends — may operate with adaptive dead time. Section 2.17 provides detailed information on this topic.
The AR control mode at address 134 allows a total of four options. On the one hand, it can be determined
whether the auto reclose cycles are carried out according to the fault type detected by the pickup of the starting
protection function(s) (only for three-pole tripping) or according to the type of trip command. On the other
hand, the automatic reclosure function can be operated with or without action time.
The setting Trip with T-action / Trip without T-action ... (default setting = Trip with T-action
... ) is preferred if single-pole or single-pole/three-pole auto reclose cycles are provided for and possible. In this
case, different dead times (for every AR cycle) are possible after single-pole tripping and after three-pole trip-
ping. The tripping protection function determines the type of tripping: Single-pole or three-pole. The dead time
is controlled in dependence on this.
The setting Pickup with T-action / Pickup without T-action ... ... (Pickup with T-action ...)
is only possible and visible if only three-pole tripping is desired. This is the case when either the ordering
number of the device model indicates that it is only suited for three-pole tripping, or when only three-pole trip-
ping is configured (address 110 Trip mode = 3pole only, see above). In this case, different dead times
can be set for the auto reclose cycles following 1-, 2- and 3-phase faults. The decisive factor here is the pickup
situation of the protection functions at the instant the trip command disappears. This operating mode enables
making the dead times dependent on the type of fault also for three-pole reclosure cycles. Tripping is always
three-pole.
The setting Trip with T-action with action time) provides an action time for each auto-reclose cycle. The
action time is started by a general pickup of all protection functions. If there is no trip command yet when the
action time has expired, the corresponding automatic reclosure cycle cannot be executed. Section 2.17 pro-
vides detailed information on this topic. This setting is recommended for time-graded protection. If the protec-
tion function which is to operate with automatic reclosure, does not have a general pickup signal for starting the
action times, select Trip without T-action... (without action time).
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
Functions
2.1 General
41
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