Functions
2.9 Teleprotection for Earth Fault Protection (optional)
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
249
2.9
Teleprotection for Earth Fault Protection (optional)
2.9.1
General
With the aid of the integrated comparison logic, the directional earth fault protection according to Section 2.8
can be expanded to a directional comparison protection scheme.
Transmission Modes
One of the stages which must be directional
Forward
is used for the directional comparison. This stage can
only trip rapidly if a fault is also detected in the forward direction at the other line end. A release (unblock) signal
or a block signal can be transmitted.
The following permissive teleprotection schemes are available:
• Directional comparison,
• Directional unblock scheme
and blocking scheme:
• Blocking of the directional stage.
Further stages can be set as directional and/or non-directional backup stages.
Information on the effect of the phase selector on the release signals can be found in Section 2.8 under margin
heading „Selection of the Earth Faulted Phase“.
Transmission Channels
For the signal transmission, one channel in each direction is required. Fibre optic connections or voice frequen-
cy modulated high frequency channels via pilot cables, power line carrier or microwave radio links can be used
for this purpose. If the same transmission channel is used as for the transmission by the distance protection,
the transmission mode must also be the same!
As an alternative, digital communication lines connected to one of the protection data interfaces can be used
for signal transmission, For example: Fibre optic cables, communication networks or dedicated cables (control
cable or twisted phone wire). In this case, send and receive signals must be linked to the remote commands
via CFC. Directional comparison pickup is suitable for these kinds of transmission.
7SD5 also allows the transmission of phase-selective signals. This has the advantage that single-pole auto-
matic reclosure can be carried out even if two single-phase faults occur on different lines in the system. If no
single-phase fault is detected, signals are transmitted for all three phases. With earth fault protection, phase-
selective transmission only makes sense if the earth faulted phase is identified by means of the phase selector
(address
3109
Trip 1pole E/F
is set to
YES
, refer also to Section 2.8 under „Tripping“).
The signal transmission schemes are also suited to three terminal lines (teed feeders). In this case, signal
transmission channels are required from each of the three ends to each of the others in both directions.
In case of disturbances on the transmission path, the teleprotection supplement can be blocked. In convention-
al signal transmission schemes, the disturbance will be signalled by a binary input.
Activation and Deactivation
The comparison function can be switched on and off by means of the parameter
3201
FCT Telep. E/F
, via
the system interface (if available) and via binary inputs (if allocated). The switch states are saved internally
(refer to Figure 2-118) and secured against loss of auxiliary supply. It is only possible to switch on from the
source from where it had previously been switched off. To be active, it is necessary that the function is switched
on from all three switching sources.
