Table of Contents
Advertisement
2.2.2
Operating Modes of the Differential Protection
2.2.2.1 Mode: Log Out Device
General
The „Log out device" mode (also: Log out device functionally) is used to log the device out of the line protection
system with the local circuit breaker being switched off. The differential protection continues to be active for the
other ends. As the local circuit breaker and the line disconnector are open, revision work can be done at the
local feeder without affecting operation at the other ends.
It has to observed that not all devices of a line protection system can be logged out as desired. The reason is
that the communication of the remaining devices always has to be ensured. For this reason, you can log out
any device in a ring topology; in a chain topology, however, only the devices at the ends of the chain can be
logged out.
It is also possible to successively log several devices out of the line protection system. It must observed that
the logout always has to start from the devices at the end of the remaining chain topology.
If all devices of a line protection system except one are logged out, the remaining device continues to operate
in differential protection mode; the special feature, however, being that only the locally measured currents are
included in the logic as differential currents. The behaviour is now comparable to a time overcurrent protection.
The set thresholds for the differential current now only evaluate the local current.
A device can be logged out and on as described below:
• Using the integrated keypad: Menu Control/Taggings/Set: „Logout"
• Via DIGSI: Control / Taggings „Logout local device"
• Via binary inputs (No. 3452 „>Logout ON", No. 3453 „>Logout OFF") if this was allocated
In all devices of the line protection system, logging out/on of a device is signalled by the indications
„Rel1Logout" to „Rel6Logout" (No. 3475 to No. 3480).
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
2.2 Protection Data Interfaces and Protection Data Topology
Functions
79
Advertisement
Table of Contents
