79 Automatic Reclosing
Overview of Functions
The cause of a high proportion of faults on an overhead line (OHL) network is transient in nature. The arc is
then sustained by energy supplied from an otherwise healthy power network. These faults can be cleared by
any circuit‑breaker trip and the network restored by reclose of the circuit‑breaker after the line has been dead
for a short time to allow the fault current arc to fully extinguish.
In distribution systems, additional high speed – low setting protection elements can be configured specifically
for this purpose which will clear these transient faults without the requirement to grade with other protection
devices. Delayed protection can then be applied which will provide correct grading with other devices and
slower protection trip time as well as greater energy which can burn-off some semi-permanent faults before
further re-close(s). Typically this autoreclose (AR) sequence of Instantaneous (Inst) trip(s) and reclose delay
(Deadtime) followed by delayed trip(s) provide the automatic optimum method of clearing all types of fault
i.e. both transient and permanent, as quickly as possible and achieving the desired outcome of keeping as
much of the net-work in-service as possible
The Automatic Reclosing function:
•
Automatically reconnects circuits following clearance of transient faults on overhead line networks where
such faults are possible
•
Can be used to save downstream fuses for transient faults
•
Can interface with external protection devices as well as internal elements
•
Integrates with circuit‑breaker control logic, monitoring and settings and provides event recording of the
sequence and instrumentation for use during testing
•
Can incorporate synchronizing check to ensure safe and stable restoration
•
Can be used to control the application of protection elements to provide initial fast fault clearance for
transient faults but revert to time graded protection following a pickup on reclose
•
Can apply repeated reclose shots up to 4 times (5 trips) with increasing dead times between attempts
•
Can apply different deadtimes for different fault types and also different deadtimes for each autoreclose
shot
•
Can be switched in and out of service locally and remotely
Figure 7-5 shows an example for a typical sequence with 2 automatic reclose attempts where the fault is still
present at the first reclose but the second attempt is successful.
[dw_7SR5_function79Overview, 1, en_US]
Figure 7-5 Sequence Diagram of a 2-Shot Autoreclose (2nd Reclosing Successful)
Structure of the Function
The Automatic Reclosing function element has group dependent settings. These settings can be different
in each settings group – group numbers (Gn) 1 to 4.
Settings for the circuit‑breaker are used by autoreclose and shared with Manual Close control.
7.3
7.3.1
7.3.2
Control Functions
7.3 79 Automatic Reclosing
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 421
C53000-G7040-C014-1, Edition 11.2019
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