Description Of Functionality - Siemens 7SG11 Argus Manual

Sequence of event records
Up to 500 events are stored and time tagged to 1ms resolu-
tion. These are available via the communications.
Fault records
The last 5 fault records are available from the Argus fascia with
time and date of trip, measured quantities and type of fault.
Disturbance recorder
The waveform recorder may be triggered from a protection
function or external input and has a configurable pre-fault
trigger. Up to 5 fault waveforms may be stored.
On all models the AC current waveforms are stored together
with the digital states of the status inputs and output relays.
7SG112n models with voltage and power metering addition-
ally store AC voltage waveforms.
Reydisp Evolution
Reydisp Evolution is common to the entire range of Reyrolle
numeric products. It provides the means for the user to apply
settings, interrogate settings, retrieve events and disturbance
waveforms from the Argus.
Application
With reference to Fig 4: Typical Applications for 7SG11
Overcurrent Series Relays
Feeder 1 is a cable circuit; auto-reclosing is not applied, so a
7SG111n relay is used. Transient faults can occur on cables,
which are initially self-sealing until the insulation is sufficiently
weakened for them to become permanent. In this time much
damage can occur. In order to protect against these and to
maintain system overcurrent grading, a delayed reset of up to
60 seconds can be set on the IDMTL algorithms.
Feeder 4 is an overhead line so a 7SG1144 with integrated
auto-reclosing is used.
The 7SG112n directional protection relay is typically applied
wherever there is a potential source of power on both sides of
the circuit breaker, i.e. fault current can flow in both
directions. If there is a fault on the incoming circuits, or the
transformers, the dual setting allows for correct grading to be
applied. This directional protection will ensure that only the
faulted circuit is tripped, and the healthy circuit remains in
service.
On feeders that form a ring where overhead lines are used e.g.
feeders 2 and 3, the dual directional 7SG1164 relay can be
employed to give integrated auto-reclosing, and correct
grading in both directions around the ring.
An inexpensive buszone protection can be formed using the
Argus relays in an overcurrent blocking scheme. The starters of
the Argus on the outgoing feeders are set to operate status
inputs of the Argus on the incomers, which are set to block the
Siemens Protection Devices Limited
lowset algorithms. If there is a fault on one of the outgoing
feeders, e.g. Feeder 1, the starter on the 7SG111n will cause
the lowset on the 7SG112n of Incomer 1 to be inhibited. Its
IDMTL characteristic will continue to function as a backup.
However, for a fault on the busbar the 7SG112n on Incomer 1
will be allowed to operate and will quickly clear the fault.

Description of Functionality

7SG11 overcurrent relays provides comprehensive overcurrent
protection with programmable input and output matrix. In
addition 8 setting groups enable a flexible approach to protec-
tion settings.
Phase Overcurrent
One IDMTL/DTL characteristic and 3 DTL characteristics provide
phase overcurrent protection, each with independent current
settings and delays. The IDMT stage has a programmable reset
with a definite time delay to improve detection of flashing
faults.
Earth Fault
One IDMTL/DTL characteristic and 3 DTL characteristics provide
phase overcurrent protection, each with independent current
settings and delays. The IDMT stage has a programmable reset
with a definite time delay to improve detection of flashing
faults.
Sensitive earth fault/Restricted Earth Fault
One current setting with two definite time delays are provided
for sensitive earth fault protection. This element operates from
fundamental frequency only, 50Hz or 60Hz, and ideally a core
balance CT should be used to improve accuracy, if low current
settings are required.
With the addition of a stabilising resistor and, where applica-
ble, non-linear resistors, the sensitive earth fault input may be
used for restricted earth fault protection in a high impedance
scheme.
Trip Circuit Supervision
The trip circuit is monitored by a status input. This is linked to
an alarm and may be configured to operate an output relay.
Circuit Breaker Fail
The circuit breaker fail function operates by monitoring the
current following a trip signal and issues an alarm if the cur-
rent does not cease within a specified time interval. A two-
stage time delayed output can be used to operate output con-
tacts to retrip the same circuit breaker, using a second trip coil,
or to backtrip an upstream circuit breaker.
CT Supervision
CT wiring is monitored by comparing the current levels of the
three line currents against each other. This is linked to an
alarm and may be configured to operate an output relay.
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