Additional Security Logic For Differential Protection Stsggio; Five Terminal Line With Master-Slave System - ABB RED670 Product Manual

Line differential protection RED670 ANSI
Customized
Product version: 1.2
RED
670
Communication Channels
RED
670
ANSI05000044 V1 EN
Figure 5.

Five terminal line with master-slave system

Current samples from IEDs located geographically apart from
each other, must be time coordinated so that the current
differential algorithm can be executed correctly. In IED, it is
possible to make this coordination in two different ways. The
echo method of time synchronizing is normally used whereas
for applications where transmit and receive times can differ, the
optional built in GPS receivers can be used.

Additional security logic for differential protection STSGGIO (11)

Additional security logic for differential protection (STSGGIO ,
11) can help the security of the protection especially when the
communication system is in abnormal status or for example
when there is unspecified asymmetry in the communication link.
It helps to reduce the probability for mal-operation of the
protection. STSGGIO (11) is more sensitive than the main
protection logic to always release operation for all faults
detected by the differential function. STSGGIO (11) consists of
four sub functions:
• Phase-to-phase current variation
• Zero sequence current criterion
• Low voltage criterion
• Low current criterion
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Protected zone
RED RED
670 670
The communication link is continuously monitored, and an
automatic switchover to a standby link is possible after a preset
time.
Phase-to-phase current variation takes the current samples as
input and it calculates the variation using the sampling value
based algorithm. Phase-to-phase current variation function is
major one to fulfill the objectives of the startup element.
Zero sequence criterions takes the zero sequence current as
input. It increases the security of protection during the high
impedance fault conditions.
Low voltage criterion takes the phase voltages and phase-to-
phase voltages as inputs. It increases the security of protection
when the three-phase fault occurred on the weak end side.
Low current criterion takes the phase currents as inputs and it
increases the dependability during the switch onto fault case of
unloaded line.
1MRK505226-BUS D
RED
670
en05000044_ansi.vsd
ABB