ABB XT7, Руководство по эксплуатации и обслуживанию

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ABB | SACE Tmax XT
Protections | 15 - Additional protections and functions 79 | © 2020 ABB | 1SDH001821A1002 - ECN000135670
Gext Protection
G
ext
I41
t
t41
I
Function
Gext protection protects against earth faults and detects the fault current with a dedicated external toroid
S.G.R.
if S.G.R. toroid current exceeds threshold I41, the protection trips and, after a time established by the value
read and by the parameter settings, transmits the TRIP command.
To check and simulate the trip times in relation to all the parameters, please consult:
• summary table of the protections with the operating characteristics (page 87)
• the graph with trip curve (page 97)
Parameters
Toroid configuration is available in the Settings menu (page 37)
Parameter Description Default
External Toroid It allows the presence of external toroid S.G.R. to be activated OFF
Toroid size
Allows the reference current of the protection to be selected from
among four available quantities, from 100 A to 800 A
IMPORTANT: the current selected from the menu must be
consistent with the size of the external toroid S.G.R.
connected to the unit
100 A
Protection configuration is available in the Advanced menu (page 35)
Parameter Description Default
Enable
Activates/deactivates the protection and its availability in the
parameters menu
OFF
Trip Enable
Activates/deactivates transmission of the open command: if disabled,
the alarm and exceedance of protection time are only managed as
information
ON
Curve
Establishes curve dynamics and the threshold or trip time calculation:
• t= k: fixed time trip
• t= k/I
2
: inverse time-delay dynamic trip
t = k
Threshold I41
Establishes the value that activates the protection and contributes
towards calculating the trip time.
The value is given as both absolute value (Amperes) and relative value
(In) and can be set within the range: 0.1 In to 1 In, in 0.001 In steps
0,2 In
Time t41
It is the trip time or contributes towards timing calculation, depending
on the type of curve selected.
The value is given in seconds and can be set within the range: 0.1 s to
1 s, in 0.05 s steps
0,4 s
Threshold I41
Warns that the measured current is near to the protection activation
threshold.
The value is given in percentage of threshold I1 and can be set within
the range 50% I41 to 90% I41, in 1% steps.
The prealarm condition deactivates in two cases:
• current lower than prealarm threshold I41
• current higher than threshold I41
90 % I41
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