[fo_function21LBimpedancesetting1, 1, en_US]
i
i
NOTE
The equivalent primary impedance to the above:
Where:
I
rated,prim
= CT primary rating (A)
I
rated,sec
= CT secondary rating (A)
I
sec
= Secondary current = 1.5 ⋅ I
rated,sec
(e.g. nominated max. reverse load current)
V
rated,prim
= VT primary rating (phase-phase V)
V
rated,sec
= VT secondary rating (phase-phase V)
Z
prim
= Primary impedance
Z
sec
= Secondary impedance
21LB-3P Angle (+ve and -ve) Setting (‘b’ and ‘c’)
A setting of 20 degrees will allow blocking of the overcurrent element for system load power factors between
0.94 and unity.
21LB-3P V
pps
Setting
The blinder is only operational during normal load levels of reverse load flow. Where reverse current flow is
caused by a system fault the positive sequence voltage will reduce significantly. To facilitate load blinder oper-
ation the system should be substantially balanced i.e. positive phase sequence voltage will be high. A setting
of 0.95 V
rated
is selected i.e. 21LB-V
1
setting = 0.95 ⋅ 63.5 = 60 V.
21LB-3P I
nps
Setting
The blinder is only operational during normal load levels of reverse load flow. The system should be substan-
tially balanced i.e negative phase sequence current will be low. A 21LB-3P I
2
setting = 0.05 I
rated
is selected.
Settings Menu
Functions > Function Config
Parameter
Range
Settings
Default Gn1
Gn2
Gn3
Gn4
21LB Load Blinder
Enabled
Disabled
Disabled
5.1.5
Protection and Automation Functions
5.1 21LB Load Blinder
148
Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019
Содержание Reyrolle 7SR5
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