Parameter: 1Ph > Angle -ve
•
Default setting: 20°
Reverse load current flow will have a relatively high power factor in comparison to reverse fault current
flow. This setting defines the positive pickup angle for the 21LB function i.e. the function will not operate
for angular measurement above this setting.
Parameter: 1Ph > Impedance
•
Default setting: 10 Ω
The secondary positive phase sequence impedance and defines the lowest level of 21LB pickup.
Parameter: 3Ph > I
nps
Setting
•
Default setting: 0.5 x I
n
(0.5 ⋅ I
rated
)
This setting for the secondary negative phase sequence current determines whether the system current
distributions are within normal operating limits e.g. flow of unbalanced fault is indicated by an increased
negative phase sequence current (I
2
). Operation of the 21LB function will be blocked for values of I
2
above this setting.
Parameter: 3Ph > V
pps
Setting
•
Default setting: 50 V
This setting for the secondary positive phase sequence voltage determines whether the system voltage is
within normal operating limits e.g. flow of fault current may be coincident with reduced positive phase
sequence voltage (V
1
) and increased negative phase sequence voltage (V
2
). Operation of the 21LB func-
tion will be blocked for values of V
1
below this setting.
Parameter: 3Ph > Angle +ve
•
Default setting: 20°
Reverse load current flow will have a relatively high power factor in comparison to reverse fault current
flow, this setting defines the positive pickup angle for the 21LB function i.e. the function will not operate
for angular measurement above this setting.
Parameter: 3Ph > Angle -ve
•
Default setting: 20°
Reverse load current flow will have a relatively high power factor in comparison to reverse fault current
flow. This setting defines the positive pickup angle for the 21LB function i.e. the function will not operate
for angular measurement above this setting.
Parameter: 3Ph > Impedance
•
Default setting: 10 Ω
The secondary positive phase sequence impedance and defines the lowest level of 21LB pickup.
Settings Example
The 3-phase load blinders (21LB-3P) are required to block the directional overcurrent relay so that tripping is
inhibited for reverse load current with a power factor greater than 0.94.
Protection and Automation Functions
5.1 21LB Load Blinder
146 Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019
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