Siemens Reyrolle 7SR5 Manual page 146

Protection and Automation Functions
5.1 21LB Load Blinder
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
•
Default setting: 0.5 x I
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
above this setting.
Parameter: 3Ph > V
•
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
tion will be blocked for values of V
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.
146
Setting
nps
(0.5 ⋅ I )
n rated
). Operation of the 21LB function will be blocked for values of I
2
Setting
pps
) and increased negative phase sequence voltage (V
1
below this setting.
1
). Operation of the 21LB func-
2
Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019
2