Siemens 7SR51 - Application and Setting Notes

•
Positive phase sequence voltage PPS (V
1
) is above setting, and
•
Zero phase sequence current ZPS (I
0
) is below setting, and
•
Measured impedance (Z) is above setting,
•
Measured impedance (Z) is within angular limits.
[lo_7SR5_21logicdiagramsinglephase, 1, en_US]
Figure 5-2 Logic Diagram: 21LB Load Blinder Single Phase
Application and Setting Notes
Parameter: 1Ph > I
zps
Setting
•
Default setting: 0.5 x I
n
(0.5 ⋅ I
rated
)
This setting for the secondary zero phase sequence current determines whether the system current distri-
butions are within normal operating limits e.g. flow of earth current is indicated by an increased zero
phase sequence current (I
0
). Operation of the 21LB function will be blocked for values of I
0
above this
setting.
Parameter: 1Ph > 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: 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.
5.1.4
Protection and Automation Functions
5.1 21LB Load Blinder
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 145
C53000-G7040-C014-1, Edition 11.2019