7SR210 & 7SR220 Description of Operation
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5.9
Load Blinder (21)
Load Blinders are used with directional overcurrent protection elements to block tripping during sustained heavy
load periods in distribution networks.
A Load Blinder element is provided in the 7SR22 relay with two operating modes, three-phase and single-phase.
5.9.1
Load Blinder (21) Three-Phase
Three-phase mode uses positive sequence impedance Z1. Both the negative sequence overcurrent threshold
(Blinder I2 > Block) and the under-voltage threshold (Blinder V< Block) are used to block the function.
21LB-3P Angle
sets the angle for the load blinder region.
21LB-3P Impedance
sets the impedance of the load blinder region.
21LB-3P VPPS
sets the level of positive phase sequence voltage.
21LB-3P IPPS
sets the level of negative phase sequence current.
Operation of the element can be inhibited from: -
Inhibit LB
A binary input, virtual input, function key or remote data communications
The design of Load Blinder 3Ph makes consideration that protection blocking should be issued only during
definable allowable system power flow conditions i.e. an overcurrent blocking signal can only be issued when: -
a. Positive Sequence Voltage
Vpps
is not significantly changed, when the
Vpps
is above the
21LB-3P
VPPS Setting.
AND
b. Negative Sequence Current
Inps
is lower than
21LB-3P INPS Setting
AND
c. Distributed generators feed in PPS current into the system. In case of high load in system due to
distributed generation hence resulting in change of
Zpps.
Zpps
is calculated from
Vpps
and
Ipps
. The magnitude and angle of
Zpps
is compared with
21LB-3P
Impedance
and
21LB-3P Angle
to determine if the impedance is in operate or block and/or FWD or
REV zone.
Figure 5.9.1-1
Logic Diagram: Load Blinder Three-Phase
Summary of Contents for Argus 7SR21
Page 1: ...Energy Management 7SR21 7SR22 Argus Overcurrent Relay Reyrolle Protection Devices ...
Page 2: ......
Page 4: ...Contents 7SR11 and 7SR12 Page 2 of 2 2018 Siemens Protection Devices Limited ...
Page 185: ...7SR210 Settings Guide Unrestricted 2018 Siemens Protection Devices Limited Page 61 of 61 ...
Page 277: ...7SR220 Settings Guide Unrestricted Page 72 of 107 2013 Siemens Protection Devices Limited ...
Page 382: ...7SR220 Technical Manual Chapter 4 Page 2 of 96 2017 Siemens Protection Devices Limited ...
Page 386: ...7SR220 Technical Manual Chapter 4 Page 6 of 96 2017 Siemens Protection Devices Limited ...
Page 398: ...7SR220 Technical Manual Chapter 4 Page 18 of 96 2017 Siemens Protection Devices Limited ...
Page 414: ...7SR220 Technical Manual Chapter 4 Page 34 of 96 2017 Siemens Protection Devices Limited ...
Page 466: ...7SR220 Technical Manual Chapter 4 Page 86 of 96 2017 Siemens Protection Devices Limited ...
Page 468: ...7SR220 Technical Manual Chapter 4 Page 88 of 96 2017 Siemens Protection Devices Limited ...
Page 470: ...7SR220 Technical Manual Chapter 4 Page 90 of 96 2017 Siemens Protection Devices Limited ...
Page 472: ...7SR220 Technical Manual Chapter 4 Page 92 of 96 2017 Siemens Protection Devices Limited ...
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