7SR210 & 7SR220 Applications Guide
© 2013 Siemens Protection Devices Limited
Page 43 of 48
5.9
Load Blinder (21)
NB: It is important to observe the convention regarding Forward and Reverse directions of current.
Load Blinders are used with directional overcurrent elements to block forward tripping during periods of high load
currents that can occur in distribution networks. The blinder is operated during user defined load conditions and is
used in conjunction with the relay protection elements.
One of the major factors contributing to high load conditions is an increase of distributed generation capacity
which can feed power back into the network contrary to the ‘normal’ direction of power flow. This can result in
current levels above the relay setting and can cause tripping of overcurrent elements.
One typical example is on paralleled incoming transformer circuits, forward directional overcurrent elements are
parametised such that they detect faults on the transformer LV connections for currents flowing in the direction
contrary to the ‘normal’ load flow. These forward elements have a relatively low current setting, typically <45% of
transformer rating, as current normally only flows in this direction during fault conditions. When embedded
generation is connected into the downstream network, these relays limit the level of current that can be fed back
into the grid.
Load Blinders measure the system impedance and are set to differentiate between a fault having a relatively low
impedance and a fault having a relatively high impedance. Additional measurands are also considered to increase
the security of operation.
Figure 5.9-1 Paralleled Transformers and Feeders
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 ...
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Page 643: ...Unrestricted ...