(1) Description of Operation 7SR224
©2009 Siemens Protection Devices Limited Page 19 of 66
Minimum Polarising Voltage
The 67 Minimum Voltage setting defines the minimum polarising voltage level. Where the measured
polarising voltage is below this level no directional output is given and operation of protection elements
set as directional will be inhibited. This prevents mal-operation under fuse failure/MCB tripped
conditions where noise voltages can be present.
Figure 3.1-1 Logic Diagram: Directional Overcurrent Element (67)
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