Siemens 7SR12 Argus Manual page 388

7SR11 & 7SR12 Applications Guide
An alternative type of load shedding scheme would be to set all underfrequency stages to about the same
frequency setting but to have different length time delays set on each stage. If after the first stage is shed the
frequency doesn't recover then subsequent stages will shed after longer time delays have elapsed.
Generator
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Figure 2.16-1 Load Shedding Scheme Using Under-Frequency Elements
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STAGE 1: Least important
STAGE 2
STAGE 3
STAGE 4
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Essential
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