Siemens 7SR10 Argus Series, Manual

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7SR10, 7SR11, 7SR12 Applications Guide
© 2018 Siemens Protection Devices Limited Chapter 7 Page 27 of 41
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
Network
Incomer
G59
300/5
STAGE 1: Least important
STAGE 2
STAGE 3
STAGE 4
Essential
Load
6
1
2 5 5 3 4 2
4
Figure 2-23 Load Shedding Scheme Using Under-Frequency Elements
2.17 Power (32)
Directional power protection is often applied to motor or embedded generator applications to detect loss of load or
loss of generation. For these applications, Real power may be a more appropriate operating quantity.
Power direction can also be used to recognise and record particular network operation arrangements such as
back feeds or embedded generation conditions.
2.18 Sensitive Power (32S)
The CT accuracy should be considered when setting this function for the application.
2.19 Power Factor (55)
Power factor limits can be set to provide alarms or even tripping for abnormal power factor load.
Power factor can also be used to switch in and out additional plant such as capacitors