55 Power Factor
Overview of Functions
The power factor protection function is used to:
•
Detect when the power factor of the load deviates outside of normal limits, above or below a set
threshold to identify connection of abnormal loading
•
Monitor agreed power factor levels and limits and provide output status indications
•
Detect starting/running transition in motor applications and can be used to inhibit stall protection
•
Detect motor underload conditions
Power factor is the ratio of real power to apparent power. Power factor can be leading or lagging depending
on the phase relationship of voltage and current.
The real and reactive power polarities can be independently inverted to suit customer preference and conven-
tion using the Configuration > Device > Export Power/ Lag Var setting.
Structure of the Function
The power factor function element has group dependent settings. These settings can be different in each
settings group – group numbers (Gn) 1 to 4.
This function corresponds to the logical node A55PDOP* and A55PDUP* in IEC 61850.
The function monitors the primary system using the 3 phase CT inputs e.g. CT1/2/3 and 3 phase VT inputs e.g.
VT1/2/3. The fundamental frequency component is measured from processing of the measured current
samples.
Each element can be set to operate for power factor over or under a settable threshold. Operation is based on
any phase being above the setting or all 3 phases.
5.21
5.21.1
5.21.2
Protection and Automation Functions
5.21 55 Power Factor
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual 295
C53000-G7040-C014-1, Edition 11.2019
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