ABB Relion 670 Series Technical Reference Manual page 836

Section 13
Scheme communication
13.8.2.1
13.8.2.2
830
Introduction
Low active power and power factor protection (LAPPGAPC, 37_55) function
measures power flow. It can be used for protection and monitoring of:
• phase wise low active power
• phase wise low power factor
• phase wise reactive power and apparent power as service values
Following features are available:
• Definite time stage for low active power protection
• Definite time stage for low power factor protection
• Individual enabling of Low active power and Low power factor functions
• Low active power trip with 2 selection modes '1 out of 3' and '2 out of 3'
• Phase wise calculated values of apparent power, reactive power, active power and
power factor are available as service values
• Insensitive to small variations in voltage and current
Principle of operation
Low active power and low power factor protection (LAPPGAPC, 37_55) calculates
power and power factor from voltage and current values. Trip signal must be set
independently for low active power and low power factor condition after definite time
delay.
Active power calculation
LAPPGAPC (37_55) calculates single phase complex power of A, B and C loop by
following equations. From this complex apparent power, the real and imaginary parts
can be respective active and reactive power values of respective phases. All the
apparent power values given out of the function are absolute values. The active power
is the real part of the calculated apparent power.
·
S V I
=
A A A
EQUATION2243-ANSI V1 EN
S = V · I
B B B
EQUATION2244-ANSI V1 EN
S = V · I
C C C
EQUATION2245-ANSI V1 EN
Power factor calculation
1MRK505222-UUS C
(Equation 149)
(Equation 150)
(Equation 151)
Technical reference manual