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This is an old revision of this page, as edited by 174.118.142.187 (talk) at 13:33, 18 June 2013 (→Under investigation). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Data Collection

  • Fairchild Application Note[1] "The power factor can vary from 0 to 1 and can be either inductive..." in lede paragraph.
  • Fluke 434 Series II Energy Analyzer[2] in specifications states "Power factor (Cos j/DPF) Measurement range: 0 to 1
Fluke 434/435 manual[3] states "Interpretation of power factor readings... PF = -1, device generates power". "If you see negative power or power factor readings and you are connected to load, check to make sure the arrows on your current clamps are pointed towards the load."
Fluke 430 Series specification states the same o to 1 and Measurement method: "Calculated total watt/VA"
  • Voltech PM1000+ Precision Power Analyzer [4] states "Power Factor: Range: 0 to +/-1.000" and on same spec page "+ indicates leading PF and - indicates lagging PF". This device does not indicate negative power factor for reverse connections but to indicate lagging PF.
  • Hioki Clamp On Power HiTester 3286-20 [5] states "[Power factor] Forward 0 to 1.000 to delay 0" and "[Phase angle] Forward 90.0° to 0 to delay 90.0°" Won't measure negative PF period.

Under investigation

  • On the resistance and electromotive forces of the electric arc[6]"
The fact that the solid arc has, at low frequencies, a negative power factor, indicates that the arc is supplying power to the alternator: this is shown to be the case by means of a wattmeter. This is not, of course, at variance with the principle of conservation of energy, as the alternating energy given out by the arc is derived from the direct current energy supplied to it." Incorrect analysis did not include the DC component in the wattmeter reading used to determine negative power factor. No mention of equipment used was found indicating lack of scientific process.
  • Expanded scale voltmeter patent[7] "It is seen that the currents I6 and If are more than 90 degrees out of phase, corresponding to a negative power factor condition and hence, the instrument will produce a negative output as compared to a condition when this angle between I6 and If is less than 90 degrees. Later the author again refers to his negative power factor as the condition incorrectly described."
The two quantities referred to are both currents and the author obviously did not adhere to acceptable definitions. Also patents have no merit as reliable references.
  • Synchrotron Power Supply Light Source Note[8]"The input power factor of the power supply varies for different values of the magnet current. When the power supply is in the rectifier mode, the power is delivered from the utility to the magnet which explains the positive values for the power factor. However, during the extraction, the power supply operates as an inverter which ,therefore, delivers power to the utility. This action cause the negative power factor."
Short term side effect running of a 12 phase power half wave supply in reverse as an inverter to feed back into the grid system loads from stored magnetic inductance energy. The author calls this negative power factor.
  • Power Conversion Scheme Employing Shorting Means to Control Current Magnitude [9] "For GTOs, the value of α is unrestricted since these devices may be turned off at any time. Since α may be of any value, the power factor may be varied between +1.0 and -1 Positive power factor represents power flow from the DC source to the AC source. Negative power factor represents power flow from the AC source to the DC source. Power factors between +1 and -1 represent a proportional amount of reactive current following the conventional definition of power factor"
For power factor calculations to be valid all parameters must be from the same source. Using DC as a source of voltage reference yields no phase angle and no power factor (cosine). Obviously the author was confused on the meaning. In the last statement the author is referring to negative power factor as leading or lagging power factor and not reverse power flow.
  • Analysis of some measurement issues in bushing power factor tests in the field[10]
  • Performance of Grid-Connected Induction Generator under Naturally Commutated AC Voltage Controller [11]
  • Comparison of closed-loop speed control schemes for a doubly fed twin stator induction motor drive [12]
  • System and Method for Controlling Power Balance in an Electrical/Mechanical System [13]
  • Analytic synthesis of a hysteresis motor [14]
  • Influence of control strategies on DFIG-based Wind Farms integration in the power systems [15]
  • More Discussion of the Terminology of Alternating Current Power [16]
  • ANSI C12.16 - 1991 Standard for SS Metrology [17]
I couldn't find online access of doc. Possibly get copy from the meter inspection lab at work.

More resources

  • Understanding Power Flow and Naming Conventions - Landis and Gyr [18] "Power Factor, is another value that I hear people sticking on the terms lead and lag. Power Factor is the ratio between true and apparent power. The ratio will always be between 0.0 and 1.0 and will not have a sign."
  • The meaning of P, Q, S, η, cos ϕ, PF [19] "When the current waveform “lags” the corresponding voltage waveform, as in the inductive circuit of Fig. 1a, the power factor (which always ranges from 0 to 1) is said to be “lagging”, while if the current waveform “ leads ” the corresponding voltage waveform, as in the capacitive circuit of Fig. 1b, the power factor is said to be “leading”."

Metering phasors

Where:

a,b,c represent phase identifiers
Ean, Ebn, Ecn represent phase to neutral voltages (volts)
Eab, Ebc, Eca represent phase to phase voltages (volts)
Ia, Ib, Ic represent phase line currents (amperes)
In represents neutral current (amperes)
represents the phase angle each current lags the listed potential (degrees)
represents total system power (watts)

3 phase 4 wire (wye) using 3 element metering

See Measurement Canada Standard Drawing[20]

Each line current and respective voltage is metered as three single phase circuits and then totalized in the meter.

3 phase 4 wire (wye) using 2.5 element metering

See Measurement Canada Standard Drawing[21]

Ia and Ic currents are metered with their respective voltages as two single phase circuits. Ib is fed, polarity reversed, through an additional (split) winding on each element. Since the reversed Ib is 60° out of phase (at system unity PF) from each potential each element will meter cos(60°) or 50% of Ib, resulting in 100% metering for Ib. The two elements are totallized in the meter. Balanced system voltages are a requirement for technique accuracy.

3 phase 4 wire (wye) using 2.0 element metering and delta connected CTs

See Measurement Canada Standard Drawing[22]

Ia and Ic currents are metered with their respective voltages as two single phase circuits. Ib is fed, polarity reversed, via a current transformer delta connection through each element. Since the reversed Ib is 60° out of phase (at system unity PF) from each potential each element will meter cos(60°) or 50% of Ib, resulting in 100% metering for Ib. The two elements are totallized in the meter. Balanced system voltages are a requirement for technique accuracy.

3 phase 3 wire (delta) using 2 element metering

See Measurement Canada Standard Drawing[23]

Two phase line currents are metered with phase to phase voltages. The odd combination of each current and voltage results in using voltages 1.732 higher and shifted by 30° resulting in 1.732 EI * cos(30°) = 1.5EI (at system unity pf) on each element. The elements are totalized to 3EI * cos() and correct metering. Balanced system voltages are a requirement for technique accuracy.

References

  1. ^ "Power Factor Correction (PFC) Basics" (PDF). Fairchild Application Note 42047. Retrieved 16 June 2013.
  2. ^ "Fluke 434 Series II Energy Analyzer". Fluke. Retrieved 16 June 2013.
  3. ^ "Fluke 434/435 User manual" (PDF). Fluke. Retrieved 16 June 2013.
  4. ^ "Voltech PM1000+ Precision Power Analyzer" (PDF). Voltech. Retrieved 16 June 2013.
  5. ^ "CLAMP ON POWER HiTESTER 3286-20". Hioki. Retrieved 16 June 2013.
  6. ^ On the resistance and electromotive forces of the electric arc, W. Duddell, Proceedings of the Royal Society of London, pp. 512-515, 1901. “The fact that the solid arc has, at low frequencies, a negative power factor, indicates that the arc is supplying power to the alternator…”
  7. ^ Expanded scale voltmeter, N.P. Millar, U.S. Patent 2,788,491, April 1957. “…are more than 90 degrees out of phase, corresponding to a negative power factor condition…”
  8. ^ Synchrotron Power Supply Light Source Note M. Fathizadeh, U.S. Gov. Contract W•3H09-ENG-38, LS-164, March 1991. “However, during the extraction, the power supply operates as an inverter which, therefore, delivers power to the utility. This action cause the negative power factor.”
  9. ^ Power Conversion Scheme Employing Shorting Means to Control Current Magnitude L.H. Walker, U.S. Patent 5,091,840, February 1992. “Positive power factor represents power flow from the DC source to the AC source. Negative power factor represents power flow from the AC source to the DC source.”
  10. ^ Analysis of some measurement issues in bushing power factor tests in the field, S. Zhang, IEEE Trans Pwr Del, Vol 21, Issue 3, pp 1350-1356, July 2006. “…(the measurement) gives both negative power factor and negative resistive current (power loss).”
  11. ^ Performance of Grid-Connected Induction Generator under Naturally Commutated AC Voltage Controller A.F. Almarshoud et al., Electric Power Components and Systems, Vol 32, Issue 7, 2004. “Accordingly, the generator will absorb active power from the grid, which leads to negative power factor.”
  12. ^ Comparison of closed-loop speed control schemes for a doubly fed twin stator induction motor drive N. Chilakapati, Proc. of the Third International Power Electronics and Motion Control Conference, vol. 2, pp 786-791, 2000. “It is to be noted that, a positive power factor denotes positive power input to the control winding while a negative power factor denotes power regeneration from the control winding.”
  13. ^ System and Method for Controlling Power Balance in an Electrical/Mechanical System, D.G. Oteman et al., European Patent EP2345147, filed October 2009. “If COSθ is negative, power factor is negative, and there is regeneration current on the system…”
  14. ^ Analytic synthesis of a hysteresis motor, L.U. Anih et al., Energy Conversion and Management, Vol 52, Issue 1, pp 391-396, January 2011. “This means negative power factor or that electric power flows out of the machine from rotor to the stator resulting in generator operation, a reversal of power flow... “
  15. ^ Influence of control strategies on DFIG-based Wind Farms integration in the power systems R. Reginatto and C. da Rocha, Proc. XVIII Congresso Brasileiro de Automática (English), pp 2570-2576, September 2010. “In this case, a negative power factor means that the wind farm is absorbing reactive power from the grid…”
  16. ^ More Discussion of the Terminology of Alternating Current Power C.B.Campbell, Power Engineering Letters, IEEE Power Engineering Review, July 1999
  17. ^ Solid-state Electricity Meters ANSI C12.16-1991, American National Standards Institute, New York, NY, 1991.
  18. ^ "Understanding Power Flow and Naming Conventions" (PDF). Landis and Gyr - Michael Bearden. Retrieved 18 June 2013.
  19. ^ "The meaning of P, Q, S, η, cos ϕ, PF" (PDF). Chris Yelland, EE Publishers. Retrieved 18 June 2013.
  20. ^ "Measurement Canada Standard Dwg. No.3403" (PDF). MEASUREMENT CANADA. Retrieved 12 December 2012.
  21. ^ "Measurement Canada Standard Dwg. No.3412" (PDF). MEASUREMENT CANADA. Retrieved 12 December 2012.
  22. ^ "Measurement Canada Standard Dwg. No.3407" (PDF). MEASUREMENT CANADA. Retrieved 12 December 2012.
  23. ^ "Measurement Canada Standard Dwg. No.3312" (PDF). MEASUREMENT CANADA. Retrieved 12 December 2012.
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