GE EPM6000 User manual

EPM 6000 Multi-function Power
Metering System
Chapter 1:
Digital Energy
Multilin
Instruction Manual
Software Revision: 1.17
Manual P/N: 1601-0215-A5
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EPM 6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE TOC–1
Table of Contents
1: THREE-PHASE
POWER
MEASUREMENT
THREE-PHASE SYSTEM CONFIGURATIONS ........................................................................... 1-1
WYE CONNECTION .............................................................................................................. 1-1
DELTA CONNECTION ........................................................................................................... 1-3
BLONDELL’STHEOREM AND THREE PHASE MEASUREMENT ......................................... 1-5
POWER, ENERGY AND DEMAND ............................................................................................... 1-8
DEMAND ...............................................................................................................................1-10
REACTIVE ENERGY AND POWER FACTOR ............................................................................. 1-12
REAL, REACTIVE, AND APPARENT POWER ........................................................................ 1-12
POWER FACTOR ................................................................................................................... 1-13
HARMONIC DISTORTION .............................................................................................................. 1-14
INDUCTIVE AND CAPACITIVE IMPEDANCE .......................................................................... 1-15
VOLTAGE AND CURRENT MONITORING ............................................................................ 1-15
WAVEFORM CAPTURE ......................................................................................................... 1-16
POWER QUALITY .............................................................................................................................. 1-17
2: OVERVIEW AND
SPECIFICATIONS
HARDWARE OVERVIEW ................................................................................................................. 2-1
VOLTAGE AND CURRENT INPUTS ...................................................................................... 2-2
ORDER CODES ..................................................................................................................... 2-2
V-SWITCH™ TECHNOLOGY ............................................................................................... 2-3
MEASURED VALUES ............................................................................................................ 2-3
UTILITY PEAK DEMAND ....................................................................................................... 2-4
SPECIFICATIONS ............................................................................................................................... 2-5
3: MECHANICAL
INSTALLATION
INTRODUCTION ................................................................................................................................ 3-1
ANSI INSTALLATION STEPS .......................................................................................................... 3-3
DIN INSTALLATION STEPS ........................................................................................................... 3-4
EPM6000 TRANSDUCER INSTALLATION ................................................................................ 3-5
4: ELECTRICAL
INSTALLATION
CONSIDERATIONS WHEN INSTALLING METERS ................................................................. 4-1
CT LEADS TERMINATED TO METER ................................................................................... 4-2
CT LEADS PASS-THROUGH (NOMETER TERMINATION) ................................................ 4-3
QUICK CONNECT CRIMP CT TERMINATIONS ................................................................... 4-3
VOLTAGE AND POWER SUPPLY CONNECTIONS .............................................................. 4-4
GROUND CONNECTIONS .................................................................................................... 4-5
VOLTAGE FUSES .................................................................................................................. 4-5
ELECTRICAL CONNECTION DIAGRAMS .................................................................................. 4-6
DESCRIPTION ........................................................................................................................ 4-6
(1) WYE, 4-WIRE WITH NO PTSAND 3 CTS, NO PTS, 3 ELEMENT ............................ 4-7
(2) WYE, 4-WIRE WITH NO PTSAND 3 CTS, 2.5 ELEMENT ........................................ 4-8
(3) WYE, 4-WIRE WITH 3 PTSAND 3 CTS, 3 ELEMENT .............................................. 4-9
(4) WYE, 4-WIRE WITH 2 PTSAND 3 CTS, 2.5 ELEMENT ........................................... 4-10
(5) DELTA, 3-WIRE WITH NO PTS, 2 CTS....................................................................... 4-11
(6) DELTA, 3-WIRE WITH 2 PTS, 2 CTS......................................................................... 4-12
(7) DELTA, 3-WIRE WITH 2 PTS, 3 CTS......................................................................... 4-13

TOC–2 EPM 6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
(8) CURRENT-ONLY MEASUREMENT (THREE-PHASE) ....................................................4-14
(9) CURRENT-ONLY MEASUREMENT (DUAL-PHASE) ...................................................... 4-15
(10) CURRENT-ONLY MEASUREMENT (SINGLE-PHASE) ................................................4-16
5: COMMUNICATION
INSTALLATION
EPM6000 COMMUNICATION ...................................................................................................... 5-1
IRDA PORT (COM 1) .......................................................................................................... 5-1
RS-485 / KYZ OUTPUT COM 2 (485P OPTION) ........................................................ 5-2
EPM6000 COMMUNICATION AND PROGRAMMING OVERVIEW .................................. 5-6
FACTORY INITIAL DEFAULT SETTINGS ...............................................................................5-6
EPM6000 PROFILE SETTINGS .......................................................................................... 5-9
CONFIGURING THE ETHERNET CONNECTION (E- OPTION) ..........................................5-15
SETTING UP THE HOST PC TO COMMUNICATE WITH THE EPM6000 METER ...........5-15
SETTING UP THE ETHERNET CARD (E- OPTION) IN THE EPM6000 METER .............. 5-18
6: USING THE METER INTRODUCTION ................................................................................................................................ 6-1
METER FACE ELEMENTS .....................................................................................................6-1
METER FACE BUTTONS ....................................................................................................... 6-2
% OF LOAD BAR ............................................................................................................................... 6-4
WATT-HOUR ACCURACY TESTING (VERIFICATION) ...........................................................6-5
INFRARED & KYZ PULSE CONSTANTS FOR ACCURACY TESTING ................................. 6-6
UPGRADE THE METER USING V-SWITCHESÂ ......................................................................6-7
7: CONFIGURING THE
METER USING THE
FRONT PANEL
OVERVIEW ........................................................................................................................................... 7-1
START UP ............................................................................................................................................. 7-3
CONFIGURATION .............................................................................................................................. 7-4
MAIN MENU ........................................................................................................................7-4
RESET MODE .......................................................................................................................7-4
CONFIGURATION MODE ......................................................................................................7-6
CONFIGURING THE SCROLL FEATURE ............................................................................... 7-7
PROGRAMMING THE CONFIGURATION MODE SCREENS ................................................ 7-7
CONFIGURING THE CT SETTING ........................................................................................7-9
CONFIGURING THE PT SETTING ........................................................................................7-10
CONFIGURING THE CONNECTION (CNCT) SETTING ......................................................... 7-11
CONFIGURING THE COMMUNICATION PORT SETTING .................................................... 7-12
OPERATING MODE ...............................................................................................................7-14
APPENDIX A: EPM6000
NAVIGATION MAPS
INTRODUCTION ..................................................................................................................APPENDIX A-1
NAVIGATION MAPS (SHEETS 1 TO 4) ..........................................................................APPENDIX A-2
EPM6000 NAVIGATION MAP TITLES: ...............................................................APPENDIX A-2
APPENDIX B: MODBUS
MAPPING FOR
EPM6000
INTRODUCTION ..................................................................................................................APPENDIX B-1
MODBUS REGISTER MAP SECTIONS ........................................................................APPENDIX B-2
DATA FORMATS .................................................................................................................APPENDIX B-3
FLOATING POINT VALUES .............................................................................................APPENDIX B-4
MODBUS REGISTER MAP ................................................................................................APPENDIX B-5
APPENDIX C: DNP
MAPPING FOR
EPM6000
INTRODUCTION .................................................................................................................APPENDIX C-1
DNP MAPPING (DNP-1 TO DNP-2) ..............................................................................APPENDIX C-2

EPM 6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE TOC–3
APPENDIX D: DNP 3.0
PROTOCOL
ASSIGNMENTS FOR
EPM6000
DNP IMPLEMENTATION ...................................................................................................APPENDIX D-1
DATA LINK LAYER .............................................................................................................APPENDIX D-2
TRANSPORT LAYER ...........................................................................................................APPENDIX D-3
APPLICATION LAYER .........................................................................................................APPENDIX D-4
OBJECT AND VARIATION .......................................................................................APPENDIX D-5

TOC–4 EPM 6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE

EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 1–1
EPM6000 Multi-function Power
Metering System
Chapter 1: Three-Phase Power
Measurement
Digital Energy
Multilin
Three-Phase Power Measurement
This introduction to three-phase power and power measurement is intended to provide
only a brief overview of the subject. The professional meter engineer or meter technician
should refer to more advanced documents such as the EEI Handbook for Electricity
Metering and the application standards for more in-depth and technical coverage of the
subject.
1.1 Three-Phase System Configurations
Three-phase power is most commonly used in situations where large amounts of power
will be used because it is a more effective way to transmit the power and because it
provides a smoother delivery of power to the end load. There are two commonly used
connections for three-phase power, a wye connection or a delta connection. Each
connection has several different manifestations in actual use.
When attempting to determine the type of connection in use, it is a good practice to follow
the circuit back to the transformer that is serving the circuit. It is often not possible to
conclusively determine the correct circuit connection simply by counting the wires in the
service or checking voltages. Checking the transformer connection will provide conclusive
evidence of the circuit connection and the relationships between the phase voltages and
ground.
1.1.1 Wye Connection
The wye connection is so called because when you look at the phase relationships and the
winding relationships between the phases it looks like a wye (Y). Fig. 1.1 depicts the winding
relationships for a wye-connected service. In a wye service the neutral (or center point of
the wye) is typically grounded. This leads to common voltages of 208/120 and 480/277
(where the first number represents the phase-to-phase voltage and the second number
represents the phase-to-ground voltage).

1–2 EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
THREE-PHASE SYSTEM CONFIGURATIONSCHAPTER 1: THREE-PHASE POWER MEASUREMENT
FIGURE 1–1: Three-phase Wye winding
The three voltages are separated by 120oelectrically. Under balanced load conditions with
unity power factor the currents are also separated by 120o. However, unbalanced loads
and other conditions can cause the currents to depart from the ideal 120oseparation.
Three-phase voltages and currents are usually represented with a phasor diagram. A
phasor diagram for the typical connected voltages and currents is shown below.
FIGURE 1–2: Three-phase Voltage and Current Phasors for Wye Winding
The phasor diagram shows the 120° angular separation between the phase voltages. The
phase-to-phase voltage in a balanced three-phase wye system is 1.732 times the phase-
to-neutral voltage. The center point of the wye is tied together and is typically grounded.
Ia
Vbn
A
B
C
Van
Vcn
N
Van
Vcn
Vbn
Ic
Ib
Ia

CHAPTER 1: THREE-PHASE POWER MEASUREMENTTHREE-PHASE SYSTEM CONFIGURATIONS
EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 1–3
The following table indicates the common voltages used in the United States for wye
connected systems.
Usually, a wye-connected service will have four wires: three wires for the phases and one
for the neutral. The three-phase wires connect to the three phases. The neutral wire is
typically tied to the ground or center point of the wye (refer to the Three-Phase Wye
Winding diagram above).
In many industrial applications the facility will be fed with a four-wire wye service but only
three wires will be run to individual loads. The load is then often referred to as a
deltaconnected load but the service to the facility is still a wye service; it contains four
wires if you trace the circuit back to its source (usually a transformer). In this type of
connection the phase to ground voltage will be the phase-to-ground voltage indicated in
the table above, even though a neutral or ground wire is not physically present at the load.
The transformer is the best place to determine the circuit connection type because this is a
location where the voltage reference to ground can be conclusively identified.
1.1.2 Delta Connection
Delta connected services may be fed with either three wires or four wires. In a three-phase
delta service the load windings are connected from phase-to-phase rather than from
phase-to-ground. The following figure shows the physical load connections for a delta
service.
Table 1–1: Common Phase Voltages on Wye Services
Phase-to-Ground Voltage Phase-to-Phase Voltage
120 volts 208 volts
277 volts 480 volts
2400 volts 4160 volts
7200 volts 12470 volts
7620 volts 13200 volts

1–4 EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
THREE-PHASE SYSTEM CONFIGURATIONSCHAPTER 1: THREE-PHASE POWER MEASUREMENT
FIGURE 1–3: Three-phase Delta Winding Relationship
In this example of a delta service, three wires will transmit the power to the load. In a true
delta service, the phase-to-ground voltage will usually not be balanced because the
ground is not at the center of the delta.
The following diagram shows the phasor relationships between voltage and current on a
three-phase delta circuit.
In many delta services, one corner of the delta is grounded. This means the phase to
ground voltage will be zero for one phase and will be full phase-to-phase voltage for the
other two phases. This is done for protective purposes.
FIGURE 1–4: Three-Phase Voltage and Current Phasors for Delta Winding
Another common delta connection is the four-wire, grounded delta used for lighting loads.
In this connection the center point of one winding is grounded. On a 120/240 volt, four-
wire, grounded delta service the phase-to-ground voltage would be 120 volts on two
phases and 208 volts on the third phase. The phasor diagram for the voltages in a three-
phase, four-wire delta system is shown below.
Ia
Ica
Iab
Ib
Ibc
Ic
Vab
Vbc
A
B
C
Vca
Vbc
Vca
Vab
Ic
Ib
Ia

CHAPTER 1: THREE-PHASE POWER MEASUREMENTTHREE-PHASE SYSTEM CONFIGURATIONS
EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 1–5
FIGURE 1–5: Three-Phase, Four-Wire Delta Phasors
1.1.3 Blondell’s Theorem and Three Phase Measurement
In 1893 an engineer and mathematician named Andre E. Blondell set forth the first
scientific basis for poly phase metering. His theorem states:
•If energy is supplied to any system of conductors through N wires, the total power in the
system is given by the algebraic sum of the readings of N wattmeters so arranged that
each of the N wires contains one current coil, the corresponding potential coil being
connected between that wire and some common point. If this common point is on one
of the N wires, the measurement may be made by the use of N-1 wattmeters.
The theorem may be stated more simply, in modern language:
•In a system of N conductors, N-1 meter elements will measure the power or energy
taken provided that all the potential coils have a common tie to the conductor in
which there is no current coil.
•Three-phase power measurement is accomplished by measuring the three
individual phases and adding them together to obtain the total three phase value. In
older analog meters, this measurement was accomplished using up to three
separate elements. Each element combined the single-phase voltage and current to
produce a torque on the meter disk. All three elements were arranged around the
disk so that the disk was subjected to the combined torque of the three elements. As
a result the disk would turn at a higher speed and register power supplied by each
of the three wires.
According to Blondell's Theorem, it was possible to reduce the number of elements under
certain conditions. For example, a three-phase, three-wire delta system could be correctly
measured with two elements (two potential coils and two current coils) if the potential coils
were connected between the three phases with one phase in common.
In a three-phase, four-wire wye system it is necessary to use three elements. Three voltage
coils are connected between the three phases and the common neutral conductor. A
current coil is required in each of the three phases.
Vca
Vab
Vbc
Vnc
Vbn
120 V
120 V

1–6 EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
THREE-PHASE SYSTEM CONFIGURATIONSCHAPTER 1: THREE-PHASE POWER MEASUREMENT
In modern digital meters, Blondell's Theorem is still applied to obtain proper metering. The
difference in modern meters is that the digital meter measures each phase voltage and
current and calculates the single-phase power for each phase. The meter then sums the
three phase powers to a single three-phase reading.
Some digital meters calculate the individual phase power values one phase at a time. This
means the meter samples the voltage and current on one phase and calculates a power
value. Then it samples the second phase and calculates the power for the second phase.
Finally, it samples the third phase and calculates that phase power. After sampling all three
phases, the meter combines the three readings to create the equivalent three-phase
power value. Using mathematical averaging techniques, this method can derive a quite
accurate measurement of three-phase power.
More advanced meters actually sample all three phases of voltage and current
simultaneously and calculate the individual phase and three-phase power values. The
advantage of simultaneous sampling is the reduction of error introduced due to the
difference in time when the samples were taken.
Blondell's Theorem is a derivation that results from Kirchhoff's Law. Kirchhoff's Law states
that the sum of the currents into a node is zero. Another way of stating the same thing is
that the current into a node (connection point) must equal the current out of the node. The
law can be applied to measuring three-phase loads. Figure 1.6 shows a typical connection
of a three-phase load applied to a three-phase, four-wire service. Krichhoff's Laws hold
that the sum of currents A, B, C and N must equal zero or that the sum of currents into
Node "n" must equal zero.
FIGURE 1–6: Three-Phase Load Illustrating Kirchhoff’s Law and Blondell’s Theorem
If we measure the currents in wires A, B and C, we then know the current in wire N by
Kirchhoff's Law and it is not necessary to measure it. This fact leads us to the conclusion of
Blondell's Theorem that we only need to measure the power in three of the four wires if
they are connected by a common node. In the circuit of Figure 1.6 we must measure the
Phase B
Phase C
Phase A
A
B
C
N
Node "n"

CHAPTER 1: THREE-PHASE POWER MEASUREMENTTHREE-PHASE SYSTEM CONFIGURATIONS
EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 1–7
power flow in three wires. This will require three voltage coils and three current coils (a
three element meter). Similar figures and conclusions could be reached for other circuit
configurations involving delta-connected loads.

1–8 EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
POWER, ENERGY AND DEMANDCHAPTER 1: THREE-PHASE POWER MEASUREMENT
1.2 Power, Energy and Demand
It is quite common to exchange power, energy and demand without differentiating
between the three. Because this practice can lead to confusion, the differences between
these three measurements will be discussed.
Power is an instantaneous reading. The power reading provided by a meter is the present
flow of watts. Power is measured immediately just like current. In many digital meters, the
power value is actually measured and calculated over a one second interval because it
takes some amount of time to calculate the RMS values of voltage and current. But this
time interval is kept small to preserve the instantaneous nature of power.
Energy is always based on some time increment; it is the integration of power over a
defined time increment. Energy is an important value because almost all electric bills are
based, in part, on the amount of energy used.
Typically, electrical energy is measured in units of kilowatt-hours (kWh). A kilowatt-hour
represents a constant load of one thousand watts (one kilowatt) for one hour. Stated
another way, if the power delivered (instantaneous watts) is measured as 1,000 watts and
the load was served for a one hour time interval then the load would have absorbed one
kilowatt-hour of energy. A different load may have a constant power requirement of 4,000
watts. If the load were served for one hour it would absorb four kWh. If the load were
served for 15 minutes it would absorb ¼ of that total or 1 kWh.
The following figure shows a graph of power and the resulting energy that would be
transmitted as a result of the illustrated power values. For this illustration, it is assumed
that the power level is held constant for each minute when a measurement is taken. Each
bar in the graph will represent the power load for the one-minute increment of time. In real
life the power value moves almost constantly.
FIGURE 1–7: Power Use Over Time
0
10
20
30
40
50
60
70
80
123456789101112131415
Time (minutes)
kilowatts

CHAPTER 1: THREE-PHASE POWER MEASUREMENTPOWER, ENERGY AND DEMAND
EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 1–9
The data from Figure 1-7 is reproduced in the table below to illustrate the calculation of
energy. Since the time increment of the measurement is one minute and since we
specified that the load is constant over that minute, we can convert the power reading to
an equivalent consumed energy reading by multiplying the power reading times 1/60
(converting the time base from minutes to hours).
As in Table 1-2, the accumulated energy for the power load profile of Figure 1-7 is 14.92
kWh.
Demand is also a time-based value. The demand is the average rate of energy use over
time. The actual label for demand is kilowatt-hours/hour but this is normally reduced to
kilowatts. This makes it easy to confuse demand with power. But demand is not an
instantaneous value. To calculate demand it is necessary to accumulate the energy
readings (as illustrated in Figure 1.7 above) and adjust the energy reading to an hourly
value that constitutes the demand.
In the example, the accumulated energy is 14.92 kWh. But this measurement was made
over a 15-minute interval. To convert the reading to a demand value, it must be
normalized to a 60-minute interval. If the pattern were repeated for an additional three 15-
minute intervals the total energy would be four times the measured value or 59.68 kWh.
The same process is applied to calculate the 15-minute demand value. The demand value
associated with the example load is 59.68 kWh/hr or 59.68 kWd. Note that the peak
instantaneous value of power is 80 kW, significantly more than the demand value.
Table 1–2: Power and Energy Relationship Over Time
Time Interval
(Minutes)
Power
(kW)
Energy
(kWh)
Accumulated
Energy (kWh)
1 30 0.50 0.50
2 50 0.83 1.33
3 40 0.67 2.00
4 55 0.92 2.92
5 60 1.00 3.92
6 60 1.00 4.92
7 70 1.17 6.09
8 70 1.17 7.26
9 60 1.00 8.26
10 70 1.17 9.43
11 80 1.33 10.76
12 50 0.83 12.42
13 50 0.83 12.42
14 70 1.17 13.59
15 80 1.33 14.92

1–10 EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
POWER, ENERGY AND DEMANDCHAPTER 1: THREE-PHASE POWER MEASUREMENT
Figure 1.8 shows another example of energy and demand. In this case, each bar
represents the energy consumed in a 15-minute interval. The energy use in each interval
typically falls between 50 and 70 kWh. However, during two intervals the energy rises
sharply and peaks at 100 kWh in interval number 7. This peak of usage will result in setting
a high demand reading. For each interval shown the demand value would be four times
the indicated energy reading. So interval 1 would have an associated demand of 240 kWh/
hr. Interval 7 will have a demand value of 400 kWh/hr. In the data shown, this is the peak
demand value and would be the number that would set the demand charge on the utility
bill.
As can be seen from this example, it is important to recognize the relationships between
power, energy and demand in order to control loads effectively or to monitor use correctly.
1.2.1 Demand
Demand is also a time-based value. The demand is the average rate of energy use over
time. The actual label for demand is kilowatt-hours/hour but this is normally reduced to
kilowatts. This makes it easy to confuse demand with power. But demand is not an
instantaneous value. To calculate demand it is necessary to accumulate the energy
readings (as illustrated in the Power Use Over Time figure above) and adjust the energy
reading to an hourly value that constitutes the demand.
In the example, the accumulated energy is 14.92 kWh. But this measurement was made
over a 15-minute interval. To convert the reading to a demand value, it must be
normalized to a 60-minute interval. If the pattern were repeated for an additional three 15-
minute intervals the total energy would be four times the measured value or 59.68 kWh.
The same process is applied to calculate the 15-minute demand value. The demand value
associated with the example load is 59.68 kWh/hour or 59.68 kWd. Note that the peak
instantaneous value of power is 80 kW, significantly more than the demand value.
The following figure illustrates another example of energy and demand. In this case, each
bar represents the energy consumed in a 15-minute interval. The energy use in each
interval typically falls between 50 and 70 kWh. However, during two intervals the energy
rises sharply and peaks at 100 kWh in interval #7. This peak of usage will result in setting a
high demand reading. For each interval shown the demand value would be four times the
indicated energy reading. So interval 1 would have an associated demand of 240 kWh/hr.
Interval #7 will have a demand value of 400 kWh/hr. In the data shown, this is the peak
demand value and would be the number that would set the demand charge on the utility
bill.

CHAPTER 1: THREE-PHASE POWER MEASUREMENTPOWER, ENERGY AND DEMAND
EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 1–11
FIGURE 1–8: Energy Use and Demand Intervals
As seen in this example, it is important to recognize the relationships between power,
energy and demand in order to effectively control loads or to correctly monitor use.
0
20
40
60
80
100
12345678
Intervals (15 mins.)
kilowatt-hours

1–12 EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
REACTIVE ENERGY AND POWER FACTORCHAPTER 1: THREE-PHASE POWER MEASUREMENT
1.3 Reactive Energy and Power Factor
1.3.1 Real, Reactive, and Apparent Power
The real power and energy measurements discussed in the previous section relate to the
quantities that are most used in electrical systems. But it is often not sufficient to only
measure real power and energy. Reactive power is a critical component of the total power
picture because almost all real-life applications have an impact on reactive power.
Reactive power and power factor concepts relate to both load and generation
applications. However, this discussion will be limited to analysis of reactive power and
power factor as they relate to loads. To simplify the discussion, generation will not be
considered.
Real power (and energy) is the component of power that is the combination of the voltage
and the value of corresponding current that is directly in phase with the voltage. However,
in actual practice the total current is almost never in phase with the voltage. Since the
current is not in phase with the voltage, it is necessary to consider both the inphase
component and the component that is at quadrature (angularly rotated 90oor
perpendicular) to the voltage. Figure 1.9 shows a single-phase voltage and current and
breaks the current into its in-phase and quadrature components.
FIGURE 1–9: Voltage and Complex Current
The voltage (V) and the total current (I) can be combined to calculate the apparent power
or VA. The voltage and the in-phase current (IR) are combined to produce the real power or
watts. The voltage and the quadrature current (IX) are combined to calculate the reactive
power.
The quadrature current may be lagging the voltage (as shown in Figure 1.9) or it may lead
the voltage. When the quadrature current lags the voltage the load is requiring both real
power (watts) and reactive power (VARs). When the quadrature current leads the voltage
the load is requiring real power (watts) but is delivering reactive power (VARs) back into the
system; that is VARs are flowing in the opposite direction of the real power flow.
Reactive power (VARs) is required in all power systems. Any equipment that uses
magnetization to operate requires VARs. Usually the magnitude of VARs is relatively low
compared to the real power quantities. Utilities have an interest in maintaining VAR
requirements at the customer to a low value in order to maximize the return on plant
invested to deliver energy. When lines are carrying VARs, they cannot carry as many watts.
V
I
I
R
θ
I
X

CHAPTER 1: THREE-PHASE POWER MEASUREMENTREACTIVE ENERGY AND POWER FACTOR
EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE 1–13
So keeping the VAR content low allows a line to carry its full capacity of watts. In order to
encourage customers to keep VAR requirements low, most utilities impose a penalty if the
VAR content of the load rises above a specified value.
1.3.2 Power Factor
A common method of measuring reactive power requirements is power factor. Power
factor can be defined in two different ways. The more common method of calculating
power factor is the ratio of the real power to the apparent power. This relationship is
expressed in the following formula:
:
(EQ 1.1)
This formula calculates a power factor quantity known as Total Power Factor. It is called
Total PF because it is based on the ratios of the power delivered. The delivered power
quantities will include the impacts of any existing harmonic content. If the voltage or
current includes high levels of harmonic distortion the power values will be affected. By
calculating power factor from the power values, the power factor will include the impact of
harmonic distortion. In many cases this is the preferred method of calculation because the
entire impact of the actual voltage and current are included.
A second type of power factor is Displacement Power Factor. Displacement PF is based on
the angular relationship between the voltage and current. Displacement power factor
does not consider the magnitudes of voltage, current or power. It is solely based on the
phase angle differences. As a result, it does not include the impact of harmonic distortion.
Displacement power factor is calculated using the following equation:
(EQ 1.2)
Where θis the angle between the voltage and the current (see Fig. 1.9).
In applications where the voltage and current are not distorted, the Total Power Factor will
equal the Displacement Power Factor. But if harmonic distortion is present, the two power
factors will not be equal.
Total PF real power
apparent power
---------------------------------------- watts
VA
--------------==
Displacement PF θcos=

1–14 EPM6000 MULTI-FUNCTION POWER METERING SYSTEM – USER GUIDE
HARMONIC DISTORTIONCHAPTER 1: THREE-PHASE POWER MEASUREMENT
1.4 Harmonic Distortion
Harmonic distortion is primarily the result of high concentrations of non-linear loads.
Devices such as computer power supplies, variable speed drives and fluorescent light
ballasts make current demands that do not match the sinusoidal waveform of AC
electricity. As a result, the current waveform feeding these loads is periodic but not
sinusoidal. Figure 1-10 shows a normal, sinusoidal current waveform. This example has no
distortion.
FIGURE 1–10: Non-distorted current waveform
Figure 1-11 shows a current waveform with a slight amount of harmonic distortion. The
waveform is still periodic and is fluctuating at the normal 60 Hz frequency. However, the
waveform is not a smooth sinusoidal form as seen in Figure 1-10.
FIGURE 1–11: Distorted current wave
The distortion observed in Figure 1.11 can be modeled as the sum of several sinusoidal
waveforms of frequencies that are multiples of the fundamental 60 Hz frequency. This
modeling is performed by mathematically disassembling the distorted waveform into a
–1000
–500
0
500
1000
t
Current (amps)
a2a
–1000
–500
0
500
1000
t
Current (amps)
a2a
–1500
1500