Download 3 Dynamic Power Factor Correction Using an SVC

Exercise
3
Dynamic Power Factor Correction Using an SVC
EXERCISE OBJECTIVE
When you have completed this exercise, you will be familiar with the reasoning
behind the usage of power factor correction in industrial applications that absorb
large amounts of reactive power from the ac power network. You will know the
operating principles of SVCs when they are used for dynamic power factor
correction (i.e., for dynamic reactive power compensation) in arc furnace
applications and other industrial applications operating with large random peaks
of reactive power demand. You will also know how an SVC controller designed
for automatic reactive power control compensates the reactive power
requirement of the industrial application to which it is connected.
DISCUSSION OUTLINE
The Discussion of this exercise covers the following points:
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DISCUSSION
Power factor correction in industrial applications
Using SVCs for dynamic power factor correction
Automatic reactive power control
Power factor correction in industrial applications
In Exercise 2, you learned that SVCs are commonly used for voltage
compensation in ac transmission lines since they allow tight, fast, and effective
control of the voltage at the receiver end of the line (and along the line when
used in transmission substations). SVCs achieve this by supplying the exact
amount of reactive power required to maintain the voltage at the receiver end (or
at any substation) of the transmission line at the desired value.
Just like ac transmission lines, various industrial applications absorb large
amounts of reactive power during normal operation. Nowadays, most electrical
power providers charge extra costs to industrial customers that have a low power
factor (i.e., industrial applications that have a high reactive power requirement in
comparison to their active power requirement). This is due to the fact that, even
though reactive power does not produce any work, it still needs to flow in the
wires of the ac power network and, thus, reduces the amount of active power that
can be supplied by the network. Because of this, most large industrial customers,
in order to lower energy costs, use certain means to minimize their reactive
power demand. The more an industrial application can supply its own reactive
power (through the use of capacitors, for example), the less reactive power the
ac power network has to supply and, therefore, the higher the power factor of the
application. This can lead to important savings in energy costs.
Correcting (increasing) the power factor of an industrial application in such a way
is called power factor correction.
In large industrial applications with a reactive power demand that varies little or
varies slowly over time, power factor correction is achieved using banks of
capacitors that can be switched in or out as required. This allows the amount of
reactive power supplied by the capacitors to be increased or decreased in order
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Discussion
to meet the exact reactive power requirement of the application and keep the
power factor as close to unity as possible.
On the other hand, the reactive power demand in certain large industrial
applications varies greatly and suddenly over time. This is the case with arc
furnace applications, as well as with several other industrial applications as
diverse as rolling mills, traction systems (e.g., railroad networks), large resistance
welders, and harbor cranes. These fluctuations in the reactive power demand of
an industrial application can be significant and can greatly increase the amount
of reactive power that the ac power network must supply, since they cannot be
rapidly and effectively compensated using capacitor banks. This, in turn, lowers
the power factor of the application and increases the energy cost (because of the
extra costs charged by the electricity provider).
Arc furnace in operation.
Another important effect of the large random peaks of reactive power demand
produced in arc furnace applications and other similar industrial applications is
that the voltage at the ac power input of the application fluctuates greatly with the
reactive power demand. The higher the reactive power demand of the industrial
application, the more important the voltage drop at the ac power input. These
voltage fluctuations, in turn, cause a number of undesirable effects in the
application, most notably light flicker (quick, repeated change in light intensity). In
industrial applications requiring a particularly high amount of reactive power,
these undesirable effects (voltage fluctuations, light flicker) are not only limited to
the industrial application site, but can affect surrounding electrical power
consumers in the ac power network. In most modern ac power networks, this
cannot be tolerated.
Figure 46. SVCs are often installed nearby large harbor cranes for power factor correction of
the crane power system.
Finally, in some industrial applications that stay in constant or near-constant
operation (such as arc furnace applications) the voltage drops caused by the
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© Festo Didactic 86370-00
Exercise 3 – Dynamic Power Factor Correction Using an SVC  Discussion
peaks of reactive power demand lead to a significant decrease in the average
value of the voltage at the ac power input of the application and, thus, in the
amount of active power that the ac power network supplies to the application.
This reduces the productivity and therefore decreases revenues.
Figure 47. SVCs can be used in railroad networks for power factor correction of the railroad
power system.
Using SVCs for dynamic power factor correction
The undesirable effects caused by the random peaks of reactive power demand
generated in arc furnace applications and other similar industrial applications can
be eliminated or minimized by the installation of an SVC at the ac power input of
the application. When used in such a way, an SVC greatly reduces the reactive
power demand of the industrial application as well as the fluctuations in this
reactive power demand. The SVC achieves this by continually monitoring the
reactive power demand of the industrial application and compensating for it by
supplying the required amount of reactive power to the application, thereby
maintaining the power factor of the application as close as possible to unity. This
process is called dynamic power factor correction (or dynamic reactive power
compensation).
Correcting the power factor in an arc furnace application or any other similar
industrial application using an SVC minimizes the amount of reactive power that
the ac power network must supply to the application and, consequently,
minimizes the energy costs. It also ensures that the voltage at the ac power input
of the application is maintained as close as possible to the nominal value of the
ac power network voltage, and that no undesirable effect (voltage drops, light
flicker) is experienced by surrounding electrical power consumers in the
ac power network. Because of these effects, the installation costs of an SVC,
although significant, can generally be recouped within a few years of the SVC
installation.
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Discussion
Voltage at the ac power input of the arc furnace
application (V)
Figure 48 illustrates the effects of adding an SVC to an arc furnace application on
the voltage measured at the ac power input of the application.
With an SVC
Gain due to the SVC
Without an SVC
Time (min)
Figure 48. Typical voltage fluctuations observed at the ac power input of an arc furnace
application, with and without an SVC.
As Figure 48 shows, the voltage measured at the ac power input of the arc
furnace application fluctuates greatly over time when it operates without an SVC
due to the peaks in reactive power demand. When an SVC is added to the
application for dynamic power factor correction, the voltage measured at the
ac power input of the application still fluctuates slightly, but does not present any
large variation as when the application operates without an SVC. The graph also
shows that the average voltage at the ac power input of the application is higher
when the application operates with an SVC than when it operates without. As a
result, the active power supplied to the industrial application is also higher when
the application operates with an SVC. Since arc furnace applications stay in
constant or near-constant operation, such an increase in the average voltage at
the ac power input of the application results in a higher amount of active power
supplied to the application and, consequently, a higher productivity and higher
revenues.
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© Festo Didactic 86370-00
Exercise 3 – Dynamic Power Factor Correction Using an SVC  Discussion
Figure 49. SVCs are often used for compensating the large random peaks of reactive power
demand of industrial plants using electric arc furnaces.
Automatic reactive power control
When an SVC is used for dynamic power factor correction (i.e., for automatic
reactive power compensation) in an industrial application operating with large
random peaks of reactive power demand, the reactive power which the
application exchanges with the ac power network is controlled so that it remains
equal to 0 var. The SVC achieves this by monitoring the reactive component (‫ܫ‬௤ )
of the line currents flowing between the ac power network and the ac power input
of the application to which the SVC is connected. The SVC uses the reactive
component ‫ܫ‬௤ of the measured line currents to determine the number of TSCs to
be switched in, as well as the TCR firing angle that is required, in order to fully
compensate the reactive power demand of the application (i.e., to zero the
reactive power exchanged between the ac power network and the application).
The block diagram of an SVC designed for dynamic power factor correction
(i.e., automatic reactive power control) is shown in Figure 50. The industrial
application is represented in the block diagram by a resistive inductive load.
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Discussion
AC Transmission
Line
Load
TCR
TSC 1
TSC 2
SVC Controller
(Automatic
Reactive Power
Control)
Reactive Current
Command
(‫ܫ‬௤ ோ௘௙Ǥ ൌ Ͳ )
Figure 50. Block diagram of an SVC designed for dynamic power factor correction
(i.e., automatic reactive power control).
In automatic reactive power
control, the controlled parameter is the reactive current ‫ܫ‬௤ flowing between the
ac power network and the
ac power input of the industrial application, and not the
reactive power which the
application exchanges with
the ac power network.
However, ensuring that
reactive current ‫ܫ‬௤ is equal
to 0 A causes the reactive
power which the application
exchanges with the
ac power network to be
equal to 0 var.
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As the figure shows, two current sensors measure line currents ‫ܫ‬௅ଵ and ‫ܫ‬௅ଶ
flowing between the ac power network and the industrial application, then send
these currents to the SVC controller (which is set for automatic reactive power
control). The SVC controller determines the reactive component ‫ܫ‬௤ of the
measured line currents. It compares the reactive component ‫ܫ‬௤ of the measured
line currents to the industry reactive current command ‫ܫ‬௤ோ௘௙Ǥூ௡ௗ௨௦௧Ǥ (0 A) of the
SVC to determine the error in the reactive component of the line currents flowing
between the ac power network and the industrial application. Using this error, the
SVC controller switches TSCs in and out, and adjusts the TCR firing angle, so
that the amount of reactive power which the SVC exchanges with the application
zeroes the reactive component in the line currents flowing between the ac power
network and the application. This ensures that the amount of reactive power
which the industrial application exchanges with the ac power network is
maintained as close as possible to 0 var. Note that a voltage sensor also
measures line voltage ‫ܧ‬஺ି஻ to properly synchronize the firing of the thyristors in
the TCR, as well as to provide the phase angle (ߠ) information required to
perform mathematical calculations in the controller. The operation of
an SVC controller designed for automatic reactive power control is covered in
further detail in Appendix D.
© Festo Didactic 86370-00
Exercise 3 – Dynamic Power Factor Correction Using an SVC  Discussion
Figure 51. SVC used for dynamic reactive power compensation at the Antamina mine complex,
in Peru. The SVC significantly increases the amount of active power that can be supplied to
the mine complex (photo courtesy of ABB).
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure Outline
PROCEDURE OUTLINE
The Procedure is divided into the following sections:
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Set up and connections
Operation without dynamic power factor correction
Operation with dynamic power factor correction
PROCEDURE
High voltages are present in this laboratory exercise. Do not make or modify any
banana jack connections with the power on unless otherwise specified.
Set up and connections
In this section, you will set up a circuit representing a three-phase
ac transmission line supplying power to an industrial application operating with
large random peaks of reactive power demand (such as an arc furnace) that is
equipped with an SVC. You will then set up the measuring equipment required to
study the operation of the SVC when it is used for dynamic reactive power
compensation.
1. Refer to the Equipment Utilization Chart in Appendix A to obtain the list of
equipment required to perform this exercise.
Install the required equipment in the Workstation.
2. Make sure the ac and dc power switches on the Power Supply are set to
the O (off) position, then connect the Power Supply to a three-phase
ac power outlet.
Connect the Power Input of the Data Acquisition and Control Interface to a
24 V ac power supply.
Connect the Low Power Input of the Power Thyristors module to the Power
Input of the Data Acquisition and Control Interface. Turn the 24 V ac power
supply on.
3. Connect the USB port of the Data Acquisition and Control Interface to a USB
port of the host computer.
4. Turn the host computer on, then start the LVDAC-EMS software.
In the LVDAC-EMS Start-Up window, make sure the Data Acquisition and
Control Interface is detected. Make sure the Computer-Based
Instrumentation and SVC Control functions for the Data Acquisition and
Control Interface are available. Also, select the network voltage and
frequency that correspond to the voltage and frequency of your local ac
power network, then click the OK button to close the LVDAC-EMS Start-Up
window.
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
5. Connect the equipment as shown in Figure 52 and Figure 53. Use the
reactors and thyristor switched capacitors in the SVC Reactors/Thyristor
Switched Capacitors module to implement the TCR and the TSCs,
respectively. Note that points A1, A2, A3, and A4 in Figure 52 are connected
to the corresponding points in Figure 53.
Before connecting the TCR, make sure that switch S1 on the Power
Thyristors module is set to the O (open) position, then set switch S2 to
the I (closed) position. Doing so connects thyristor ܳଵ in series with
thyristor ܳସ , thyristor ܳଶ in series with thyristor ܳହ , and thyristor ܳଷ in series
with thyristor ܳ଺ . This reduces the number of leads required to implement
the TCR.
When connecting TSC 1, make sure to close the open branch by shortcircuiting the terminals linked by a dotted line.
This circuit represents an ac transmission line supplying power to an
industrial application operating with large random peaks of reactive power
demand. The industrial application is represented by the resistive and
inductive loads. By adjusting the resistance of the resistive load and the
reactance of the inductive load, it is thus possible to vary the active power
and reactive power demand of the application. An SVC is shunt-connected
between the receiver end of the ac transmission line and the industrial
application (resistive and inductive load) for dynamic power factor
correction (i.e., for dynamic reactive power compensation).
© Festo Didactic 86370-00
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
AC power network, transmission line, and resistive and inductive loads
Three-Phase Transmission
Line module
L1
ܺ௅
ܴଵ
ܴଶ
ܴଷ
L2
Resistive
load
ܺ௅
ܺ௅ଵ
ܺ௅ଶ
L3
ܺ௅ଷ
ܺ௅
Inductive
load
N
A1
A2
A3
A4
To SVC
Local ac power network
Load resistors
ࡾ૚ , ࡾ૛ , ࡾ૜
(ȍ)
Load
inductors
ࢄࡸ૚ , ࢄࡸ૛ , ࢄࡸ૜
(ȍ)
Voltage
(V)
Frequency
(Hz)
Line inductive
reactance ࢄࡸ
(ȍ)
120
60
60
’
’
220
50
200
’
’
240
50
200
’
’
220
60
200
’
’
Figure 52. Circuit for studying the operation of an SVC used for dynamic power factor
correction (i.e., for dynamic reactive power compensation) in an industrial application
operating with large random peaks of reactive power demand.
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
Static var compensator
Three-Phase Transformer Bank module
To receiver end of the
transmission line
A1
L1
1
2
3
ܳସ
15
L2
6
7
8
ܳହ
13
A3
ܺ௅ଷ
ܺ௅ଵ
5
A2
ܳଵ
11
12
ܳଶ
ܺ௅ଶ
10
ܳଷ
ܳ଺
L3
A4
TCR
L1
L2
L3
ܺ஼ଵ
ܺ஼ଶ
TSC 1
ܺ஼ଷ
ܺ஼ଵ
ܺ஼ଷ
ܺ஼ଶ
TSC 2
Figure 53. Circuit for studying the operation of an SVC used for dynamic power factor
correction (i.e., for dynamic reactive power compensation) in an industrial application
operating with large random peaks of reactive power demand.
© Festo Didactic 86370-00
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
a
In the circuit of Figure 52 and Figure 53, inputs E4, I3, and I4 of the Data
Acquisition and Control Interface are used to measure the circuit parameters
necessary for automatic reactive power control at the receiver end of
the ac transmission line. Because of this, inputs E4, I3, and I4 cannot be used
for parameter measurement using the LVDAC-EMS instrumentation.
6. Make sure the I/O toggle switch on the Three-Phase Transmission Line is set
to the I position.
On the Three-Phase Transmission Line, set the inductive reactance selector
to the value indicated in the table of Figure 52 corresponding to your local
ac power network voltage and frequency.
Make the necessary switch settings on the Resistive Load and on the
Inductive Load so that the resistance of the three-phase resistive load and
the reactance of the three-phase inductive load are infinite.
7. Connect the Digital Outputs of the Data Acquisition and Control Interface to
the Firing Control Inputs of the Power Thyristors module using the provided
cable with DB9 connectors.
Connect Digital Output 1 and Digital Output 2 of the Data Acquisition and
Control Interface to the TSC 1 Switching Control Input and TSC 2 Switching
Control Input, respectively, on the SVC Reactors/Thyristor Switched
Capacitors module using miniature banana plug leads.
Connect a common (white) terminal of the Digital Outputs on the Data
Acquisition and Control Interface to the common terminal of the TSC
Switching Control Inputs on the SVC Reactors/Thyristor Switched Capacitors
module using a miniature banana plug lead.
8. In LVDAC-EMS, open the Metering window. In the Option menu of the
Metering window, select Acquisition Settings to open the corresponding
dialog box. Set the Sampling Window to 8 cycles, then click OK to close the
dialog box. This enables a better accuracy when measuring the different
parameters (e, g., reactive power) of the SVC and is necessary to measure
the harmonic components produced by the SVC.
In the Metering window, make the required settings in order to measure the
rms values (ac) of the voltage ‫ܧ‬ௌ (input E1) at the sender end of the
ac transmission line, and the voltage ‫ܧ‬ூ௡ௗ௨௦௧Ǥ (input E2) at the industrial
application. Set two other meters to measure the three-phase active
power ܲூ௡ௗ௨௦௧Ǥ and reactive power ܳூ௡ௗ௨௦௧Ǥ used by the industrial
application [metering function PQS2 (E2, I2) 3~]. Set another meter to
measure the amount of energy ܹூ௡ௗ௨௦௧Ǥ supplied to the industrial
application [metering function W (E2, I2) 3~]. Also, set a meter to measure
the numerical integral ȭܳூ௡ௗ௨௦௧Ǥ of the reactive power used by the
application [metering function ȈQ (E2, I2) 3~]. Finally, set two meters to
measure the three-phase power factor ܲ‫ܨ‬ூ௡ௗ௨௦௧Ǥ of the industrial
application [PF (E2, I2) 3~]. On one of these two meters, modify the type of
measured power factor from True to Disp in order to measure the
displacement power factor ‫ܨܲܦ‬ூ௡ௗ௨௦௧Ǥ of the industrial application. These
meter settings are explained in more detail below.
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
The three-phase reactive power ܳூ௡ௗ௨௦௧Ǥ represents the amount of reactive power
that the industrial application absorbs from the ac transmission line. This value
should remain as close as possible to 0 var when the SVC operates properly.
The reactive power ܳூ௡ௗ௨௦௧Ǥ does not represent the reactive power demand of the
industrial application, which will be set to a value other than zero and made to
vary randomly in this exercise, just as in real-life industrial applications, such as
arc furnaces.
The energy ܹூ௡ௗ௨௦௧Ǥ supplied to the industrial application represents the total
amount of watt-hours (i.e., the active power integral) supplied to the application,
while the numerical integral ߑܳூ௡ௗ௨௦௧Ǥ of the reactive power represents the total
amount of var·hours exchanged between the ac power network and the industrial
application. In other words, the numerical integral ߑܳூ௡ௗ௨௦௧Ǥ of the reactive power
is the equivalent of the energy ܹூ௡ௗ௨௦௧Ǥ related to the active power ܲூ௡ௗ௨௦௧Ǥ .
Modifying the setting of one of the two power factor meters from True to Disp
causes this meter to measure the displacement power factor ‫ܨܲܦ‬ூ௡ௗ௨௦௧Ǥ of the
industrial application instead of the power factor ܲ‫ܨ‬ூ௡ௗ௨௦௧Ǥ . The displacement
power factor, as opposed to the power factor, only takes into account the
fundamental component of the measured parameters (all harmonic components
are discarded).
Operation without dynamic power factor correction
In this section, you will study the operation of the industrial application without
dynamic power factor correction (i.e., without dynamic reactive power
compensation by the SVC). You will vary the resistance of the resistive load, as
well as the reactance of the inductive load representing the industrial application,
and let the application operate for 1 minute at each load setting. While doing so,
you will record the sender voltage, the voltage at the industrial application, the
active power supplied to the application, the reactive power absorbed by the
application, the power factor of the application, and the displacement power
factor of the application. Finally, you will record the amount of energy supplied to
the industrial application (expressed in watt-hours), as well as the numerical
integral of the reactive power absorbed by the industrial application (expressed in
var·hours) when operating without power factor correction.
9. In LVDAC-EMS, open the Data Table window. Set the timer to
make 900 records with an interval of 1 second between each record. This
corresponds to a 15 minute period.
Set the Data Table to record the sender voltage ‫ܧ‬ௌ , the voltage ‫ܧ‬ூ௡ௗ௨௦௧Ǥ at the
industrial application, the active power ܲூ௡ௗ௨௦௧Ǥ supplied to the application, the
reactive power ܳூ௡ௗ௨௦௧Ǥ absorbed by the application, the power factor ܲ‫ܨ‬ூ௡ௗ௨௦௧Ǥ
of the application, and the displacement power factor ‫ܨܲܦ‬ூ௡ௗ௨௦௧Ǥ of the
application. Also, set the Data Table to record the time associated with each
record.
10. Turn the three-phase ac power source in the Power Supply on.
In the Data Table window, start the timer to begin recording data.
© Festo Didactic 86370-00
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
11. Make the necessary switch settings on the Resistive Load and on the
Inductive Load in order to obtain the combinations of resistance values (for
resistors ܴଵ , ܴଶ , and ܴଷ ) and reactance values (for inductors ܺ௅ଵ , ܺ௅ଶ ,
and ܺ௅ଷ ) indicated in Table 6 (1st to 10th values) corresponding to your local
ac power network voltage and frequency. For each resistance and reactance
combination, wait for 1 minute, then proceed to the next combination.
a
Local ac power network
Voltage
(V)
Frequency
(Hz)
120
60
220
240
220
50
50
60
For optimal results, modify the switch settings simultaneously on the three legs
of the Resistive Load and Inductive Load in order to avoid operation with an
unbalanced load as much as possible.
Table 5. Combinations of resistance values (for resistors ࡾ૚ , ࡾ૛ , and ࡾ૜ ) and reactance
values (for inductors ࢄࡸ૚ , ࢄࡸ૛ , and ࢄࡸ૜ ) to be used in the circuit of Figure 52 and Figure 53.
1
ܴൌ
st
Resistance values of ࡾ૚ , ࡾ૛ , and ࡾ૜ , and reactance values of ࢄࡸ૚ , ࢄࡸ૛ , and ࢄࡸ૜
2
nd
3
rd
4
th
5
th
6
th
7
th
8
th
9
th
10
th
600
600
600
400
400
1200
1200
1200
1200
400
1200
400
600
600
400
400
1200
400
1200
1200
ܴൌ
2200
2200
2200
1467
1467
4400
4400
4400
4400
1467
4400
1467
2200
2200
1467
1467
4400
1467
4400
4400
ܴൌ
2400
2400
2400
1600
1600
4800
4800
4800
4800
1600
4800
1600
2400
2400
1600
1600
4800
1600
4800
4800
ܴൌ
2200
2200
2200
1467
1467
4400
4400
4400
4400
1467
4400
1467
2200
2200
1467
1467
4400
1467
4400
4400
ܺ௅ ൌ
ܺ௅ ൌ
ܺ௅ ൌ
ܺ௅ ൌ
12. Turn the three-phase ac power source in the Power Supply off.
13. In the Data Table window, stop the timer, then save the recorded data.
Clear all recorded data without modifying the record and timer settings.
14. In the Metering window, measure the amount of energy ܹூ௡ௗ௨௦௧Ǥ supplied to
the industrial application, as well as the numerical integral ߑܳூ௡ௗ௨௦௧Ǥ of the
reactive power used by the application when the application operates without
dynamic power factor correction. Record both values below.
Energy ܹூ௡ௗ௨௦௧Ǥ ൌ
W·h
Numerical integral ߑܳூ௡ௗ௨௦௧Ǥ ൌ
var·h
When the values are recorded, reset both meters (i.e., the meter measuring
the energy supplied to the industrial application and the meter measuring the
numerical integral of the reactive power used by the industrial application).
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
Operation with dynamic power factor correction
In this section, you will study the operation of the industrial application with
dynamic power factor correction (i.e., with dynamic reactive power compensation
by the SVC). You will set the SVC for automatic reactive power compensation.
You will then vary the resistance of the resistive load, as well as the reactance of
the inductive load representing the industrial application, and let the application
operate for 1 minute at each load setting. While doing so, you will record the
sender voltage, the voltage at the industrial application, the active power supplied
to the application, the reactive power absorbed by the application, the power
factor of the application, and the displacement power factor of the application.
You will plot on a graph the different parameters of the industrial application as a
function of time, compare the curves obtained with dynamic power factor
correction to those obtained without dynamic power factor correction, and
analyze the results. Finally, you will record the amount of energy supplied to the
industrial application (in watt-hours) as well as the numerical integral of the
reactive power used by the industrial application (in var·hours) when operating
with dynamic power factor correction. You will compare the values obtained with
power factor correction to those obtained without dynamic power factor
correction, and analyze the results.
15. Make the necessary switch settings on the Resistive Load and on the
Inductive Load so that the resistance of the three-phase resistive load and
the reactance of the three-phase inductive load are infinite.
16. In LVDAC-EMS, open the SVC Control window and make the following
settings:
Make sure the Function parameter is set to Static Var Compensator.
Set the Control Mode parameter to Automatic Reactive Power
Control. This control mode allows the amount of reactive power used
by the application connected to the SVC to be automatically
controlled and maintained as close as possible to 0 var. This ensures
that the power factor of the application connected to the SVC is
maintained at unity. In order to implement this control mode, the
Data Acquisition and Control Interface requires inputs E4, I3, and I4
to be connected as shown in the circuit of Figure 52 and Figure 53.
Make sure the Controller Proportional Gain Kp is set to 0.5.
Make sure the Controller Integral Gain Ki is set to 6.
Start the Static Var Compensator function by clicking the Start/Stop
button or by setting the Status parameter to Started.
17. Turn the three-phase ac power source in the Power Supply on.
In the Data Table window, start the timer to begin recording data.
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
18. Make the necessary switch settings on the Resistive Load and on the
Inductive Load in order to obtain the combinations of resistance values (for
resistors ܴଵ , ܴଶ , and ܴଷ ) and reactance values (for inductors ܺ௅ଵ , ܺ௅ଶ ,
and ܺ௅ଷ ) indicated in Table 6 (1st to 10th values) corresponding to your local
ac power network voltage and frequency. For each resistance and reactance
combination, wait for 1 minute, then proceed to the next combination.
a
For optimal results, modify the switch settings simultaneously on the three legs
of the Resistive Load and Inductive Load in order to avoid operation with an
unbalanced load as much as possible.
19. Turn the three-phase ac power source in the Power Supply off.
In the SVC Control window, stop the Static Var Compensator function by
clicking the Start/Stop button or by setting the Status parameter to Stopped.
20. In the Data Table window, stop the timer, then save the recorded data.
21. Using the data you recorded, plot on the same graph the reactive
power ܳூ௡ௗ௨௦௧Ǥ used by the industrial application, with and without dynamic
power factor correction, as a function of the recording time.
Compare the curves of the reactive power ܳூ௡ௗ௨௦௧Ǥ used by the industrial
application obtained with and without dynamic power factor correction. What
do you observe? Explain briefly.
22. Using the data you recorded, plot on the same graph the power
factor ܲ‫ܨ‬ூ௡ௗ௨௦௧Ǥ and the displacement power factor ‫ܨܲܦ‬ூ௡ௗ௨௦௧Ǥ of the industrial
application, obtained with and without dynamic power factor correction, as a
function of the recording time.
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
Compare the curves of the power factor ܲ‫ܨ‬ூ௡ௗ௨௦௧Ǥ of the industrial application
obtained with and without dynamic power factor correction. What do you
observe? Explain briefly.
Compare the curve of the power factor ܲ‫ܨ‬ூ௡ௗ௨௦௧Ǥ of the industrial application to
that of the displacement power factor ‫ܨܲܦ‬ூ௡ௗ௨௦௧Ǥ of the application, obtained
with dynamic power factor correction. What can you conclude? Explain
briefly.
23. Using the data you recorded, plot on the same graph the sender voltage ‫ܧ‬ௌ
and the voltage ‫ܧ‬ூ௡ௗ௨௦௧Ǥ at the industrial application, obtained with and without
dynamic power factor correction, as a function of the recording time.
Is the sender voltage ‫ܧ‬ௌ obtained with dynamic power factor correction
approximately equal to the sender voltage ‫ܧ‬ௌ obtained without dynamic
power factor correction, thus indicating that power factor correction has no
effect on the sender voltage (i.e., on the ac power network line voltage)?
‰ Yes
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‰ No
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Procedure
Compare the curves of the voltage ‫ܧ‬ூ௡ௗ௨௦௧Ǥ at the industrial application
obtained with and without dynamic power factor correction. What do you
observe? Explain briefly.
24. Using the data you recorded, plot on the same graph the active power ܲூ௡ௗ௨௦௧Ǥ
supplied to the industrial application, obtained with and without dynamic
power factor correction, as a function of the recording time.
Compare the curves of the active power ܲூ௡ௗ௨௦௧Ǥ supplied to the industrial
application obtained with and without dynamic power factor correction. What
do you observe? Explain briefly.
25. In the Metering window, measure the amount of energy ܹூ௡ௗ௨௦௧Ǥ supplied to
the industrial application, as well as the numerical integral ߑܳூ௡ௗ௨௦௧Ǥ of the
reactive power used by the application when the application operates with
dynamic power factor correction. Record both values below.
Energy ܹூ௡ௗ௨௦௧Ǥ ൌ
W·h
Numerical integral ߑܳூ௡ௗ௨௦௧Ǥ ൌ
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var·h
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Conclusion
26. Compare the amount of energy ܹூ௡ௗ௨௦௧Ǥ and the value of the numerical
integral ߑܳூ௡ௗ௨௦௧Ǥ of the reactive power you measured in the previous step
when the industrial application operates with dynamic power factor correction
to those you measured in step 14 when the industrial application operates
without dynamic power factor correction. What can you conclude? Explain
briefly how these values affect the productivity and energy costs of the
industrial application.
27. Do your observations in this exercise confirm that an SVC can be used to
effectively correct the power factor (through reactive power compensation) of
an industrial application generating large random peaks of reactive power
demand?
‰ Yes
‰ No
28. Close LVDAC-EMS, then turn off all the equipment. Disconnect all leads and
return them to their storage location.
CONCLUSION
© Festo Didactic 86370-00
In this section, you familiarized yourself with the reasons behind power factor
correction in industrial applications that absorb large amounts or reactive power
from the ac power network. You learned the operating principles of SVCs when
they are used for dynamic power factor correction (i.e., dynamic reactive power
compensation) in arc furnace applications and other industrial applications
generating large random peaks of reactive power demand. You also learned how
an SVC controller designed for automatic reactive power control compensates
the reactive power requirement of the industrial application to which it is
connected.
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Review Questions
REVIEW QUESTIONS
1. What is the primary reason for large industrial consumers to use some
means to compensate for their reactive power demand? Explain briefly.
2. Why is it impossible to correct the power factor in industrial applications
operating with large random peaks of reactive power demand using the same
means as those used in industrial applications operating with a reactive
power demand that does not vary or varies slowly over time? Explain briefly.
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Exercise 3 – Dynamic Power Factor Correction Using an SVC  Review Questions
3. What is the effect of the large random peaks of reactive power demand
generated in arc furnace applications and other similar industrial applications
on the voltage at the ac power input of the application and the voltage at the
ac power input of the power network electrical power consumers? Explain
briefly.
4. Explain briefly how SVCs can be used to minimize the undesirable effects
caused by the large random peaks of reactive power demand in arc furnace
applications and other similar industrial applications.
5. Explain briefly why the installation costs of an SVC used for dynamic power
factor correction in an arc furnace application or any similar industrial
application can generally be recouped within a few years of the installation of
the SVC.
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