Lab Report Power Quality 1

LAB REPORT KKKZ 4044 POWER QUALITY LAB 1 SESSION 2015/2016 SINGLE PHASE POWER QUALITY MACHINE

NAME : ABDUL HAKIM BIN ABDULLAH MATRIC ID : A 141188 LECTURER : PROF. DR. M. A. HANNAN DEMO : MOHD FIRDAUS HAFIDZUDDIN

1.0 ABSTRACT Single phase machine normally is not very sensitive as three phase machine since the load for single phase usually consume low voltage demand compared to load in the industrial area which demand high voltage in its load system. Moreover, the load for single phase are not seem to be affected if power quality problem such as voltage sag, voltage swell or flicker occurs. But it may affected if the high power load was connected in the electrical system such as air conditioning, refrigerator and microwave was used at the same time using inappropriate electrical connection. In other cases, circuit breaker in industrial factories may tripped if the voltage supply not enough for load consumption in three phase machine because it is very sensitive to any power quality problem in the electrical system. Fluke 434 Power Quality Analyzer is an electrical equipment which is used in this experiment to locate, predict, prevent and troubleshoot problems in three- and single-phase power distribution systems. Troubleshooting is faster with on-screen display of trends and captured events, even while background recording continues. The new IEC (International Electrotechnical Commission) standards for transient, flicker, harmonics and power quality are built right in to take the guess work out of power quality. In this experiment, we have used NE9102 Distribution Trainer and Induction Motor as load to test the Fluke 434 Power Quality Analyzer to view the effect on dips & swells, transients, flicker and harmonics.

2.0 INTRODUCTION A utility may define power quality as reliability and show statistics demonstrating that its system is 99.98 percent reliable. Criteria established by regulatory agencies are usually in this vein. A manufacturer of load equipment may define power quality as those characteristics of the power supply that enable the equipment to work properly. These characteristics can be very different for different criteria. Power quality is ultimately a consumer-driven issue, and the end user’s point of reference takes precedence. In general, power quality problem can be defined as any occurrence manifested in voltage, current or frequency deviations which results in failure or frequency deviations which results in failure or misoperation of end-use equipment.

There are many misunderstandings regarding the causes of power quality problems. Figure 1 below show the result of the survey conducted by Courtesy of Georgia Power Company. Power quality sources can cause from inside and outside of the electrical system. For examples single phase to ground shorts on the distribution system, lightning, weather, utility switching, equipment failure, human error, common mode transients from load switching, grounding problem, load interactions, harmonic generating loads and total harmonic distortions.

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Figure 1 : Results of a survey on the causes of power quality problems. (Courtesy of Georgia Power Co.)

In a single phase electrical system, there are many types of power quality problem may occurs. Voltage sag, voltage swell, transient, harmonic distortion, electrical noise, flickering, notching and spikes are example of power quality problem in electrical system. There are a few method which can be used to overcome this power quality problem. For example, voltage sag problem can be solve by using mitigating devices such as ferroresonant transformer, magnetic synthesizers, active series compensator, UPS systems, motor generator set, dynamic voltage restorer, static transfer switch, flywheel energy storage systems and superconductor magnetic energy storage (SMES) device.

3.0 METHODOLOGY

1. Phase A(L1) conductor in main switchboard panel was clamped with current clamp of Fluke 434. 2. Banana-inputs was connected to ground, phase A(L1) and neutral conductor for voltage connection. Phase 2(L2) was connected to investigate the line-to-line voltage. 3. Choose single phase split phase configuration on the analyzer. 4. Configure the nominal voltage and frequency of the single phase power system for the analyzer. 5. Press the Menu button to enter measurement menu of the analyzer. 6. Select Volts/Amps/Hertz option to measure the voltage, current, frequency and crest factor for phase L1, L2 and Neutral of single phase power system before introducing any disturbance in the system. Observe the numerical values of the Volts/Amps/Hertz table. 2

Then, observe the waveforms trends of the voltage and current of the single phase power system. 7. Repeat step 5 and select Dips & Swells option to measure and record the numerical values and waveform trends of voltage and current for phase L1, L2 and Neutral of single phase power system before and after the disturbance injected into the power system. 8. Switch on the distribution trainer, induction motor set and DC compound wound motor set consecutively for a few seconds to create a power quality disturbance in the system. Observe the waveform trends of the phases and neutral voltages and current. 9. Record and compare the minimum and nominal values of each set of measurement. 10. Repeat step 7 to select Harmonics option to measure and record the numerical values and waveform trends of the voltage and current harmonics and Total Harmonics Disturbance (THD) value for phase L1, L2 and Neutral of single phase power system before and after the disturbance is injected into the power system. Repeat step 8. Observe the bar graphs of the phase and neutral current and voltage and record the THD value. 11. Repeat step 7 and select Flicker option. Leave the analyzer for measurement without any disturbance for one minutes to obtain the short-term flicker value Pst (1 min). Turn on and off the lighting switch of the fluorescent lamps on the table in the laboratory repeatedly and continuously for 1 minutes. Then, record the short-term flicker value Pst (1 min) and observe the flicker waveform trend. Then, wait another 1 minute for whole system settling down and record the short-term flicker value Pst (1 min) and observe flicker waveform trend again. 12. Repeat step 7 and select Transients option. Repeat step 8 and observe the current and voltage waveforms for phase L1, L2 and Neutral of the single phase power system. Record the numerical values appear on the screen.

4.0 RESULTS

4.1 Setup Configuration Before conducting the experiment we need to configure the nominal voltage and frequency. Figure 4.1 shows the result of configuring the nominal voltage and frequency of the single phase power system. The single phase connection from banana-input can be view in the setup configuration as shown in figure 2.

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Figure 2 : Nominal voltage and frequency

Figure 3 : Single phase connection

4.2 Volts/Amps/Hertz

Figure 5 : Numerical value for delta connection

Figure 4 : Numerical value for star connection

Figure 4 and 5 shows the differences between numerical value of star and delta connection. In figure 5, the phase L1 and L2 share the same value of their own rms voltage, peak voltage, crest factor and frequency. Moreover, rms current, peak current and crest factor for L2 was not displayed in the analyzer screen. Earlier, the nominal frequency was 50 Hz was decreases to 49.96 Hz. A change in system frequency will cause change in speed of motors, change in magnetizing current will be there for transformers and induction motors will be affected with change in inductances. A huge increase will cause increase in harmonic currents and will cause heating of the system with insulation failure. Frequency of a system also decides the real power balance in a power system as line parameters will change with change in frequency. Figure 15 shows the nominal frequency of the single phase power system.

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Figure 6 : Phase L1 Vrms

Figure 7 : Phase L1 Irms

Figure 8 : Phase L2 Vrms

Figure 9 : Phase L2 Irms

Figure 10 : Phase N Vrms

Figure 11 : Phase N Irms

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Figure 12 : Phase L1 Ipeak

Figure 13 : Crest factor

Figure 14 : Phase L2 Ipeak

Figure 15 : Nominal frequency

Figure 16 : Phase N Ipeak

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4.3 Dips & Swell

Figure 17 : Phase L1 Irms before disturbance

Figure 18 : Phase L1 Vrms before disturbance

Figure 19 : Phase L2 Irms before disturbance

Figure 20 : Phase L2 Vrms before disturbance

Figure 21 : Phase N Irms before disturbance

Figure 22 : Phase N Vrms before disturbance

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Figure 23 : Phase L1 Irms during disturbance

Figure 24 : Phase L1 Vrms during disturbance

Figure 25 : Phase L2 Irms during disturbance

Figure 26 : Phase L2 Vrms during disturbance

Figure 27 : Phase N Irms during disturbance

Figure 28 : Phase N Vrms during disturbance

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Figure 29 : Phase L1 Irms after disturbance

Figure 30 : Phase L1 Vrms after disturbance

Figure 31 : Phase L2 Irms after disturbance

Figure 32 : Phase L2 Vrms after disturbance

Figure 33 : Phase N Irms after disturbance

Figure 34 : Phase N Vrms after disturbance

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Figure 17 until 22 shows the Irms and Vrms of the phase L1, L2 and Neutral before the power system experienced the load disturbance. From all those figures, we can see the waveform trends of all the phases are most likely to be smooth without any power quality problem either voltage dips or swells in this case. But it still occurs in small scale as can be seen in figure 18 and 20. This problems are causes by the switching on or off the load from other room at the old faculty building.

Figure 23 until 28 shows the Irms and Vrms of the phase L1, L2 and Neutral during the power system experienced the load disturbance. Figures in this range had shown a lot of problem compared to the previous waveform trends before injecting the load disturbance. All the phases for rms currents and voltages for phase L1, L2 and Neutral during load disturbance shows a dips and swells in their trends since the load was switch on at the same room as the fluke meter was measured.

Figure 29 until 34 shows the Irms and Vrms of the phase L1, L2 and Neutral after the power system experienced the load disturbance. In this situation, the load was switch off but it seem to have few dips and swells before it was stabilize into its steady state voltage and current after switching off the load. The correct waveform trends should be taken few minutes later after switching the load to observe a correct waveform trends.

The 90% level provides an indication of performance for the most sensitive equipment. The 80% level corresponds to an important break point on the ITI curve and some sensitive equipment may be susceptible to even short sags at this level. The 70% level corresponds to the sensitivity level of a wide group of industrial and commercial equipment and is probably the most important performance level to specify. The 50% level is important, especially for the semiconductor industry, since they have adopted a standard that specifies ride through at this level.

Interruptions affect all customers so it is important to specify this level separately. These will usually have longer durations than the voltage sags. The first range of durations is up to 0.2 seconds (12 cycles at 60 Hz). This is the range specified by the semiconductor industry that equipment should be able to ride through sags as long as the minimum voltage is above 50%. The second range is up to 0.5 seconds. This corresponds to the specification in the ITIC standard for equipment ride through as long as the minimum voltage is above 70%. It is also an important break point in the definition of sag durations in IEEE 1159 (instantaneous vs. momentary). The third duration range is up to 3 seconds. This is an important break point in IEEE 1159 and in IEC standards (momentary to temporary).

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4.4 Harmonics

Figure 35 : THD Voltage before disturbance

Figure 36 : THD Voltage after disturbance

Figure 37 : THD current before disturbance

Figure 38 : THD current after disturbance

Figure 39 : THD power before disturbance

Figure 40 : THD power after disturbance

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Harmonic distortion originates in the nonlinear characteristics of devices and loads on the power system. Harmonic distortion levels are described by the complete harmonic spectrum with magnitudes and phase angles of each individual harmonic component. It is also common to use a single quantity, the total harmonic distortion (THD), as a measure of the effective value of harmonic distortion.Figure 35 shows the THD voltage with value 1.6% drop to 1.5% after injecting load disturbance as shown in figure 36. In figure 37 and 38 the THD current was drop drastically from 187.9% to 43.2%. In a while, figure 39 and 40 shows a drop from 1.0% to 1.1% after injecting the load disturbance into the power system.

IEEE Standard 519-2014 is a standard developed for utility companies and their customers in order to limit harmonic content and provide all users with better power quality. Some of the key areas of the standard are detailed in the following tables. Bear in mind that dealing with harmonics may still be required, whether or not the goal is to meet IEEE 519 standards. In low-voltage systems (600 V or less), capacitors are typically the lowest impedance at harmonic frequencies, and experience very high RMS currents and increased heat which causes them to fail.

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4.5 Flicker

Figure 41 : Before load disturbance

Figure 42 : During load disturbance

Figure 43 : Settling down after load disturbance

Figure 44 : Flicker waveform trend

From figure 41 until 43, the short-term flicker (Pst) for phase L1 increases from 0.08 to 0.14 while decreases from 0.14 to 0.07 for phase L2. The flicker signal is defined by its rms magnitude expressed as a percent of the fundamental. Voltage flicker is measured with respect to the sensitivity of the human eye. Typically, magnitudes as low as 0.5 percent can result in perceptible lamp flicker if the frequencies are in the range of 6 to 8 Hz. In this case, the frequency is not affected by the load disturbance then producing the normal flicker waveform trend without any critical power quality problem as shown in figure 44.

IEC 61000-4-15 defines the methodology and specifications of instrumentation for measuring flicker. The IEEE Voltage Flicker Working Group has recently agreed to adopt this standard as amended for 60 Hz power systems for use in North America. This 13

standard devises a simple means of describing the potential for visible light flicker through voltage measurements. The measurement method simulates the lamp/eye/brain transfer function and produces a fundamental metric called short-term flicker sensation (Pst). This value is normalized to 1.0 to represent the level of voltage fluctuations sufficient to cause noticeable flicker to 50 percent of a sample observing group. Another measure called long-term flicker sensation (Plt) is often used for the purpose of verifying compliance with compatibility levels established by standards bodies and used in utility power contracts. This value is a longer-term average of Pst samples.

4.6 Transients

Figure 45 : Voltages before load disturbance

Figure 46 : Voltages during load disturbance

Figure 47 : Currents before load disturbance

Figure 48 : Currents during load disturbance

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Figure 49 : Phase Neutral before disturbance

Figure 50 : Phase Neutral during disturbance

Figure 51 : Phase L1 before disturbance

Figure 52 : Phase L1 during disturbance

Figure 53 : Phase L2 before disturbance

Figure 54 : Phase L2 during disturbance

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Figure 55 : Voltages after load disturbance

Figure 56 : Currents after load disturbance

Figure 57 : Phase Neutral after disturbance

Figure 58 : Phase L1 after disturbance

Figure 59 : Phase L2 after disturbance

Figure 60 : Transients configuration

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Figure 45 until 54, shows the differences of waveform trends between the condition before injecting the load disturbance and during injected load disturbance. It seem to have some problem in power quality during the load disturbance as shown in figure 48, 50, 52 and 54. However, the waveform trends of the transient return to be same as before injecting the load when the load disturbance was turned off.

Transients are power quality disturbances that involve destructive high magnitudes of current and voltage or even both. It may reach thousands of volts and amps even in low voltage systems. However, such phenomena only exist in a very short duration from less than 50 nanoseconds to as long as 50 milliseconds. This is the shortest among power quality problems, hence, its name. Transients usually include abnormal frequencies, which could reach to as high as 5 MHz. Transients are also known as surge. According to IEEE 100, surge is a transient wave of voltage, current or power in an electric circuit. Other IEEE definitions suggest that it is the part of the change in a variable that disappears during transition from one steady-state operating condition to another. Such description is too vague, which could be used to describe just about any unusual events occurring in the electrical system. Moreover, most electrical engineers would refer to the damped oscillatory transient phenomena in a RLC circuit when hearing such term.

Sources of transients may come from switching activities such as opening and closing of disconnects on energized lines, capacitor bank switching, reclosing operations, tap changing on transformers, accidents, human error, animals and bad weather conditions and neighboring facilities. Damages due to such power quality problems are uncommon as compared to voltage sags(dips) and interruptions, but when it does occur it is more destructive. To protect against transients, end-users may use Transient Voltage Surge Suppressors (TVSS), while utilities install surge arresters.

5.0 DISCUSSION 5.1 Dips & Swell A voltage sag also known as voltage dips is a decrease to between 0.1 and 0.9 p.u. in rms voltage or current at the power frequency for durations from 0.5 cycle to 1 min. The power quality community has used the term sag for many years to describe a short-duration voltage decrease. Although the term has not been formally defined, it has been increasingly accepted and used by utilities, manufacturers, and end users. The IEC definition for this phenomenon is dip. The two terms are considered interchangeable, with sag being the preferred synonym in the U.S. power quality community. Terminology used to describe the magnitude of a voltage sag is often confusing. A“20 percent sag” can refer

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to a sag which results in a voltage of 0.8 or 0.2 p.u.. The preferred terminology would be one that leaves no doubt as to the resulting voltage level: “a sag to 0.8 p.u.” or “a sag whose magnitude was 20 percent.” When not specified otherwise, a 20 percent sag will be considered an event during which the rms voltage decreased by 20 percent to 0.8 p.u.. The nominal, or base, voltage level should also be specified.

Figure 61 : Voltage Dips A swell is defined as an increase to between 1.1 and 1.8 p.u. in rms voltage or current at the power frequency for durations from 0.5 cycle to 1 min. As with sags, swells are usually associated with system fault conditions, but they are not as common as voltage sags. One way that a swell can occur is from the temporary voltage rise on the unfaulted phases during a Single-Line to Ground (SLG) fault. Figure 62 illustrates a voltage swell caused by an SLG fault. Swells can also be caused by switching off a large load or energizing a large capacitor bank. Swells are characterized by their magnitude (rms value) and duration. The severity of a voltage swell during a fault condition is a function of the fault location, system impedance, and grounding. On an ungrounded system, with an infinite zero-sequence impedance, the line-to-ground voltages on the ungrounded phases will be 1.73 p.u. during an SLG fault condition. Close to the substation on a grounded system, there will be little or no voltage rise on the unfaulted phases because the substation transformer is usually connected delta-wye, providing a low-impedance zero-sequence path for the fault current. Faults at different points along four-wire, multi grounded feeders will have varying degrees of voltage swells on the unfaulted phases. A 15 percent swell, like that shown in figure 62, is common on U.S. utility feeders. The term momentary overvoltage is used by many writers as a synonym for the term swell.

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Figure 62 : Voltage Swells

5.2 Harmonics Harmonics are sinusoidal voltages or currents having frequencies that are integer multiples of the frequency at which the supply system is designed to operate (termed the fundamental frequency; usually 50 or 60 Hz). Periodically distorted waveforms can be decomposed into a sum of the fundamental frequency and the harmonics. Harmonic distortion originates in the nonlinear characteristics of devices and loads on the power system. Harmonic distortion levels are described by the complete harmonic spectrum with magnitudes and phase angles of each individual harmonic component. It is also common to use a single quantity, the total harmonic distortion (THD), as a measure of the effective value of harmonic distortion. Figure 63 illustrates the waveform and harmonic spectrum for a typical adjustable-speed-drive (ASD) input current. Current distortion levels can be characterized by a THD value, as previously described, but this can often be misleading. For example, many adjustable-speed drives will exhibit high THD values for the input current when they are operating at very light loads. This is not necessarily a significant concern because the magnitude of harmonic current is low, even though its relative distortion is high. To handle this concern for characterizing harmonic currents in a consistent fashion, IEEE Standard 519-1992 defines another term, the total demand distortion (TDD). This term is the same as the total harmonic distortion except that the distortion is expressed as a percent of some rated load current rather than as a percent of the fundamental current magnitude at the instant of measurement. IEEE Standard 519-1992 provides guidelines for harmonic current and voltage distortion levels on distribution and transmission circuits.

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Figure 63 : Current waveform and harmonic spectrum for an ASD input current.

5.3 Flicker Voltage fluctuations are systematic variations of the voltage envelope or a series of random voltage changes, the magnitude of which does not normally exceed the voltage ranges specified by American National Standard Institute (ANSI) C84.1 of 0.9 to 1.1 p.u. IEC 61000-2-1 defines various types of voltage fluctuations. We will restrict our discussion here to IEC 61000-2-1 Type (d) voltage fluctuations, which are characterized as a series of random or continuous voltage fluctuations. Loads that can exhibit continuous, rapid variations in the load current magnitude can cause voltage variations that are often referred to as flicker. The term flicker is derived from the impact of the voltage fluctuation on lamps such that they are perceived by the human eye to flicker. To be technically correct, voltage fluctuation is an electromagnetic phenomenon while flicker is an undesirable result of the voltage fluctuation in some loads. However, the two terms are often linked together in standards. Therefore, we will also use the common term voltage flicker to describe such voltage fluctuations. An example of a voltage waveform which produces flicker is shown in figure 64. This is caused by an arc furnace, one of the most common causes of voltage fluctuations on utility transmission and distribution systems. The flicker signal is defined by its rms magnitude expressed as a percent of the fundamental. Voltage flicker is measured with respect to the sensitivity of the human eye. Typically, magnitudes as low as 0.5 percent can result in perceptible lamp flicker if the frequencies are in the range of 6 to 8 Hz. IEC 61000-4-15 defines the methodology and 20

specifications of instrumentation for measuring flicker. The IEEE Voltage Flicker Working Group has recently agreed to adopt this standard as amended for 60Hz power systems for use in North America. This standard devises a simple means of describing the potential for visible light flicker through voltage measurements. The measurement method simulates the lamp/eye/brain transfer function and produces a fundamental metric called short-term flicker sensation (Pst). This value is normalized to 1.0 to represent the level of voltage fluctuations sufficient to cause noticeable flicker to 50 percent of a sample observing group. Another measure called long-term flicker sensation (Plt) is often used for the purpose of verifying compliance with compatibility levels established by standards bodies and used in utility power contracts. This value is a longer-term average of Pst samples.

Figure 64 : Flicker

5.4 Transients The term transients has long been used in the analysis of power system variations to denote an event that is undesirable and momentary in nature. The notion of a damped oscillatory transient due to an RLC network is probably what most power engineers think of when they hear the word transient. Other definitions in common use are broad in scope and simply state that a transient is “that part of the change in a variable that disappears during transition from one steady state operating condition to another.” Unfortunately, this definition could be used to describe just about anything unusual that happens on the power system. A utility engineer may think of a surge as the transient resulting from a lightning stroke for which a surge arrester is used for protection. End users frequently use the word indiscriminantly to describe anything unusual that might be observed on the power supply ranging from sags to swells to interruptions. Because there are many potential ambiguities with this word in the power quality field, we will generally avoid using it unless we have specifically defined what it refers to. Transients can be classified into two categories, impulsive and oscillatory. 21

Figure 65 : Transients

6.0 CONCLUSION Evolution of technology has create a lot of digital and graphical measuring devices in order to obtain and observe a data/result in a detail and efficient ways. Before digital and graphical device is used, analog device was a very important devices to be used in power system measurement. Nowadays, analog measuring devices was replaces by the digital and graphical measuring devices such as multimeter, oscilloscope, fluke clamp meter, insulation meter and many other devices. In this experiment, we are using fluke clamp meter to measure the voltage, current and frequency then observing the waveform trends of the power quality problem. The Fluke 434 power quality analyzers can locate, predict, prevent and troubleshoot problems in three- and single-phase power distribution systems. Troubleshooting is faster with on-screen display of trends and captured events, even while background recording continues. The new IEC standards for flicker, harmonics and power quality are built right in to take the guess work out of power quality.

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Figure 66 : Summary of power quality problem

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7.0 REFERENCES

Roger C. Dugan, Mark F. McGranaghan, Surya Santoso, H. Wayne Beaty. Electrical Power System Quality. 2nd Edition. M. A. Hannan. 2016. Introduction to Power Quality. Lecture Slide. http://www.testequip.com/sale/details/HTS0174.html http://ecmweb.com/power-quality-archive/power-quality-standards-industry-update http://electrical-engineering-portal.com/9-most-common-power-quality-problems http://www.power-solutions.com/power-quality http://www.fluke.com/fluke/caen/community/fluke-news-plus/articlecategories/clamps/ac -dc-clamp-meter https://www.quora.com/How-does-a-change-in-AC-frequency-affect-an-electrical-system http://www.powerstandards.com/tutorials/sagsandswells.php http://www.myronzucker.com/Asset/PDF-and-Excel-Charts/IEEE-519-Tables.html

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