Power Quality Training_ by Engr Dr Omeje2.pptx

Power quality

1. INSTRUCTOR: Engr. Osita U. Omeje Training Delivered to the Staf f of Olorunsogo Power Plant (Phase I) June 5, 2013 POWER QUALITY ASSESSMENT IN ELECTRICAL POWER SYSTEMS

2. PART 1 FUNDAMENTALS OF POWER QUALITY

3. Definition of Power Quality What is Power Quality? Power quality is loosely defined as the study of powering and grounding electronic systems so as to maintain the integrity of the power supplied to the system A power quality problem is any occurrence manifested in voltage, current, or frequency deviation that results in failure or misoperation of customer equipment.

4. CLASSIFICATION OF POWER QUALITY PROBLEMS Waveform Distortion Harmonics DC Offset Interharmonics Notching Electric Noise Voltage Fluctuation and Flicker Classes of Power Quality Problems

5. Power Frequency Variation Transient Impulsive Oscillatory Short Duration Variation Voltage Sag Voltage Swell Interruption Classes of Power Quality Problems

6. Long Duration Variation Sustained Interruption Undervoltage Overvoltage Voltage Imbalance Classes of Power Quality Problems

7. HARMONICS Harmonics are sinusoidal voltages or currents with Frequencies that are integral multiples of the power system (fundamental) frequency, f 1 (usually 50 or 60Hz). For example, harmonic 2 = f 2 = 2f 1 , harmonic 3 = f 3 = 3f 1 , harmonic 4 = f 4 = 4f 1 , etc. Figure 1: A Distorted Waveform Waveform Distortion

8. Figure 2: A sinusoidal waveform with fundamental frequency 50Hz and its harmonics: (a) second (100Hz); (b) third (150Hz); (c) fourth (200Hz); (d) fifth (250Hz) Waveform Distortion

9. Sources of Harmonics Electronic and power electronic equipment such as static converter based equipment (variable speed controllers, UPS units, ac/dc converters), switch mode power supplies (SMPS), static var compensator, etc Arc furnaces, arc welders, high-pressure discharge lamps, etc Magnetic core equipment, like transformers, electric motors, generators, etc Waveform Distortion

10. Effects of Harmonics Maloperation of control devices Additional losses and possible damages in capacitors, transformers, and rotating machines Additional noise from motors and other apparatus Telephone interference Voltage amplifications at remote location from the distorting load due to parallel and series resonance Overheating of phase and neutral conductors Skin effects Nuisance Tripping of Circuit-Breakers Errors in measuring equipment Waveform Distortion

11. Mitigations of Harmonics Installation of harmonic filters (passive, active or hybrid) Application of high-pulse rectification Installation of custom power devices such as active-power line conditioners (APLCs) and unified power quality conditioners (UPQCs) Reduction of the magnitude of voltage harmonics Waveform Distortion

12. INTERHARMONICS These are current or voltage waveforms whose frequencies are not integral multiple of the fundamental frequency. They appear as discrete frequencies or as a band spectrum. Sources Static frequency converters, cycloconverters , induction motors, arcing devices, and computers Waveform Distortion

13. Effects Interharmonics cause flicker, low- freqency torques, additional temperature rise in induction machines, and malfunctioning of protective (under-frequency) relays Waveform Distortion

14. DC OFFSET This is the presence of DC current and/or voltage component in an AC system. Sources Employment of rectifiers and other electronic switching devices Geomagnetic disturbances Effects Half-cycle saturation of transformer core Generation of even harmonics in addition to odd harmonics Waveform Distortion

15. Additional heating in appliances leading to a decrease of the lifetime of transformers, rotating machines, and electromagnetic devices Electrolytic erosion of grounding electrodes and other connectors Mitigation Use of three-limb transformers with a relatively large air gap between core and tank Waveform Distortion

16. NOTCHING Notching is a periodic voltage disturbance caused by line-commutated thyristor circuits. It appears in the line voltage waveform during normal operation of power electronic devices when the current commutation from one phase to another. Waveform Distortion Figure 3: Notching in Three-Phase Rectifier

17. ELECTRIC NOISE Electrical noise is defined as unwanted electrical signal with broadband spectral content lower than 200kHz superimposed on the power system voltage or current in phase conductors, or found on neutral conductors or signal lines Sources Faulty connections in transmission or distribution systems, arc furnaces, electrical furnace, power electronic devices, corona, etc Waveform Distortion

18. Mitigation use of filters line conditioners dedicated lines or transformers. Waveform Distortion

19. VOLTAGE FLUCTUATIONS AND FLICKERS Voltage Fluctuation is defined as the cyclic variation of voltage with amplitude that does not exceed 10%. Flicker is defined as the unpleasant sensation experienced by the human visual system when subjected to changes occuring in the illumination intensity of light sources. The illumination variations appear as a consequence of voltage fluctuation. Figure 4: Voltage fluctuation Voltage Fluctuations and Flickers

20. Sources Loads that produce rapid voltage fluctuations such as arc furnaces, welding machines, electric boilers, capacitor banks, etc Mitigation Decreasing power variations (mainly reactive power variations) of the loads Increasing the short-circuit power level Voltage Fluctuations and Flickers

21. VOLTAGE SAG A brief decrease in the rms line-voltage of 10 to 90% of the nominal line-voltage. The duration of sag is 0.5 cycle to 1minute. The main sources of sags are the starting of large induction motors and utility faults Figure 5. Voltage Sag Short-Duration Variations

22. VOLTAGE SWELL the converse to the sag. A swell is a brief increase in the rms line-voltage of 110 to 180% of the nominal line-voltage for a duration of 0.5 cycle to 1 minute. Sources of voltage swells are line faults and incorrect tap settings in tap changers in substations. Short-Duration Variations Figure 6. Voltage Swell

23. INTERRUPTION a reduction in Line-voltage or current to less than 10% of the nominal, not exceeding 60 seconds in length. Figure 7: Interruption Short-Duration Variations

24. SUSTAINED INTERRUPTION Most sever and oldest power quality event Voltage drops to zero and does not return automatically Duration is more than 3 min (or 1 min base on IEEE definition) Sources Fault occurrence in a part of power systems with no redundancy or with the redundant part out of operation Incorrect intervention of protection relay leading to outage Long-Duration Variations

25. Scheduled interruption in a low voltage network with no redundancy UNDERVOLTAGE Occurs when the rms voltage decreases to 0.8-0.9 pu for more than 1 min OVERVOLTAGE Increase in the rms voltage to 1.1-1.2 pu for more than 1 min Categorized into 3 main groups viz : lightning overvoltages , switching overvoltages and overvoltages caused by insulation faults, alternator regulator faults, tap changer transformer, or overcompensation Long-Duration Variations

26. IMPULSE TRANSIENT A brief, unidirectional variation in voltage, current, or both on a power line Most common causes are lightening strikes, switching of inductive loads, or switching in the power distribution system Can be mitigated by voltage suppressors such as Zener diodes and MOV (metal-oxide varistors ) Figure 8: Impulse Transient Transients

27. OSCILLATORY TRANSIENT A brief bidirectional variation in voltage, current, or both on power line Caused by switching of power factor correction capacitors, or transformer ferroresonance Transients Figure 9: Oscillatory Transient

28. POWER FREQUENCY VARIATION Variation of power system fundamental frequency from its specified nominal value Majorly caused by the variation of the balance between generation and demand (load) Power Frequency Variation

29. VOLTAGE IMBALANCE Occurs when the three-phase system are not identical in magnitude and/or the phase difference between them are not exactly 120 degrees Two main ways of computing the degree of imbalance are: maximum deviation from average of the three-phase voltages Average of three-phase voltages Ratio of the negative- (or zero-) sequence component to the positive-sequence components Voltage Imbalance

30. Causes of Imbalance Unbalanced single-phase loading in a three-phase system Overhead transmission lines that are not transposed Blown fuses in one phase of a three-phase capacitor bank Severe voltage imbalance ( eg ., > 5%), which can result from single phasing conditions Voltage Imbalance

31. CONCLUSION The mitigation of power quality problems are usually neglected especially in third world countries such as Nigeria. The outlined classes of power quality problems and their effects shows that power quality problems should be handled appropriately to avoid equipment breakdown and power system unreliabilty Conclusion

32. Thank You For further inquiry on this part of the training, you can contact the instructor as follows: Email: [email protected] or [email protected] Phone: [phone]

33. PART 2 POWER QUALITY MEASUREMENT USING SUPPLY NETWORK ANALYZER (MODEL AR5-L) INSTRUCTOR: Engr. Osita U. Omeje

34. WHAT IS AR5 POWER SUPPLY ANALYZER ? AR5-L Power Supply Analyzer is a programmable instrument that measures, calculates, and stores in memory the main parameters of three phase electrical supply networks. Measurement is done by the means of three A.C. voltage inputs and three A.C. current inputs (through current clamps) that permit a simultaneous analysis of voltage, current, active power and frequency. Calculation is done by the means of an internal processor that calculates the rest of electrical parameters such as power factor, inductive or capacitive reactive power of the three phases, as well as the active and reactive (inductive and capacitive) energies.

35. Data are recorded in an internal memory ( 256 kbytes or 1 Mbytes according to the model) which are in turn downloaded into a PC for further analysis. Measured and calculated data are periodically saved in that memory at user- defined time intervals (from 1s to 4 h). PHYSICAL FEATURES LCD graphic display (160 x 160 pixels): for viewing instantaneous, maximum and minimum values of all parameters Membrane Type Keyboard (9 keys): to perform controlling and setting actions over the diverse operation modes of the instrument Ports: for connecting current clamps, voltage leads, power cord and RS-232 communication cable to the analyzer

36. Figure 1: AR5 Power Network Analyzer LCD GRAPHIC DISPLAY KEYS

37. Figure 2: Input Ports of the AR5 Analyzer

38. ACCESSORIES Current Clamps (x3) Voltage leads (x4) Alligator clamps (x4) RS-232 communication cable (x1) Power supplier set 230 / 12 V (x1) Connection cord between the power supplier set and the 230 V a.c . main (x1) 1 Connection cable between the AR5-L and the power supplier set (x1) KEYBOARD FUNCTIONS The AR5-L analyzer has a 9 buttons keyboard that is used to configure and control the operations of the instrument.

39. [ON]: to turn the AR5-L on [OFF]: to turn the AR5 off [▼] , [▲] , [►] & [◄]: to select among several options [SET]: to access setting options [ENTER]: to validate a setting option or to program some parameters of the visualization screens [ESC]: to select different visualization screens or to exit the setting actions  However, some keys have dual functions.   CONNECTION MODES There are basically four connection modes of AR5-L Analyzer. These are (1) Three phase – three wire (2) Three phase – four wire, (3) One phase and (4) 3PT – 2CT mode. The connection diagrams are as shown below:

40. Figure 3: Three Phase – four wire Mode Connection Diagram

41. Figure 4: 3PT – 2CT Mode Connection Diagram

42. HOW TO OPERATE THE ANALYZER To turn the instrument on: Press the key <ON> at the analyzer keyboard. The analyzer’s introduction screen appears with a list of available programs such as Harmonics, Flicker, Disturbance, etc Use keys [▲] & [ ▼ ] to select the desired program Press [ENTER] or wait for a while to confirm this operation NOTE : If nothing is shown on the display, a discharged battery or a problem with the display contrast might exist.   Initial Considerations after the Analyzer Startup Format the memory if necessary Clear maximum and minimum values as well as energy counters if necessary

43. Open a file with a desired name. All data will be automatically saved in this file until a new one is opened. The analyzer internal memory can contain several files (different analysis). Caution: Note that when the memory is formatted all previously stored data is lost. If a new file with a different file name is opened, the previous files/data in the internal memory are not deleted. When starting new measurements at any installation the meter settings must be checked and modified if necessary. Otherwise, the AR5-L will work according to the setup of the last used program (this is saved in memory even after powering the meter off). Settings that are normally

44. checked are: Ratio of ammeter clamps Voltage transformer ratio Recording period DATA VIEW ON SCREEN Different programs have virtually similar data view on screen. For emphasis and clarity, most of the data views shown in this section are from Harmonics Program.   All measured instantaneous values as well as maximum and minimum values can be read on a 160 x 160 pixel liquid crystal display. An indication of the type of data being displayed is shown at the upper right corner.

45. SCREEN OF INSTANTANEOUS VALUES This screen appears when the analyzer is put on as shown below: Figure 5: Instantaneous Value Screen

46. Voltage : Reading of the instantaneous voltage RMS value measured at each phase (L1, L2 & L3) and the average value of the instantaneous voltage values of the three phases. Current : Reading of the instantaneous current RMS value measured at each phase (L1, L2 & L3) and the average value of the instantaneous current values of the three phases (III). Active power : The active power is calculated from instantaneous voltage and current data. The readout gives the instantaneous values of the active power of each phase and also the three phase total instantaneous active power, which is the addition of each phase active power value.

47. Inductive reactive power : The inductive reactive power is calculated from instantaneous voltage and current data. The readout gives the instantaneous values of the inductive reactive power of each phase and also the three phase total instantaneous inductive reactive power, which is the addition of each phase value.   Capacitive reactive power: The capacitive reactive power is calculated from instantaneous voltage and current data. The readout gives the instantaneous values of the capacitive reactive power of each phase and also the three phase total instantaneous capacitive reactive power, which is the addition of each phase value. Power factor : Reading of the power factor of each phase and the three phase average value..

48. Frequency : Reading of the instantaneous value of the frequency (Hz). Apparent power : Reading of the three phase total instantaneous apparent power, which is the addition of all the phase values. Energies : Reading of active, inductive reactive and capacitive reactive energy counters from the moment the energy counters were reset to zero. Time and Date (Time/Date): Reading of present time and date.

49. SCREEN OF MAXIMUM AND MINIMUM VALUES Figure 6: Screen of Maximum Values   As shown above, an indication of the type of data being displayed is shown at the upper right corner: INST (Instantaneous), MAX (Maximum) or MIN (Minimum).

50. Maximum and minimum values displayed correspond to the maximum and minimum values obtained from the instantaneous values. The negative energy counters are then displayed in place of positive energies. OTHER DATA VIEWS Through the [ESC] key other additional screens can be displayed.   View of Three Parameters in a Big Size Mode Three instantaneous parameters of your choice can be bigger-size displayed for a clearer reading.  

51. Figure 7: Big Size View of Parameters Bar Graphs Simultaneous graphical representation on display of the three phase (L1, L2 & L3) values of the selected parameter as shown below

52. Figure 8: Bar-graphical view of parameters Oscilloscope The display concurrently shows the wave forms of voltage and current of each phase (L1, L2 & L3) as shown below

53. Figure 9(a): Three Phase: Voltage – Current Figure 9(b): Zoom Figure 9(c): Harmonic Factorization

54. Setup Visualization This screen shows all Setup parameters in the analyzer. The screen on the left is the one shown on the analyzer’s display. The screen on the right explains the meaning of each term. Figure 10 (a): Setup Screen Figure 10(b): Explanation

55. HOW TO PROGRAM THE ANALYZER To access the analyzer’s setup options, press the key [SET] . The analyzer will then inquiry for a password. The default password is: [◄] [SET] [ ▲ ] [SET] Once this password is entered, the analyzer will permit the user to modify any Setup parameters. Diverse setting MENUS are available as shown below:

56. Select one option with keys [▼] & [▲] . To access any menu option use [►] or [ENTER]. To close the menu press [◄] or [ESC] . If any of these keys are pressed when only the main menu is open, the menu will be closed without any confirmation request. However, whenever modification on any setup parameter was done and any of the keys are pressed, a confirmation request is displayed and must be authenticated before exiting or closing the setup menu.   SETUP MENU The AR5-L meter can be user-configured to different performances involving its data analysis and recording modes, as shown below:

57. MEASURE menu This menu enables the setting of such measuring conditions as connection type (3PT-2CT, 3  4wire, 1, etc ), current transformation ratio (CT) and voltage transformation ratio(VT). RECORD menu This menu is used to set the following recording conditions Period : is used to set the time period that will elapse before the average values of data measured within that period will be saved in memory. It ranges from 1s to 4hours for the standard type files (.A5M)

58. Trigger : is used to program certain conditions so that values are saved in memory only when these conditions are met. The two types are Time trigger and Parameter trigger. Time trigger (TIME) is used to program the DATE/TIME of ON (start measurement process) and/or OFF (end measurement process). However, Parameter trigger (LEVEL) is used to set the maximum threshold value (measured value must be higher) and/or the minimum threshold value (measured value must be lower) required before data can be stored in memory. The analyzer can only store data in its internal memory (STORE ON) when both trigger conditions are met. If any of the conditions is not met, no value will be stored in memory (STORE OFF state) and the display will show the message TRIG?

59. Meanwhile if trigger conditions are not requires, the Time ON & OFF are set to zero and the parameter LEVEL is set to AUTO. Name: This sub-menu is used to type the recording file name (8 characters, no extension). Type: This sub-menu is used to select the file type required for the analyzer recording action. The two common file types are Standard (pre-defined parameters) and Custom (user-selected parameters). The former is distinguished in memory with the extension .A5M while the later is distinguished in memory with the extension .A5T PARA: This sub-menu is used to choose the parameters that will be saved in memory.

60. COMM (Communication Parameters): This is used to program the parameters of the built-in RS-232 serial output. The default setting is shown below: CLOCK: This is used to set the analyzer internal clock – date/time. RECALL: This is used to recall a ‘standard’ configuration of the analyzer. RUN: is used to enable or disable data storage in the memory

61. FILE menu: is used to check file directory, delete files or format the internal memory of the analyzer. Figure 11: File Menu CLEAR menu: This menu is used to reset the energy counter to zero. It also clears maximum and minimum recorded data stored in the memory.

62. Thank You For further inquiry on this part of the training, you can contact the instructor as follows: Email: [email protected] or [email protected] Phone: [phone]

63. PART 3 PQ MEAUREMENT RESULTS ANALYSIS INSTRUCTOR: Engr. Osita U. Omeje

64. OVERVIEW Data stored in AR5 Supply Network Analyzer can be downloaded into a personal computer (PC) for further analysis. The equipment comes with a software pack (Power Vision Software) that makes this data analysis on a PC possible. The software must be installed in the PC before the stored data can be downloaded to the PC. HOW TO DOWNLOAD DATA INTO A PC Connect the analyzer to the power supply (main) through the power supply set (though download can be successfully done if the analyzer battery is fully charge). Connect the analyzer to the PC through the power supply set. RS232 connector will connect the power supply set to the PC while the other connection cable will connect the

65. analyzer to the power supply set. Ensure that communication parameters of the analyzer and the PC are compatible as stated earlier Exit the setup menu of the analyzer before starting the download Launch the installed software in the PC. The following base screen will appear as shown in figure 12 Left click the mouse over the icon on the toolbar or click the ‘File’ menu and select the “Portable Devices” sub-menu After the authentication of the device, select a desired path location and download the file(s)

66. Figure 12: Power Vision Main Screen

67. NOTE: The minimum requirement for the installation and proper running of “Power Vision” software in a PC is as follows: Windows Me, NT (4.0 or greater), 2000 or XP Screen resolution of 800x600 minimum 128 Mbytes of RAM Pentium II 300 MHz 30 MBytes hard drive free space HOW TO ANALYZE A FILE Open the file using any of the following options Left click on the icon of the toolbar Right click on a blank space and select “Open File” menu

68. Left click on the ‘File’ menu at the menu bar and select ‘Open’ sub-menu in the drop down menu that appears. When any of the above actions has been taken, a dialog box for opening of the file will appear. Trace the file and double click on it or select the file and right click on the ‘open’ button A pop up window containing possible actions that can be taken will appear. Select any of the options, eg , Graph, Quality, Lists, Table, etc When any of the above options are selected, another pop menu that demands more specific selections will appear.

69. CLASS DEMONSTRATION!!! OBJECTIVE: To Ensure that every participant knows how to analyze data retrieved from the analyzer YOU ARE ADVISED TO RUN THE SOFTWARE ON YOUR PC AS INSTRUCTED EARLIER AND PRACTISE ALONGSIDE THE INSTRUCTOR

70. Some of the graphs obtained in the field results analysis are as shown below: Figure 13. Total Harmonic Distortion Analysis at PCC to Phoenix Steel

71. As shown in figure 13, the maximum recorded voltage total harmonic distortion (THD) is 23.6 and the corresponding minimum value is 5.9. Similarly, the maximum recorded current THD is 6.0 and the corresponding minimum value is 1.1. With this information, we can conclude that the harmonic distortion introduced at PCC by Phoenix Steel company is beyond the admissible value (below 5.0 for voltage THD) and should be mitigated to avoid the propagation of this destructive event to the entire network.

72. Figure 14: Harmonic Factorization Analysis at PCC to Phoenix Steel

73. Figure 14 shows the harmonic factorization recorded, that is, individual harmonic values obtained at the PCC to Phoenix steel company. It is observed that some individual voltage harmonic values are very much higher than the admissible values; for instance, voltage harmonics – 35 th , 11 th , 13 th , 23 rd , 25 th , 27 th , etc.

74. Figure 15: Frequency Analysis at PCC to Phoenix Steel

75. As shown in each of the preceding graphs, the actual values on both the vertical and perpendicular axes at the cursor position are given at the bottom left corner of the graphs. The upper value is the horizontal axis value, usually time, while the lower value is the vertical axis value. Besides, maximum and minimum values for both axes are shown at the bottom centre and bottom right side respectively. These data are found on every graph, whether the graph is normal or special type. More graphical analysis of the field results are shown below:

76. Figure 16: Short Term Flicker ( Pst ) Analysis at PCC to Sankyo Steel

77. Figure 17: Long Term Flicker ( Plt ) Analysis at PCC to Sankyo Steel

78. Thank You For further inquiry on this part of the training, you can contact the instructor as follows: Email: [email protected] or [email protected] Phone: [phone]