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HARMONIC TREATMENT IN INDUSTRIAL POWER SYSTEMS

HARMONIC TREATMENT IN INDUSTRIAL POWER SYSTEMS. Presented by Stefanos Manias. CONTACT INFORMATION. Stefanos N. Manias National Technical University of Athens Phone: +3010-7723503 FAX: +3010-7723593 E-mail: manias@central.ntua.gr Mailing Address

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HARMONIC TREATMENT IN INDUSTRIAL POWER SYSTEMS

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  1. HARMONIC TREATMENT IN INDUSTRIAL POWER SYSTEMS Presented by Stefanos Manias JUNE 2002

  2. CONTACT INFORMATION Stefanos N. Manias National Technical University of Athens Phone: +3010-7723503 FAX: +3010-7723593 E-mail: manias@central.ntua.gr Mailing Address National Technical University of Athens Department of Electrical and Computer Engineering 9, Iroon Polytechniou Str, 15773 Zografou Athens, Greece IEEE PESC-02

  3. PLAN OF PRESENTATION • DEFINITIONS • CATEGORIES OF POWER QUALITY VARIATIONS • HARMONIC DISTORTION SOURCES IN INDUSTRIAL POWER SYSTEMS • EFFECTS OF HARMONICS ON ELECTRICAL EQUIPMENT • HARMONIC MEASUREMENTS IN INDUSTRIAL POWER SYSTEMS • HARMONIC STANDARDS • HARMONIC MITIGATING TECHNIQUES • GENERAL PASSIVE AND ACTIVE FILTER DESIGN PROCEDURES • DESIGN EXAMPLES • CONCLUSIONS IEEE PESC-02

  4. WHY HARMONIC ANALYSIS ? When a voltage and/or current waveform is distorted, it causes abnormal operating conditions in a power system such as: • Voltage Harmonics can cause additional heating in induction and synchronous motors and generators. • Voltage Harmonics with high peak values can weaken insulation in cables, windings, and capacitors. • Voltage Harmonics can cause malfunction of different electronic components and circuits that utilize the voltage waveform for synchronization or timing. • Current Harmonics in motor windings can create Electromagnetic Interference (EMI). IEEE PESC-02

  5. Current Harmonics flowing through cables can cause higher heating over and above the heating that is created from the fundamental component. • Current Harmonics flowing through a transformer can cause higher heating over and above the heating that is created by the fundamental component. • Current Harmonics flowing through circuit breakers and switch-gear can increase their heating losses. • RESONANT CURRENTS which are created by current harmonics and the different filtering topologies of the power system can cause capacitor failures and/or fuse failures in the capacitor or other electrical equipment. • False tripping of circuit breakers ad protective relays. IEEE PESC-02

  6. HARMONIC SOURCES a) Current Source nonlinear load Thyristor rectifier for dc drives, heater drives, etc. Per-phase equivalent circuit of thyristor rectifier b) Voltage source nonlinear load Diode rectifier for ac drives, electronic equipment, etc Per-phase equivalent circuit of diode rectifier IEEE PESC-02

  7. TYPE OF NONLINEAR LOAD TYPICAL WAREFORM THD% 1-φ Uncontrolled Rectifier 80%(high 3rd component) 1-φ Semicontrolled Rectifier Bridge 2nd, 3rd, 4th,...... harmonic components 6 –Pulse Rectifier with output voltage filtering and without input reactor filter 80% 5, 7, 11, ………. INPUT CURRENT OF DIFFERENT NOLINEAR LOADS IEEE PESC-02

  8. 6 - Pulse Rectifier with output voltage filtering and with 3% reactor filter or with continues output current 40% 5, 7, 11, ……….. 6 - Pulse Rectifier with large output inductor 28% 5, 7, 11, ……….. 12 - Pulse Rectifier 15% 11, 13, ……….. IEEE PESC-02

  9. HARMONIC HARMONIC P.U PULSE P.U PULSE IEEE 519 std 1 1 1.00 1.00 - 5 5 0.2 0.03-0.06 5.6% 7 7 0.143 0.02-0.06 5.6% 11 11 0.05-0.09 0.09 2.8% 13 13 0.077 0.03-0.08 2.8% THD 17 0.059 7.5%-14.2% 7.0% 19 0.053 23 0.04 CURRENT HARMONICS GENERATED BY 6-PULSE CSI CONVERTERS CURRENT HARMONICS GENERATED BY 12-PULSE CSI CONVERTERS IEEE PESC-02

  10. RECENT CURRENT MEASUREMENTS TAKEN IN AN INDUSTRIAL PLANT WITH 600 KVA, 20 KV/400 V DISTRIBUTION TRANFORMER Current waveform and its respective spectrum at the inputs of a motor drive system IEEE PESC-02

  11. Current waveform and its respective spectrum at the inputs of a motor drive system IEEE PESC-02

  12. Current waveform and its respective spectrum at the secondary of the distribution transformer ( i.e. at the service entrance) IEEE PESC-02

  13. DEFINITIONS f (t) = Fourier Series of a periodic function f (t) = (1) (2) (3) (4) h = harmonic order IEEE PESC-02

  14. Percentage of the Total Harmonic Distortion of a nonsinusoidal voltage waveform (5) Percentage of the Total Harmonic Distortion of a nonsinusoidal current waveform (6) harmonic component of the voltage harmonic component of the current RMS value of the voltage distortion IEEE PESC-02

  15. RMS value of the current distortion RMS value of a nonsinusoidal current = (7) RMS value of a nonsinusoidal voltage = (8) (9) (10) Harmonic Factor = IEEE PESC-02

  16. Full load kVA rating of the Drive system Short Circuit kVA of the distribution system at the point of connection SINUSOIDAL VOLTAGE NONSINUSOIDAL CURRENT (11) (12) (13) IEEE PESC-02

  17. (14) (15) NONSINUSOIDAL VOLTAGE AND NONSINUSOIDAL CURRENT (16) (17) IEEE PESC-02

  18. (18) (19) IEEE PESC-02

  19. (20) (21) (22) (23) IEEE PESC-02

  20. Harmonic sequence is the phase rotation relationship with respect to the fundamental component. Positive sequence harmonics ( 4th, 7th, 10th , ……. (6n+1) th ) have the same phase rotation as the fundamental component. These harmonics circulate between the phases. Negative sequence harmonics ( 2nd, 5th, 8th ……… (6n-1) th ) have the opposite phase rotation with respect to the fundamental component. These harmonics circulate between the phases. Zero sequence harmonics ( 3rd, 6th, 9th, ….. (6n-3) th ) do not produce a rotating field. These harmonics circulate between the phase and neutral or ground. These third order or zero sequence harmonics, unlike positive and negative sequence harmonic currents, do not cancel but add up arithmetically at the neutral bus. IEEE PESC-02

  21. EXAMPLE 1 SINUSOIDAL VOLTAGE-NONSINIMUSOIDAL CURRENT A periodic, sinusoidal voltage of instantaneous value Is applied to a nonlinear load impedance. The resulting instantaneous current is given by: Calculate the components P, Q, D of the apparent voltamperes and hence calculate the displacement factor, the distortion factor and the power factor. Solution The presence of the nonlinearity causes frequency components of current (i.e. the second and third harmonic terms) that are not present in the applied voltage. The rms voltage and current at the supply are: IEEE PESC-02

  22. The apparent voltamperes at the input is therefore given by In this example only the fundamental frequency components are common to both voltage and current. Therefore, the real power P and the apparent power Q are = displacement angle between the fundamental of the voltage and the fundamental of the current IEEE PESC-02

  23. Displacement factor Distortion factor Therefore, the power factor is IEEE PESC-02

  24. EXAMPLE 2 NONSINUSOIDAL VOLTAGE-RL LOAD A periodic, sinusoidal voltage given by is applied to a series, linear, resistance-inductance load of resistance 4Ω and fundamental frequency reactance 10Ω. Calculate the degree of power factor improvement realizable by capacitance Compensation when Solution. The rms terminal voltage is given by Therefore IEEE PESC-02

  25. The instantaneous load current is given by The rms load current is therefore given by IEEE PESC-02

  26. Apparent voltamperes at the load terminals in the absence of capacitance is therefore Average power In this case is The power factor before compensation is therefore IEEE PESC-02

  27. EXAMPLE 3 NONSINUSOIDAL VOLTAGE AND NONSINIMUSOIDAL CURRENT A periodic, nonsinusoidal voltage with instantaneous value given by is applied to a nonlinear impedance. The resulting current has an instantaneous value given by Calculate the components of the load apparent voltamperes and compare thee with the classical values respectively. Solution. Note that the presence of the load nonlinearity causes a frequency component of load current (I.e. the third harmonic term) that is not present in the supply voltage. IEEE PESC-02

  28. The rms voltage and current at the supply are given by The load apparent voltamperes therefore has a value defined in terms and Instantaneous expressions of the hypothetical currents are given by IEEE PESC-02

  29. Note that current components contain only those harmonic terms which are common to both voltage and current. These are therefore consistent with the terms. The rms load current components are found, as expected to sum to the total rms load current Components of the apparent voltamperes can now be obtained IEEE PESC-02

  30. The component voltamperes are seen to sum to the total apparent voltamperes Components of are found as follows: IEEE PESC-02

  31. From the possible compensation viewpoint it is interesting to note that and differ by significant amount. could be defined as “that component of the load apparent voltamperes that Is obtained by the combination of supply voltage harmonics with quadrature Components of corresponding frequency load current harmonics”. IEEE PESC-02

  32. Similarly the definition of active voltamperes could be given by “that component of the load apparent voltamperes that is obtained by the combination of supply voltage harmonics with in-phase components of corresponding frequency load current harmonics”. Both and are entirely fictitious and non-physical. The active voltamperes Is not to be compares in importance with the average power which is a real physical property of the circuit. Term Is merely the analytical complement of term the energy-storage reactive voltamperes, is that component Term of the load apparent voltamperes that can be entirely compensated (for sinusoidal supply voltage) or minimized (for nonsinusoidal supply voltage) by energy-storage methods. IEEE PESC-02

  33. Voltage and current profiles in a commercial building IEEE PESC-02

  34. HARMONIC STANDARDS • International Electrotechnical Commission (IEC) European Standards. - EN 61000-3-2 Harmonic Emissions standards were first published as IEC 55-2 1982 and applied only to household appliances. It was revised and reissued in 1987 and 1995 with the applicability expanded to include all equipment with input current 16A per phase. However, until January 1st, 2001 a transition period is in effect for all equipment not covered by the standard prior to 1987. - The objective of EN 61000-3-2 (harmonics) is to test the equipment under the conditions that will produce the maximum harmonic amplitudes under normal operating conditions for each harmonic component. To establish limits for similar types of harmonics current distortion, equipment under test must be categorized in one of the following four classes. IEEE PESC-02

  35. CLASS-A: Balanced three-phase equipment and all other equipment • except that stated in one of the remaining three classes. CLASS-B: Portable electrical tools, which are hand held during normal operation and used for a short time only (few minutes) • CLASS-C: Lighting equipment including dimming devices. • CLASS-D: Equipment having an input current with special wave shape • ( e.g.equipment with off-line capacitor-rectifier AC input • circuitry and switch Mode power Supplies) and an active • input power 600W. • - Additional harmonic current testing, measurement techniques and instrumentation guidelines for these standards are covered in IEC 1000-4-7. IEEE PESC-02

  36. IEEE 519-1992 United States Standards on harmonic limits • IEEE limits service entrance harmonics. • The IEEE standard 519-1992 limits the level of harmonics at the customer service entrance or Point of Common Coupling (PCC). • With this approach the costumer’s current distortion is limited based on relative size of the load and the power supplier’s voltage distortion based on the voltage level. • IEEE 519 and IEC 1000-3-2 apply different philosophies, which effectively limit harmonics at different locations. IEEE 519 limits harmonics primarily at the service entrance while IEC 1000-3-2 is applied at the terminals of end-user equipment. Therefore, IEC limits will tend to reduce harmonic-related losses in an industrial plant wiring, while IEEE harmonic limits are designed to prevent interactions between neighbors and the power system. IEEE PESC-02

  37. Source: IEEE Standard 519-1992. Note: Even harmonics are limited to 25 percent of the odd harmonic limits above. Current distortions that result in a direct current offset; for example, half wave converters are not allowed. Table I is for 6-pulse rectifiers. For converters higher than 6 pulse, the limits for characteristic harmonics are increased by a factor o f q/6 , where q is the pule number, provided that the amplitudes of noncharacteristic harmonics are less than 25 percent.  *All power generation equipment is limited to these values of current distortion, regardless of actual ISC/IL. Where ISC = Maximum short circuit at PCC. And IL = Average Maximum demand load current (fundamental frequency component at PCC). POWER QUALITY STANDARDS – IEEE 519-1992 STANDARDS TABLE I CURRENT DISTORTION LIMITS FOR GENERAL DISTRIBUTION SYSTEMS (120-69000 V) IEEE PESC-02

  38. Source: IEEE Standard 519-1992. Note: The value AN for another than 480Volt systems should be multiplied by V/480 . The notch depth, the total voltage distortion factor (THD) and the notch area limits are specified for line to line voltage. In the above table, special applications include hospitals and airports. A dedicated system is exclusively dedicated to converter load. *In volt-microseconds at rated voltage and current. TABLE II LOW VOLTAGE SYSTEM CLASSIFICATION AND DISTORTION LIMITS IEEE 519-1992 STANDARTS IEEE PESC-02

  39. TABLE III LIMITS OF THD% IEEE 519-1992 STANDARDS IEEE PESC-02

  40. TABLE IVPROPOSED IEC 555-2 CLASS D STANDARDS for power from 50 to 600W IEEE PESC-02

  41. METHODOLOGY FOR COMPUTING DISTORTION Step 1: Compute the individual current harmonic distortion at each dedicated bus using different Software programs (i.e. SIMULINK, SPICE, e.t.c.) or tables that provide the current distortion of nonlinear loads. Step 2: Compute the voltage and current harmonic content at the Point of Common Coupling (PCC) which is located at the input of the industrial power system. - Each individual harmonic current at the PCC is the sum of harmonic current contribution from each dedicated bus. - The load current at PCC is the sum of the load current contribution from each dedicated bus. - The maximum demand load current at PCC can be found by computing the load currents for each branch feeder and multiply by a demand factor to obtain feeder demand. Then the sum of all feeder demands is divided by a diversity factor to obtain the maximum demand load current. IEEE PESC-02

  42. Step 3: Choose a base MVA and base KV for the system use the following equations in order to compute individual and total current and voltage harmonic distortions at PCC and any other point within the power system. Ib= Base current in Amps (24) (25) = System impedance = MVAb= Base MVA, MVAsc= short circuit MVA at the point of interest VH= Percent individual harmonic voltage distortion = (26) IEEE PESC-02

  43. (27) h = harmonic order (28) IH = Percent individual harmonic distortion = Isc = Short Circuit current at the point under consideration. IL = Estimated maximum demand load current S.C. Ratio = Short circuit Ratio (29) MVAD = Demand MVA IEEE PESC-02

  44. K Factor = Factor useful for transformers design and specifically from transformers that feed Adjustable Speed Drives (30) ONCE THE SHORT CIRCUIT RATIO IS KNOWN, THE IEEE CURRENT HARMONIC LIMITS CAN BE FOUND AS SPECIFIED IN TABLE I OF THE IEEE 519-1992 POWER QUALITY STANDARDS USING THE ABOVE EQUATIONS VALUES OF IDIVINDUAL AND TOTAL VOLTAGE AND CURRENT HARMONIC DISTORTION CAN BE COMPUTED AND COMPARED WITH THE IEEE LIMITS IEEE PESC-02

  45. Step 4: If the analysis is being performed for CSI-type drives then the area of the voltage notch AN should also be computed. • At this point an impedance diagram of the under analysis industrial power system should be available. • The Notch Area AN at the PCC can be calculated as follows. AN = AN1 + AN2 + …………. V . microsec (31) AN1 , AN2 , …… are the notch areas contribution of the different busses (32) ANDR1 : Notch area at the input of the drive IEEE PESC-02

  46. Step 5: Determine preliminary filter design. Step 6: Compute THDv and THDi magnitudes and impedance versus frequency plots with filters added to the system, one at a time. SIMULINK or PSPICE software programs can be used for final adjustments. Step 7: Analyze results and specify final filter design. IEEE PESC-02

  47. EXAMPLE OF A SYSTEM ONE LINE DIAGRAM IEEE PESC-02

  48. System impedances diagram which can be used to calculate its resonance using PSPICE or SIMULINK programs IEEE PESC-02

  49. TYPES OF FILTERS 1) Parallel-passive filter for current-source nonlinear loads • Harmonic Sinc • Low Impedance • Cheapest • VA ratings = VT (Load Harmonic current + reactive current of the filter) IEEE PESC-02

  50. 2) Series-passive filter for voltage-source nonlinear loads • Harmonic dam • High-impedance • Cheapest • VA ratings = Load current (Fundamental drop across filter + Load Harmonic Voltage) IEEE PESC-02

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