Roadmap For Power Quality Standards Development IEEE Power Quality Standards Coordinating Committee Authors: David B. Vannoy, P.E., Chair Mark F. McGranghan, Vice Chair S. Mark Halpin, Vice Chair D. Daniel Sabin, Vice Chair William A. Moncrief, P.E., Secretary IEEE PCIC 2005 Production Technical Session September 14, 2005 Denver, Colorado
The PQ Standards Roadmap What is the role of PQ standards? What about North American vs International Standards? What needs to be in PQ standards? What are the existing standards? What s being done now? What needs to be done? How do we get the rest of the way?
The Role of PQ standards Role - Provide a common basis for evaluating PQ concerns, system performance, and equipment performance Goal Achieve coordination between the characteristics of the power system and the requirements of end use equipment
Role of PQ Standards, cont. Definitions, Indices Measurement and monitoring procedures (standardized characterization) Benchmarking (expected power quality levels) Power Quality Guidelines and Limits Compatibility Levels PQ requirements for the supply system PQ immunity for equipment PQ disturbance generation limits for equipment and customer systems Application guidelines (including economics)
Who develops PQ standards? Power Quality Standards in North America IEEE (mostly PES & IAS) Generally not equipment specific Voluntary compliance SCC22 (PQ Standards Coordination) International Power Quality Standards International Electotechnical Commission (IEC) Electromagnetic Compatibility (EMC) Standards Individual countries may adopt as performance requirements
IEEE Power Quality Standards Activities IEEE Power Quality Standards Coordinating Committee Created in 1991 as coordinating body for Power Quality Standards within IEEE Historically focused primarily on Power Quality Standards Development in IAS and PES Provided home of last resort for standards projects not within scope of other sponsoring societies More recently adjusted focus to include international Power Quality Standards efforts Membership consists of persons actively involved in Power Quality Standards Development
SCC22 Scope The Committee is responsible for coordinating IEEE activities related to the quality of electric power as it affects equipment, users, utilities, power and communications systems. This scope also includes development of guides, recommended practices, standards, common definition of terms and phenomena. The SCC22 will identify needed standards within the area of power quality and locate sponsors within IEEE to undertake the development of such standards including designation of appropriate Working Groups (Subcommittees) to serve as the sponsor for the project.
IEEE Power Quality Standards Activities, cont. Industry Applications Society Color Books IEEE Std. 1100 Emerald Book Joint IAS/PES Standards IEEE Std 519-1992 Harmonic Distortion IEEE Std 1436 Power System and Process Equipment Compatibility IEEE P1564 Voltage Sag Indices Power Engineering Society IEEE Std 1159 Monitoring Power Quality IEEE Std 1250 Equipment Sensitive to Voltage Disturbances IEEE P1409 Custom Power IEEE Std 1453 Flicker
IEC Power Quality Standards Activities Subcommittee 77A Low Frequency Phenomena, of IEC Technical Committee 77: Electromagnetic Compatibility IEC 77A Power Quality Related Working Groups WG 1 Harmonics and other Low frequency disturbances WG 2 Voltage Fluctuations (flicker) and other low Frequency Disturbances WG 6 Low Frequency Immunity Tests WG 8 Electromagnetic Interference Related to the Network Frequency WG 9 Power Quality Measurement Methods
Structure of basic and generic EMC Standards - IEC Part 1: General (IEC Pub 61000-1-x) fundamental principles, definitions, terminology Part 2: Environment (IEC Pub 61000-2-x) description, classification and compatibility levels Part 3: Limits (IEC Limits 61000-3-x) emission and immunity limits, generic standards Part 4: Testing and measurement (IEC Pub 61000-4-x) techniques for conducting Part 5: Installation and mitigation (IEC Guide 61000-5-x) installation guidelines, mitigation methods and devices Part 6: Generic and Product Standards (IEC Pub 61000-6-x) immunity levels required for equipment
PQ Concerns Steady State Power Quality Characteristics Voltage regulation Unbalance Harmonics and Interharmonics Flicker Disturbances Voltage sags (dips) and swells RMS variations Transients Momentary interruptions Outages (reliability)
Voltage Regulation and Unbalance Power system constantly adjusting to changes in load Long duration voltage variations result from these changes. Best expressed with profiles and statistics Undervoltages and overvoltages IEEE Std 1159 defines long duration as those > 1 minute ANSI C84.1-1995 limits: +6%, -13% EN 50160 limits: +/-10%, 95% of 10 minute values for a week
Voltage Regulation
Voltage Unbalance Unbalance ANSI C84.1-1995 limit: 3% Maximum at the meter under no load conditions Motors operating between 1% and 5% unbalance should be derated EN 50160 limit: 2% for systems with three phase load, 3% for systems with single phase load, 95% of 10 minute values for a week
Flicker Voltage fluctuations associated with flicker usually do not exceed ranges specified by C84.1 Result in visible fluctuation in light intensity North American defacto Standard GE Flicker Curve recently replaced with IEEE 1453 that is based on IEC 61000-4-15 IEC flicker meter output P st Short term flicker severity - made up of 10 minute samples P lt Long term flicker severity - made up of 12 successive P st values 12 1 3 P 3 lt 12 Pst j j 1
Flicker, cont. Comparison of 120 volt and 230 volt flickermeter weighting curves (P st =1 curves for rectangular variations)
Flicker What is needed? Method of applying flicker limits to end users, taking into account circumstances of individual systems Application guidelines for characterizing impacts of individual users and loads Economics where is best place to correct flicker problems?
Harmonics and Interharmonics Voltage Harmonic Distortion Interaction of harmonic currents with system impedance IEEE 519-1992 IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems End users limit harmonic currents injected into system Suppliers control harmonic voltage distortion addressing resonances Guidelines for acceptable levels of voltage distortion on the utility system at the Point of Common Coupling (PCC) Bus Voltage Maximum Individual Harmonic Component (%) Maximum THD (%) 69 kv and below 3.0% 5.0% 115 kv to 161 kv 1.5% 2.5% Above 161 kv 1.0% 1.5%
Harmonics and Interharmonics, cont. Voltage Harmonic Distortion, cont. At end use location 8% V THD normally acceptable IEC 61000-2-2 compatibility level for LV and MV systems is 8% Power factor correction capacitors and non-linear loads on the same bus often result in resonances Current Harmonic Distortion Harmonic current limits dependent on the strength of the system at point of connection (ratio of I L to I SC ) Total Demand Distortion TDD I 2 n n 2 100% I L where: I n = magnitude of individual harmonic components (rms amps) n = harmonic order I L = maximum demand load current (rms amps)
Harmonics and Interharmonics, cont. IEEE 519-1992 Harmonic current limits for individual end users expressed in % of rated load current
Harmonics and Interharmonics, cont. EN 50160 limits based on IEC 61000-2-2 compatibility levels Individual harmonic component limits up to 25 th harmonic Total Harmonic Voltage Distortion 8% Evaluated using measurement procedure in IEC 61000-4-7 Uses 3 second periods, combined to obtain 10 minute values Limits based on 95% of 10 minute values during an assessment period of one week Revision to IEEE Std 519-1992 will propose adopting the IEC measurement procedure
Harmonics and Interharmonics, cont. Interharmonics Those harmonic components that are not integer multiples of the fundamental New revision to IEEE Std 519-1992 will include recommended limits for interharmonics Voltage limits are based on lamp flicker with a P ST =1.0 using the measurement techniques described in IEEE Std 1453 and IEC 61000-4-30 Current limits may be calculated using the specific voltage limit and the system impedance at the PCC
Harmonics and interharmonics What is needed? Common method of measurement and assessment Benchmarking of international harmonic levels Method of assessing impact of individual customers (harmonic source location) Limits and practical methods of implementation Interharmonic limits and assessment methods Higher frequency limits and assessment methods Economics where to solve distortion problems?
Transients Normally refers to fast (sub cycle) changes in the system voltage or current waveform ANSI/IEEE C62.41-1991 IEEE Guide to Surge Voltages in Low Voltage AC Power Circuits Defines transient environment Specifies test waveforms Measured by triggering on abnormality involved Peak magnitude Rate of rise Change in waveform IEEE 1159-Characterization of typical transient waveshapes Oscillatory transients Impulsive transients
Transients, cont. Capacitor switching waveform one of the most important oscillatory transients Created when capacitor Is energized
Transients, cont. Capacitor switching transients can be either attenuated or amplified based on the system impedance Effects: ASDs trip UPS transfer to backup power source Worst case component damage
Transients What is needed? Equipment performance for a wider variety of transient characteristics (e.g. response to capacitor switching transients) Methods of characterizing system performance Application guidelines for transient control
Voltage sags and interruptions Defined as short duration voltage variations according to IEEE Std 1159 and IEC definitions Best characterized by RMS Voltage vs. Time Can be characterized by voltage Magnitude, and Duration voltage is outside specified limits Example Voltage Sag Waveform from Field Measurement % % 120 110 100 90 80 70 150 100 50 0-50 -100-150 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Time (Seconds) 0 25 50 75 100 125 150 175 Time (mseconds) Duration 0.117 Sec Min 74.70 Ave 94.11 Max 98.58 Ref Cycle 48462
Voltage sags and interruptions, cont. Voltage Sags typically caused by a fault on the power system Can be experienced over a significant area Voltage returns to normal on unfaulted portion when fault is cleared Typical duration 6 cycles (100ms) dependent on protection philosophy Voltage magnitude during sag dependant on distance from the fault and system characteristics
Voltage sags and interruptions, cont. IEEE Std 1346 provides methodology for economic evaluation power conditioning equipment based on the expected sag performance of the power supply system and equipment sensitivity Contour plot of sag magnitude and duration Superimpose equipment sensitivity to obtain estimate of number of times process will be disrupted In te rru p tio n a n d S a g R a te P ro b a b iltie s a s a F u n c tio n of Ev ent Voltage Magnitude and Duration 90 80 1 5-2 0 70 10-15 events 5-1 0 e v e n ts p e r site per year 60 50 40 M agnitude (%) 0-5 e v e n ts p e r site per year 30 20 10 1 2 4 6 8 10 20 30 40 50 60 180 300 >3 0 0 0 Duration (Cycles)
Voltage sags and interruptions, cont. Work under way to define indices for characterizing voltage sag performance IEEE P1564 Voltage sag agreed to be characterized by the remaining voltage, i.e., voltage sag to 70% One method under consideration System Average RMS (Variation) Frequency Index (SARFI) Average number of voltage sags experience each year with a specified characteristic SARFI X Index includes all voltage sags where the minimum remaining voltage was less than x.
Voltage sags and interruptions, cont. Average SARFI statistics for US distribution system Avg. SARFI Statistics for US Distribution Systems 50 49.7 45 Avg. No. of Events per Year 40 35 30 25 20 15 10 17.7 27.3 5 0 SARFI-70 SARFI-80 SARFI-90
Voltage sags and interruptions What is needed? Common method of measurement and assessment (indices) Benchmark performance as a function of system characteristics Statistical methods of characterizing performance Application guidelines for performance improvement options (e.g. IEEE 1409) Equipment performance standards (e.g. SEMI F47) Economic evaluation with a system perspective
Future Direction for Power Quality Standards Benchmarking efforts have provided initial basis for defining expected power quality performance of supply systems Need statistical means of characterizing performance to permit better risk analysis for end users Equipment manufacturers must provide sensitivity of equipment to power quality variations Monitoring of power quality should be standard part of system monitoring for both supplier and user Need tools to help find optimum design based on system performance and equipment sensitivity
Compatibility Levels, cont. Compatibility levels Basic expectation for supply system performance Basis for equipment design for immunity to supply system power quality variations EN 50160 Physical characteristics of electricity supplied by public distribution systems Voltage Characteristics Harmonics Voltage fluctuations Unbalance Interruptions Voltage Dips
Compatibility Levels, cont. Planning Limits Established by Utilities for comparison with actual power quality levels Problem indicated if planning limit exceeded Need margin between planning level and required voltage characteristics Equipment Immunity Disturbance magnitude Equipment immunity test levels Compatibility level Utility planning levels Assessed level Equipment should be capable of operating within full range of possible power quality levels Need margin between immunity level and required voltage characteristics time
Compatibility Levels Steady State characteristics Trends, statistical distributions Defined by a range of values
Standards needed for each type of PQ Concern System Performance Expectations Compatibility Levels Customer System and Equipment Immunity Requirements Customer System Impact Limits Equipment PQ Limits Customer and equipment solutions to limit impact on system System Solutions and their implementation Measurement and Assessment Methods Customer and equipment solutions for immunity improvement
What should we do? Participate in IEEE Standards Development Participate in IEC Standards development to make sure the standards apply to North American systems (SCC22 has official Category D liaisons on the following IEC SC77A working groups) WG1 Mark Halpin WG2 Rao Thallum WG6 Alex McEachern WG8 Mark McGranaghan WG9 Erich Gunther Develop Application Guides
Application guidelines - How to apply the standards IEEE Std. 519.1 - Harmonics IEEE Std. 1346 - Voltage sags
Roadmap example - harmonics Definitions, Indices (updates in progress) IEEE 1159 Benchmarking EPRI DPQ Miscellaneous projects Need coordinated effort Application Guides IEEE 519.1 Harmonic source location Harmonic filters Active filters Economics Monitoring and Characterization (updates in progress) IEEE 1159 Compatibility and Limits (updates in progress) IEEE 519
Compatibility is the Goal of Power Quality Standards Development
Questions
IEEE IEC Standards Cross-reference
Voltage regulation and unbalance IEC 61000-2-2 IEC 61000-2-4 IEC 61000-2-12 EN 50160 ANSI C84.1 Regulations from individual states ITIC and other equipment standards IEC 61000-4-27 (unbalance) IEC 61000-4-30
Flicker IEC 61000-2-2 IEC 61000-2-4 IEC 61000-2-12 EN 50160 IEEE 1453 IEC 61000-3-3 IEC 61000-3-5 IEC 61000-3-7 IEC 61000-4-15
Harmonics and Interharmonics IEC 61000-2-2 IEC 61000-2-4 IEC 61000-2-12 EN 50160 IEEE 519 IEEE 519.1 IEEE 1159 IEC 61000-3-2 IEC 61000-3-4 IEC 61000-3-6 IEC 61000-3-9 (interharmonics) Filter Design IEC 61000-4-7 IEC 61000-4-13 (immunity)
Transients, cont. IEC Standards similar to C62.41 standards Lightning performance and insulation coordination ANSI/IEEE C62.41 Lightning performance standards and insulation coordination standards IEEE 1100 UL 1449
Voltage sags and interruptions IEC 61000-2-8 IEC 61000-4-11 (immunity testing) IEC 61000-4-30 CIGRE SC36 IEEE 1564 (voltage sag indices) IEEE 1346 (compatibility) ITIC (equipment immunity) SEMI F47 standards (equipment immunity)