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Power Quality Monitoring

Power Quality Monitoring. and Cost-of-Service Measurement. GE Electronic Meter School Somersworth, NH. Causes Voltage sags/swells Voltage Interruptions Harmonics Non-linear Loads Transformers. Symptoms Customer Complaints Equipment Shutdown or Damage Flicker Timekeeping Problems

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Power Quality Monitoring

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  1. Power Quality Monitoring and Cost-of-Service Measurement GE Electronic Meter School Somersworth, NH

  2. Causes Voltage sags/swells Voltage Interruptions Harmonics Non-linear Loads Transformers Symptoms Customer Complaints Equipment Shutdown or Damage Flicker Timekeeping Problems Transformer Heating and Derating Capacitor Bank Failures Increased Line Losses Overheated Neutrals Power Quality Issues Power Quality Problems Lead to Dissatisfied Customers and Higher Cost

  3. Supply Side Sources • Line switching • Breaker operations • Reclosers • Capacitor banks • Voltage controls • Natural occurrences • Weather related events ... lightning, floods, etc. • Accidents

  4. Load side sources • Industrial/Commercial • Arc furnaces • Fluorescent & HID lighting • Thyristor-controlled loads • Pumps • Rectifiers • Computers • PCs • Copiers • Fax • Residential/Commercial • oven and range controls • rectifier circuits on stereos, TVs, computers, etc. • variable speed heat pumps • Design/Application • improper wiring & installation • less tolerant equipment designs

  5. Traditional Measurements Traditional Tariff Measurement is Energy (kWh) • All ANSI Meters, Electromechanical and Electronic do a good job of measuring energy. • Electronic meters have a better frequency response but there’s very little energy in the harmonics in most loads. (better frequency response doesn’t mean bigger numbers) • Useful measure of incremental generation costs, doesn’t tell much about cost of service. Demand(active Power - Kw) Is the Traditional Cost of Service Measurement • Good measure for resistive heating and incandescent lighting loads • Easy and inexpensive to measure, EM and electronic meters do it well. • Neglects the costs associated with reactive and non-linear loads. • Not useful for sizing systems components (Apparent Power (kVA) is used for sizing) 3/5/96

  6. Traditional Measurements (cont.) Phasor Power (kVA) [Formerly Vector] • This what we meant when we said “kVA” before electronic meters. • Very useful cost of service measurement and traditionally used to size system equipment. • Difficult measurement for EM meters (required phase shifting transformers), but done well by electronic meters. • Includes Active and Reactive Power but neglects distortion power. • Works well if non-linear loads are not a significant part of the total load. • Performs well with balanced and unbalanced loads in symmetrical and asymmetrical circuits. 3/5/96

  7. S Reactive Power Apparent Power Q U P Active Power D Distortion Power Power Definitions P = Active Power = EhIh cos h (h= harmonic number) Q = Reactive Power = EhIh sin h D = Distortion Power =(U2 - P2 - Q2) U = Apparent Power “3D” Vector Apparent Power = VRMSIRMS = (P2 + Q2 + D2) Note: P, Q, and D are Quadrature Components and can be added like scalars (but no P’s and Q’s)

  8. Newer Measurements Arithmetic Apparent Power (kVA) [ a.k.a. RMS VA] • Often called “Apparent Power” • Includes active, reactive, distortion and mesh(or imbalance) power. • Easy to calculate and verify using simple instruments. • Works well for balanced loads in symmetrical circuits. • Gives largest “kVA” and smallest “PF” numbers. • May give surprising numbers with unbalanced loads or asymmetrical circuits . PF can be very significantly lower than expected or than measurements made using other techniques. • May overstate cost of service • May be difficult to justify with technically sophisticated customers 3/5/96

  9. S Reactive Power Apparent Power Q U F P Active Power D Distortion Power Other Power Definitions S = Phasor Power - Traditional “kVA” measurement = (P2+Q2) F = Fictitious Power (AKA Fuzzy vars) = (U2 -P2) = (Q2 + D2) Sometimes used as a proxy for Reactive Power (Q) Move to change Fictitious Power to Non-Active Power

  10. Other Power Definitions Time Delay Method widely used in practical electronic meters. The time-shift is correct for the fundamental, and 5th, 9th, 13th, 17th, ... harmonics. For other odd harmonics, pure quadergy is measured with the wrong sign. The even harmonic measurements are actually pure energy measurements with alternating signs. The 2nd, 6th, 10th, ... , are negative; 4th, 8th, 12th, ... , positive. On practical loads the resulting measurements are usually surprisingly accurate.

  11.  Power Measurement Dot Product 1 2 E 1) I 2) EIcos 1 2 IN IN K/2  E I [KsinEIsin IN IN EIcos 1 2 OUT 2 1 E 2) I 1) Dot Product Newest DSP approach to Reactive Power Measurement Most accurate measurement technique available

  12. Newest Measures “3D” Vector Apparent power (kVA) • IEEE definition requires vector addition of per phase quantities. Electricity meters have lacked the computational horsepower to do vector calculations in the past. • Excellent measurement of cost of service includes active, reactive, and distortion components of power. • Performs well with balanced and unbalanced loads in symmetrical and asymmetrical circuits. • Easier to sell to engineers who expect vector calculations and resistors with power factors of one than Arithmetic Apparent Power

  13. Newest Measures (Cont.) Distortion Power (kVA) [a.k.a. Deformation Power] • An indication of the presence of harmonics • A measure of load quality • An indication of load non-linearity • A useful measurement of load quality and its effect on power quality 3/5/96

  14. +5% 12PM 12AM 12AM -5% Power Quality - Voltage Alerts • Voltage tolerance • Programmable upper & lower “% of nominal” threshold • Programmable phase balance alert • Alerts for potential equipment stress situations • Monitors conformance to power contracts • Interruptions/Outages • Counter • Cumulative outage time clock • Date & time of last outage

  15. Distortion Power (D)Apparent Power (U) What is “D/U”? • P/U is the well known quantity “Active Power Factor” - a measure of the efficiency of the distribution system • Q/U is a less known quantity “Reactive Power Factor” - a measure of the inefficiency caused by reactive and capacitive loads • D/U is a new quantity “Distortion Power Factor” which is an indication of the harmonic content of the load - a measure of the inefficiency caused by poor power quality • For any ac circuit, sinusoidal or non-sinusoidal, balanced or unbalanced the following expression holds true: • (P/U)2 + (Q/U)2 + (D/U)2 = 1

  16. S Cost of Service (Reactive Power) Q Total (Apparent Power) U P Tariff (Active Power) Power Quality (Distortion Power) D Measurement Model Cost of Service Measurement Components 1). Active Power (P) Tariff Measurement Lighting and Heating Loads 2). Reactive Power (Q) Starting and Charging Motor Loads Current Costs 3). Distortion Power (D) Power Quality Cost Distorted Loads Apparent Power (U) includes all 3 measures

  17. Measurement Examples • Four Real Measurement Examples • Manufacturing Plant - 15 MVA • Oil Well Pump - 500 kVA • Newspaper Printing Press - 150 kVA • City Water Pumps - 750 kVA • Collected by National Research Council of Canada

  18. Example #1Manufacturing Plant - 15 MVA • Large induction and DC motors • Low distortion levels • Poor power factor • Typical of older style industrial equipment • 1 VTHD 0.8% • 0.5 V • 0 • 0 • 0.5 • 1 • -0.5 PF 74.7% dPF 74.7% RF 66.4% D/U 3.4% Reactive MethodIndex Reactive Power () 1.0000 Fictitious Power 1.0043 Reactive(Time Delay) 1.0000 Index = Method/ Theoretical • -1 • 1 ITHD 2.9% • 0.5 I • 0 • 0 • 0.5 • 1 • -0.5 • -1 Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

  19. Example #2Oil Well Pump - 500 kVA • 6 pulse VSD • Very heavy current distortion • Moderate voltage distortion • High D/U tracks ITHD VTHD 3.3% • 0.5 V • 0 • 0 • 0.5 • 1 PF 42.1% dPF 53.3% RF 65.2% D/U 63.1% Index Reactive Power () 1.0000 Fictitious Power 1.3915 Reactive(Time Delay) 1.0192 Index = Method/ Theoretical • -1 ITHD 60.9% I • 0 • 0 • 0.5 • 1 Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

  20. Example #3Newspaper Plant Printing Press - 150 kVA • Moderately high voltage distortion • High current distortion • D/U tracks ITHD • 1 VTHD 5.2% • 0.5 V • 0 • 0 • 0.5 • 1 • -0.5 PF 88.6% dPF 90.0% RF 42.3% D/U 19.3% Index Reactive Power () 1.0000 Fictitious Power 1.0989 Reactive(Time Delay) 1.0284 Index = Method/ Theoretical • -1 • 1 ITHD 16.3% • 0.5 I • 0 • 0 • 0.5 • 1 • -0.5 • -1 Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

  21. Example #4City Water Pumps - 750 kVA • 6 pulse VSD • Excellent power factor • High current distortion • High D/U identifies troublesome load • Undetected by traditional meter practice • 1 VTHD 2.8% • 0.5 V • 0 • 0 • 0.5 • 1 • -0.5 PF 92.5% dPF 95.2% RF 29.3% D/U 24.3% Index Reactive Power () 1.0000 Fictitious Power 1.2992 Reactive(Time Delay) 1.0159 Index = Method/ Theoretical • -1 • 1 ITHD 23.2% • 0.5 I • 0 • 0 • 0.5 • 1 • -0.5 • -1 Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

  22. More Measurement Choices Q Hour Apparent Power Phasor Power Arithmetic Apparent Demand (3D Vector) Power (2D Vector) (Scalar) Basic Measures o Active Energy (kWh) K Switch adds o Active Power (kW) o Distortion kVAh o Distortion Power Factor o Average Power Factor Electronic Detent And VARS (pick one) Energy (pick one) o Apparent kVAh o Lagging only o Received only o Apparent Power (kVA) o Leading only o Delivered only Or o Unidirectional o Unidirectional o Bidirectional o Bidirectional o Quadergy (kvarh) • Pick Fundamental only or Fundamental plus Harmonics • Pick Distortion Power, Reactive Power, Apparent Power, Phasor Power, “Q-Hours”, or Arithmetic Apparent Power (kVA) o Reactive Power (kvar) Harmonics o Fundamental only or ... o Fundamental plus harmonics 3/5/96 3

  23. Power Guard System Power Quality Measurement in every meter Power Guard ... A tool to improve power quality • Alerts and Counters • Distortion Alert With Counter • High Neutral Current Alert With Counter • High Demand Alert • Power Factor Alert • Under Voltage Alert With Counter • Over Voltage Alert With Counter • Outage Counter • Voltage Imbalance Alert • Date & Time of Last Outage(TOU or Recording) • 200 Event Log of Diagnostics and Cautions (with E Switch) • Instantaneous Measures • Per Phase Voltage • Per Phase Current • V&I Phase Angles • Active power • Reactive power, • Power factor • Distortion power factor(D/U) • Cumulative Measures • Distortion kVAh(with k Switch) • Cumulative power outage duration

  24. Cost-of-Service Measurement Cost-of-Service Components • Tariff information Energy and Energy Demand - meets the needs of the energy supplier But distribution utilities also need to know to get paid for their costs: • Reactive Power - Losses and reduction in system capacity associated with higher current requirements • Distortion Power - Losses and reduction in system capacity associated with current and voltage distortion “3D” Vector Apparent Power - The best overall measurement of service costs. Works for all service types and includes all components of cost. Knowing the cost of servicing a customer is essential in today’s deregulated environment

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