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**Power Quality Monitoring**

and Cost-of-Service Measurement GE Electronic Meter School Somersworth, NH

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**Power Quality Problems Lead to Dissatisfied Customers and Higher Cost**

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

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**Supply Side Sources Line switching Breaker operations Reclosers**

Capacitor banks Voltage controls Natural occurrences Weather related events ... lightning, floods, etc. Accidents

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**Load side sources Industrial/Commercial Residential/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

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**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) These measurements handled our early need to measure lighting loads and still work well for smaller and less complicated loads. During the thirties we had to develop new measures to handle large motor loads. During the seventies and eighties we saw a significant increase in load created distortion on the distribution system. Variable speed drives created extremely non-sinusoidal waveforms. PCs, copiers, FAX machines, all with switching power suppliers only added to the problem. Interestingly, many of these devices are the devices most sensitive to the effects of distortion. These distortion creating devices have become so common that we are now putting the capability to measure their impact on the distribution system in every meter. 3/5/96

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**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. Traditional kVA Before electronic meters, Phasor Power is what we were referring to when we said “kVA”. Obviously talking about power as kVA can be confusing because all power measurements are kVA measurements. We worked around this problem by calling the “kVAs” that can be converted to heat as watts and those associated with ‘energizing” currents as “vars”. Two methods for calculating Apparent Power and the ability to measure Distortion Power have again forced us to be more careful in how we describe measurements. EEI Handbook for Electricity Metering IEEE changed name from Vector Power to Phasor Power circa 1955 but we didn’t really change in metering until around 1990. Discussion in EEI Handbook for Electricity Metering 8th and 9th editions about Vector Power is actually talking about Phasor Power (I believe) (see pg. 223 Solid State Kilovolt-Ampere Metering) This discussion appears to be misleading, it argues that the biggest number is best but neglects to mention the impact of using bigger Apparent Power values on Power Factor. Non-Linear Loads Typical non-linear loads are SCR and TRIAC Motor Controls, High Efficiency Lighting, and switching power supplies (PCs, copiers, and FAX machines). 3/5/96

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**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) P S Q D Active Power Reactive Power U Apparent Power Distortion Power Choose the measurement approach you need. GE meters have offered Phasor measurements in the past that correctly measured energy and Quadergy but that did not include the distortion component. Other popular electronic meters has measured Fictitious Power (D+Q) and called it Reactive Power, overstating Reactive Power. They have also computed arithmetic apparent power and called it Apparent Power. The result is overstated Apparent Power values and understated Power Factors. The kV’s “3D” vector calculations provide correct measurement of Q, D, and U. This provides Power factor measurements that make sense in every application. No more resistive loads with .866 power factors. However, if a customer is committed to arithmetic apparent power we provide it. 7

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**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 Only new to electricity metering Traditional measurement when using instruments (Voltage and current) but new to electricity meters. “Arithmetic” modifier often dropped. Scalar Quantity Unlike the other power measurements Arithmetic Power is a scalar quantity not a vector. Arithmetic Power is calculated by adding the magnitude the Apparent Power vectors from each phase. Asymmetrical Circuits Arithmetic Apparent Power doesn’t work well in Network or 4 wire delta circuits because a neutral with equal voltage magnitudes or a true neutral can’t be established (required by definition). Often manufacturers will state in the Instruction Book that Arithmetic Apparent Power is not defined for these circuit types. In 3 wire delta circuits it’s hard to find the true neutral but it can be calculated or simulated using a resistor network. 3/5/96

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**Other Power Definitions**

Q D Active Power Reactive Power U Apparent Power Distortion Power F 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 Choose the measurement approach you need. GE meters have offered Phasor measurements in the past that correctly measured energy and Quadergy but that did not include the distortion component. Other popular electronic meters has measured Fictitious Power (D+Q) and called it Reactive Power, overstating Reactive Power. They have also computed arithmetic apparent power and called it Apparent Power. The result is overstated Apparent Power values and understated Power Factors. The kV’s “3D” vector calculations provide correct measurement of Q, D, and U. This provides Power factor measurements that make sense in every application. No more resistive loads with .866 power factors. However, if a customer is committed to arithmetic apparent power we provide it. 7

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**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. Choose the measurement approach you need. GE meters have offered Phasor measurements in the past that correctly measured energy and Quadergy but that did not include the distortion component. Other popular electronic meters has measured Fictitious Power (D+Q) and called it Reactive Power, overstating Reactive Power. They have also computed arithmetic apparent power and called it Apparent Power. The result is overstated Apparent Power values and understated Power Factors. The kV’s “3D” vector calculations provide correct measurement of Q, D, and U. This provides Power factor measurements that make sense in every application. No more resistive loads with .866 power factors. However, if a customer is committed to arithmetic apparent power we provide it. 7

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**Most accurate measurement technique available**

Power Measurement Newest DSP approach to Reactive Power Measurement 1 2 E 1) I E I 2) I 1) E 2) K/2 EIcos 1 2 EIcos 1 2 [KsinEIsin OUT IN Dot Product Most accurate measurement technique available

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**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 I don’t believe there are any electricity meters currently in volume production today that measure Apparent Power. The closest approximation I’m aware of is a meter that measures Arithmetic Apparent Power and multiplies it by This is a reasonable approximation for balanced circuits. I don’t know how it handles asymmetrical services and load imbalance. New meters now coming into the market will have the capability to measure Apparent Power. “3D” Apparent Power looks like the best choice for accurate measurement of “Cost of Service” for Distribution Utilities.

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**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 The addition of Distortion Power measurement to our tool kit now allows us to simply explain Apparent Power and Cost of Service. We can break it into three piece Active Power, Reactive Power, and Distortion Power. This three piece (Active Power, Reactive Power, and Distortion Power) explanation of Cost of Service gives us an intuitive and easy to explain model. With Distortion Power, We now, for the first time, have a measure of the cumulative amount of Distortion. Using Distortion Power alerts (like Power Factor alerts) we can identify high distortion conditions and use Distortion Power to tell us how sustained and cumulative is the distortion. 3/5/96

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**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 +5% -5% 12AM 12PM

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**Distortion Power (D) Apparent Power (U)**

What is “D/U”? Distortion Power (D) Apparent Power (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

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**Apparent Power (U) includes all 3 measures**

Measurement Model P S Q D Tariff (Active Power) (Reactive Power) Cost of Service U Total (Apparent Power) (Distortion Power) Power Quality 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

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**Measurement Examples Four Real Measurement Examples**

Manufacturing Plant - 15 MVA Oil Well Pump kVA Newspaper Printing Press kVA City Water Pumps kVA Collected by National Research Council of Canada

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**Example #1 Manufacturing 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 0.5 1 -0.5 PF 74.7% dPF 74.7% RF 66.4% D/U 3.4% Reactive Method Index Reactive Power () Fictitious Power Reactive(Time Delay) Index = Method/ Theoretical -1 1 Low distortion and poor Power Factor Traditional metering works well. This is what it was designed to do. Active, Reactive, and Phasor Power tell us all we need to understand Cost of Service and Power Quality. Note: PF Power Factor dPF Displacement Power Factor, PF calculated using values for fundamental only (used in this example to represent what an electromechanical meter would measure for Power Factor) RF Reactive Factor D/U Distortion Power Factor ITHD THD for a single phase current, all phases assumed to be the same ITHD in this example VTHD THD for a single phase voltage, all phases assumed to be the same VTHD in this example ITHD 2.9% 0.5 I -0.5 0.5 1 -1 Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610) 12

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**Example #2 Oil 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 0.5 1 PF 42.1% dPF 53.3% RF 65.2% D/U 63.1% Index Reactive Power () Fictitious Power Reactive(Time Delay) Index = Method/ Theoretical -1 High distortion and poor Power Factor Traditional measurements (Active, Reactive, and Phasor Power) warn of a problem but might lead to the wrong corrective action. Traditional measurements understate the cost of service. Arithmetic Apparent Power will give us a better measurement than Phasor Power if this is a symetrical service and the load is balanced. Apparent Power would give the best cost of service measurement with no concern about load balance and type of service. Distortion Power would lead us to best methods to improve the load and explain service costs not included in Reactive Power. ITHD 60.9% I 0.5 1 Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

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**Example #3 Newspaper Plant Printing Press - 150 kVA**

Moderately high voltage distortion High current distortion D/U tracks ITHD 1 VTHD 5.2% 0.5 V -0.5 0.5 1 PF 88.6% dPF 90.0% RF 42.3% D/U 19.3% Index Reactive Power () Fictitious Power Reactive(Time Delay) Index = Method/ Theoretical -1 1 High current distortion is probably producing high voltage distortion. Traditional measurements with an electromechanical or electronic meter would not report any problem. Distortion Power would report high distortion. ITHD 16.3% 0.5 I -0.5 0.5 1 -1 Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

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**Example #4 City 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 -0.5 0.5 1 PF 92.5% dPF 95.2% RF 29.3% D/U 24.3% Index Reactive Power () Fictitious Power Reactive(Time Delay) Index = Method/ Theoretical -1 1 ITHD 23.2% 0.5 I -0.5 0.5 1 -1 Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

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**More Measurement Choices**

Apparent Power Phasor Power Arithmetic Apparent Q Hour (3D Vector) (2D Vector) Power (Scalar) Demand 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 Energy (pick one) VARS (pick one) o Apparent kVAh o Received only o Lagging only o Apparent Power (kVA) o Delivered only o Leading only Or o Unidirectional o Unidirectional o Bidirectional o Bidirectional o Quadergy (kvarh) o Reactive Power (kvar) Harmonics o Fundamental only or ... Modern electricity meters give us a large menu of measurement choices. They provide the Cost of Service and Power Quality measurements in addition to traditional billing quantities.. The challenge is to pick meters today that will meet your future needs to make non-traditional measurements. o Fundamental plus harmonics Pick Fundamental only or Fundamental plus Harmonics Pick Distortion Power, Reactive Power, Apparent Power, Phasor Power, “Q-Hours”, or Arithmetic Apparent Power (kVA) 3/5/96 3

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**A tool to improve power quality**

Power Guard System Power Quality Measurement in every meter 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 Power Guard ... A tool to improve power quality 5

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**Cost-of-Service Measurement**

Knowing the cost of servicing a customer is essential in today’s deregulated environment 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.

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