Power Quality Monitoringand Cost-of-Service Measurement

GE Electronic Meter SchoolSomersworth, NH

GE Meter 02/25/96 2

Power Quality Issues

Causes Voltage sags/swells Voltage Interruptions Harmonics

– Non-linear Loads

– Transformers

Power Quality Problems Lead to Dissatisfied Customers and Higher Cost

Symptoms Customer Complaints

– Equipment Shutdown or Damage

– Flicker

– Timekeeping Problems Transformer Heating and

Derating Capacitor Bank Failures Increased Line Losses Overheated Neutrals

GE Meter 02/25/96 3

Supply Side Sources

Line switching Breaker operations Reclosers Capacitor banks Voltage controls Natural occurrences

– Weather related events ... lightning, floods, etc.– Accidents

GE Meter 02/25/96 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

GE Meter 02/25/96 5

3/5/96

Traditional MeasurementsTraditional 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)

GE Meter 02/25/96 6

3/5/96

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.

GE Meter 02/25/96 7

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)

Power Definitions

P

S

Q

D

Active Power

Re

act

ive

Po

we

r

U

Apparent Power

Dis

torti

on P

ower

GE Meter 02/25/96 8

3/5/96

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

GE Meter 02/25/96 9

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

Other Power Definitions

P

S

Q

D

Active Power

Re

act

ive

Po

we

r

U

Apparent Power

Dis

torti

on P

ower

F

GE Meter 02/25/96 10

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.

Other Power Definitions

Time Delay Method

GE Meter 02/25/96 11

1

2 1

2

E 1)

IE

I 2)

I 1)E 2)

K/2

EIcos 1 2

EIcos 1 2

[KsinEIsin

OUT

IN

IN IN

IN

Dot Product

Dot Product

Ksin vs. Frequency

.5

.6

.7

.8

.9

1.0

10 100 1000 10000f (Hz)

Ks

in

Power Measurement

Newest DSP approach to Reactive Power Measurement

Most accurate measurement technique available

GE Meter 02/25/96 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

GE Meter 02/25/96 13

3/5/96

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

GE Meter 02/25/96 14

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%12AM12AM

12PM

GE Meter 02/25/96 15

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

Distortion Power (D)Apparent Power (U)

GE Meter 02/25/96 16

Measurement Model

Cost of Service Measurement Components1). 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

P

S

Q

D

Tariff(Active Power)

Co

st o

f S

erv

ice

(Re

act

ive

Po

we

r)

UTotal

(Apparent Power)

Pow

er Q

ualit

y(D

isto

rtio

n P

ower

)

GE Meter 02/25/96 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

GE Meter 02/25/96 18

Example #1Manufacturing Plant - 15 MVA

Large induction and DC motors

Low distortion levels Poor power factor Typical of older style

industrial equipment

I

V

–-1

–-0.5

–0

–0.5

–1

–0 –0.5 –1

–-1

–-0.5

–0

–0.5

–1

–0 –0.5 –1

Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

VTHD 0.8%

ITHD 2.9%

PF 74.7% dPF 74.7%

RF 66.4% D/U 3.4%

Reactive Method IndexReactive Power () 1.0000Fictitious Power 1.0043Reactive(Time Delay) 1.0000

Index = Method/ Theoretical

GE Meter 02/25/96 19

Example #2Oil Well Pump - 500 kVA

6 pulse VSD Very heavy current distortion Moderate voltage distortion High D/U tracks ITHD

PF 42.1%dPF 53.3%

RF 65.2%D/U 63.1%

IndexReactive Power () 1.0000Fictitious Power 1.3915Reactive(Time Delay) 1.0192

Index = Method/ Theoretical

Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

V

I

–-1

–0

–0.5

–0 –0.5 –1

–0–0 –0.5 –1

VTHD 3.3%

ITHD 60.9%

GE Meter 02/25/96 20

Example #3Newspaper Plant Printing Press - 150 kVA

Moderately high voltage distortion

High current distortion D/U tracks ITHD

PF 88.6%dPF 90.0%

RF 42.3%D/U 19.3%

IndexReactive Power () 1.0000Fictitious Power 1.0989Reactive(Time Delay) 1.0284

Index = Method/ Theoretical

Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

V

I

–-1

–-0.5

–0

–0.5

–1

–0 –0.5 –1

–-1

–-0.5

–0

–0.5

–1

–0 –0.5 –1

VTHD 5.2%

ITHD 16.3%

GE Meter 02/25/96 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

PF 92.5%dPF 95.2%

RF 29.3%D/U 24.3%

IndexReactive Power () 1.0000Fictitious Power 1.2992Reactive(Time Delay) 1.0159 Index = Method/ Theoretical

Source: National Research Council Report for the Canadian Electrical Association (report no. 043-D610)

V

I

–-1

–-0.5

–0

–0.5

–1

–0 –0.5 –1

–-1

–-0.5

–0

–0.5

–1

–0 –0.5 –1

VTHD 2.8%

ITHD 23.2%

GE Meter 02/25/96 22

3/5/96 3

More Measurement Choices

Pick Fundamental only or Fundamental plus Harmonics Pick Distortion Power, Reactive Power, Apparent Power,

Phasor Power, “Q-Hours”, or Arithmetic Apparent Power (kVA)

Apparent Power(3D Vector)

Phasor Power(2D Vector)

Arithmetic ApparentPower (Scalar)

Q HourDemand

o Active Energy (kWh)

o Active Power (kW)

o Distortion Power Factor

Basic Measures

Electronic Detent

Energy (pick one)

o Received only

o Delivered only

o Unidirectional

o Bidirectional

VARS (pick one)

o Lagging only

o Leading only

o Unidirectional

o Bidirectional

o Fundamental only or ...o Fundamental plus harmonics

Harmonics

K Switch adds

o Quadergy (kvarh)

o Reactive Power (kvar)

o Apparent kVAh

o Apparent Power (kVA)

o Distortion kVAh

o Average Power Factor

And

Or

GE Meter 02/25/96 23

Power Guard System

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

Power Quality Measurement in every meter

GE Meter 02/25/96 24

Cost-of-Service Measurement

Cost-of-Service ComponentsTariff 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 requirementsDistortion 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