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Power Quality Monitoring

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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

Transformer Heating and Derating

Capacitor Bank Failures

Increased Line Losses

Overheated Neutrals

Power Quality Problems Lead to Dissatisfied Customers and Higher Cost

- Line switching
- Breaker operations
- Reclosers
- Capacitor banks
- Voltage controls
- Natural occurrences
- Weather related events ... lightning, floods, etc.
- Accidents

- 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

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

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

S

Reactive Power

Apparent Power

Q

U

P

Active Power

D

Distortion Power

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)

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

S

Reactive Power

Apparent Power

Q

U

F

P

Active Power

D

Distortion Power

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

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.

Dot Product

1

2

E 1)

I 2)

EIcos 1 2

IN

IN

K/2

E

I

[KsinEIsin

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

“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

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

+5%

12PM

12AM

12AM

-5%

- 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

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

S

Cost of Service

(Reactive Power)

Q

Total

(Apparent Power)

U

P

Tariff

(Active Power)

Power Quality

(Distortion Power)

D

Cost of Service Measurement Components

1). Active Power (P)Tariff MeasurementLighting and Heating Loads

2). Reactive Power (Q)Starting and Charging Motor Loads

Current Costs

3). Distortion Power (D)Power Quality CostDistorted Loads

Apparent Power (U) includes all 3 measures

- 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

- 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 Power1.0043

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)

- 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 Power1.3915

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)

- 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 Power1.0989

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)

- 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 Power1.2992

Reactive(Time Delay)1.0159

Index = Method/ Theoretical

- -1

- 1

ITHD 23.2%

- 0.5

I

- 0

- 0

- 0.5

- 1

- -0.5

- -1

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

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

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