power quality

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GRIDTechnical Institute

Power Quality Monitoring

> Power Quality Monitoring: Basic Principles and Application Examples2

Measure of disruptions in the power supply

Availability

Reliability

Power Quality Events recorded to an existing standard

Power System Analysis

What is Power Quality?

M571 Compact Disturbance Recorder


Power Quality Standards

Some existing Power Quality standards

EN 50160 Standard (Europe)

IEEE 1159 Recommended Practice (North America)

NRS-048 standards (South Africa)

also ITIC (CBEMA) curve for computer equipment

Defining the technical criteria for voltage quality


Power Quality definitions: Dips and Surges

Voltage dips

Amplitude and duration

0

20

40

60

80

100

120

110%

100%

90%

Time

Surge/Swell - Above 110% of Nominal value

Dip/Sag - Below 90% of Nominal Value

Short time 1min to 60min

Very Short time 1 sec to 1min duration

RMS Value calculated over 10 minute period


Power Quality definitions: DISDIP

Distribution of Dips Report

Tabular distribution of dip events


ITIC CurvePower Quality Envelope

ITIC Curve: 1996

0%

50%

100%

150%

200%

250%

300%

350%

400%

450%

500%

0 3 20 500 10000

Rating

Time mS

Voltage tolerance

ITIC (CBEMA) Curve revised 1996

Single phase IT operating parameters

Swells or Overvoltage: rating very short over 110%(towards 0ms)

Sags or Undervoltage: rating very short under 70% (500ms) Financial Costs


Power Quality definitions: Interruptions

Voltage interruptions

Amplitude and duration

Interruption below 1% of Nominal value EN50160

Interruption below 10% of Nominal value IEEE 1159

Time duration depends on equipment tolerance, generally more than 1 cycle

0

20

40

60

80

100

120

110%

100%

90%

10%

1%

InterruptionTime


Power Quality definitions: Harmonics and Signalling voltages

Voltage harmonics

Losses proportional

to Frequency 2

Total Harmonic Distortion (THD%)

Measured according IEC 61000-4-7

Measure every 200ms using FFT, 10min RMS average

Signalling voltages, 3 sec RMS average

0%

2%

4%

6%

8%

10%

12%

50HZ

63HZ

100H

Z

153H

Z

200H

Z

Limit


Power Quality definitions: Flicker

Voltage flicker

Severity

Time

Measured according IEC 61000-4-15, over a 2hour period (Plt) over a 10 min period (Pst)

Modulation of the RMS voltage that can be seen by the human eye ~8.8HZ

Classified by a severity index:1 = good

<1 = better

>1 = worse

0

20

40

60

80

100

120

110%

100%

90%


Power Quality definitions: Unbalance

Voltage unbalance

Percentage

Time

Where the voltage vectors do not add to zero

Where the voltage magnitudes are unequal

10 minute average of RMS values

0

20

40

60

80

100

120

110%

100%

90%

Time


Power Quality definitions: Frequency

Frequency change

Swiss- Italian Fault September 2003

EN 50160 : 50 Hz +4% / -6%

NRS048 : ±2.5% for grid network


Sources of poor Power Quality

Power Quality flows

Power Quality as a polluter

Sources:

Industrial sites

Domestic rural sites

Utility network

Exported to others

Imported from others

Circulate within the site


Cause and Effect of poor Power Quality 1

Dips / Sags

Remote fault, load switching

Trips, process control restarting, motors stalling

Surges / Swells

Lightning strikes, arcing and switching

Trips, damage to insulation and winding, destruction of sensitive devices

Interruption

Faults, equipment failure, protection operation

Production down time

Financial costs



Voltage Variation

Load variation (e.g. welding, furnaces..)

Trips, damage to insulation and winding

Harmonics and Interharmonics

Power electronics, non-linear loads; signalling voltages

Equipment mal-operation, damage to motors, generators and transformers

Flicker

Load variations at a particular frequency(e.g. arc furnaces..)

Noticable effects in the lighting

Financial costs



Voltage Unbalance

Unbalanced Load variation

Overheating in motors and generators

Frequency

Loss of generation, governors

Generator trip (extreme)

Financial costs


Why monitor Power Quality? 1

SUPPLIERS

Network Planning

• accurate forecast of demand

• load profiling

• optimise transformer load

• optimise PQ remedy location

Legislation (de-regulated energy markets)

Monitor Consumers

Proactively respond to complaints

Asset management and customer care


Why monitor Power Quality? 2

CONSUMERS

Identify source of PQ problems

Reduce Financial Costs

• Lost production

• Replacement of equipment

Reduce Operational Costs

• Interruption of services

• Working environment (Flicker)

Compliance

• With supply agreements

Asset management and customer care


Most prevalent Power Quality problems

0

10

20

30

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Dat

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Pro

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wh

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Ove

rhea

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Neu

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Pro

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Nu

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Uti

lity

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s

Industry Utility

European Copper Institute (2001): 1400 sites in 8 countries


Financial cost of poor Power Quality

Semi conductor Industry 3,800

Financial Trading 6,000 per hour

Computer centre 750

Telecommunications 30 per minute

Steel Works 350

Glass Industry 250

Typical financial loss per event € ‘ 000s


Power Quality Benefits

SUB TRANSMISSION

DISTRIBUTION

SECONDARY DISTRIBUTION

LV NETWORK

G

G

G

G

G

SECONDARY (RURAL)DISTRIBUTION

HeavyIndustry

Medium Industry

Light Industry

POW GEN

IPPPOW GEN

IPP

Renewable Sources/IPP/ Municipal

CO-GENDOMESTIC

URBANTRANSFORMERS

CHEMICAL PLANTS

STEEL WORKS

GRID LOAD FLOW IMPROVEMENT

END USER VOLTAGE IMPROVEMENT

DEFINED IN PQ STANDARDS

DEFINED BY PLANNING LEVELS

TRANSMISSION NETWORK


Solutions: Improving Power Quality

UN-INTERRUPTIBLE POWER SUPPLIES

Dips, surges, spikes and interruptions

EARTHING PRACTICES

Harmonics

FILTERS (passive and active)

Harmonics

STATIC VAR COMPENSATION (SVC)

Dips, surges and Power Factor

FERRO-RESONANCE TRANSFORMERS (Stored Energy)

Dips, surges, spikes and interruptions

Important to place at the correct location


M570 Compact Family Typical IED

Fixed option configurations

20A fault current

Up to 14 Channels

Optional 4 DI & 4 DO

Unlimited AO by Analog Output Controller

Optional Ethernet

70 Series Firmware

70 Series Software


Magnitude- Duration list

Global view of the events over the

assessmentperiod

Win DR Manager (QR Monitor+ viewer)

Event viewing:


1/2 cycle

Programmed thresholds

%RMS


Event viewing:

Zoom of the events global view: 1/2 cycle


Voltage

Frequency


Trend viewing (average 10min)


EN50160 viewing of history data(average 10 min)

Display of events during the assessment period.


Trend viewing


Simultaneous display of evolution of THD and the accordingly full harmonic content with peak detection :

THD evolution

Spectrum at time cursor position

Peak detection


Trend viewing

Harmonic investigation


TIHD

Inter-harmonics at cursor 1 position

06h00 22h30

Group 2(150-200Hz)

(average 10 min)


Trend viewing

History viewing: inter-harmonic spectrum view



PQ report creation and generation

Creation




Creation: use of an existing profile (template)

Available actions




Generation: PQ report on a single unit

Events PQ reports




Generation: PQ report on a single unit

Events PQ reports


Istat M2x3 Measurement Centre Family

M253 Network Analyser (Power Quality)


PQ to EN50160

Permanent monitoring for up to 3 years

Monitoring parameters:

Frequency variations

Voltage variations

Voltage Dips

Voltage Interruptions

Voltage Unbalance

Transients

Flicker

THD

Harmonics

M253 Power Quality compliance monitoring


True RMS measurements over 140 parameters

128 samples per cycle

Programmable analogue outputs

Measured parameters:

U, I, P, Q, S, PF, PA, f, φ

Maximum Demands

THD

Harmonics up to 63

Energy

Cost Management

Min / Max values

M253 Harmonic Measurements

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