Power quality

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?


Power Quality Standards

Some existing Power Quality standardsEN 50160 Standard (Europe)

IEEE 1159 Recommended Practice (North America)

NRS-048 standards (South Africa)

also ITIC (CBEMA) curve for computer equipment

Defines 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 proportionalto 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

Z15

3HZ

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 / SagsRemote fault, load switching

Trips, process control restarting, motors stalling

Surges / SwellsLightning strikes, arcing and switching

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

InterruptionFaults, equipment failure, protection operation

Production down time

Financial costs



Voltage VariationLoad variation (e.g. welding, furnaces..)

Trips, damage to insulation and winding

Harmonics and InterharmonicsPower electronics, non-linear loads; signalling voltages

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

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

Noticable effects in the lighting

Financial costs



Voltage UnbalanceUnbalanced Load variation

Overheating in motors and generators

FrequencyLoss of generation, governors

Generator trip (extreme)

Financial costs


Why monitor Power Quality? 1

SUPPLIERSNetwork 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

CONSUMERSIdentify 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

Com

puto

r Lo

ckup

s

Flic

ker

Equ

ipm

ent d

amag

e

Dat

a pr

oces

sing

PFC

ove

rload

ing

Pro

blem

s w

hen

switc

hing

heav

y lo

ads

Ove

rhea

ted

Neut

ral

Pro

blem

wot

h lo

ng li

nes

Nuis

ance

Tri

ppin

g

Util

ity M

eter

ing

clai

ms

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 SUPPLIESDips, surges, spikes and interruptions

EARTHING PRACTICESHarmonics

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


Disturbance Recording

All records saved in memory as comtrade files

Record fault details as waveform records

Record short term variations as disturbance records

Record long term variations (10 minute averages) as trend records

Trend records used as basis for power quality conformance analysis


Magnitude-Duration list

Global view of the events over the

assessmentperiod

Power Quality Event Viewing

Voltage Fluctuations


Programmed thresholds

%RMS


Event viewing:Voltage surges, dips and interruptions


Voltage

Frequency

Power Quality Event ViewingTrend viewing (average 10min)


View of historical data of 10 minute averages

Check for compliance against EN50160 limits


Trend viewing



Trend viewingVoltage Harmonics

Limit for Total Harmonic distortion

Also limit for each individual hamonic


TIHD

Inter-harmonics at cursor 1 position

06h00 22h30

Group 2(150-200Hz)

10 min average


Trend viewingInter-harmonic total and spectrum views



PQ report creation and generationCreation


Power Quality reportPQ report creation and generation

Creation: use of an existing profile (template)

Available actions



Generation: PQ report on a single unit

Events PQ reports


PQ to EN50160

Long term monitoring for up to 3 years

Monitoring parameters:

Frequency variations

Voltage variations

Voltage Dips

Voltage Interruptions

Voltage Unbalance

Transients

Flicker

THD

Harmonics

EN50160 Power Quality compliance monitoring


Power Quality report to EN50160

EN50160 Power Quality compliance monitoring


True RMS measurements

High sample rate

128 samples per cycle to measure harmonics up to 63 order

Instantaneous measurements

U, I, P, Q, S, PF, PA, φ, f

Maximum Demands

THD

Energy

Min / Max values

Power Quality Measurements

Power quality

Documents

Transcript of Power quality