Impact of Power Quality on Indian Industries

October 2011

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Power Quality

• Power Quality is a measure of ideal power supply

system.

• It looks into the

� Voltage magnitude

� Frequency

� Wave shape

• It refers to maintaining a near sinusoidal voltage to a bus

at rated magnitude and rated frequency.

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Voltage Power Quality Problems

1. Impulses/Transient: High magnitude for extremely short duration.

2. Voltage Sag: A momentary voltage dip last for a few seconds.

3. Voltage Swell: A momentary voltage rise which last for a few seconds

4. Over Voltage: A steady state voltage rise last for SEVERAL seconds

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Voltage Power Quality Problems

5. Under Voltage: A steady state voltage dip last for SEVERAL seconds

6. Flicker: A perceptible change in lamp output due to a sudden change in voltage

Example voltage waveforms showing flicker created by an arc furnace

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7. Harmonics: The non-fundamental frequency components of a distorted power frequency waveform.

8. Voltage Interruption: A complete loss of voltage for a few seconds to several hours

9. Voltage Notch: Periodic transient that rides on the supply voltage

–

Distorted Voltage Waveform

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10. Outage: Interruption that has duration lasting in excess

of one minute.

11. Frequency Deviation: Variation in frequency from the

nominal supply frequency above/below a predetermined

level, normally + 0.1%.

Why power quality has become important?

• Increased use of power electronic

equipment

• These create PQ problems; also affected by

PQ problems

• Consumers are more aware

• Instruments available to measure PQ

indices

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Effects of PQ Problems

• Voltage dips: Machine/process downtime, scrap cost, clean up costs, product quality and repair costs all contribute to make these types of problems costly to the end-user

• Transients: Tripping, component failure, hardware reboot required, software ‘glitches‘, poor product quality

• Harmonics: Transformer and neutral conductor heating leading to reduced equipment life span; audio hum, video ‘flutter’, software glitches, power supply failure

• Flicker: Visual irritation

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Sources of Power Quality Problems

• Power electronic devices

• IT and office equipments

• Arcing devices

• Load switching

• Large motor starting

• Embedded generation

• Sensitive equipment

• Storm and environmental related damage

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Power Quality Parameters to be Monitored

• Voltage sags and swells

• Voltage unbalance

• Frequency deviations

• Voltage harmonics and sub-harmonics

• Current harmonics

• Flickers and fluctuations

• Power factor

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Existing Standards

• IEEE Recommended Practices and Requirements for

Harmonic control in electric power systems, IEEE Std.

519- 1992, an update done in 2008.

• IEC 61000: Classification of power quality, Transients etc.

• EN 50160

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IEEE 519-1992 Standard

• Sources of harmonics

• Effects of harmonics

• Limits on harmonic level of current and voltage that

can be generated by any consumer for different power

levels

• Solutions for eliminating power quality problems

• Case studies

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IEC 61000-4-30 Standard

• How to measure power quality disturbances and interpret data

• Applicable to both 1-phase and 3-phase systems of 50 Hz and 60 Hz.

• How much disturbance can be tolerated

• For how long

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EN50160 Standard

• This is written from the utilities point of view- soft

towards them.

• Limits of disturbances that can be tolerated

• How frequently the power quality parameters are to be

sampled

• For example, the voltage should not be below 90% of

its rated value for 95% of the measurements that have

been taken over a period of 1 week for every one

hour.

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Importance of Power Quality

For the past 100 years, the utility’s job has been to keep the

‘lights on’. For today’s high-tech factories, that is not

enough.

• Increase in industrial automation and importance of

productivity in a competitive global market have driven PQ

awareness.

• Power quality is a financial problem – not a technical

problem alone. PQ causes $120B/year in economic loss in

the US (EPRI, DOE).

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Need of Survey

• Industry requires Standards and/or Guidelines to observe

and follow norms in handling effectively such issues of

concern.

• In India, essentially IEEE standards are referred as

guidelines in electricity sector.

• In manufacturing sector normally IEC standards are being

referred to.

• Bureau of Indian Standards (BIS) is facilitating to bring in

such standards to compliment global effort in

Harmonization of Standards.

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Methodology

• Collect information from various industrial sectors to get an

estimate of the damage caused by PQ related problems.To

collect information:

� Desktop based literature survey and web based research with

industry (particularly identified industries which are severely

affected by poor PQ)

� Discussions with consultants and research organizations, interview/

interaction based inputs on current practices followed in industries

have been the various ways of collecting information about PQ

problems.

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• Queries related to these problems are combined in the form

of questionnaire.

• This questionnaire is sent to various industries like paper and

pulp, textiles, IT sector, aviation, medical electronics etc. to

estimate the adverse impact of power quality problems on

the performance and production.

• The survey results are mainly categorized into various parts

like – sector, total energy consumption, incoming voltage

level, equipment used in the industries, power quality related

problems such as voltage dips, short interruptions, long term

power interruption, voltage and current harmonics, flicker,

unbalance and neutral voltage and current.

•

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Problem Faced

• It is a big challenge to survey the various power quality

problems that are existing in industries.

• The industries are not aware of the importance of power

quality and standards, so they do not pay attention to respond

to the PQ questionnaire.

• Many of the industries are not willing for PQ assessment to

be done in their premises as they do not have necessary

instrumentation and infrastructure

• Many of them are not interested to know about solutions to

PQ problems.

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Statistics of Various Industries

• Responses from the different industries related to power

quality problems are obtained.

• Many manufacturing sectors that are big such as iron and

steel, cement and heavy electricals, have back-up power

generation that they do not suffer from long and short

term interruptions.

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Main Power Quality Problems in Industries

• Capacitor Bank Failure: Iron & Steel, Paper and Pulp,

Manufacturing Sector of Heavy Electricals, IT, Sector,

Plastic & Rubber, Food Processing and Power Generation

sectors, University, Pharmaceuticals, Cement, Automobile,

Aviation, Hospital, Telecom Services/Towers

• Computer Screen Freeze: Paper And Pulp, Manufacturing

Sector of Heavy Electricals, IT Sector, Textiles, Metallurgy,

Power Generation, Plastic & Rubber, Pharmaceuticals,

Cement, Insurance Broker, Aviation

• Loss of Data: Iron & Steel, Chemicals/ Fertilizers,

Textiles, Power Generation, Pharmaceuticals, Aviation

• Overheating of Motors due to negative sequence and

neutral currents: Manufacturing Sector of Heavy

Electricals, Metallurgy, Power Generation,

Pharmaceuticals, Cement, Automobile, Telecom

Services/Towers, Textiles

• Flickering of Lights: Manufacturing Sector of Electronics

Goods, Chemicals / Fertilizers, Textiles, IT Sector, Power

Generation, University, Oil & Petroleum, Pharmaceuticals

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Conclusions

• Almost all the industries suffer due to various power quality

problems.

• Many of the industries are not even aware of various PQ

problems like harmonics, flickers etc.

• It is a must to educate and create awareness among industries

regarding power quality.

• This calls for BIS taking a firm and bold step to introduce

power quality standards that are suited for our country.

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• For this, academicians, industrialists, consumers, utilities

and regulatory bodies should come together and have

several thorough brainstorming sessions.

• This will go a long way in creating a healthy and reliable

power grid and utility in our country enhancing

productivity and GDP growth.

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