Power Quality Improvement

INTRODUCTION OF POWER

QUALITY

Power Quality is a combination of Voltage profile,

Frequency profile, Harmonics contain and reliability of

power supply.

The Power Quality is defined as the degree to which

the power supply approaches the ideal case of stable,

uninterrupted, zero distortion and disturbance free supply.

This presentation represents an overviews of electric

power quality with special emphasis on power quality

problems.

The adverse impact on utility of customers and their

mitigation techniques.

This presentation also deals with serious power quality

problems such as voltage distortion due to current

harmonics, flicker ,voltage sag and voltage surge..etc

Power quality is related to deliver of “CLEAN”

electric power that compile with industry standards.

CAUSES OF POOR POWER

QUALITY

Variation in voltage magnitude and frequency.

Variation in magnitude can be due to sudden rise or fall of

load , outages, repetitive varying loading pattern in rolling

mills, power electronic converters, inverters, lightning..etc

Variation in frequency can rise of out of system dynamics

or harmonics injection.

POWER QUALITY COVERS

1. Reliability :- continuous availability,

interruption/breakdown/outage free

2. Parameters:-

Voltage- flicker, swell, sag/dip, unbalance

Frequency- drop or rise

Harmonics contains- SCR, converters, inverters etc.

Transients

SOURCES OF POOR POWER

QUALITY

Non linear loads

Arcing loads

Switching operation

Reactive loads

Atmospheric condition

Unstable loads

Neighboring unbalance system

TYPICAL POWER QUALITY

PROBLEMS

Voltage Sags :- A reduction in RMS voltage or

current at the power frequency.

Voltage Surge:- voltage variation can be

positive (higher than normal) or negative (lower

than normal)

Transients:- it manifest only as a short duration

change in voltage due to switching ON and OFF the

loads.

Harmonics:- it is an integer multiple of fundamental

frequency in the sine wave of power supply or simply

distortion of waveforms.

Lightning:- It produces very high currents, for a short

time interval, but enough to cause fires or to destroy

microcircuits.

IMPACT OF POOR POWER QUALITY

The effect of poor power quality problems has serious implication on

the utilities and customers.

Higher losses in transformers, cables .

Neutral wire burning due to third harmonics generated by non linear

loads.

Power factor capacitors may punctures.

Energy meters will give faulty readings.

Solid state protective relays may damaged .

Speed drives may shut down.

Motor will increase core and cu losses

Non sinusoidal waveforms will reduce the efficiency of motors.

Electronic computer may loss data due to voltage variation .

Domestics TV and other equipments are affected by the poor quality.

SYMPTOMS OF POWER QUALITY

PROBLEM

Electronic controlled system that stop unexpectedly

Abnormal failure of electronic systems

Transformer overheating

Motor failing

Power factor capacitors failing

Test results will unreliable

TECHNIQUES TO MITIGATE

POWER QUALITY PROBLEMS

Compensation techniques can be broadly classified into

two main categories:-

1. Passive techniques

2. Active techniques

Passive techniques employ the following devices.

* Passive Shunt L-C Filters

* Power Factor Correction Capacitors

Active techniques employ the following devices.

*PWM Active Filters.

SOME OTHER TECHNIQUES

Segregate sensitive loads on separate branch

circuits , fed from a separate panel board , fed from

a separate feeders

Use of harmonics rated circuit breakers, panel

board and transformers.

Use surge and lightning protection.

Oversize phase conductors to minimize voltage

drop.

Choose material of superior quality.

CONCLUSION

The wide spread applications of non-linear power

electronics loads increases the poor power quality in the

electric systems. This presentation has focused broadly on

the utilities and customers in the power system. At the

same time, the sources of poor power quality and their

mitigations techniques has discussed in brief. The

effectives means of compensation through various

techniques have also been highlighted.

THANK YOU…!!!