TECHNICAL SEMINAR ONPOWER QUALITY DISTURBANCES AND

MONITORING

CONTENTSDefinitionPower quality eventsSources of power quality problemsScopeCausesPower quality monitoringMonitoring objectivesPower quality monitorsBenefits of MonitoringConclusion

DEFINITION“Power quality is the set of parameters

defining the properties of the power supply as delivered to the user in normal operating conditions in terms of the continuity of voltage and voltage characteristics”.

Power quality mainly deals with 1.Continuity of the supply. 2.”Quality” of the voltage

Power Quality eventsOccasionally, the voltage or current deviates

significantly from the nominal or ideal wave shape. These sudden deviations are called events. Monitoring of events take place by using a triggering mechanism where recording of voltage or current starts the moment, a threshold is exceeded.

Various power quality events are given below: 1. Interruptions 2. Voltage sags / swells 3. Transients 4. Voltage – magnitude events

Fig showing Interruption

Disturbance due to voltage sag and swell

Sources of Power quality problemsInternal Sources

•Individual Loads –Lighting, Elevators, Coolers, HVAC

•Uninterruptible Power Supplies

•Variable Frequency Drives

•Battery Chargers

•Large Motors During Startup

•Electronic Dimming Systems

•Arc Welders, and Other Arc Devices

•Medical Equipment, e.g. MRIs and X-Ray Machines

•Office Equipment and Computers

Utility Sources Lightning PF Correction

Equipment Faults Switching

ScopeFor economic operation of a power system, the

level of power quality should be properly maintained.

The adverse effects due to over voltages, also the losses incurred due to the under voltages have to be seriously dealt.

Nonlinear loads introduce harmonics in the system which have their own adverse effects Hence, power quality provides a good platform to deal with all these problems

CAUSESFaults at power stations.Damage to electric transmission lines,

substations or other parts of the distribution system.

Short circuit, or the overloading of electricity mains.

Power quality monitoringPower providers and users alike are

concerned about reliable power, whether the focus is on interruptions and disturbances or harmonic distortion or flicker.

One of the most critical steps in ensuring reliability is monitoring power quality.

Power quality monitoring can help to identify the cause of power system disturbances and even help to identify problem conditions before they cause interruptions or disturbances

Monitoring ObjectivesThe objectives of a monitoring program

determine the choice of measuring equipments and triggering thresholds, the methods for collecting data, data storage and analysis requirements and the overall level of effort needed.

General classification of objectives for power quality monitoring is explained in the following

1.Proactive approach2.Reactive approach

Power quality MonitorsThe first step to troubleshooting power quality

problems is to have a monitor that accurately measures voltage and current waveforms. The role of monitor for troubleshooting power quality problems is undeniable.

1. Portable monitors a. Voltage recorders b. Disturbance analyzer 2. Permanent monitors

Portable Monitor

Real time monitoring system

Benefits of monitoringEnsures power system reliability.Identify the source and frequency of events.Helps in the preventive and predictive maintenance.Evaluation of incoming electrical supply and

distribution to determine if power quality disturbances are impacting.

Determine the need for mitigation equipments. Reduction of energy expenses and risk avoidances.Process improvements – monitoring systems allows

to identify the most sensitive equipments and install power conditioning systems where necessary

ConclusionTraditional monitoring methods are based on

the RMS measurements and constrained by their accuracies. Recently proposed approaches for automated detection and classification of power quality disturbances are based on wavelet analysis, artificial neural networks, hidden Markov model and bispectra. The use of such advanced techniques makes the power quality monitoring system more accurate and the power system more reliable.

THANK YOU