dr. hannan week9 power quality monitoring
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Power Quality Monitoring
Power quality monitoring is the process of gathering, analyzing and interpreting raw measurement
data into useful information. The process of gathering data is usually carried out by continuous
measurement voltage and current over and extended period.
Why needed?
What are the objectives/consideration?The monitoring objectives often determines the choice monitoring equipment, triggering threshold,
methods of data acquisition and storage, analysis and interpretation requirements. There are
several common objectives of power quality monitoring such as
i) Monitoring to characterize system performance
ii) Monitoring to characterize specific problems
iii) Monitoring as a part of an enhanced power quality service
iv) Monitoring as a part of predictive or just-in-time maintenance
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Monitoring as part of a facility site survey
Site survey are performed to evaluate concerns for power quality and equipment performance
throughout a facility. The survey will includes inspection of wiring and grounding concerns,equipment connections, and voltage and current characteristic etc. This information is specially
important when monitoring objective intended to address specific PQ problems. This information
are as follow;
i) nature of problems
ii) Characteristics of sensitive equipment experiencing problems
iii) time at which problems occur
iv) Coincident problems or known operationv) possible source of power quality variations
vi) existing power conditioning equipment being used
vii) Electrical system data
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Forms for RecordingForms for Recording
Data forms that can used for initial verification of
PQ disturbances are as follows;
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Locations &permanent PQ monitoring equipment
Some categories of equipment that
are used for permanent PQmonitoring system such as;
i) Digital fault recorder
ii) Smart relays and other LEDs
iii) Voltage recorderiv)In-plant power monitor
v) Special purpose PQ monitor
vi)Revenue meter etc.
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Historical perspective of PQ measuring instruments
►The instrument makes an impulse-like mark on strip-chart paper to record lighting strikes.
►Analog oscilloscope with logarithmic chart sweep rate and recorded quantitative voltage waveform
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Historical perspective of PQ measuring instruments
►Microprocessor based monitor
analyzer 1st manufac. in 1975.
This text based printout of adisturbance, still in service.
►2nd generation PQ instrument
debuted in mid 80’s. Feature full
graphic display, digital memoryto view and store captured
events. Capable data
transmission from remote to
central location for further
analysis and also have triggeringmechanism.
►3rd generation are in mid 90’s
inspirited by EPRI DPQ project,
more appropriate than previous,complete PQ monitoring,
software based data collection
and analysis.
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Power Quality Measuring InstrumentsPower Quality Measuring Instruments
►There are numbers of PQ measuring instruments that can measure power quality are as follows;
i) Wiring and grounding test device
ii) Multimeters
iii) Oscilloscopes
iv) Disturbance analysers
v) Harmonic analysers and spectrum analysersvi) combination disturbance and harmonic analysers
vii) Flicker and
viii) Energy monitor
Besides these meters, there are some other meters that can help to solve PQ problems bymeasuring ambient conditions such as;
i) Infrared meter
ii) magnetic gauss meter
iii) Static electricity meters
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Wiring and grounding tester/multimetersWiring and grounding tester/multimeters
►Many power quality problems are reported by end users are caused by problems with wiring and
or grounding within the facility. Important capability for a wiring and grounding test
includes;
i) Detection of isolated ground short and neutral-ground bonds.
ii) Ground impedance and neutral impedance measure
iii) Detection open neutral, open ground and open hot wires
iv) Detection of hot/neutral reversals or neutral/ground reversals
After wiring test, a quick check of voltage and current measurements within the facility are to be to
Be taken for overloading, under and over voltage and unbalance problems detection. Signal also
used to check as follows;
i) Phase to ground voltages
ii) Phase to neutral voltages
iii) Neutral to ground voltages
iv) Phase to phase voltages
v) Phase currentsvi) Neutral currents
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Oscilloscope/Disturbance analyzersOscilloscope/Disturbance analyzers
Digital oscilloscope: data storage available for analysis i. e. energy calculation and spectrum analysis
Communication to pc for additional analysis using software.Over
Hand-held oscilloscope: Display waveform, performing signal processing, portable and permits
connection with PC for further data analysis.
Disturbance Analyzer: Disturbance analyzer and monitor measure a wide variety of systemdisturbances from short duration transients to long duration outage or undervoltage. Basically,
there are two types;
Conventional analyzers: Over voltage/under voltage magnitudes, sag and surge magnitude and
duration, transient magnitude and duration
Graphics-based analyzers:Display, save and print the actual waveform of the disturbances
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Oscilloscope/Disturbance analyzersOscilloscope/Disturbance analyzers
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Spectrum analyzers and harmonic analyzers
►FFT calculation for determining low order harmonics. There some important Capabilities of
this instrument:
i) Capability to measure both voltage and
current to get harmonic power flow information
ii) Capability to measure both magnitude and phase
angle of individual harmonic also to get powerflow information
iii) Synchronization and fast sampling to obtain
accurate harmonic component
iii) Capability to characterise nature of harmonic
distortion level
There are basically three types of instrument to
consider for harmonic analysisi) Simple meter ii) General purpose spectrum
analyser iii) Special purpose power system harmonic analyser.
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Flicker meter
►Flicker meter measures the level of flicker. The flicker evaluation level can be divided into two
Categories such as follows;
i) Short term Pst: Evaluation of flicker severity based on an observation period of 10 minute
Where the percentages P0.1, P1.0s, P3.0s, P10.0s and P50.0s are the flicker level that are exceeded0.1, 1.0, 3.0, 10,0 1nd 50.0 percent of time, respectively.
ii) Long term PLT: The long term variation flicker assessment of flicker severity is determined by
using PST equation
Where N is the number of PST reading and is determined by the duty cycle of flicker producing load
SSSSST PPPPPP5010311.0
08.028.00657.00525.00314.0 ++++=
N
P
P
N
i
ST
LT
∑== 1
3.
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IEC Flicker meter
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Flicker meter
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Summary of Monitoring Equipments CapabilitiesSummary of Monitoring Equipments Capabilities
Digital oscilloscope: data storage available for analysis i. e. energy calculation and spectrum analysis
Communication to pc for additional analysis using software.
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Assessment of PQ Measurement DataAssessment of PQ Measurement Data
Data assessment of PQ is meant by the data management, analysis, and interpretation function of
overall PQ monitoring efforts. As well as shifting off-line to on-line operation for automatic
problems identification.
There are two stream of power quality data assessment such as follows;
i) Off-line PQ data assessment: the off-line PQ data assessment is performed off-line i.e. it is
carried out separately from the monitoring instruments that is at the central processing
locations.
ii) On-line PQ data assessment: On-line data assessment is performed within instrument for
immediately information dissemination
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PQ Off PQ Off --line Data Assessmentline Data Assessment
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PQ OnPQ On--line Data Assessmentline Data Assessment
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PQ OnPQ On--line Data Assessmentline Data Assessment
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Application of Intelligent Systems
►The application of intelligent systems or
expert system in monitoring instrument help
engineer the system condition rapidly. Theimplementation of intelligent systems within
a monitoring Instrument can significantly
increase the value of monitoring application
since it generate information rather than just
collect data. Intelligent system module performto analyse capacitor switching transient and
determine the location of capacitor bank,
determine fault location etc.
Basic Design of an expert system for monitoringapplication
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Voltage Sag Direction Module
►An autonomous expert system module called voltage sag direction module is designed just for to
detect and identify of a voltage sag event and subsequently determine the origin (upstream/
downstream) of the voltage sag event. The module can displayed computer screen using web browser
Software, displayed printed paper format, or sent as an e-mail etc.
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Types of Intelligent PQ monitoring Systems
►There are many advance PQ monitoring system are equipped with off-line and on-line
intelligent systems to evaluate disturbances and system conditions so as make conclusionabout the cause of the problems before they occur. Out of many, the three types are
as follows.
i)Industrial PQ monitoring application
ii)Power system performance assessment and benchmarking
iii)System maintenance, operations and reliability applications
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Industrial PQ Monitoring Applications
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Power Sys. Perfm. Assessment and Benchmarking
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Application for System Main. Optn. and reliability
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PQ Monitor and the Internate
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Power Sys. Perfm. Assessment and Benchmarking