Download Introduction to Power Quality Monitoring

The BEST Group
THE BUFFALO ENERGY SCIENCE AND TECHNOLOGY GROUP
-Winter Lecture Series
Introduction to Power Quality Monitoring
Presented by:
Syed Khundmir T
Department of Electrical Engineering
University at Buffalo
[email protected]
Prime reference: Electrical Power Systems Quality By Roger C. Dugan, Mark F. McGranaghan, Surya Santoso, H. Wayne Beaty Introduc)on
•  Power Quality Monitoring (PQM) is the process of gathering, analyzing and interpre>ng raw measurement data into useful informa>on. •  PQM is o@en done to improve the system-­‐wide power quality performance. •  Data usually measured is the voltage and current but is not limited to these quan>>es. Objec)ves
•  Characterizing system performance •  Characterizing specific problems •  As part of an Enhanced Power Quality Service •  As part of Predic>ve or Just-­‐In-­‐Time Maintenance Monitoring as part of a facility site survey
•  Inspec>on of wiring and grounding concerns. •  Inspec>on of equipment connec>ons. •  Monitoring voltage and current characteris>cs throughout the facility. Determining what to monitor
•  To know what to monitor, characteriza>on of disturbances in the system is required. •  Extensive monitoring of all the different types of power quality varia>ons can be very expensive. Choosing Monitoring loca)ons
•  Cannot monitor at each and every point in the system. •  Can be expensive and hard to manage the data. •  Measurements at some strategic loca>ons should be done. Permanent power quality monitoring equipment
1.  Digital fault recorders (DFRs): •  It typically triggers on fault events and record the voltage and current waveforms that characterize the event. •  Helps in characterizing disturbances like voltage sags, during power system faults. •  Can also capture periodic waveform for calcula>ng harmonic distor>on levels. Smart relays and Intelligent Electronic Device
•  Recently, manufacturers of relays that monitor the current anyways are adding on the capability to record disturbances and make the informa>on available to an overall monitoring system controller. •  Loca>on can be at the feeder circuits as well as at the substa>on. Voltage recorders
•  A variety of voltage recorders are used to monitor voltage varia>ons on distribu>on systems. •  Typically, the voltage recorder provides a trend that gives maximum, minimum and average voltage with a resolu>on of less than 2seconds. In-­‐plant power monitors
•  Mostly located at the service entrance. •  Captures waveshape for evalua>on of harmonic distor>on levels, voltage profile for rms varia>ons and triggered waveshape captures for voltage sag condi>ons. •  May also posses capabili>es to have transient monitoring capabili>es. Special-­‐purpose power quality monitors
•  Were developed for the EPRI DPQ Project. •  Simultaneous voltage and current monitoring with triggering of all channels during a disturbance is an important capability of these instruments. Revenue meters: •  The revenue meters monitor the voltage and current and these days, many of the manufacturers are including advanced monitoring that could include recording of power quality informa>on. SeEng monitor thresholds
•  It is important to define the range of condi>ons that can be considered normal. •  Some of the monitors have preselected thresholds that can be used as a star>ng point. •  Whereas some of the monitors come with adjustable thresholds based on the equipment specifica>ons. Finding source of disturbance
•  First step to iden>fy source of a disturbance is to correlate the disturbance with possible causes. •  The general guidelines are: 1.  High-­‐frequency voltage varia>ons will be limited to loca>ons close to the source of the disturbance. 2.  Power interrup>ons close to the monitoring loca>on will cause a very abrupt change in the voltage whereas the ones far from it will result in decaying voltage. 3.  The highest harmonic voltage distor>on levels will occur close to capacitors causing resonance problems. Conclusion
•  Thus, the power quality monitoring can be effec>ve only when proper study is done about the objec>ve of the monitoring system and source of the problem. Only a@er these are known, we can move forward to decide the suitable point at which the monitors are to be connected and then assessment of the data is done.