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- Power Quality Monitoring Analysis and Enhancement Part 15 pptx
Electric power quality , or simply power quality , involves voltage, frequency, and waveform. Good power quality can be defined as a steady supply voltage that stays within the prescribed range, steady a. In general, it is useful to consider power quality as the compatibility between what comes out of an electric outlet and the load that is plugged into it. Without the proper power, an electrical device or load may malfunction, fail prematurely or not operate at all.
There are many ways in which electric power can be of poor quality and many more causes of such poor quality power. The electric power industry comprises electricity generation AC power , electric power transmission and ultimately electric power distribution to an electricity meter located at the premises of the end user of the electric power.
The electricity then moves through the wiring system of the end user until it reaches the load. The complexity of the system to move electric energy from the point of production to the point of consumption combined with variations in weather, generation, demand and other factors provide many opportunities for the quality of supply to be compromised. While "power quality" is a convenient term for many, it is the quality of the voltage —rather than power or electric current —that is actually described by the term.
Power is simply the flow of energy and the current demanded by a load is largely uncontrollable. It is often useful to think of power quality as a compatibility problem: is the equipment connected to the grid compatible with the events on the grid, and is the power delivered by the grid, including the events, compatible with the equipment that is connected?
Power Quality Monitoring Provides Additional Value
Compatibility problems always have at least two solutions: in this case, either clean up the power, or make the equipment tougher. The tolerance of data-processing equipment to voltage variations is often characterized by the CBEMA curve , which give the duration and magnitude of voltage variations that can be tolerated.
Ideally, AC voltage is supplied by a utility as sinusoidal having an amplitude and frequency given by national standards in the case of mains or system specifications in the case of a power feed not directly attached to the mains with an impedance of zero ohms at all frequencies. Each of these power quality problems has a different cause.
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Some problems are a result of the shared infrastructure. For example, a fault on the network may cause a dip that will affect some customers; the higher the level of the fault, the greater the number affected.
Harmonic problems can be dealt with by a combination of good design practice and well proven reduction equipment. Power conditioning is modifying the power to improve its quality. An uninterruptible power supply can be used to switch off of mains power if there is a transient temporary condition on the line.
However, cheaper UPS units create poor-quality power themselves, akin to imposing a higher-frequency and lower- amplitude square wave atop the sine wave.
This remanufactured sine wave is of higher quality than the original AC power feed. A surge protector or simple capacitor or varistor can protect against most overvoltage conditions, while a lightning arrester protects against severe spikes. Electronic filters can remove harmonics. Modern systems use sensors called phasor measurement units PMU distributed throughout their network to monitor power quality and in some cases respond automatically to them. Using such smart grids features of rapid sensing and automated self healing of anomalies in the network promises to bring higher quality power and less downtime while simultaneously supporting power from intermittent power sources and distributed generation , which would if unchecked degrade power quality.
A power quality compression algorithm is an algorithm used in the analysis of power quality. In order to sufficiently monitor unforeseen events, Ribeiro et al. For instance, at a sampling rate of 32 samples per cycle, 1, samples are collected per second. For three-phase meters that measure both voltage and current waveforms, the data is times as much. More practical solutions developed in recent years store data only when an event occurs for example, when high levels of power system harmonics are detected or alternatively to store the RMS value of the electrical signals.
Nisenblat et al. This algorithm referred to as PQZip empowers a processor with a memory that is sufficient to store the waveform, under normal power conditions, over a long period of time, of at least a month, two months or even a year. The compression is performed in real time, as the signals are acquired; it calculates a compression decision before all the compressed data is received.
For instance should one parameter remain constant, and various others fluctuate, the compression decision retains only what is relevant from the constant data, and retains all the fluctuation data. It then decomposes the waveform of the power signal of numerous components, over various periods of the waveform. It concludes the process by compressing the values of at least some of these components over different periods, separately.
This real time compression algorithm, performed independent of the sampling, prevents data gaps and has a typical compression ratio. A typical function of a power analyzer is generation of data archive aggregated over given interval.
A significant archive sizes are created during an operation of such instrument. As Kraus et al. By using prediction and modeling on the stored time series in the actual power quality archive the efficiency of post processing compression is usually further improved. This combination of simplistic techniques implies savings in both data storage and data acquisition processes.
From Wikipedia, the free encyclopedia. Electric power systems: a conceptual introduction. Distributed photovoltaic grid transformers.
Power Quality Monitoring Analysis and Enhancement Part 15 pptx
Archived from the original on Retrieved IECON '01, vol. Dugan, Roger C. Wayne Beaty Electrical Power Systems Quality. McGraw-Hill Companies, Inc. Meier, Alexandra von Complete System Inspection 2. The parameters that will be recorded are kW demand, kVA demand, kVAR demand and maximum demand throughout the durations of the measurement.
The readings recorded are of average value. Results at the end of the measurement can be peak, minimum and maximum and average of the parameters. The parameters that will be recorded are Voltage and Current RMS value for each individual phase throughout the durations of the measurement.