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Electric power quality is the degree to which the voltage, frequency, and waveform of a power supply system conform to established specifications. Good power quality can be defined as a steady supply voltage that stays within the prescribed range, steady AC frequency close to the rated value, and smooth voltage curve waveform. 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. The term is used to describe electric power that drives an electrical load and the load's ability to function properly. Without the proper power, an electrical device 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.
A power conditioner is a device intended to improve the quality of the power that is delivered to electrical load equipment. The term most often refers to a device that acts in one or more ways to deliver a voltage of the proper level and characteristics to enable load equipment to function properly. In some uses, power conditioner refers to a voltage regulator with at least one other function to improve power quality
A phasor measurement unit (PMU) is a device used to estimate the magnitude and phase angle of an electrical phasor quantity in the electricity grid using a common time source for synchronization. Time synchronization is usually provided by GPS or IEEE 1588 Precision Time Protocol, which allows synchronized real-time measurements of multiple remote points on the grid. PMUs are capable of capturing samples from a waveform in quick succession and reconstructing the phasor quantity, made up of an angle measurement and a magnitude measurement. The resulting measurement is known as a synchrophasor. These time synchronized measurements are important because if the grid’s supply and demand are not perfectly matched, frequency imbalances can cause stress on the grid, which is a potential cause for power outages.
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Dynamic voltage restoration (DVR) is a method of overcoming voltage sags and swells that occur in electrical power distribution. These are a problem because spikes consume power and sags reduce efficiency of some devices. DVR saves energy through voltage injections that can affect the phase and wave-shape of the power being supplied.
Power-line flicker is a visible change in brightness of a lamp due to rapid fluctuations in the voltage of the power supply. The voltage drop is generated over the source impedance of the grid by the changing load current of an equipment or facility. These fluctuations in time generate flicker. The effects can range from disturbance to epileptic attacks of photosensitive persons. Flicker may also affect sensitive electronic equipment such as television receivers or industrial processes relying on constant electrical power.
A unified power flow controller (UPFC) is an electrical device for providing fast-acting reactive power compensation on high-voltage electricity transmission networks. It uses a pair of three-phase controllable bridges to produce current that is injected into a transmission line using a series transformer. The controller can control active and reactive power flows in a transmission line.
FNET is a wide-area power system frequency measurement system. Using a type of phasor measurement unit (PMU) known as a frequency disturbance recorder (FDR), FNET/GridEye is able to measure the power system frequency, voltage, and angle very accurately. These measurements can then be used to study various power system phenomena, and may play an important role in the development of future smart grid technologies. The FNET/GridEye system is currently operated by the Power Information Technology Laboratory at the University of Tennessee (UTK) in Knoxville, Tennessee, and Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee.
A voltage sag or voltage dip is a short-duration reduction in the voltage of an electric power distribution system. It can be caused by high current demand such as inrush current or fault current elsewhere on the system.
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A Josephson voltage standard is a complex system that uses a superconducting integrated circuit chip operating at a temperature of 4 K to generate stable voltages that depend only on an applied frequency and fundamental constants. It is an intrinsic standard in the sense that it does not depend on any physical artifact. It is the most accurate method to generate or measure voltage and has been, since an international agreement in 1990, the basis for voltage standards around the world.
In electrical engineering, current sensing is any one of several techniques used to measure electric current. The measurement of current ranges from picoamps to tens of thousands of amperes. The selection of a current sensing method depends on requirements such as magnitude, accuracy, bandwidth, robustness, cost, isolation or size. The current value may be directly displayed by an instrument, or converted to digital form for use by a monitoring or control system.
Wide-area damping control (WADC) is a class of automatic control systems used to provide stability augmentation to modern electrical power systems known as smart grids. Actuation for the controller is provided via modulation of capable active or reactive power devices throughout the grid. Such actuators are most commonly previously-existing power system devices, such as high-voltage direct current (HVDC) transmission lines and static VAR compensators (SVCs) which serve primary purposes not directly related to the WADC application. However, damping may be achieved with the utilization of other devices installed with the express purpose of stability augmentation, including energy storage technologies. Wide-area instability of a large electrical grid unequipped with a WADC is the result of the loss of generator rotor synchronicity, and is typically envisioned as a generator oscillating with an undamped exponential trajectory as the result of insufficient damping torque.
In visual perception, flicker is a human-visible change in luminance of an illuminated surface or light source which can be due to fluctuations of the light source itself, or due to external causes such as due to rapid fluctuations in the voltage of the power supply or incompatibility with an external dimmer.
Power Quality Data Interchange Format (PQDIF) is a binary file format specified in IEEE Std. 1159.3 that is used to exchange voltage, current, power, and energy measurements between software applications with a focus on the power quality domain.
Conducted emissions are the effects in power quality that occur via electrical and magnetic coupling, electronic switch of semiconductor devices, which form a part of electromagnetic compatibility issues in electrical engineering. These affect the ability of all interconnected system devices in the electromagnetic environment, by restricting or limiting their intentional generation, propagation and reception of electromagnetic energy.
Low-frequency electromagnetic compatibility is a specific field in the domain of electromagnetic compatibility (EMC) and power quality (PQ), which deals with electromagnetic interference phenomena in the frequency range between 2 kHz and 150 kHz. It is a special frequency range because it does not fit in the PQ problems, with range of up to 2 kHz, where relative levels of voltage and current can have massive impact on efficiency and integrity of electric systems, and neither in the conducted EMC range, which starts at 150 kHz and influences mainly informational systems, and already too far from radiated EMC range, which starts at 30 MHz and goes up to 1 GHz.
References
- ↑ Barros, J.; de Apráiz, M.; Diego, R.I.; Gutiérrez, J.J.; Saiz, P.; Azcarate, I. (2017). "Minimum requirements for rapid voltage changes regulation based on their effect on flicker". 2017 IEEE International Workshop on Applied Measurements for Power Systems (AMPS). pp. 1–5. doi:10.1109/AMPS.2017.8078346. ISBN 978-1-5386-0343-7. S2CID 22581598.
- 1 2 Barros, Julio; Gutiérrez, Jose Julio; de Apráiz, Matilde; Saiz, Purificación; Diego, Ramón I.; Lazkano, Andoni (2016). "Rapid Voltage Changes in Power System Networks and Their Effect on Flicker". IEEE Transactions on Power Delivery. 31 (1): 262–270. doi:10.1109/TPWRD.2015.2452967. hdl: 10902/13664 . ISSN 1937-4208. S2CID 11804026.
- ↑ de Apraiz, M.; Barros, J.; Diego, R. I.; Gutiérrez, J. J.; Redondo, K.; Azcarate, I. (2014). "Detection and analysis of rapid voltage changes in power system networks". 2014 IEEE International Workshop on Applied Measurements for Power Systems Proceedings (AMPS). pp. 1–6. doi:10.1109/AMPS.2014.6947712. ISBN 978-1-4799-5643-2. S2CID 13007424.
- ↑ Schlabbach, J.; Blume, D.; Stephanblome, T. (2001-01-01). Voltage Quality in Electrical Power Systems. IET Digital Library. doi:10.1049/pbpo036e. ISBN 978-0-86341-982-9.
- ↑ Macii, David; Petri, Dario (2017). "On the detection of Rapid Voltage Change (RVC) events for power quality monitoring". 2017 IEEE International Instrumentation and Measurement Technology Conference (I2MTC). pp. 1–6. doi:10.1109/I2MTC.2017.7969783. ISBN 978-1-5090-3596-0. S2CID 24278710.