Introduction to Electric Power Quality
– Electric power quality refers to the ability of electric power to properly drive an electrical load.
– Poor power quality can cause malfunctions, premature failures, or complete non-operation of electrical devices.
– The electric power industry includes electricity generation, transmission, and distribution to end users.
– Various factors, such as weather, generation, demand, and system complexity, can compromise the quality of power supply.
– Power quality can be seen as a compatibility issue between the grid and the connected equipment.
Parameters and Deviations in Power Quality
– Continuity of service is important to avoid voltage drops or overages that can lead to blackouts or brownouts.
– Variation in voltage magnitude is a key parameter of power quality.
– Transient voltages and currents can affect the performance of electrical devices.
– Harmonic content in AC power waveforms is another aspect of power quality.
– Real-life power sources can deviate from ideal conditions in several ways.
– Voltage variations, both in peak and RMS, are significant for different types of equipment.
– Swells and dips in voltage can occur, causing temporary deviations from the nominal voltage.
– Random or repetitive variations in voltage can lead to flickering in lighting equipment.
– Spikes or surges in voltage can be caused by inductive loads or lightning.
Frequency-related Issues
– Variations in the frequency of power supply can impact its quality.
– Nonzero low-frequency impedance can cause voltage drops when a load demands more power.
– Nonzero high-frequency impedance can result in voltage dips or spikes due to sudden changes in load demand.
– Harmonics at lower frequencies and interharmonics at higher frequencies can affect the waveform of power supply.
– Distortions in voltage and current waveforms, referred to as harmonics, can be caused by generators and loads.
Power Conditioning Solutions
– Power conditioning involves modifying power to improve its quality.
– Uninterruptible power supplies (UPS) can switch to battery power during transient conditions.
– High-quality UPS units utilize double conversion topology to remanufacture a higher-quality AC sine wave.
– Dynamic voltage regulators (DVR) and static synchronous series compensators (SSSC) are used for series voltage-sag compensation.
– Surge protectors, capacitors, varistors, and lightning arresters can protect against overvoltage and spikes.
– Electronic filters can remove harmonics from the power supply.
Importance of Monitoring Power Quality and Standards
– Monitoring power quality is essential for providing high-quality electric power service.
– It helps to understand the factors leading up to unforeseen events such as power outages and blackouts.
– Monitoring is particularly critical in institutions where public safety is at risk, such as hospitals, sewage treatment plants, and mines.
– It allows utilities to constantly monitor waveforms and currents at various network locations.
– Monitoring power quality helps to ensure the reliability and stability of the electrical power network.
– EN50160 is the European standard for power quality, defining acceptable limits of distortion for voltage parameters.
– IEEE-519 is the North American guideline for power systems, addressing both voltage and current distortion.
– IEC 61000-4-30 is the standard defining methods for monitoring power quality, including current measurements.
– These standards and their local derivatives are adopted by different countries.
– Compliance with these standards ensures the quality and reliability of electricity supplied. Source: https://en.wikipedia.org/wiki/Electric_power_quality
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 (which resembles a sine wave). 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 (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.
