Frequently Asked Questions (Power Quality)

Power quality means different things to different people, but it is generally an all-encompassing term used to describe the consistency and desirable characteristics, or lack thereof, of electrical power from its generation, delivery and usage. In nearly all cases, power quality is 

For most people, power quality problems are anything related to electric power that interferes with the proper operation of their electrical devices. There are numerous specific types of power quality problems, each with its ow

The causes of poor power quality run the gamut from squirrels or hot summer days to the failure of equipment on the electric utility’s system. Some causes can be corrected or eliminated while many others are out of anyone’s control, at any price.

In simple terms, harmonics are extra frequencies that when present in an electrical circuit, distort the AC sine wave. A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency. For example, if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. Harmonic frequencies are equally spaced by the width of the fundamental frequency and can be found by repeatedly adding that frequency. In the case of the U.A.E. electricity supply, the fundamental frequency is 50Hz. The frequencies of the harmonics are 100Hz, 150Hz, 200Hz, 250Hz, 300Hz, 350Hz and so on.150Hz is called the ‘third’ harmonic (3 x 50Hz), 250Hz is called the ‘fifth’ harmonic (5 x 50Hz), etc. The presence of harmonics in an electrical system distorts the clean shape of a sine wave.

If you occasionally experience some unexplained occurrences such as flickering lights, alarms going off, or MCB’s, MCCB’s, RCD’s and Earth Leakage devices tripping for no apparent reason, you are most likely experiencing harmonics in your electrical environment. Other signs are cables running hot, hot switchboards or overheating motors. If you are replacing your motor’s bearings & insulation often, that’s a strong indication of the presence of harmonics.

Harmonics are very harmful within an electrical system and can have serious consequences. For example, the presence of harmonics reduces the life of the equipment. It is possible that the investment that you made in your motors & drives will not be realised if they are damaged and need replacing before their expected life span. This can be very expensive. Harmonics cause things to run hot, which cause stress on the cables and equipment. In the long term, this degrades an electrical system. The presence of harmonics will also mean that although you will get billed for the power that you are supplied; a large percentage of that power may be unusable. Harmonic mitigation is acting to minimise the presence of harmonics in your electrical system and can achieve grea

There are five different types of solutions to attenuate harmonics: (1) Smoothing the flow: reactors and chokes, (2) Cancel out the problem: 12-pulse drives, (3) The low-cost option: passive filters, (4) Measure and counteract: active filters and (5) Swap out the source: low harmonic drive. Each of these harmonic mitigation solutions has advantages and disadvantages. When choosing, you need to consider the application and factors of compactness, simplicity, harmonic mitigation effectiveness, energy efficiency, and overall value for the money. For more information on this topic, please contact Emicon. Email: Admin@emiconconsultants.net

(1.) A professional consultant (act as the third party) would conduct a detailed study on the project electrical scheme, switchgear, power quality issues and the analysis and solutions recommendations would be based on the international standards, local authority’s regulations and would represent the interests of the client in an independent and honest manner whereas switchgear sales staff are not independently representing the interests of the project owner and authority requirements. (2.) Consultants would only recommend solutions and materials with specifications and procurement advice to the client, whereas switchgear sales staff may have sales targets.

(1.) The resonance frequency must be chosen correctly according to the harmonic analysis of the system (2.) The voltage across the terminals of the capacitor will increase because of the inductive reaction of the reactor. The rated voltage of the capacitors must be chosen according to the resonance frequency. (3.) In detuned power factor correction systems, the presence of higher voltage rated capacitors and reactors causes a difference between rated capacitor power and obtained reactive power. The obtained power must be calculated to avoid low compensation (4.) The reactors will generate extensive heat due to the heavy harmonic load on them. The cabinets must be designed to disperse this heat.

Active Harmonic filters use IGBT fired circuits to mitigate harmonic distortions in the load or the network of loads where they are installed. The advanced AHF system is constructed of one or several filter modules with a system controller. AHF eliminate harmonic injected into the mains supply by non-linear loads. Its response time is extremely fast and is connected in parallel to the load which is to be compensated. Current harmonic elimination is achieved by sensing load current & extracting harmonic current signal. This and the reactive current signal together are used to generate a reference for the controlled current source connected at the PCC (point of common connection) of source and load. These results in Mains supplying only real power for the load and reactive & harmonics being sourced from the AHF. This is carried out dynamically so that any change in the load pattern or its nature is immediately responded to without any manual intervention.

Active Harmonic filters are connected in parallel with the loads to be compensated. They measure the current of the non-linear load and inject the same harmonics, but with opposite phase angle. The current of the active harmonic filter thus cancels out the harmonic currents of the load, and only the fundamental frequency current component is left to be supplied from the power system. In addition to current and voltage profile smoothing by harmonic current mitigation, the active filters also provide fast fundamental frequency reactive power compensation and balance loads in three-phase systems. Reactive power compensation stabilizes voltage, mitigates flicker, releases additional capacity for transferring more active power in the existing electrical network and improves the power factor. Fast response to reactive power changes is important, for example, in electric arc furnaces. A typical case where load balancing is needed is a phase-to-phase connected welding equipment that burdens only two of the three lines and can thus create voltage unbalance between the phases.

Benefits are: (1.) The Filter Capacity can be easily expanded at the site by adding extra Filter Modules (2.) The AHF System is constructed of one or several Filter Modules with Advance Controller (3) IGBT Paralleling Technology is used with intelligent air cooling arrangement (4) Compensates a wide range of Harmonics from 2nd order to 50th order Harmonics (5) Widely used in Data Centers, IT Industries and process industries such as Cement, Metal, Chemicals and Pharmaceuticals etc. (6) Ensures the Total Current Harmonic Distortion less than 5%. (7) Reduce Power Losses in cables and other components to improve the reliability of Cables, switchgear etc. (8) User-friendly controller with communication option. Compact Design with Modular concept (9) Can be easily configured with Real-Time Power Factor Correction System to form Hybrid Configuration. (10) Follows IEEE Standards to mitigate the Harmonics in the electrical distribution system. (11) Compatible with DG (12) Fast Return on investment in terms of Savings.

Electromagnetic compatibility (EMC) is the branch of electrical engineering concerned with the unintentional generation, propagation and reception of electromagnetic energy which may cause unwanted effects such as electromagnetic interference (EMI) or even physical damage in operational equipment. Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.

An EMC problem (or Electromagnetic Compatibility problem) occurs when one piece of electronic equipment or an electromagnetic system has adversely affected the operation of another. One example might be a breakthrough by the high field strengths produced by a nearby radio transmitter. EMC problems are not always due to defects in the transmitter, and so do not necessarily require improvements in the radio transmitter design, such as reducing its radiated harmonics. It may be that the immunity of the affected equipment is poor due to inadequate shielding, or filtering of sensitive inputs. EMC problems can have a range of effects on equipment, and there are ways to mitigate or eliminate them in practice. Effective EMC mitigation techniques may differ by the type of equipment that malfunctions, and by the nature of the strong radiofrequency field.

Electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. Shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. Electromagnetic shielding that blocks radiofrequency electromagnetic radiation is also known as RF shielding.

Active Harmonic Filters (AHF) are parallel filters (which means the current does not go through the filter) that are used to reduce or mitigate, harmonics to tolerable levels as defined by IEEE-519. Active Harmonic Filters (AHF) are easy to install and cannot be overloaded. When required harmonic compensation exceeds capacity, the AHF will simply supply its maximum continuously. Multiple units can be connected in parallel to increase compensation. Active filters can work with multiple drives; when the active filter reaches its limit, it will not overload. In addition, if an active filter breaks, it will not stop the motor or load (since the current is not going through the filter); it just will not filter the current wave.