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1. What are Harmonics?
Harmonics are currents, usually in multiples of the supply fundamental frequency, produced by non- linear loads such as the AC to DC power conversion circuits. For example, on a 50Hz supply, the 5 th harmonic is 250Hz, 7 th Harmonics is 350 Hz etc. These are called “integer harmonics – ie, exact multiples of the supply frequency. These power conversion circuits draw only short pulses of current from supply network and combine with the source impedance resulting in distortion of the supply voltage. |
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2. What happens to the fundamental frequency's sinusoidal waveform when harmonics are present?
The fundamental frequency's sinusoidal waveform which is always predominant becomes distorted by the addition of harmonic sinusoidal waveforms. The measure of distortion is given as Percent Total Harmonic Distortion of the Fundamental Waveform ( % THDv [voltage] & THDi [current] ). |
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3. What causes harmonic currents?
Non linear loads are the source if harmonic currents. All electronic loads generate positive and negative sequence harmonic currents. Single phase electronic loads, connected phase- neutral in a three phase, four-wire distribution system, also generate zero sequence harmonic currents. That is, the load's current waveform is non-sinusoidal. As a result, the distorted current waveform is rich in sinusoidal harmonic current waveforms. |
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4. What causes harmonic voltages?
The electrical distribution system's harmonic impedances cause the load generated harmonic currents to produce harmonic voltages (E H = I H x Z H ) transformers, and feeder and branch circuit impedances will cause maximum voltage distortion at the nonlinear loads. |
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5. What type of equipment generates harmonics?
Single phase:
• Computers, fax machines, photocopier, UPSs, TVs, VCRs etc
• Lighting dimmers and electronic ballasts for high efficiency lighting
• Single phase AC DC drives Three phase:
• Variable sped AC & DC drives
• UPS systems
• Arc furnaces
• Battery chargers
• In fact any single or three phase electrical power conversion equipment which converts AC to DC. |
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6. What hazards are created by Harmonics?
• Amplification of harmonic levels resulting from series and parallel resonance.
• Ageing of the installation of electrical plant components and as a consequence the shortening of their useful life.
• Plant mal -operation.
• Malfunctioning and failure of electronic components.
• Overheating and failure of electric motors.
• Overloading, overheating and failure of power factor correction capacitors. Resonance due to interaction of capacitors with harmonics.
• Overloading and overheating of distribution transformers and neutral conductors.
• Excessive measurement errors in metering equipments.
• Spurious operation of fuses, circuit breakers and other protective equipments.
• Voltage glitches in computer systems results in lost data.
• Electromagnetic interference with TV, radio, communication and telephone systems.
• Damage and disruption to standby generators and associated AVR control equipments. |
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7. Is there really a harmonics problem?
Yes, there is a problem. In fact, there ate so many significant harmonics problems that hundreds, if not thousands of thesis, papers, articles and case studies have been published on this subject. To define and limit harmonic problems , IEEE has published a standard entitled – “Recommended practices and requirements for Harmonic Control in Electrical Power Systems “(ANSI/IEEE Std 519- 1992). |
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8. Is there really a harmonics problem?
Yes, there is a problem. In fact, there ate so many significant harmonics problems that hundreds, if not thousands of thesis, papers, articles and case studies have been published on this subject. To define and limit harmonic problems , IEEE has published a standard entitled – “Recommended practices and requirements for Harmonic Control in Electrical Power Systems “(ANSI/IEEE Std 519- 1992). |
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9. What will happen if the harmonic problems are not solved?
• Higher power cost
• Premature office equipment failure
• Data Corruption or Loss
• Computer and system lock-ups
• Loss of productivity
• Higher coast for products and/or services
• Reduced product and or service quality
• Reduced quality assurance
• Loss of Customer Confidence
• Loss of revenue |
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10. Are there any signs / indications other than measuring, to indicate I could have a Harmonic problem?
Signs indicating a serious harmonic problem include the premature failing of electric motors and transformers, cables overheating, spurious tripping of protection devices and loss or corruption of computer data. ( See FAQ – 6 for more comprehensive list) |
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11. Would doing nothing be an option?
Not addressing the problem can lead to unnecessary and costly disruptions in production and equipment failure , even ending in causing a fire. Addressing the problem can sometimes expensive, but it usually ends up being the least expensive option. |
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12. What options do I have to improve the harmonic Distortion levels?
Methods of harmonic mitigation include:
• Passive filters
• Active filters |
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13. What is passive filter?
Passive filter are series capacitor and reactor resonant circuits “tunes “ to present a low impedance path to a specific frequency ( ie, 5th - 205 Hz , 7th – 350 Hz) They are more commonly used at the PCC to prevent harmonics “escaping” in to the utility power supply, but can be connected to individual loads in the plant. Due topossible system resonance and interaction problems, a harmonic study of the power system is often necessary. |
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14. What are the disadvantages of passive filters?
• The source impedance strongly affects filtering characteristics.
• As both harmonic and fundamental components flow in to filter, the filter must be rated by taking in to account of both.
• When the harmonic current component increases, the filter can be overloaded
• Parallel resonance between the power system and the passive filter causes amplification of harmonic currents on the source side at a specific frequency.
• The passive filters may fall in to series resonance with the power system so that voltage distortion produces excessive harmonic currents flowing into the passive filters. |
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15. What is an active filter and how does it works?
Parallel (shunt) active filters are most technically advanced and effective recognized solution to current and reactive power compensation of non linear loads. The principle ofoperation of active filters is based on the current harmonics required by the load. The active filters inject anti- phase harmonics that add to and so cancel the offendingharmonics. An advanced digital single processor uses inputs from current transformers to measure the magnitude and phase angle of the harmonic currents. IGBTs andreactors reproduce an equal but opposite harmonic current that is then injected back into the system to give a resultant “cleaner” wave form. |
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16. What is the basic principle of the STATCOM –H filter?
The STATCOM –H filter continuously monitors the harmonic current demanded by the load and generates and adaptive wave form, which matches exactly the shape of anon linear portion of the load current. It injects this adaptive current into the load at the point of connection. Only fundamental (50Hz) current is drawn for the source by theload. The STATCOM-H filter compensates from the 2nd to the 13th harmonics in a response time less than 100 microseconds. |
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17. Is it possible to achieve unity power factor by capacitor banks for non-linear loads?
No it is not possible. If only non linear loads are used there is an increase in harmonic current, which result in the failure of capacitor banks. |
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18. Is there a solution to the problems caused by harmonics?
Yes there is a solution. The reduction of harmonic current will solve all of the harmonic related problems. The solutions offered by HYKON are given below: |
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| Power Quality Issues |
Hykon Power Quality Products |
Benefits |
| Harmonics |
STATCOM-H
Harmonic Compensation |
1. Harmonic current filtering in compliance with IEEE 519.
2. Avoided damage of equipments. |
| Power Factor |
STATCOM-P Power Factor correction |
1.Maintains Grid Power Factor near unity
2.Brings down Maximum Demand (MD- KVA) |
| Harmonics, Power Factor |
STATCOM-HP Harmonic Compensation & Power Factor Correction |
1. Harmonic current filtering in compliance with IEEE 519
2.Maintains Grid Power Factor near unity
3.Brings down Maximum Demand (MD- KVA) |
Power Factor, voltage
sags / swells, voltage
interruptions, Over
voltage, Under voltage |
UPQC Unified Power Quality Conditioner |
1. Regulates load voltage against sag / swell and other voltage fluctuations.
2. Individual phase compensation of the load voltages to eliminate
voltage unbalance.
3. Reactive current filtering by STATCOM.
4. Maintains Grid Power Factor near unity.
5. Brings down Maximum Demand (MD- KVA).
6. Uninterrupted production and supply. |
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19. Which model should I select?
After conducting the power quality audit, priority is given for both harmonics and power factor. If only harmonic compensation is required you can choose HYKON STATCOM –H. if only power factor correction is required you can choose HYKON STATCOM –HP. |
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20. What are the advantages of bringing in the power factor to unity?
Maintaining the grid power factor near to unity brings own Maximum Demand (MD). The electricity power compensation will be less. |
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21. Why should I choose STATCOM series over other options?
STATCOM series are the most technically advanced and effective solution or power factor correction and in reducing the total harmonic current distortion to below 5%, in line with IEEE 519 – 1992 harmonics standards.The STATCOM series has the following features :
• IGBT PWM voltage source converter technology with DSP based digital controller.
• Novel control strategy for reactive power compensation of highly fluctuating loads.
• Maintain grid power factor near to unity and brings down Maximum Demand(MD)
• Harmonic current filtering in compliance with IEEE 519 – 1992.
• Advanced control strategy to realize simultaneous filtering of different harmonics
• Programmable task priorities for power factor correction and harmonic filtering.
• No overloading of the system
• Response time ~ 100 micro seconds
• Especially suitable for dynamic loads
• Easy to install, operate and maintain. |
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22. How would I select the correct STATCOM for my requirements?
To apply, a STATCOM selection process must be performed. For assistance sizing a STATCOM please contact us. HYKON offer full HARMONIC SURVEYS, where yoursite is visited, measurements taken and results reported. To receive quotations please contact us.
Send one line diagram indicating:
• Number of loads
• Type of loads
• Redundancy
• Source impedance |
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23. What will happen in case if STATCOM fails?
STATCOM is an active shunt filter connected in parallel to the grid. Ion case of any failure, it will not affect the grid and the loads connected to it. |
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24. Is the STATCOM difficult to install?
No. Because the STATCOM is a Shunt device. The STATOM required 4 power cables (3 phase 4 wires). The power cables required to be sized according to the total currentinjected by the STATCOM. |
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25. Does the STATCOM need much on going service and maintenance?
No. Depending up on the environment that the HYKON STATCOM is located only preventive maintenance would be required and that involves ensuring the door and internalfans are fully operational and that all filters are free of dust and not blocked. |
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26. Where can I find technical data on the STATCOM?
The technical data is different for each rating but we do produce a technical data sheet for each rating and configuration. Please ask. |
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27. Whether HYKON STATCOM technology is street proven?
Yes. Two numbers of 500 KVR STATCOM is installed and working perfectly in a steel industry. 3 nos of 150KVR STATCOM is working in a Latex industry. Bothinstallations are in South India. |
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28. Is the technology is developed by HYKON?
The technology is transferred from CDAC – which is a project supported by Dept of IT, Ministry of Communication and Information Technology, Govt. of India andmanufactured at HYKON. |
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29. What services and support do you offer for your products?
Because the STATCOM is a parallel device and is therefore not mission critical, we do supply a full service and support facility. |
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30.My question is not on the list – how can I get an answer to my query?
Please go to our FAQ form. We will answer your questions directly as quickly as possible. |
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