Role of harmonics standards in reducing power quality problems in the grid by Ravichandran Purushothaman, President, Danfoss India Industries Pvt Ltd.
The term harmonics for decades has been a terminology or a buzz word, making many people reconsider the effectiveness of their building’s wiring system. But over the years, it has shaped new meanings. The presence of harmonics in electrical systems means that the current and voltage are distorted and deviate from sinusoidal waveforms. Harmonics have short and long-term effects on grids, grid connected electronics and power electronics equipment such as malfunction, failure and losses. These reduce reliability, lifetime and efficiency of the electricity networks. Harmonics can also cause overloading of conductors and transformers and overheating of utilisation equipment, such as motors. Harmonic frequencies in the power grid are a frequent cause of power quality problems, and reduction of harmonics optimises productivity, thus, increasing efficiency. Harmonics in power systems result in increased heating in the equipment and conductors, misfiring in variable speed drives, and torque pulsations in motors. Harmonics can also have detrimental effects on transformers, cables, fuses, circuit breakers, lighting, etc. However, technology development has kept pace with demands of the power sector in the country. Technology such as advanced active filters are now available which can lead to reduction in grid harmonic pollution and hence clean grids.
How to diagnose and fix harmonics:
One needs to first detect and recognise harmonics in the system. Once you’ve recognised that harmonics exist in a circuit or electrical system, the next step is to carry out tests to determine the magnitude and type of harmonics. If there are huge harmonic components present, one should first learn what the electrical system is carrying on its lines. To do this, it is a must to use harmonic measurement meters.
A harmonics analyser is the most effective instrument for performing a detailed analysis of power quality to determine the wave shapes of voltage and current on respective frequency spectrums. A harmonics analyser is also useful in instances where the lack of obvious symptoms prevents you from determining if harmonics are a cause for concern. A harmonics analyser is used to provide a detailed analysis of the suspect source. We need convincing graphics and quantitative evidence along with an authoritative reference.
Using an oscilloscope:
Oscilloscopes have traditionally been used to troubleshoot electronic and electrical circuits. The digital storage-style scopes, in addition to performing their traditional functions, have the capability to acquire and store signals and perform mathematical operations for determining frequency characteristics. These units collect and store the waveform data using voltage and current probes. This data then is downloaded into computers and synthesised to determine the waveform frequency characteristics.
Reducing harmonics to curb carbon footprint
A poor power grid system can have significant economic and technical consequences for a facility. If harmonics are not suitably addressed, it will create losses which could be minimal at the beginning, but will increase as the load factors and other variables increase. This will create efficiency losses thereby increasing the overall load requirements. By addressing harmonics effectively, we can avoid overloading electrical systems, reducing losses and power demand, and increasing the equipment lifetime. When we look at the cyclical nature of investments, we can see that by investing in mitigating harmonics we have avoided many other investments which would have added to the cost and footprint. Thus, by examining harmonic voltage and current data, you can get important information about the operating characteristics of a power system and work towards its mitigation.
Any electrical system’s reliability and normal operation of the equipment relies profoundly upon a clean distortion-free power supply. It is hoped that harmonic mitigation techniques if used wisely, will provide useful information to help make selection of an appropriate harmonic reduction method for a given application an easier task.