Quality of power
The objective of the power quality standards is to ensure reliable and quality power to the electricity consumers. The Electricity Act 2003 has enshrined the basic need of consumers to be provided with continuous, reliable and quality supply by the distribution utilities. India is the fourth largest consumer of electricity in the world but in spite of being one of the leaders both in electricity generation and consumption; it is facing major issues related to power quality. The issue of power quality remained largely ignored in the electricity supply industry of India. There are many reasons like huge gap between demand and supply just a decade back, lack of awareness and capacity to understand issues and challenges associated with quality of power, restricted availability of technology in detecting and overcoming such challenges.
Power quality is drawing increasing attention due to the heavy penetration of power electronics-based loads in every walk of our lives. Power quality parameters like frequency, voltage quality (interruptions, variations, unbalances, flicker, sags, and swells), harmonics and power factor are key matrices/indicators for defining a good power quality environment. Poor quality of power lead to premature failure or reduced/degraded performance of equipment.
At present, a few parameters related to power quality are covered under the Central Electricity Authority (CEA) and SERCs Regulations. The grid code, supply code and standard of performance laid by various SERCs do mandate the quality of power to be maintained. The State Regulations, when dealing with the aspect of power quality through supply code/grid code or standards of performance are not harmonious across different States and does not cover all aspects of power quality. Even there are lot of variations in similar power quality parameters specified by different SERCs. Business and the economy in digital era also depend upon reliable and quality power supply. So far, the focus of the sector was limited to providing uninterrupted power supply to consumers. This was understandable at the time of deficit when the limited supply of power was available to meet peak demand and the expectation of end consumers was availability of power supply. But now India has become one of the surplus power country, thus, the quality power supply becomes the priority.
What is power quality?
The reliability and quality are two important aspects of any electrical power supply system. Power reliability means availability of power supply 24x7, which constitutes adequacy of electrical system at all levels from generation, transmission to distribution. However, power quality refers to both the extent of deviation or distortion in pure supply waveform and the continuity of supply. Any significant deviation in the magnitude, frequency, waveform or symmetry of line voltages is a potential power quality problem.
Typical electrical loads, such as lighting, heating, and motor, are less sensitive to variations in the supply voltage, and more sensitive to availability (free from interruptions) of supply. However, electronic/digital equipment is more sensitive to variations in supply voltages. Characteristics that affect power quality are voltage fluctuation, harmonic distortion, voltage unbalance, flicker, supply interruptions, voltage sags, voltage swells and transients, etc.
Need of quality power
The devices and equipment used presently in industrial, commercial and domestic facilities are more sensitive to supply variations than equipment used in the past. It is due to increased use of power electronics and microprocessor-based technologies in equipment and appliances.
In India, various sectors are prone to both generation of higher power quality pollution as well as susceptible to power quality disturbances. The losses due to power quality issues are economic as well as technical. Both utilities as well as consumers are heavily impacted due to the techno-economic losses arising out of poor power quality. Poor power quality not only causes performance degradation and premature failure of electrical equipment but also results in increased system losses, financial loss, etc. Therefore, apart from the reliability i.e. continuous supply, the preference of the electricity consumers is shifting towards quality power supply from the distribution licensees. Optimum power quality can enhance productivity and reduce losses.
Power quality parameters
The standards for voltage and other technical criteria are there which can be used to measure power quality. Parameters affecting power quality can be divided into two categories, i.e. Steady-state (or continuous) and disturbances. Steady-state power quality parameters include harmonics (waveform distortion), frequency deviation, voltage unbalance, voltage fluctuations and flicker. Disturbances include outages, momentary interruptions, momentary or transient overvoltage or surges, voltage dips and voltage swell.
The existing regulations cover the power factor, frequency, reliability of supply and voltage regulations as power quality parameters. While there is a strong system of frequency regulation, enforcement of the standards specified for reliability parameters are required to be strictly monitored and implemented. Issues of voltage regulations, transients, and harmonics are not given the attention they deserve.
March 2019 issue of Electrical India. Article authored by Ashok Upadhyay, Dy. Director (Generation), M.P. Electricity Regulatory Commission, Bhopal.
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