Power quality is increasingly becoming a key area of concern and is being widely regarded as a vital constituent of a well-developed power distribution segment. While issues associated with power quality are largely perceived as a problem related to the distribution system, these originate in power transmission systems as well. Power quality issues broadly include any fault in voltage, current, or frequency, which results in the failure or inefficient operation of equipment.
The several benefits of enhancing the quality of power supply include reduction in equipment and transmission and distribution (T&D) network losses, decrease in demand and demand charges, and improvement in the voltage profile, which ensure the proper functioning of various sophisticated equipment and devices.
Any change in the magnitude and shape of voltage and current can deteriorate the power quality. These changes can be caused by natural factors (lightning strikes, or stormy conditions), switching on and off of large loads, capacitor or feeder switching, transformer energisation, etc. Some common types of power quality problems are harmonic distortions, transients and imbalance in voltage and current, flickers, voltage sags and swells, and frequency excursions, as well as problems associated with reactive power.
Significance of power quality
Poor power quality has a deleterious impact on industrial operations. Power quality issues may lead to blocked capacity, increased capital investment, premature failure of equipment due to electrical and thermal stresses, unplanned outages, poor power factor and over-current surges.
The direct costs of power quality disturbances include equipment damage, loss of production, loss of raw material, salary costs during non-productive periods and restart costs. In addition, large industrial consumers with continuous processes like steel manufacturing incur additional costs on account of alternative power sources such as captive power plants. Meanwhile, small and medium consumers opt for power conditioning devices.
To ensure a reliable power supply, it is essential to minimise the duration and number of power cuts. The data on the duration and number of power cuts in a month shows significant variations across states. As per the data available on the URJA dashboard (the web portal for monitoring discom performance) for February 2017, the average duration of power cuts stands at 7.27 hours per month while the average number of power cuts in the country are 8.66 times per month.
State-wise, in February 2017, the best performing states with the minimum average duration of power cuts (hours per month) were West Bengal (1:16 hours per month), Andhra Pradesh (2:10 hours per month), Gujarat (3:07 hours per month), Chhattisgarh (3:24 hours per month) and Telangana (3:34 hours per month).
On the other hand, the top five states in terms of the average number of power cuts per month were Maharashtra (1.89 times), West Bengal (2.04 times), Rajasthan (2.46 times), Gujarat (4.65 times) and Andhra Pradesh (5.16 times).
Power quality issues are present in every power system. The ones that require immediate attention are reactive power and harmonic distortion. Harmonic currents increase the heat level in electrical cables, leading to premature ageing and overstressing of the electrical insulation. Meanwhile, though reactive power is essential for the functioning of any alternating current (AC) power system, it needs to be managed in order to reduce demand, improve voltage stability margins and reduce T&D network losses.
The adoption of technology solutions to tackle power quality issues is quite popular. For reactive power compensation, flexible AC transmission system devices – static var compensators (SVCs) and static synchronous compensators (STATCOMs) – are used. While SVCs improve power quality by enhancing transfer capability, reducing transmission losses, etc., STATCOMs also have a unique feature that is their maximum reactive power output is not affected by the voltage magnitude, even if system voltage drops significantly. Another popular device for managing reactive power is the shunt capacitor. It is inexpensive to install and maintain.
Meanwhile, in order to control the harmonics in the system, harmonic filters are deployed, which are divided into three broad categories – passive (require constant loading condition), active (provide harmonic mitigation under any load conditions) and hybrid (utilise the properties of both active and passive filters).
Another technology solution that helps in protecting the electrical system from spikes and electrical noise is the constant voltage transformer (CVT). CVTs help in voltage regulation and sag mitigation. They ensure that the iron core of the transformer’s secondary section is saturated, thus generating a constant voltage output. In addition to technology solutions, energy storage and distributed generation units enable uninterrupted power supply. Smart grids also play a vital role in reliable power supply. A smart grid that capture real-time load data, and has self-healing capabilities and resilient infrastructure can significantly improve power quality.
Gaps in regulatory provisions
A strong regulatory framework is required for tackling power quality issues. Broadly, at the central level, regulatory provisions such as the deviation settlement mechanism, the electricity grid code and availability-based tariff provide a framework for quality power. However, at the state level, there are considerable gaps in standards and their implementation. According to a report published by the Forum of Regulators, a major challenge is inconsistency in regulations. The voltage variations specified by a state do not match with the central sector regulations and regulations by other states. On the other hand, some states do not specify voltage variation limits. Besides, many states lack the appropriate regulations for controlling harmonics. Meanwhile, penalties on discoms for non-compliance with regulations are low. Further, few states have specified provisions and mechanisms for penalising consumers for dumping harmonics on to the licensee’s network.
Another area that requires attention is the lack of proper monitoring mechanisms to keep a check on the quality of power supply. In this regard, energy think tank Prayas Energy developed the Electricity Supply Monitoring Initiative in 2015, a technology tool using remote monitoring and internet of things, which allows regulators and utilities to check the quality of supply over a period.
To ensure quality power supply, various interventions are required for strengthening the regulatory framework. Most importantly, there is a need to bring consistency in standards across the country among central and state regulations, and align these with widely acceptable international norms. There is also a need to establish procedures for monitoring and managing all aspects of power quality – continuity of supply, voltage regulation and harmonics – for all voltage levels. At present, some of the existing regulations do specify voltage monitoring and management provisions but only at select voltage level. This needs to be extended to the sub-T&D substation levels. Besides this, power quality indices including voltage variation, neutral voltage variation, voltage imbalance, dips, swells, transient, interruption at point of supply and harmonics need to be considered while evaluating a discom’s standard of performance.
The way forward
Going forward, the proliferation of sensitive electronic devices and sophisticated automation equipment poses a threat to quality power supply. The increase in the use of control electrical equipment such as adjustable speed AC and direct current drives and uninterrupted power supply devices, and energy-efficient lighting cause huge changes in electric loads. LED lights without proper inbuilt filters cause harmonic pollution and also operate at a low load power factor. Besides, the influx of variable power from renewable energy sources has induced greater unpredictability in grid operations, leading to imbalance in the production and consumption of power in the system.
Therefore, measures such as reactive power compensation and harmonics filtering need serious attention. Undertaking cost analysis in adoption of technology solutions is essential to ensure quality power supply in a cost-efficient manner. Besides this, bridging gaps in the regulatory framework for quality power and the imposition of penalty for deviations in the quality of supply will be beneficial.