The monitoring and measurement of power quality is one of the key requirements for ensuring a reliable supply of power. A number of power quality standards have been specified by the Central Electricity Authority (CEA) such as in the Grid Standards Regulations, 2010, the Technical Standards for Connectivity to the Grid Regulations, 2007 and also by the Central Electricity Regulatory Commission (CERC) in the Indian Electricity Grid Code Regulations, 2010. Other than these, the state electricity regulatory commissions (SERCs) have also issued relevant regulations. However, all these regulations are not comprehensive and hence lack key parameters/details pertaining to the standards for measurement, reporting and maintaining of power quality. To address these issues, the Forum of Regulators (FoR) has released a Report on Power Quality of Electricity Supply to the Consumers, which includes a draft model regulation on the key parameters for power quality monitoring.
Existing standards and regulations
The existing standards for power quality are broadly discussed under the regulations by the CEA, CERC as well as some SERCs. One of the applicable power quality regulations issued by the CEA is the Grid Standards Regulations, 2010, which specify the norms for operations and maintenance of transmission lines, the limits for voltage fluctuation and the limits for harmonics to be maintained across voltage levels. These are applicable to generating companies, transmission licensees, distribution licensees, bulk electricity consumers connected at the 33 kV voltage levels, load despatch centres and regional power committees. Another CEA regulation on power quality standards is the Technical Standards for Connectivity to the Grid Regulations, 2007. These lay down grid connectivity standards pertaining to voltage and current harmonics, and voltage unbalance and fluctuations for distribution systems and bulk consumers. The limits specified in the regulations are similar to the Institute of Electrical and Electronics Engineers’ (IEEE) 519-1992 standards. A draft second amendment to the regulations by the CEA proposes to revise the limits for voltage and current harmonics in line with the IEEE’s 519-2014 standards. The other changes proposed under the regulations include measurement of harmonics at the power control centre (which is the point in a power supply system electrically nearest to the load), installation of power quality meters by utilities within three years, and a continuous measurement of quality parameters for consumers with load more than the threshold limit. Further, the draft amendment proposes that the utilities should record and report in public the data pertaining to harmonics, voltage sag, and swells and disruptions on a monthly basis, and that consumers should submit the data as required. Another CEA regulation pertaining to power quality standards for distributed generation is the Technical Standards for Connectivity of the Distributed Generation Resources Regulations, 2013. These are applicable to generating stations feeding electricity directly into the grid at the 33 kV level or below. A draft amendment has been issued to among other things rename the regulations as the Technical Standards for Connectivity below 33 kV Regulations, 2018.
The CERC has described some important power quality norms under the Indian Electricity Grid Code Regulations, 2010. The regulations prescribe limits for voltage variation across different voltage levels, ranging from +5 per cent and -5 per cent (at the 765 kV and 400 kV levels) to +11 per cent and -10 per cent (at the 220 kV level). Apart from this, the electrotechnical division council of the Bureau of Indian Standards (BIS) has set up a technical committee, ET-45, to formulate power quality standards. The standards pertain to power quality indices and assessment methods, and measuring equipment. It is expected that other subject-related topics will be included by the committee.
FoR’s key recommendations for the formulation of power quality regulations
The grid code, the supply code and the standard of performance put in place by the SERCs mandate that the quality of power should be maintained; however, power quality parameters other than frequency and voltage interruptions have not been given due attention. Besides, these regulations do not specify a monitoring mechanism. Also, there is a lot of variation in power quality parameters specified by the different SERCs. The Report on Power Quality of Electricity Supply to the Consumers, released by a subgroup on power quality under the FoR, lays emphasis on the need for regulations on power quality, the necessary standards and limits, an incentive/disincentive mechanism and a procedure for monitoring, management and control of power quality. The subgroup has also suggested a draft model regulation on power quality.
One of the key recommendations of the subgroup is the adoption of the model regulations on power quality by the states. The model regulations include power quality indices, roles and responsibilities of various entities, the standards/ limits to be followed, the incentive/disincentive mechanism to be deployed and the procedure for monitoring, management and control of all aspects of power quality.
On the key power quality parameter front, the FoR report notes that harmonics distortions, voltage variations and flicker, voltage unbalance, voltage sags/ swells, and short and long supply interruptions are important factors. With regard to the monitoring of power quality parameters at the transmission and sub-transmission levels, the report recommends that for maintaining the power quality, the regulators should introduce appropriate reporting and incentive/disincentive mechanisms in their grid/supply codes or standards of performance regulations. On reporting of compliance, the report suggests that the information extracted from power quality meters on various power quality parameters should be reported in a standard format at regular intervals to the regulators.
Thus, in order to maintain the desired power quality, the adoption of a dedicated regulation on power quality at the SERC level is paramount. Furthermore, with large-scale integration of renewable energy sources and penetration of electric vehicles on the horizon, strict adherence to the power quality standards will be essential for ensuring a stable grid and reliable power supply.