Ensuring grid discipline

Grid frequency indicates the over- or undergeneration of electrical power, and deviations therein signify an unstable power system network. Therefore, grid discipline has a crucial role to play in ensuring grid stability.

Before the introduction of availability-based tariff (ABT) in 2002, power generators and state electricity boards pumped in and withdrew power from the grid in an unregulated manner, causing large frequency fluctuations. A three-part tariff (capacity charge, energy charge and unscheduled power interchange) scheme, ABT aimed at maintaining grid discipline through incentives and disincentives during unscheduled power interchange (UI). It also helped in tightening the normal operating grid frequency range to 49.5 Hz-50.2 Hz.

However, even after the introduction of the UI mechanism, distribution utilities continued to draw excess power from the grid to meet consumer demand and overlooked the need to plan for sufficient generation. Similarly, generation utilities resorted to either underinjection or overinjection of power, deviating from their schedules. Both distribution and generation utilities used the UI platform as a de facto trading platform, leading to massive frequency excursions and eventually some big grid failures in 2012.

Thus, in 2014, the Central Electricity Regulatory Commission (CERC) brought in the deviation settlement mechanism (DSM) regulations for improving grid discipline and security. Under DSM, strict volume limits for overdrawal/underdrawal and over/underinjection of electricity were set, and additional deviation charges were introduced for any breach. The operational frequency band was also tightened further (to 49.7-50.1 Hz), and the deviation charges payable were revised, keeping in mind the improved frequency profile of the grid.

While the DSM regulations have helped in maintaining grid balance and stability, with the increased penetration of variable renewable energy, accurate forecasting and scheduling have become crucial. This should be complemented by capacity building and training of power system operators and technical staff on new technologies and developments in the forecasting and scheduling space. Since electricity is a concurrent subject, each state has set its own targets/deviation charges under DSM. However, bringing in uniformity across states on penalties and incentives related to DSM regulations can enable consistency in implementation.

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