The implementation of ABT was proving to be a successful tool for enforcing better grid discipline, also, as a way forward the commission and government was continuously taking various initiatives regarding better grid infrastructure. The ceiling rate has increased from 570 paise per kWh in 2002-03 to 745 paise per kWh in 2006-07 and finally to Rs. 10 per kWh in 2007-08 for the frequencies below 49.0 Hz or more precisely below 49.02 Hz. It is noted that the commission continued to raise the ceiling rate till 2007-08 while the permissible frequency range remained untouched. Figure 1 shows the UI rate variance with corresponding average grid frequency of three different years and it shows the year-wise changed picture of UI price vector.
ABT in 2008-09
Until 2007-08 the commission’s amendments regarding ABT hovered around changing the UI rates only while the permissible frequency range remained untouched. In the annual report of 2008-09, the commission reduced operable permissible frequency range to 49.2 – 50.3 Hz as against the 49 – 50.5 Hz earlier. Also, the ceiling UI rate was reduced to 735 paise per kWh at grid frequency of 49.2 Hz and below against the earlier UI rate 1000 paise per kWh at 49.0 Hz and below.
Table 6 shows the new UI rates and operable frequency band which replaced the old UI rates w.e.f. 1.04.2009, this year the commission released a separate UI regulation and showed that the sole objective of UI is to maintain grid discipline. Also, CERC’s tariff regulation exempted customers from the pressure of paying income tax on the amount of money received by UI charges.
ABT in 2010-11 to 2018-19
In the year 2010-11, the commission further reduced the operable frequency range from earlier 49.2 – 50.3 Hz to 49.5 to 50.2 Hz. Correspondingly, the payments for deviation from the schedule were also raised with a further penalty in the form of additional 40 percent UI charges for deviation when the frequency is below 49.5 Hz and an additional 100 percent UI charge when the frequency is below 49.2 Hz. In order to uphold stronger grid discipline, the new IEGC regulations of 2009 also prohibited the over-drawl of electricity from the grid when the frequency drops below 49.2 Hz.
Fig.1. UI rate vs. Grid Frequency for the year 2005-06, 2006-07.
The commission again stiffened the permissible operating frequency range from 49.5 – 50.2 Hz to 49.7 – 50.2 Hz w.e.f. 17-09-2012 with a view of improving grid frequency. The IEGC regulations were amended on 5 March 2012 and the revised UI charges are given in Table 7.
Fig.2. UI rate vs. Grid Frequency for the year 2011-12.
The commission also launched the provision of additional UI charges payable when the frequency is below 49.7 Hz, with additional UI charges ranging from 20 percent of UI charges to 49.5 Hz and rising up to 100 percent of UI charges for frequencies below 49.2 Hz for over drawing.
Frequency band has been further tightened from 49.7-50.2 Hz to 49.90 to 50.05 Hz w.e.f. 17.02.2014 by the CERC and the commission took a strict measure that any purchaser’s over-drawl / under-drawl of electricity during the time period shall not surpass 12% of its schedule draw or 150 MW, whichever is lower, whether the grid frequency is ‘49.70 Hz and above and below 50.10 Hz’ also, provided that no over-drawl of electricity is permitted by any purchaser when the grid frequency is “below 49.70 Hz” and no under-drawl of electricity by any purchaser is permitted when the grid frequency is “50.10 Hz and above”. This step can be suspected somewhere as an attempt to weaken the ABT from the tariff structure as the commission banned the over-drawl / under-drawl completely except for the limit given above and this step the obscured the presence of UI charges. Figure 2 is for the UI rate variation with average grid frequency as per the new amendments published in the 2011-12 annual report of CERC.
This article will be continued in the next issue as Part 3
B-Tech third-year student of Madan Mohan Malaviya University of Technology, Gorakhpur (U.P.) in Electrical Engineering
Dr. Prabhakar Tiwari
Associate Professor, Department of Electrical Engineering, Madan Mohan Malaviya University of Technology
Prof. S.N. Singh
Vice-Chancellor, Madan Mohan Malviya University of Technology, Gorakhpur