Availability-based tariff

Availability-based tariff (ABT) is a frequency based pricing mechanism applicable in India for unscheduled electric power transactions. The ABT falls under electricity market mechanisms to charge and regulate power to achieve short term and long term network stability as well as incentives and dis-incentives to grid participants against deviations in committed supplies as the case may be.

Availability-based tariff (ABT) is a frequency based pricing mechanism applicable in India for unscheduled electric power transactions. The ABT falls under electricity market mechanisms to charge and regulate power to achieve short term and long term network stability as well as incentives and dis-incentives to grid participants against deviations in committed supplies as the case may be.

ABT drawbacks

As per DSM / UI procedure, the incentives and penalty to the grid participants are charged based on the average grid frequency in a time block of 15 minutes duration. During a time block, it is normal that frequency goes above rated 50 Hz frequency and comes down below rated frequency as the number of frequency excursions above 50 Hz are more than 100 in a day. Thus the average frequency in a time block remains close to the 50 Hz without giving much benefit in the applicable UI tariff for a distribution company who is consuming the surplus power available in the grid or generators with valid scheduling who is reducing the generation when frequency is above 50 Hz. Similarly, the generators and distribution companies who are not adhering to grid discipline are not penalised with UI tariff in excess of normal tariff when average grid frequency in a time block is used for fixing UI/DSM charges. Each time block is further needs to be separated into two parts for application of UI charges. One for the duration the frequency is more than 50 Hz whose average frequency is considered for fixing UI/ DSM charges to consume the excess power in the grid or reduce excess power generation. Another for the duration the frequency is less than 50 Hz whose average frequency is considered for fixing UI/DSM charges to reduce over drawl and encourage additional power generation. Whenever distribution feeders from a substation are switched on after a breakdown or scheduled power cut, it should be done only when grid frequency is above 50 Hz such that it does not lead to steep drop in the frequency . The total numbers of feeders switching on, in a day are substantial at national level to cause load (≥ 500 MW) increase on the grid to cause wide fluctuations. The incentives and disincentives are prefixed (annually/periodically) by the electricity regulator (CERC) for the variation in the grid frequency which may not reflect the actual situation temporally and spatially on day-to-day basis. There is a need to decide the electricity tariff by the grid participants (generators, distribution companies, transmission companies and final consumers) on day-to-day basis for achieving further fine tuning. To correct these anomalies, CERC has proposed 100% sale and purchase of power produced in day ahead market. The ABT mechanism aims to maintain grid frequency at 50 Hz but does not permit the grid participants to decide the optimum frequency within the permitted frequency band (say 49.20 to 50.80 Hz) on day-to-day basis. This is required not to impose additional load shedding/power cuts when frequency is within the safe variation limits. Transmission system operator (TSO) is obliged to provide non-discriminatory transmission access to electricity generators and consumers in order to promote competition. ABT mechanism does not bring at par all the grid participants whether in private or central sector or state sector ownership. ABT mechanism does not encourage to install the generating units at advantageous locations to offer least cost electricity to the final electricity consumers. ABT mechanism is suitable in an electricity grid suffering from perennial power shortages to prevent overdrwals but it is not suitable for the grid with surplus electricity generation with non-discriminatory responsibility. CERC regulation on ancillary services operations, are permitting only inter state power generating stations to provide these services which are discriminatory by not allowing rest of electricity generators. Every state is conducting independently load management to avoid overdrawal from other states by using mix of generation sources (ex: hydro power or peaking power plants) to adhere to their power drawal commitments on 15 minutes period basis in ABT mechanism. Thus hydro power stations are ending up to cater base load instead of peak load in non-monsoon months also (ex: Kerala, Karnataka, Telangana, HP, J&K, Uttarakhand, etc.). TSO is responsible to ensure the provision of reserves (including spinning reserve for base load power plants by operating in frequency follow mode with upper & lower generation caps) that will allow for sudden contingencies by determining the optimal combination of generating stations and reserve providers for each grid trade bloc. The available hydro power stations in a region/grid should be used to cater peaking load only at regional/national level. Using hydro power stations to cater peak load, would improve the peaking load capability of a regional/national grid and maintain safe grid frequency and network stability. The 24 hours duration of a day should be divided into four parts only (i.e. daytime peak load period, daytime off peak load period, nighttime peak load period and nighttime off peak load period) instead of 96 number 15 minutes periods for commercially settling the power transactions to cater better to the peak load requirements within the safe frequency range. Many gas turbine power stations are not operating due to perennial natural gas shortage. Recently, many DG sets (large & medium sizes) are also idling throughout the year due to better availability of grid power. Alternatively, these power generation units can be put to use for grid reserve service either with liquid / gas fuels when there is unexpected tripping of operating power plants (five nos of 660 MW stations in a short duration) or tripping of a high voltage transmission line to prevent the grid operation below safe limit. This would also allow all the available transmission lines at their full capacity in service without the need to maintain n+1 reserve capacity for meeting any break down and thus accruing savings in high voltage transmission losses. The unified national grid stability can also be enhanced further by converting the existing back to back HVDC links into HVAC links bypassing the existing converter stations. These are Chandrapur back to back HVDC converter station, Vizag back to back HVDC converter station, Sasaram back to back HVDC converter station, Vindhyachal back to back HVDC converter station and HVDC Sileru–Barsoor link. The yearly cost of ensuring grid safety would be less than 2 paisa per Kwh for the total electricity generation in India.

Natural gas transmission

The Petroleum and Natural Gas Regulatory Board (PNGRB) was created in the year 2005 to regulate downstream activities in the petroleum and natural gas sector. There is requirement of natural gas TSO also for imparting optimum use of the gas on hourly basis for meeting peak load in the electricity grid and minimize gas transport distances. The available gas should be stored up to rated pressure in the pipe grid for generating power during peak demand hours on a daily (or more) basis. The natural gas carrying capacity utilization of GAIL pipelines is not exceeding 33%. Thus available limited gas quantity is used to meet the peak electricity loads by all gas based power stations. Gas turbine power plants are operated at 32.6% capacity factor as peaking power plants only in the US though being a surplus natural gas producer with lower price and the natural gas contributes largest portion (35.06%) of the total electricity produced. Also gas should not be transported from a power deficit region to a power surplus region by the gas grid and generated power from gas there shall not be transmitted back to the power deficit region to avoid misuse of the gas and power grid infrastructure. Natural gas TSO would also serve other sectors such as petro-chemical plants, CNG, fertilizer plants, PNG, LNG, etc. as per their hourly requirement in addition to receive gas from various types of natural gas producers and importers. Indian Gas Exchange (IGX) started online gas trading platform for physical delivery of natural gas. Initially, the company has identified Dahej, Hazira and Kakinada as delivery points and will subsequently include Dhabol, Kochi, Ennore and Mundra terminals.

References

COMPASS an Availability Based Tariff software from Engineering Consultants Group Inc

Text derived from https://en.wikipedia.org/w/index.php?oldid=1296644082 under CC BY-SA 4.0; modifications have been made.