Availability Based Tariff



What is ABT?



  • The ABT mechanism has laid out on financial principles.
  • Wherein all generators and beneficiaries must declare a schedule for generation and drawl every 15 minutes (time block) one day in advance.
  • Any deviation from the schedule is charged at rates, which are dependent on frequency at that point of time.
  • The ABT mechanism has laid out on financial principles.
  • Wherein all generators and beneficiaries must declare a schedule for generation and drawl every 15 minutes (time block) one day in advance.
  • Any deviation from the schedule is charged at rates, which are dependent on frequency at that point of time.



Why ABT at Inter State?

  • To induce better grid discipline & better system operation.
  • Induce better system operation and grid discipline through a mechanism of commercial incentives and disincentives in bulk power & transmission tariff.
  • This will assist in meeting demand with the marginal cost supply.
  • Higher voltage can also bring down the conductor sizes on account of lower currents handled.
  • Regional grids work at vastly varying operational parameters Frequency level is one such operational parameter.
  • The target frequency prescribed by the Electricity Rules is Integrated grid operations require the normalization of frequency across all five Regions.
  • The alternative is to establish Back to Back HVDC links between each Regional Grid. This is an expensive option.
  • Normalization of frequency requires proactive load management by beneficiaries and despatch discipline by generators.
  • A need of financial incentives to promote grid discipline.



The problems in grid operation Prior to introduction of ABT:

  • Low frequency during peak load hours with frequency going down to 48.0 – 48.5 Hz for many hours every day.
  • High frequency during off peak hours, with frequency going up to 50.5 to 51 Hz for many hours every day.
  • Rapid and wide changes in frequency.
  • Very frequent grid disturbances causing tripping of generating stations, interruption of supply to larges blocks of consumers, and disintegration of the regional grid / grid failure causing long duration (3-4 hrs) for restoration of normality



The main objectives of ABT mechanism:

  • Encourage grid discipline
  • Promote trade in energy and capacity
  • Economic load dispatch
  • Encourage higher generation availability



What are the Components in ABT? & Payments mechanisms


The availability based tariff comprise of three Components
  • Capacity charge, towards reimbursement of the fixed cost of plant linked to the plants capability to supply in MW(s) (Ex-bus)
  • Energy charge: The energy charge to reimburse the fuel cost, for scheduled generation.
  • U.I. charge: Payment for deviation from schedule ( i.e U.I means unscheduled interchange.) at a rate dependent on system conditions i.e frequency



Payment under ABT Regime- Monthly:



  • The Beneficiaries have to pay the monthly capacity charge for the generating plants in proportion to their share of allocation in the respective plants.
  • This payment shall be dependent on declared out put capability of the plan. The monthly energy charge to be paid by a Beneficiary to a CGS for energy scheduled from the power plants.



Payment under ABT Regime – Weekly:



  • In addition, in case a draws more power from the regional grid than what was scheduled to CGS at a particular time block (15 Min.) he shall have to pay for excess drawls at rate at which avg. frequency rate fixed by the commission time to time.
  • The rate will be low if the average frequency is high and high if the average frequency is low.



Dispatch and scheduling mechanism

  • The process would start with central generating stations in the region declaring their expected out put capability for the next day to the regional load dispatch center, before 10 A.M.
  • The RLDC would breakup and tabulated these output capabilities declaration as per beneficiaries plant wise share and convey the same to state load dispatch center. (SLDC) by 11 A.M
  • The state load dispatch center furnish their time wise M.W requisition, plant wise and schedule of bilateral exchange if any after carrying out the exercise to see how best they can meet the load of their consumers by considering state own generation and their entitlement in the CGS by 3 P.M.
  • The RLDC compiles these and determine the generation schedules for the CGS and drawl schedules for the beneficiaries by 5 P.M.
  • There is a provision to revise the out put capabilities declaration by CGS and requisition by the beneficiaries if required by any new development during the day before 10.00 P.M.
  • Final dispatch and schedules are frozen for the next day by 11P.M and regional constitutions would expect to generally regulate their generation and drawl by the beneficiaries.

Move to Top