Available transfer capability (atc) sbw ppt


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Available transfer capability (atc) sbw ppt

  1. 1. Introduction  The restructuring of the electric industry throughout the world aims to create competitive markets to trade electricity and generates a host of new technical challenges to market participants and power system researchers.  For transmission networks, one of the major consequences of the non-discriminatory open-access requirement is a substantial increase of power transfers, which demand adequate available transfer capability (ATC) to ensure all transactions are economical.  With the introduction of competition in the utility industry, it is possible for customers to buy less expensive electrical energy from remote location. As a result, system operators face the need to monitor and coordinate power transactions taking place over long distances in different areas. Therefore, it becomes essential to evaluate multi-area ATC
  2. 2. What is ATC  Available Transfer Capability (ATC) is a measure of the transfer capability remaining in the physical transmission network for further commercial activity over and above already committed uses. Mathematically, ATC is defined as the Total Transfer Capability (TTC) less the Transmission Reliability Margin (TRM), less the sum of existing transmission commitments (which includes retail customer service) and the Capacity Benefit Margin (CBM). ATC = TTC – TRM – CBM - Existing Transmission Commitments
  3. 3. ATC and Related Terms  ATC and related terms are depicted graphically below. They form the basis of a transmission service reservation system that will be used to reserve and schedule transmission services in the new, competitive electricity market.
  4. 4. ATC and Related Terms  Transfer capability is the measure of the ability of interconnected electric systems to reliably move or transfer power from one area to another over all transmission lines (or paths) between those areas under specified system conditions. The units of transfer capability are in terms of electric power, generally expressed in megawatts (MW).  Limits to Transfer Capability:  The ability of interconnected transmission networks to reliably transfer electric power may be limited by the physical and electrical characteristics of the systems including any one or more of the following:  Thermal Limits — Thermal limits establish the maximum amount of electrical current that a transmission line or electrical facility can conduct over a specified time period before it sustains permanent damage by overheating or before it violates public safety requirements.  Voltage Limits — System voltages and changes in voltages must be maintained within the range of acceptable minimum and maximum limits. For example, minimum voltage limits can establish the maximum amount of electric power that can be transferred without causing damage to the electric system or customer facilities.  Stability Limits — The transmission network must be capable of surviving disturbances through the transient and dynamic time periods following the disturbance.
  5. 5. Some Terminology  Total Transfer capability (TTC)  TTC is the amount of electric power that can be transferred over the interconnected transmission network in a reliable manner based on certain conditions.  TTC = Minimum of {Thermal Limit, Voltage Limit, Stability Limit}
  6. 6. Transmission Transfer Capability Margins  Two types of transmission transfer capability margins includes:  Transmission Reliability Margin (TRM) — to ensure the secure operation of the interconnected transmission network to accommodate uncertainties in system conditions.  Capacity Benefit Margin (CBM) — to ensure access to generation from interconnected systems to meet generation reliability requirements.  Individual systems, power pools, subregions, and Regions should identify their TRM and CBM procedures used to establish such transmission transfer capability margins as necessary.  TRM and CBM should be developed and applied as separate and independent components of transfer capability margin. The specific methodologies for determining and identifying necessary margins may vary among Regions, sub-regions, power pools, individual systems, and load serving entities.
  7. 7. TTC & ATC Calculation Techniques  Linear sensitivity: This method gives fast but low accuracy calculation of the ATC by using linear sensitivity without solving power flow solution. The method employs the DC Power Transfer Distribution Factor (DC-PTDF).  The repeated power flow method: It is performed by slightly increase demand at the receiving zone and increase dispatched power generation from the sending zone to cover increased demand and losses in the considered power system.  The continuation power flow method: is used to find the bifurcation point or point of voltage collapse when load in power system increases up to a certain amount.  Optimization method : The conventional optimization methods that are applied to solve the power flow calculation can be employed to determine the ATC value with typical considered constraints. Methods like the heuristic optimization such as Genetic Algorithm (GA), Tabu Search (TS), Simulated Annealing (SA) etc. can be used to calculate the ATC associated with the power flow calculation.
  8. 8. TTC & ATC Calculation Techniques  Probabilistic approach: In it, the variation of power generation is taken into account. Therefore, they give more information of the practical system which normally has demand and supply fluctuations.  Statistic approaches such as Monte Carlo simulation , stochastic programming and bootstrap technique can be implemented.  Due to its robustness, speed and ability to deal with incomplete or noisy data, the Artificial Neural network (ANN) becomes interesting method for ATC estimation under a certain condition of power system.  OPF Method: formulates some objective functions constrained by equality and inequality equations, so it could take transient stability constraint and dynamic stability constraint into account and may optimize the distribution of generation and load patterns. AC power transfer distribution factors (ACPTDF)
  9. 9. Performance Comparisons of ATC Methods