Estimation of Distribution System Reserve Capacity and Its Impact on System Reliability considering load growth

Abstract

Abstract:The major objective of any electric distribution system (DS) operators in the present competitive market is to increase the service quality with improved reliability and lesser energy cost. This objective can be achieved by maintaining the balance between the reliability and cost of investments. In this work, system reliability is improved by using reserve capacity considering load growth. A sequential load growth model is presented for addition of load in non-integer years which is essential for sequential Monte Carlo simulation method. A model is presented to estimate the required reserve capacity if planning duration is known and vice versa. The concept of minimum allowable reserve capacity (MARC) is introduced to overcome the risk due to uncertain load growth. The system reserve capacity is increased by two ways i.e. up-gradation of distribution substation and integration of distributed generation (DG). The impact of load growth rate and reserve capacity level on system reliability is evaluated for a practical Indian distribution system. The required reserve capacity levels and capacity expansion duration are evaluated for different load growth rates and MARC values.Keyword: Sequential load growth, reserve capacity, capacity expansion, reliability, distributed generation. IntroductionIn the present competitive deregulated environment, the distribution system (DS) operators are under high pressure to improve the system reliability, reduce the energy cost and increase the profit simultaneously. The deregulation of energy market brings in the concept of performance based rates (PBR), which is a contract of reward/penalty for system operators based on the system performance i.e. reliability. However, the PBR introduces the financial risk to the system operators [1] i.e. imposing penalty for not maintaining predefined reliability levels. To reduce the financial risk associated with the use of PBR, proper estimation of future system reliability, planning of system capacity expansion and maintaining appropriate reserve capacity are necessary.In the literature, different reliability evaluation methods are developed for distribution system reliability evaluation. In reference [2], reliability of a test system is evaluated using analytical approach and the results considered as benchmark. The analytical methods are fail to consider the uncertainty involved in the assessment due to uncertainty of system failures and repair times. Monte Carlo simulation (MCS) methods are used for reliability evaluation [3], [4] to overcome the disadvantage of analytical method. The MCS methods has the ability to include the uncertainty associated with the distributed generators (DGs) output power. System reliability is evaluated in [5], [6] with the integration of DGs. The computational efficiency of MCS method is less and takes more time for evaluation. Authors in [7], [8] are used variance reduction techniques in association with MCS method to improve the computational efficiency of MCS method.The loading of the system is not...