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TEMPERATURE EFFECT TO DISTRIBUTION FEEDER LOAD PROFILE AND LOSSES TECHNICAL PAPER

Authored by: C.H. Lin, C. S. Chen, M. S. Kang, T.T. Ku, J.S. Huang, Z.S. Chiou, and C.W. Huang

ABSTRACT--A systematic procedure is proposed to study the effect to temperature change to distribution feeder load profiles and losses by using the typical load patterns of customer classes. The database of an automated mapping/facility management (AM/FM) system is used to retrieve the component attributes and the topology process is executed to determine the electrical network configuration and the customers served by each distribution transformer.

By using the monthly energy consumption of customers in customer information system (CIS) and the typical daily load patterns of customer classes, the hourly loading profiles of distribution transformers and service zones can be derived to solve the loadings of each primary feeder and lateral.

The sensitivity analysis of load demand with respect to the temperature change for each customer class is performed by statistic regression according to the actual customer power consumption and temperature data. The load contribution by each customer class is updated by the corresponding temperature sensitivity and integrated together to form the new load profile of a service district with temperature change. To investigate the temperature effect to the distribution feeder, two of the Taipower distribution feeders are selected for computer simulation. The power demand at each load bus of the distribution feeder is calculated by applying the temperature sensitivity and the three-phase load flow analysis is then executed to find the new feeder loading and power loss with the temperature change.

INTRODUCTION. The distribution system of Taiwan Power Company (Taipower) has contributed more than 50% of total system loss and has become a critical issue to pursue higher system operation efficiency. The air conditioning load has consumed more than 35% of Taipower system peak demand because more and more air conditioners are used in the commercial, office and residential sections. Many main transformers in the substations and distribution feeders, which serve the urban areas, have become overloaded during the summer season. A single contingency always causes serious outage problem in Taipower distribution system. Although the planning department has tried to enhance the distribution system capability, the construction of new substations always becomes the nightmare for Taipower due to stricter environment protection and land acquisition problem. It is important to estimate the system loss in a very effective manner so that the distribution feeder with poor operation efficiency can be identified for loss reduction. Up to now, different methodologies such as percent loading method, simplified feeder model, load duration curve and load window etc [1-5] have been applied for distribution system loss analysis. Both the exact and simplified loss models [6] have been considered for each service district in Taipower to solve the line loss and transformer loss for distribution feeders.

CONCLUSIONS. The AM/FM system is used to generate distribution network models and input data files automatically to support load flow analysis of distribution systems to solve the power profiles and losses of distribution feeders. By executing customer-to-transformer mapping, the customers served by each distribution transformer are identified. The hourly loading of each distribution transformer is then derived by integrating the customer power demands, which has been solved by considering the typical load patterns and energy consumption of customers served. By this manner, the power profiles and losses of distribution feeders obtained will be more accurate as compared to the conventional load allocation using the transformer capacity.

The increase of customer power consumption due to temperature rise is derived for each customer class. It is found that the power consumption of Taipei city district is increased by 92 MW or 4% when the temperature rises by 1°C. This is mainly introduced by the high loading percentage of air conditioners. To solve the temperature effect to the feeder loading and power loss, two practical Taipower feeders are selected for computer simulation. It is updated by applying the temperature sensitivity to find the new power demand with the temperature rise. The three-phase load flow analysis has been executed to find the feeder loading and power loss of the test feeders under different temperatures. It is found that temperature change has very significant impact to the power consumption of distribution feeders in the commercial and residential areas.

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