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Load and Loss Factors: Understanding them Better in Power Systems
This paper will be primarily concerned with computing Load and Loss Factors based on the I2R losses in the system. These losses may only be accurately computed by determining the average load on each component during each hour and doing a separate loss calculation for each hour during the time period in question. Due to the computational complexity of this approach, a simplified method of finding system energy losses using load and loss factors is often attempted.
Loss studies are often performed on a customer, primary or secondary feeder, transmission line, piece of equipment, or a complete system to determine the amount of energy lost during some period of time. Determining total system energy losses is often simply done by subtracting metered energy sold from metered energy purchased. However, a loss study my also attempt to determine how much of this energy is being lost on different parts of the system, and how much is being lost through theft or inaccurate metering. This information is valuable in economic planning for future growth, or for use in a loss reduction program to improve utility efficiency.
In the United States 9% of gross generation is lost each year in the distribution and transmission system 4% of which is accounted for by the transmission system. Recommended distribution system losses are between 5%-11% of their input energy depending upon how urban the distribution system location is.
Constant losses may be computed if the number of transformers and the tested characteristics of those transformers are known. The I2R losses are more difficult to determine since they vary at every point in the system due to variations in conductor resistance and current. Theft and metering error losses may be determined if the other two types of losses may be calculated and the total system loss is known by subtracting the constant and I2R losses from the total system losses.
To minimize the necessary calculations when performing loss studies, utilities often measure load factors, try to determine the loss factor, and use the estimated loss factor to determine system losses. This paper examines the relationship between load and loss factors, and discusses the validity of common methods used to determine losses using load and loss factors.
|A Better Understanding of Load and Loss Factors in Power Systems|