1. Field of the Invention
The present invention relates generally to a system and method for reducing power loss in a power grid, and more particularly to a system and method for reducing power loss in a feeder circuit of a power grid by analyzing at least one aspect of demand response.
2. Related Art
A power grid may include one or all of the following: electricity generation, electric power transmission, and electricity distribution. Electricity may be generated using generating stations, such as a coal fire power plant, a nuclear power plant, etc. For efficiency purposes, the generated electrical power is stepped up to a very high voltage (such as 345K Volts) and transmitted over transmission lines. The transmission lines may transmit the power long distances, such as across state lines or across international boundaries, until it reaches its wholesale customer, which may be a company that owns the local distribution network. The transmission lines may terminate at a transmission substation, which may step down the very high voltage to an intermediate voltage (such as 138K Volts). From a transmission substation, smaller transmission lines (such as sub-transmission lines) transmit the intermediate voltage to distribution substations. At the distribution substations, the intermediate voltage may be again stepped down to a “medium voltage” (such as from 4K Volts to 23K Volts). One or more feeder circuits may emanate from the distribution substations. For example, four to tens of feeder circuits may emanate from the distribution substation. The feeder circuit is a 3-phase circuit comprising 4 wires (three wires for each of the 3 phases and one wire for neutral). Feeder circuits may be routed either above ground (on poles) or underground. The voltage on the feeder circuits may be tapped off periodically using distribution transformers, which step down the voltage from “medium voltage” to the consumer voltage (such as 120V). The consumer voltage may then be used by the consumer.
Distributing current through the power grid (such as through the electric power transmission, and electricity distribution) results in loss. Specifically, the loss, termed Joule heating (or resistive heating), occurs when the passage of an electric current through a conductor releases heat. The amount of loss is I2R, where I is the current through the conductor and R is the resistance of the conductor. These losses in the power grid may be significant. It has been reported that transmission and distribution losses in the United States were estimated at 7.2% in 1995, and in the UK at 7.4% in 1998.
One type of analysis to reduce losses is a power flow study. A power flow study (also known as a load-flow study) involves a complex numerical analysis applied to a power system. The power flow study analyses the power systems in normal steady-state operation. There exist a number of software implementations of power flow studies. The goal of a power flow study is to obtain complete voltage angle and magnitude information for each bus in a power system for specified load and generator real power and voltage conditions. Once this information is known, real and reactive power flow on each branch as well as generator reactive power output can be analytically determined. Due to the nonlinear nature of this problem, numerical methods are employed to obtain a solution that is within an acceptable tolerance. The solution, however, requires complex iterative analysis and takes considerable time to solve. Therefore, a need clearly exists to provide a solution, which may be determined quickly and in real time, to reduce the losses due to Joule heating.
USPTO Backgrounds
USPTO Backgrounds