Power Delivery Laws

The complex interaction of a power delivery system is governed by a number of physical laws relating to the natural phenomena that have been harnessed to produce and move electric power. These interactions have created a number of “truths” that dominate the design of delivery systems:

• It is more economical to move power at high voltage. The higher the voltage, the lower the cost per kilowatt, to move power any distance.

• The higher the voltage, the greater the capacity and the greater the cost of otherwise similar equipment. Thus, high voltage lines, while potentially economical, costs a great deal more than low voltage lines, but have a much greater capacity. They are only economical in practice if they can be used to move a lot of power in one block.

• Utilization voltage is useless for transmission of power. Transmitting power at utilization voltage level results in unacceptably high electrical losses, severe voltage drops, and astronomical equipment cost.

• It is costly to change voltage level. Voltage transformation is a major expense, which does nothing to move the power any distance in and itself.

• Power is more economical to produce at very large amounts. Large generators produce power more economically than small ones., thus it is most efficient to produce power at a few locations utilizing large generators.

• Power must be delivered in relatively small quantities at low voltage level.

Source: Power Distribution Planning Reference Book, H. Lee Willis

The Delivery System's Mission

A delivery system’s primary mission is to deliver electric power to the consumers at their place of consumption and in read-to-use form. The system must deliver power to the customers, which means it must be dispersed throughout the utility franchise in uneven proportions.

There are a bulk of customers in central downtown area of a city but are scattered as it goes to the outskirts. The primary requirement for the power delivery system is to reach every customer through an electrical path, sufficient enough to satisfy the customer’s demand.

The electrical path reaching the customers is not enough; it must be a reliable one. A reliable path provides an uninterrupted flow of power to the customers. A reliable delivery system delivers all of the power demanded, not just a part of what is needed, in a sustained manner. A 99.9% reliability of service means nearly 9 hours of electric service interruption each year, in percentage it’s impressive but the truth it is not. And it is unacceptable to nearly all first world countries.

Aside from providing the customers with highly reliable power, the delivery system must also make sure that the delivered power is of acceptable quality. Mostly, the quality of the power delivered can be measured through the state of the voltage of the electricity being delivered. Delivery voltage range is about ten percent of the utilization voltage. Voltage fluctuations have different and mostly damaging effect on the appliances thus a ten percent voltage fluctuation from the utilization voltage is unacceptable. If the fluctuation is too great or happens too often, then it is a sign of poor quality.

Introduction to Power Delivery Systems

A transmission and distribution system moves power from a utility's power production and purchase points to it's customers. Retail sale of electric energy involves the delivery of power in ready to use form to the final consumers. This electric power must flow through a power delivery system beginning at it's production until it reached the end-users. The delivery system is called the transmission and distribution system and it consists of lines, substations, transformers, and other equipment scattered over a wide geographic strategically located. The transmission and distribution's function is to mainly deliver power as needed to the utility's customers.

Normally, power generation is concentrated at few large, and usually isolated, power stations. The transmission and distribution moves this power to the customers. But in some cases, power stations are small, but numerous, and strategically located throughout the power system in proximity of the customers.

However, even which scenario of power delivery is available, Transmission and Distribution requires investment in billions of dollars. It will be the main objective of the Power Distribution Planner to make the power system deliver readily and widely available, economical, and reliable energy to the customers.

We will discuss the concepts and principles, objectives, and missions of Transmission and Distribution on later posts.

What is Power Distribution?

Before we discuss about Power Distribution Planning, we might as well go back to learn, review, and refresh the basic concepts of power distribution.

What is a power distribution?

Power distribution is the final stage of the delivery of power from its generation to the end-users. This delivery process consists of several stages which basically consist of:

1. Generation
2. Transmission
3. Distribution

The process of power delivery starts at the generating facility, the first stage, where electricity is being generated. There are a many ways to generate electricity and mostly it is by rotating a turbine which is coupled to a generator rotor through the use of steam, water, and air. Once the power is generated, it goes to a transformer where the voltage is transformed up to transmission voltage to travel across high voltage transmission lines. The transmission lines generally connects to the grid then to substations which step down the voltage to distribution level. These substations are generally owned by the electric utilities which will be responsible in distributing the electricity to the end-users, mostly through another voltage transformation for safe customer use.

Simple enough? Not quite as this simple concept holds all schools of electrical engineering and all our discussions will revolve on this simple foundation.

Welcome to Power Distribution Planner

Hi all! Welcome to DistributionPlanner, a site were aspiring electric utility engineers would learn the basic arts and sciences of power distribution planning. Being the oldest and most traditional subgenre within the electrical engineering, power engineering has been subjected to intense modernization challenges in both technology and industry structure. DistributionPlanner hopes to be a source of information for the electrical distribution planners to meet up the demands for greater performance at optimum resources with the ever changing requirements of the modern electrical engineering world.

This site hopes to make the challenging areas in power distribution planning as simple as it can get. Feel free to give your comments and queries.

Thank you and let's mark the start of a documented journey, an experience exploding with learnings, purpose, and meaning...