Leviton Online Knowledgebase : Discussion List - Understanding Electricity

Voltage (Volts)

CommunityAdmin@leviton.com — Tue, 14 Sep 2010 15:16:08 GMT

Voltage is the amount of electrical pressure from a source that is used to generate the current. A volt is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power, and is the unit used to express the quantity of electrical pressure.

To understand better, think of it in terms of water flowing in pipes. Current (amperage) is the flow of water, voltage is the pressure pushing the water and resistance is how easily the pipes allow the water to flow.

Smart Grid (modernization of the national electric grid)

CommunityAdmin@leviton.com — Thu, 23 Sep 2010 19:59:40 GMT

The electric grid delivers electricity from points of generation to consumers, and the electricity delivery network functions via two primary systems: the transmission system and the distribution system. The transmission system delivers electricity from power plants to distribution substations, while the distribution system delivers electricity from distribution substations to consumers. The grid also encompasses myriads of local area networks that use distributed energy resources to serve local loads and/or to meet specific application requirements for remote power, village or district power, premium power, and critical loads protection.

" The Smart Grid: An Introduction" is a publication sponsored by DOE's Office of Electricity Delivery and Energy Reliability that explores - in layman's terms - the nature, challenges, opportunities and necessity of Smart Grid implementation. Additional books, released in 2009, target the interests of specific stakeholder groups: Consumer Advocates, Utilities, Technology Providers, Regulators, Policy Makers and Environmental Groups, to explain in greater detail what the Smart Grid will mean to each us.

DOE is conducting a series of Smart Grid E-Forums to discuss various issues surrounding Smart Grid including costs, benefits, value proposition to consumers, implementation, and deployment.

The Federal Smart Grid Task Force was recently established under Title XIII of the Energy Independence and Security Act of 2007 to coordinate smart grid activities across the Federal government.

Grid 2030 vision (PDF 1.1 MB) calls for the construction of a 21st century electric system that connects everyone to abundant, affordable, clean, efficient, and reliable electric power anytime, anywhere. We can achieve this through a smart grid, which would integrate advanced functions into the nation's electric grid to enhance reliability, efficiency, and security, and would also contribute to the climate change strategic goal of reducing carbon emissions. These advancements will be achieved by modernizing the electric grid with information-age technologies, such as microprocessors, communications, advanced computing, and information technologies.

Electric grid stakeholders representing utilities, technology providers, researchers, policymakers, and consumers have worked together to define the functions of a smart grid. Through regional meetings convened under the Modern Grid Strategy project of the National Energy Technology Laboratory (NETL), these stakeholders have identified the following characteristics or performance features of a smart grid:

Self-healing from power disturbance events
Enabling active participation by consumers in demand response
Operating resiliently against physical and cyber attack
Providing power quality for 21st century needs
Accommodating all generation and storage options
Enabling new products, services, and markets
Optimizing assets and operating efficiently

source

http://www.oe.energy.gov/smartgrid.htm

What is LEED?

CommunityAdmin@leviton.com — Thu, 23 Sep 2010 19:46:07 GMT

What is LEED?

Single phase electricity

CommunityAdmin@leviton.com — Thu, 23 Sep 2010 19:00:25 GMT

Generated AC power is commonly in three phase in which the waveforms of three supply conductors are offset from one another by 120 degrees. The power generator has three sets of coils placed 120 degrees apart while rotating in a magnetic field, thus creating three separate sine waves of electricity that are displaced from each other in time by 120 degrees of rotation (1/3 of a circle).

Voltage across any pair of these three conductors or between a single conductor and a ground (in a grounded system) is known as single phase electric power. Single phase electric power is what is most commonly used by residential and light-commercial customers in most distribution power grids.

Three-phase electricity

CommunityAdmin@leviton.com — Wed, 15 Sep 2010 20:21:57 GMT

Three-phase electricity is a method of alternating-current electric power transmission using three wires.

Most power is distributed in the form of three-phase A.C. It is the most common method used by electric power distribution grids worldwide to distribute power. It is also used to power large motors and other large loads.

How it works is, the power company generators produce electricity by rotating three coils or windings through a magnetic field within the generator . These coils or windings are spaced 120 degrees apart. As they rotate through the magnetic field they generate power which is then sent out on three lines as in three-phase power. Three-Phase transformers must have three coils or windings connected in the proper sequence in order to match the incoming power and therefore transform the power company voltage to the level of voltage we need and maintain the proper phasing or polarity.

Three-phase systems may have a neutral wire. A neutral wire allows the three-phase system to use a higher voltage while still handling lower-voltage single-phase appliances. In high-voltage distribution situations, it is common not to have a neutral wire as the loads can simply be connected between phases (phase-phase connection).

Most household loads are single-phase. In North America and some other countries, three-phase power generally does not enter homes. Even in areas where it does, it is typically split out at the main distribution board and the individual loads are fed from a single phase. Sometimes it is used to power electric stoves and washing machines.

Kilowatt Hour (kWh)

CommunityAdmin@leviton.com — Tue, 14 Sep 2010 17:07:54 GMT

The kilowatt-hour (symbolized kWh) is a unit of energy eqivalent to one kilowatt (1kW) of power expended for one hour of time. It is the standard measure of electrical energy and the typical billing unit used by electrical utilities for electricity use.

For example, a 100-watt lamp operated for 10 hours consumes 1000 watt-hours (100 x 10) or one kilowatt-hour. If the utility charges $.10/kWh, then the electricity cost for the 10 hours of operation would be 10 cents (1 x $.10). The average annual electrical energy consumption of a household in the United States is about 8,900 kilowatt-hours, equivalent to a steady power consumption of about 1 kW for an entire year.

Kilowatt (kW)

CommunityAdmin@leviton.com — Tue, 14 Sep 2010 16:37:05 GMT

A kilowatt is the measure of electrical power equal to 1000 watts.

Watt

CommunityAdmin@leviton.com — Tue, 14 Sep 2010 15:59:25 GMT

A Watt is a measure of the amount of electricity being used - a rate of electrical power consumption. A very simple mathematical formula can be used to determine how many watts an electrical circuit can carry or how many watts an electrical device will require: Watts = Volts x Amps. Wattage ratings of lamps actually measure the power consumption not the illuminating capability.

Amperage (Amps)

CommunityAdmin@leviton.com — Mon, 13 Sep 2010 18:59:23 GMT

Amperage or current is a measure of the amount of electrons moving in a circuit.

In other words, amperage is how fast electricity is moving. The "water pressure in pipes" analogy is commonly used to help better understand the concept. In these terms, voltage is equivalent to the water pressure, amperage is equivalent to the flow rate and resistance is like the pipe size. Having higher "pressure" in a pipe (or electrical conductor) means that conductor is capable of delivering more energy to the user. For example, a ten-amp 240V electrical service is capable of handling approximately twice the energy to the end-user than a ten-amp 120V electrical service.

Alternating Current (AC)

CommunityAdmin@leviton.com — Thu, 09 Sep 2010 16:16:30 GMT

When a conductor spins within a magnetic field, an alternating voltage is induced across the wire and an alternating current flows through the wire. That is, current flows first in one direction through the wire and then it flows in the opposite direction.

Residential Circuits

CommunityAdmin@leviton.com — Fri, 10 Sep 2010 19:14:08 GMT

Power that is provided for residential circuits is generated at very high voltage and is stepped down to 7200VAC by transformers located at substations throughout the distribution route. A distribution transformer located somewhere near your home steps down the voltage one last time to 240VAC.

With a grounded, center-tapped transformer (i.e., with 0Vat the center tap), the 240VAC is therefore split into two separate 120VAC "hot legs." The grounded, center tap wire of the secondary is called the neutral wire. The neutral wire serves as a current return path for both hot legs.

The hot legs and neutral wires (and the earth-grounded wire - not shown in illustration below) terminate at a service panel (or "breaker box") located in your home.

The service panel provides a set of bus bars to allow for the insertion of circuit breakers, which protect each branch circuit from a current overload.