Electrical Grid - EnergyGroove.net

The Electrical Grid

The electrical grid is a network that allows for the distribution of electricity from suppliers to consumers.

Grid Operation

Operationally the conventional electrical grid starts at power generating systems such as power stations (see Power Stations article this web site) that generate 3 phase alternating current (AC) electricity. The 3 phase AC current is passed through a transmission substation that uses transformers to step up (increase) the voltage from thousands of volts to hundreds of thousands of volts. Increasing the voltage allows for efficient transmission of electricity over long distances. After being converted to high voltage, the 3 phase electricity is sent over long distance transmission lines through three lines, one for each phase. Before it can be distributed to end users, the electricity must pass through a power substation that steps down (decreases) the voltage with transformers so that it can be distributed to communities and used in homes and businesses at the correct voltage.

A 3 phase current is used because electricity is generated in a sine wave that has peaks and troughs, meaning that power strength for a single phase fluctuates between weaker and stronger moments. By generating three phases and offsetting them by 120 degrees, the moment of peak power is evenly distributed between the three phases, allowing for more consistent peak power output. Having consistent peak power output is important mainly for industrial purposes, e.g., industrial 3 phase motors.

Alternating current is used because it is easier to change voltages with it than with DC, and a very high voltage is fundamental to long distance electrical transmission because it reduces energy loss by lowering resistance in the wires. To find out more about this, see the following article:

http://en.wikipedia.org/wiki/War_of_Currents

Grid Distribution System

As a distribution system the electrical grid can be organized in several ways. How an electrical grid is set up depends on factors such as topology, geography and the level of grid interaction for an area. Electrical grids systems include:

Radial
Mesh
Looped (Parallel path flow)

Radial

A radial type grid is the simplest setup. Known as a radial network, it involves a series of networks and sub-networks organized as radial trees that begin with a power source and distribute electricity through networks with progressively lower voltages, eventually ending with communities, homes and businesses.

Mesh

A mesh network involves the radial structure but includes redundant lines, which are in addition to the main lines and organized as backups for the purpose of rerouting power in the event of failure to a main line.

Looped (Parallel path flow)

Looped or parallel path flow systems involve the way different grid networks are connected to each other. Having one network connected to another allows networks to share and balance the flow of electricity as required, where one network can act as either a backup or additional supplier. In this setup each network can run its own transmission line to the same (often high demand) distribution point via parallel transmission lines. It is also possible for electricity to flow from one network to the other and then back again to the original, i.e., a looped flow. In a looped/parallel flow setup issues can arise with controlling the flow of electricity at the point(s) of network contact.

Grid Network

Electrical grids are composed of many smaller electrical networks that are linked together into a larger network called a Wide Area Synchronous Grid, also known as an “interconnection”. A Wide Area Synchronous Grid allows all the independent electrical networks in a particular area to be connected by synchronizing the electrical frequency between them. North American interconnections are synchronized at 60Hz and European ones at 50Hz (see images below).

Images courtesy of Wikipedia

The advantages of grid network interconnections include coordinating (or pooling) electricity generation, load distribution and backup assistance.

Grid Developments

Much of today’s grid networks are setup for conventional power generation and cannot always handle the varied conditions that integration with newer alternative energy technologies demand. As a result, redesigning the grid is becoming high on the agenda for many world governments. The future includes several directions, which include:

Distributed generation
Smart grid
Super grid

Distributed Generation

Distributed generation, also known as “micro grid”, takes advantage of advances in electrical generating systems, e.g., solar panels, wind turbines and cogeneration, which allow for creating and distributing electrical power outside the traditional grid system. As such these systems are smaller, more locally focused and can act in addition to or separate from the traditional grid supply. Because distributed generation systems transmit electricity over short distances, i.e., they are local, they reduce the amount of energy loss compared to the grid. On the other hand, because they rely on alternative energy technologies, they can have a large initial cost. Distributed generation systems can generate between 3kW – 10,000kW of electricity.

Smart Grid

The Smart Grid refers to updating the conventional grid configuration from what is essentially a unidirectional “analog” system to a multidirectional digital system. The conventional grid was designed and developed based on the needs and technologies of the last century. In this capacity it has basic control over how electricity is transmitted and distributed. Given what is possible with today’s technologies, this basic control has become very inefficient and creates comparatively huge losses for both electricity and cost. The objective of a smart grid is to modernize the transmission and distribution of electricity to allow for:

Facilitating greater competition between providers
Enabling greater use of variable energy sources (distributed generation)
Establishing the automation and monitoring capabilities needed for bulk transmission at cross continent distances
Enabling the use of market forces to drive energy conservation [1]

According to the United States Department of Energy‘s Modern Grid Initiative report[26], a modern smart grid must:

Be able to heal itself
Motivate consumers to actively participate in operations of the grid
Resist attack
Provide higher quality power that will save money wasted from outages
Accommodate all generation and storage options
Enable electricity markets to flourish
Run more efficiently
Enable higher penetration of intermittent power generation sources [2]

Some of the main variables that will define a smart grid system are:

Optimizing electricity usage for on and off peak periods
Creating greater integration with distributed generation resources, e.g., solar panel, wind power
Advanced monitoring for supply and demand of electricity
Increased metering of household appliances
Developing communication systems within grid operations that increase transparency and control

A smart grid configuration at a national level can create savings of between 500 million – 6 billion dollars per year [3] [4].

Super Grid

The super grid is a longer term project that will have the advanced micro control properties of a smart grid, as well as the advanced macro control properties of an intercontinental Wide Area Synchronous Grid with the objective of opening up energy markets to levels of free trade similar to the way the free trade of goods is possible today. In this capacity it will have many network properties that are similar to the internet, where the exchange of electricity in the super grid will be comparable to the exchange of information on the internet.

References

Links

http://en.wikipedia.org/wiki/Electrical_grid

http://en.wikipedia.org/wiki/Electric_power_distribution

http://en.wikipedia.org/wiki/Smart_grid

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

http://en.wikipedia.org/wiki/Microgrid

http://en.wikipedia.org/wiki/Super_grid

http://en.wikipedia.org/wiki/HVDC

http://science.howstuffworks.com/environmental/energy/power.htm