The Electrical System
The Electrical System |
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The electrical system is the entire system that distributes electrical power from the source of the electricity through to the end users of the electricity. There are a number of components to this system. This includes Generating Plants, Substations, Transmission Lines, and Distribution Lines. Each of these components of the electrical system will be dealt with separately in the sections that follow.
The electrical process for most people begins at the generating plant where generators produce electricity. In generating stations, a turbine is turned using a number of different means. The turbine can be turned by steam (called thermal generation), by water (called hydro generation) or by other means. The turbine then turns a shaft that goes to a generator to produce electricity. Each generating plant is different in how it is set up and how it is laid out. It can be stated, however, that generating stations deal with electricity at very high voltages. The voltage can range from a couple of thousand volts to several tens of thousands of volts. Generally there will be signs posted to warn of the associated dangers.
From the generating station, the electricity passes over transmission lines. Transmission lines are suspended on large insulators that are mounted on steel or wooden towers. Insulators hold conductors on towers or poles and prevent electrical current from going down our transmission towers or poles to reach ground. Generally, there are danger signs posted on tower structures. Please obey what the signs say and stay away. If you respond to an incident where someone has climbed one of these structures you should contact the local power supplier immediately! Anyone who makes contact with the structure AND gets too close to a wire could be electrocuted!!!
Electricity is transmitted from generating stations along transmission lines to substations. At the substation, the voltage is stepped down for distribution to power customers. All switching and substations have what is called a ground grid for tying the entire station together. This grounding grid functions to keep the entire 'non-electrical' structure at the same voltage. The grid is usually covered with a substantial layer of crushed rock. A metal fence normally surrounds the physical structure. The fence is there for a reason - to keep people on the outside and safe from the hazards within. The substation is a dangerous place to be for people who are untrained. All substations have signs to warn of dangers. The danger signs mean what they say. Substations deal with electricity at very high voltage.
Transformers perform the task of stepping up or stepping down the voltage of electricity. This is one of the major functions of substations. Therefore, substations usually contain numerous types and sizes of transformers. Transformers are made up of an iron core with a number of connective coils. The number of turns in these coils determines how the voltage flowing within is changed. These coils are insulated from each other by large amounts of oil. It is widely known that oil is a highly combustible substance. Many utilities have removed polychlorinated biphenyls (also known as PCBs) from their equipment filled with large amounts of oil, reducing the content below 50ppm (the amount that can be effectively measured). Depending on the province or country where you reside, this may vary. It is best to assume that this oil may contain PCBs. PCBs can be harmful to health and the environment. This is especially true when they are involved with a fire! There are regulations concerning PCBs that must be observed. This entire transformer structure, including the metal core, the coils and the insulating oil, are housed in a large metal tank. The tank may have an additional conservator tank on top of it that stores additional oil. There are also venting pipes on the top of the transformer structure that allow pressure to vent. Porcelain insulating bushings allow the high voltage to flow through the transformer without the tank becoming energized. These porcelain bushings also contain insulating oil and can explode if exposed to high temperatures.
Substations also have circuit breakers. These are large control switches. These circuit breakers may have porcelain bushings and insulating oil. Capacitors are another aspect of the power system. A capacitor bank is comprised of a number of smaller units. These units deal with very high amounts of electricity (even with the power off). Capacitors may explode if exposed to heat. The capacitors can also contain PCBs, which can be extremely harmful when involved in a fire.
Substations are often built with internal overhead structures. These structures provide support to the insulators and conductors contained therein. Large aluminum pipes that look like they are a part of the framework are actually live conductors.
Substations are generally not attended. However, there may be an automatic signaling system to alert personnel of the local power supplier of any unauthorized entry or other associated problems.
The distribution of electricity throughout the electrical system involves distribution transformers of different shapes and sizes. 'Pole top' transformers contain oil and can explode when involved in fire. The oil in distribution transformers may contain PCBs. These PCBs can be dangerous to personal health and to the environment. In this situation, it is important to remember that there are regulations concerning PCBs that MUST be observed. The best practice is to protect people in the vicinity and adjacent property.
Some distribution transformers are found at the top of power poles. Another type of distribution transformer is a padmount transformer. You will usually find these cabinets outside of shopping malls, apartment buildings, and sometimes in school yards where a lot of power is needed. The electrical wires come into the transformer underground and are attached inside. Please note: wherever you see a padmount transformer, there are always electrical wires going underground.
Transformers deal with high voltages. The padmount case is normally locked with special locks to protect people from these hazards. For this reason, there is normally no need to place a fence around them. The padmount transformers have a grounded case and the base of the transformer is well connected to the ground. These pieces of equipment are quite safe to touch on the outside but if someone gets curious and decides to look around on the inside, they can be very dangerous. Some transformers may buzz, be warm to the touch in the winter, and often are a source of attractive curiosity for youngsters. However, these components of the electrical system are not playthings. It is best practice to stay well away from them. If you do come across one that someone has opened secure the scene and contact your local power supplier right away.
The power lines you see in your neighborhood are not insulated. Most power lines are bare metal (i.e., not insulated), and are made out of aluminum. All conductors (wires) even the "neutral wire" are capable of carrying large amounts of electrical current. No overhead power line is safe to touch.
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This section has examined some of the main components of the electrical system. This knowledge will be important to you in making informed decisions with regards to emergency situations involving electricity. |
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