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Power Generation, Your house, Your shack.

Discussion in 'Amateur Radio News' started by Guest, Apr 11, 2001.

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  1. Guest

    Guest Guest

    WA2AEH writes "We as hams communicate on a day-to-day basis with amateurs all over the world. We very seldom think where the power to perform these feats of magic comes from except in cases where we use batteries. Use of a handheld or operating from the car, we know the power is coming from a DC source - the battery or batteries. We are well aware and cognizant of this fact because if the batteries are exhausted, we are off the air. Therefore, we try to conserve and limit the amount of on the airtime in order to extend the available power.



    However, have you ever thought about the complexity of a system that delivers reliable power to your home that allows you to virtually transmit for as long as you desire without ever running out of power?



    This is where Power Generation starts and is a very complex arrangement of natural resources, equipment, expertise and manpower that when put together properly, will perform as expected and provide you with virtually unlimited power.



    Ignoring other exotic forms of power generation such as solar, wind etc., power generation starts out with boiling water. Lot’s of water. Boiling water is the power behind most power generation. Make water hot enough and it packs enormous power and pressure. This power (steam) is directed into a turbine constructed of special metals that can withstand the high temperatures coupled with the enormous mechanical stresses encountered in this environment. The turbine is simply a shaft with many “Buckets” or blades that are optimally configured to rotate the turbine and it’s shaft. This is very similar to a child’s handheld pinwheel that will rotate under wind pressure.



    These turbines come in all sizes but units used in utilities are very large devices and are found on a “Turbine Deck”. A turbine deck is simply the floor where the turbine is located. A large turbine can weigh up to 30 tons or more. The turbine will start to spin under the steam pressure eventually reaching a regulated speed of 3600 RPM. The 3600-RPM is regulated through a device called a speed governor. This device will constantly monitor the RPM of the turbine making tiny adjustments as required thereby providing the highly accurate 60 hz frequency we are all familiar with.



    A generator field is directly coupled, (shaft to shaft) to the turbine. Depending on the rating of the generator, the field can weigh about 20 tons and be 20-30 feet long. This is not a small piece of equipment and that is only the field. The stator which is constructed around the field is much larger. A DC voltage of high amperage (usually around 120vdc) is introduced into the field windings making a very strong magnetic field – a spinning electro magnet. Hence, the turbine spins, the field spins and the magnetic field spins.



    This rotating magnetic field cuts or passes over the stator windings in the generator. An alternating magnetic field passing through or over a conductor will induce a voltage in that conductor. This is the basis of all power generation (remember basic electricity). This arrangement in the generator provides 60 Hz, 3 phases at about 13,800 AC volts although it could be higher. The familiar 60 hz frequency is arrived at by the coil arrangements inside the generator stator.



    Now that we have high voltage, what do you do with it now? How does it get to your house and then to your rig and not burn it out? Well, just boost the 13,800 volts to say 250,000 volts or higher and send it on it’s way, to your house! That’s how.



    Upon exiting the utility generation facility, the 13,800 volts is boosted to the higher voltage by a very large transformer. These transformers are typically sized in the 300-1000 mva range. MVA means mega volt-amperes. For size comparison, a typical plate transformer in your amplifier may be sized at 1-3 kva or kilo volt-amperes. That is 1000-volt amperes or 3000-volt amperes. The 1000 mva utility transformer is 1,000,000,000-volt amperes (thats billion with a "B"). A very large transformer indeed.



    These transformers boost the voltage from the generator up to transmission voltages through circuit breakers designed to handle these voltages. These circuit breakers are operated (tripped) if need be through carefully adjusted protective relays, the voltage is then fed and synchronized to the power grid thereby adding it’s power to the overall grid capability. The grid power is shared between all users. It does however have a finite power handling ability. Overload a grid or draw too much current than the total amount available then; just like the breakers in your house, these high voltage circuit breakers will be ordered to trip to protect the grid from failure.



    These very high voltage circuit breakers are huge affairs able to withstand voltage stresses up to 1 million volts per phase! As stated earlier, these circuit breakers are operated through protective relays that are marvels themselves in the exquisite protection they provide. Protective functions include: synchronization, phase balance, reverse current, over current, phase reversal, phase loss, distance relays etc. In addition, unbelievably, in this age of advanced electronic design, most of these relays are of the electrical mechanical type and design from the 1960’s and earlier. However, these relays are extremely accurate and are very rugged when compared to solid-state relays.



    Fully protected and carefully checked for any anomalies, this very high voltage is then transmitted along lines supported by towers that most everyone has seen out in the western deserts or running alongside the NJ Turnpike. The actual conductors or lines are supported by very large and long porcelain insulators, which in turn are supported by the transmission towers. The length of the insulators gives a rough idea of the voltage supported. The lines hang from these large, usually brown multi-layered or skirted devices. Ever wonder why these insulators are not just smooth and straight. Why the skirts? By skirting the insulator, the tracking or arcing distance is increased dramatically when compared to a straight, smooth insulator. They also provide a convenient drip edge for rain. The insulators are there to prevent flashover or arcing to the tower support or ground.



    These towers carry bulk power from utility generating stations. At certain intervals or locations along these transmission routes, taps are made that bring this very high voltage to what are known as sub-transmission stations. Keep in mind there is no clear delineation between distribution, sub-transmission and transmission voltages. For our purposes, we will call 34.5kv sub-transmission. The 34.5kv voltage is then sent along the street or underground to additional substations, which further transform the voltage to lower levels. Eventually these lower voltages ~ 13.8kv and 4.16kv reach the pole near you house. On the pole near your house, is a pole-mounted transformer, which then transforms the voltage to an even lower value usually 220 vac. This is then dropped into your billing meter (watt hour meter) and then to your fuses or circuit breakers in your house.



    As you can see, it takes a lot of expertise, manpower, equipment and property to bring 120 vac to an outlet near you. It all starts with boiling water and using this boiling water and steam in a way then benefits all mankind. So, the next time you are making coffee or tea and see steam jetting out of the kettle, think about this vapor and how it has transformed the world and has become an absolute necessity in our way of life."
     
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