Towers For Different Types of Currents
It is possible to install circuits for different types of current on the same tower. In principle, it is possible to install AC circuits of different frequency and phase-count or AC and DC circuits on the same pylon.
Usually all circuits of such lines have voltages of 50 kV and more. However, there are some lines of this type for lower voltages, for example when the masts of an overhead wire of a railway carry also circuits of the public three-phase AC grid.
However only two very short sections exist where pylons carries as well AC as DC main line circuits: these are the pylons in the terminal of HVDC Volgograd-Donbass on Volga Hydroelectric Power Station and 2 pylons south of Stenkullen, which carry one circuit of HVDC Konti-Skan and üne circuit of the three-phase AC line Stenkullen-Holmbakullen.
Pylons carrying as well AC circuits as conductors of DC electrode lines exist in a section of the powerline Adalp Static Inverter Plant to Marble Substation, where between Adalph Static Inverter Plant and Brookston the pylons carry the electrode line of HVDC Square Butte.
The overhead section of the electrode line of Pacific DC Intertie from Sylmar Converter Station to the grounding electrode in the Pacific Ocean near Will Rogers State Beach is also installed on AC pylons. It runs from Sylmar East Converter Station, via Sylmar Converter Station, Rinaldi Electrical Substation, Southern California Edison Northridge Substation, DWP Receiving Station U to Southern California Edison Malibu Substation, where the overhead line section ends. Remarkable at this line is that in the section between Rinaldi Electrical Substation and Southern California Edison Northridge Substation the conductors of the overhead electrode line of Pacific DC Intertie are installed on pylons of two paralell running AC lines, whereby on each line one of the two ground conductors is replaced by the electrode line.
Pylons carrying three-phase AC circuits of different frequencies may exist in areas, where grids operated with two frequencies come together, e.g. in Japan.
The most important case is given when pylons carry as well three-phase AC circuits for the public grid and single-phase AC for railway use. Such towers exist in Germany, Austria and Switzerland in order to better use right of ways. In Germany such pylons usually carry two electric circuits for traction current and two for three-phase alternating current. If the three-phase circuits are not arranged in one level, the lowest cross bar carries the traction current circuits. The highest crossbars are, if three-phase circuits are arranged in two or three levels, used for these circuits. In Switzerland, hybrid pylons with three crossbars are used. One half of the pylon carries a three-phase system; the other half carries two traction current circuits. If the traction current line shares the pylon with a three-phase alternating current line operated by more than 220kV, the isolation of the traction current line must be designed for 220kV. Otherwise, over voltages,which overtax an insulation for 110kV—can occur in some failure cases of the 380kV line along the traction current line.
Read more about this topic: Transmission Tower
Famous quotes containing the words towers, types and/or currents:
“Was this the face that launch’d a thousand ships,
And burnt the topless towers of Ilium?”
—Christopher Marlowe (1564–1593)
“Our children evaluate themselves based on the opinions we have of them. When we use harsh words, biting comments, and a sarcastic tone of voice, we plant the seeds of self-doubt in their developing minds.... Children who receive a steady diet of these types of messages end up feeling powerless, inadequate, and unimportant. They start to believe that they are bad, and that they can never do enough.”
—Stephanie Martson (20th century)
“It is true, we are such poor navigators that our thoughts, for the most part, stand off and on upon a harborless coast, are conversant only with the bights of the bays of poesy, or steer for the public ports of entry, and go into the dry docks of science, where they merely refit for this world, and no natural currents concur to individualize them.”
—Henry David Thoreau (1817–1862)