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Because it is easier to get something to conduct to one phase as opposed to two or more. Lightning usually strikes closest to one phase, and may ionize the air enough to cause one phase to flash over to ground. Farmers sometimes run equipment into power lines; they usually stop when they hit the first wire (may blow the tires right off the vehicle they're driving, cook the engine, etc.). Birds, and small animals usually can't bridge the distance sufficiently between two conductors to cause a flash over, but they sometimes can for a single phase to ground by moving along one string of insulators. The exception to this is large Birds of Prey - sometimes they like to perch on top of power lines, and they have been known to dive between phases to catch an animal - if this happens, and they're big enough, they won't make it.
Also, faults are very often cleared quickly, before more phases can get involved. I looked over some fault records for a line that was taken down when a small town decided to dynamite the ice in the river to prevent flooding- the ice dam came down river and broke the legs of an H frame. The fault record for one end indicated a single phase to ground fault. The fault record for the other end (cleared slower) indicated 1, then 2, then 3 phases as the line collapsed.
What else can I help you with?
What is a symmetrical fault?
generally faults are of symmentrical and unsymmentrical faults that occur in majorly occurs in transmission lines........ the fault in electrical transmission line which give rise to symmetrical fault current is called symmetric fault. e.g; L-L-L-G fault. if they are in low values then system is said to be "protected" .... In order to avoid those NEUTRAL SHOULD GROUND with resistor or reactor etc,,,,,,,,...........
Why delta connections used in overhead transmission lines?
There are essentially 2 types of connections for a 3 phase AC transmission lines Star and Delta , Star is a 4 wire connection with each phase supplying potential with respect to a common ground wire , while delta is 3 wire connection with any single phase at one given time acting as a ground , for transmission reducing one wire makes a lot of cost difference hence it is favored
What is the basic parameters of transmission lines?
the basic parameters of transmission lines are R,L,C and G...........
Why 22kv 11kv 33kv 132kv 220 kv are standard transmission voltages in transmission lines why not 20kv 10kv etc?
Its just a matter of standard. In my area, for instance, we use 13.2 KV for distribution lines, and 69 KV / 138 KV for transmission lines.
What is the sizes of cable for transmission lines?
336 776 and 795
What are the types of faults in ehv transmission lines?
The three types are Line to ground faults line to line fault double line to ground fault three phase line to ground fault
What is the purpose of ground wires in overhead transmission lines?
connection of the ground of all the transmission lines and used as a communication cable between protection devices
What is a symmetrical fault?
generally faults are of symmentrical and unsymmentrical faults that occur in majorly occurs in transmission lines........ the fault in electrical transmission line which give rise to symmetrical fault current is called symmetric fault. e.g; L-L-L-G fault. if they are in low values then system is said to be "protected" .... In order to avoid those NEUTRAL SHOULD GROUND with resistor or reactor etc,,,,,,,,...........
When the ground slips at fault lines the movement the earth undergoes is called what?
earthquakes
When the ground slips at fault lines the movement the earth undergoes is called?
an earthquake
Are there fault lines in Haiti?
yes there are fault lines in haiti
Are fault lines caused by earthquakes?
No, fault lines cause earthquakes
What is it when you have had a new transmission put in and it is still leaking transmission fluid what could that be from on a 1995 Ford Aspire?
transmission cooler lines are common to leak
Why delta connections used in overhead transmission lines?
There are essentially 2 types of connections for a 3 phase AC transmission lines Star and Delta , Star is a 4 wire connection with each phase supplying potential with respect to a common ground wire , while delta is 3 wire connection with any single phase at one given time acting as a ground , for transmission reducing one wire makes a lot of cost difference hence it is favored
Where are South Dakotas fault lines?
South Dakota lies within a relatively seismically stable region, so fault lines are not as common compared to other areas. However, the state does have some known fault lines, such as the Madison fault zone in the eastern part of the state and the related Platteville fault zone in the southwest. These faults are considered to have low seismic activity compared to areas along plate boundaries.
Show you a map of all US fault lines?
wheres all the canadian fault lines
What fault lines are in Scotland?
Some notable fault lines in Scotland include the Highland Boundary Fault, the Great Glen Fault, and the Southern Uplands Fault. These fault lines contribute to the geology and landscape of Scotland, with distinct features such as hills, valleys, and lochs. While Scotland is not as seismically active as other regions, these fault lines have the potential to cause earthquakes.
