CIRCUITS AND SAFETY. SUBSTATION and DISTRIBUTION GRID. Find pictures of Orland park substation, and distribution grid. DISTRIBUTION GRID. ONE LINE DIAGRAM.
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Equivalent Transmission and Generation Grid
STEP DOWN TRANSFORMER
Arrows represent Houses
The amount of resistance a wire offers depends on the length, cross sectional area, and material the wire is made of
ρ = RA/l
Silver 1.59 x 10-8
Copper 1.7 x 10-8
Gold 2.4 x 10-8
Aluminum 2.8 x 10-8
Tungsten 5.6 x 10-8
Iron 10 x 10-8
Platinum 11 x 10-8
Lead 22 x 10-8
Nichrome 150 x 10-8
Carbon 3.5 x 10 5
Polystyrene 107 - 1011
Polyethylene 108 - 109
Glass 10 10 – 10 14
Hard Rubber 10 13
Birds can safely rest on high-voltage power lines without getting shocked: they make contact with the circuit at only one point.
Many times, one side of a power system will be intentionally connected to earth ground, and so the person touching a single wire is actually making contact between two points in the circuit (the wire and earth ground):
If your body resistance is 100,000 ohms, then the current which would flow would be:
But if you have just played a couple of sets of tennis, are sweaty and barefoot, then your resistance to ground might be as low as 1000 ohms. Then the current would be:
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/shock.htmlTHE ROLE OF RESITANCE IN SHOCK
Because electric current must pass through the boot and the body and the glove to complete its circuit back to the battery, the combined total (sum) of these resistances opposes the flow of electrons to a greater degree than any of the resistances considered individually.