From: SFPhysics@aol.com
Date: Wed Oct 11 2000 - 17:15:58 PDT
From: SFPhysics@aol.com Message-ID: <a9.c2bed68.27165cbe@aol.com> Date: Wed, 11 Oct 2000 20:15:58 EDT Subject: Re: Power Surges
> A student in my 8th grade science class asked me what causes power surges
> (I assume he meant when the power goes out and comes back on). I was
> stumped. Any one have an idea? Thanks, Mike Schulist, Miller Creek Middle
>School
>>
Greetings Mike:
The whole of the western United States is tied into WAPA (Western Area Power
Association). It is a power grid where all of the power generation plants
from Canada to San Diego and from San Francisco to Salt Lake City is tied
into along with the power drains of cities, agricultural pumping, and
industrial plants. When lightening strikes a line in Oregon, California,
Washington, Idaho, etc., the line transmits that "surge" to both ends of the
line. Normally there are surge protectors that keep the lightening strike
from going any farther that the two ends of the line it struck but sometimes
the protectors cannot handle the energy spike. Lights will flicker for a
good portion of the grid. Then too there is the sun which generates huge
unbelievably high pulses of particles and magnetic storms which strike the
earth and cross the power lines. When a power line is crossed over a
distance of hundreds or thousands of miles by a magnetic pulse, it picks up
an induced current, a large induced current. The grid reacts by having
automatic disconnects and shunting the power spikes. Sometimes the lights
will get bright then come back down to normal. This is a power spike. The
voltages in all circuits may rise for a short duration.
The other occurrence is the brownout where the lights dim, flicker, and
sometimes the power goes off completely. Brownouts may be caused by too much
of a load on the grid as we have had this summer. The local power companies
turned off large blocks to ease the load drain. Usually this is just having
the power drop all at once. When you have dimming, flickering, then the
power goes off that is usually a localized problem with a shorted power line,
an automobile knocking down a pole, a transformer failing, a tree falling
across wires, and the like. Local grids are called block feeds.
Most local power feed blocks today have several possible sources of power.
If a car knocks down a pole and stops the feed from one side of the block
then the opposite side of the block feed automatically comes on. The lights
will dim, flicker, and if the downed pole has shorted the wires, the power
will fail completely. The repairs crews first have to repair the short
circuit then they turn on the power again.
Hope my explanations have helped,
Al Sefl
p.s. When you get your new utilities bills in the coming months remember
they will be a WAPA too!
This archive was generated by hypermail 2b29 : Tue Oct 16 2001 - 12:21:58 PDT