August 2011 - Kauai Island Utility Cooperative

Effects of Lightning
18 KIUC CURRENTS
By Jessika­Lyn Garcia
We have all been shaken by a bad thunderstorm.
We have seen the big white strikes in the eerie dark
sky, and even though we may have experienced
times like these, many of us do not understand the
science of lightning.
Lightning is produced by the mixture and
collisions of ice crystals in the higher part of the
thunderstorm, and hail and raindrops in the lower
part. When the lighter ice crystals become
positively charged, they are carried into the higher
parts of the cloud. At the same time, heavier hail
and rain gathers to form a negative charge and fall
toward the lower part of the cloud.
Normally, the earth’s surface has a slight
negative charge. However, as the negative charges
in the lower part of the cloud build up, the ground
directly below the cloud and its surrounding
locations become positively charged.
Air usually acts as an insulator between the
differing charges. But when the electrical charges
between the two charges become too great, a
discharge of electricity occurs, creating lightning.
Lightning and Electrical Systems
To understand how lightning affects electrical
lines, we first must understand how electricity
travels.
Energy cannot be stored. Therefore, moving
electricity requires packing power as heavily as
possible onto transmission lines. Increasing
electricity’s voltage causes it to move more
efficiently. Substations are “transit” points in this
system, giving it the ability to raise or lower voltage.
While high voltage equals efficient moving of
electricity, if electricity enters your home at too
high a level, electronics could be damaged. That is
what happens when lightning strikes.
Each substation contains an array of equipment,
including transformers, lightning arrestors, circuit
breakers and insulators. Transformers perform the
heavy work, altering voltage as needed.
Power blinks are created when a breaker, or
switch, opens along any portion of the power
system. Breakers usually open because of a large,
quick rise of electrical current. Large rises,
commonly known as a fault condition, can occur
when a tree branch touches a line, lightning
strikes or a wire breaks.
When such a fault condition happens, a relay
senses it and tells the breaker to open, preventing
the flow of power to the problem site. After
quickly opening, the breaker closes. A brief
delay—or power blink—allows the fault to clear.
Typically, that lasts less than two seconds.