A landscape crew is in the process of trimming a tall hedge the day after a heav
ID: 2292754 • Letter: A
Question
A landscape crew is in the process of trimming a tall hedge the day after a heavy rairn. Four workers, using various types of equipment, are trimming the hedge as described below. List the severity of the possible electrical hazards that each of the four workers may experience, in order from 1 (least hazardous) to 4 (most hazardous) 7. Worker A is standing on an aluminum ladder and using an electric hedge trimmer with a metal housing. The earth ground of the trimmer has been eliminated, as it is powered using an old two-pronged extension cord without a ground wire. Worker B is standing on a wooden ladder and using an electric hedge trimmer with a plastic housing. The trimmer is powered using a new extension cord with an earth ground, plugged into a GFCI outlet. Worker C is standing on a wooden ladder and using a manual hedge trimmer, and wearing a rubber suit. A. B. C. D. Worker D is standing on an aluminum ladder and using an electric hedge trimmer with a metal housing. The trimmer is powered using a new three-prong extension cord, plugged into a grounded three-prong outlet. For the most hazardous situation described above, determine the maximum current that could flow through the worker if the resistance of the worker's body, between her hand holding the trimmer and her feet standing on the ladder, is 1000 ?.Explanation / Answer
LEVEL 4(Most hazardous):(A): There is no earth pin so if there is a leakage current through the metal body of the electric hedge trimmer it would prove fatal for the operator as the leakage current would discharge through her body.This is highly hazardous as the user is not even wearing a rubber suit and there was an occurernce of heavy rain.
LEVEL 3:(D): In this case a three pronged cord is used,so there is a ground pin which would protect the operator from the leakage current from the metallic body of the hedge trimmer.But the operator is not using any protective equipment like GFCI and no rubber suit is worn.
LEVEL 2:(B): In this case a new three prong extension with GFCI is used and even the housing of the trimmer is plastic which is an insulator.A GFCI is an equipment which measures the imbalance in the current flowing from the hot wire to the neutral wire.So, if there is any leakage current the GFCI can detect it.It is sensitive towards even milliamperes of current and its operating time is minimal.
LEVEL 1(Least hazardous):(C):This case is least hazardous as a manual trimmer is used instead of electric trimmer.And also the operator is wearing a rubber suit protecting her even if there is any open wire
For level 4:Neglecting earth resistance,
Acc. to US standards,
Maximum current=110/1000 A
=0.11 A
Acc. to indian standards
Maximum current=230/1000 A
=0.23 A
Currents between 0.1 A to 0.2 A is lethal
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.