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High Voltage

Danger! High Voltage!



Danger High Voltage Sign
This sign is often used in hazardous high voltage areas.
A high voltage sign is reminiscent of daunting electrical fences or tall transformers buzzing with energy, but to most construction workers and electrical engineers, high voltage and hazardous energy are part of the job. But what does high voltage mean, and why should you care?
There is no fixed definition for the amount of volts the government considers high voltage because of the many variables involved in electricity, like amplitude and environment. All these factors together determine if an electrical system could harm you and must be labeled “high voltage” or “hazardous energy.” Some would say anything over 500 volts is high voltage. However, there’s still potential for a lower voltage system like a power outlet to be dangerous under the right conditions, though.
Electricity is everywhere, but often only accessible to the experts; anyone who has experienced a blackout can tell you how frustrating it is to not to be able to turn on the lights. While generators and equipment might feel out of the layman’s reach, every building and work space has dangerous amounts potential energy.
These are some voltages of familiar machines – and living creatures.
Voltages of  human body, wall socket, electric eel, defibrillator, powerlines, and lightning.
Image credits after the article.
Despite the common phrase “high voltage,” the voltage of a current isn’t the only thing to be aware of. Anyone who has taken high school physics will remember the tedious conversions between volts, amps, joules, and watts.
A joule represents a unit of energy, work, or heat, while one watt is one joule being dissipated or radiated in one sec.
Amps measure the amount of charge flowing per second. That’s why a static shock can be thousands of volts, but since it’s measured in only microamps, it’s harmless. Therefore, OSHA elects to explain the dangers of electricity in amplitude:
Electricity's affect on the body measured in amps.
Potential energy (volts) can be slowed by a low current (amps). Electric shocks affect the body differently according to these factors:
  • Number of volts
  • Strength of current
  • Waveform of the current (e.g., DC, 60 Hz AC, RF, impulse)
  • The current’s path through the body
  • Length of shock
However, factory employees, appliance installers, and construction workers face dangerous high current equipment every day (potentially fatal arc flashes happen 10 times a week). This is important because in commercial settings, dangerous electrical currents are everywhere, and they are oftentimes exposed. Companies spend billions of dollars every year repairing the infrastructure for our cities, but thousands of injuries and fatalities still result from poor safety practices. NIOSH has identified the three most common mistakes that result in injury or death:
  • Failure to fully de-energize, isolate, or block high voltage equipment
  • Failure to lockout and tagout energy control devices and isolation points after high voltage equipment has been de-energized
  • Failure to confirm that the high voltage equipment is de-energized before starting work
How do they recommend fixing these problems? One important requirement is making sure already established OSHA regulations, lockout/tagout programs, and prevention practices are followed correctly. Supervisors must train new employees, re-educate workers, and always post instructions wherever constant reminder and complete safety are needed.
Lock Out Equipment Before Entering Sign
Employers use these signs to remind workers to lockout.
A simple reminder to lockout before working on equipment can prevent accidents. Keep regular safety conversations going throughout the workplace. Employees and supervisors must follow rules, create reminders, and instill a sense of mutual responsibility to make safety the number one priority.

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