All electrical systems have the potential to cause harm. Electricity can be either "static" or "dynamic." Dynamic electricity is the uniform motion of electrons through a conductor (this is known as electric current). Conductors are materials that allow the movement of electricity through it. Most metals are conductors. The human body is also a conductor. This document is about dynamic electricity.
Note: Static electricity is accumulation of charge on surfaces as a result of contact and friction with another surface. This contact/friction causes an accumulation of electrons on one surface, and a deficiency of electrons on the other surface. The OSH Answers document on How Do I Work Safely with Flammable and Combustible Liquids? (Static Electricity) has more information.
Electric current cannot exist without an unbroken path to and from the conductor. Electricity will form a "path" or "loop". When you plug in a device (e.g., a power tool), the electricity takes the easiest path from the plug-in, to the tool, and back to the power source. This is also known as creating or completing an electrical circuit.
Purpose
- The objective of the Electrical Safety Program to protect employees from electrical hazards during the performance of inspection activity.
- Ensure the reliability of electrical installations according to their intended use.
- Prevent the hazards due to electricity:
- the dangers of direct touch
- the dangers of indirect touch
- fire hazard
Scope
1. Plan, manufacture, installation or assembly, use or operate and maintenance of electrical installations.
2. Responsibility in OSH electrical
Laws (click on the law for details)
- Law no. 1 of 1970 on Occupational Safety
- Ministerial Regulation No. 02 / MEN / 1989 (K3 Lightning)
- Ministerial Regulation No. 03 / MEN / 1999 (K3 Lift)
- Decree of Director General of Binawas. 407 / BW / 1999 (Lift Technician)
Definitions
Electrical Hazard: A dangerous condition such that contact or equipment failure can result in electric shock, flash burn, thermal burn, or blast.
Flash Hazard Analysis: A study investigating a worker’s potential exposure to arc flash energy, conducted for the purpose of injury prevention and the determination of safe work practices and the appropriate levels of PPE.
Flash Protection Boundary: An approach limit at a distance from exposed live parts within which an OSHA employee could receive a second-degree burn if an electrical arc flash were to occur.
PPE: Personal Protective Equipment.
Qualified OSHA Employee: An employee training on and knowledgeable of the electrical equipment to be evaluated, safe methods of using test equipment, and in the recognition of electrical hazards that might be present with respect to that equipment and the voltages involved. These are the only employees allowed to enter a flash protection boundary after approved by an Area Director/Unit Manager.
Electrical Hazards
People are injured when they become part of the electrical circuit. Humans are more conductive than the earth (the ground we stand on) which means if there is no other easy path, electricity will try to flow through our bodies.
There are four main types of injuries: electrocution (fatal), electric shock, burns, and falls. These injuries can happen in various ways:
- Direct contact with exposed energized conductors or circuit parts. When electrical current travels through our bodies, it can interfere with the normal electrical signals between the brain and our muscles (e.g., heart may stop beating properly, breathing may stop, or muscles may spasm).
- When the electricity arcs (jumps, or "arcs") from an exposed energized conductor or circuit part (e.g., overhead power lines) through a gas (such as air) to a person who is grounded (that would provide an alternative route to the ground for the electrical current).
- Thermal burns including burns from heat generated by an electric arc, and flame burns from materials that catch on fire from heating or ignition by electrical currents or an electric arc flash. Contact burns from being shocked can burn internal tissues while leaving only very small injuries on the outside of the skin.
- Thermal burns from the heat radiated from an electric arc flash. Ultraviolet (UV) and infrared (IR) light emitted from the arc flash can also cause damage to the eyes.
- An arc blast can include a potential pressure wave released from an arc flash. This wave can cause physical injuries, collapse your lungs, or create noise that can damage hearing.
- Muscle contractions, or a startle reaction, can cause a person to fall from a ladder, scaffold or aerial bucket. The fall can cause serious injuries.
Direct contact
refers to a person coming into contact with a conductor which is live in normal circumstances
Indirect contact
refers to a person coming into contact with an exposed-conductive-part which is not normally alive, but has become alive accidentally (due to insulation failure or some other cause).
Responsibilities
The responsible Manager(s) has the primary responsibility for implementation of the Electrical Safety Program.
- Provide appropriate PPE and make it available to employees
- Provide appropriate and approved electrical testing equipment
- Ensure that PPE and electrical testing equipment are properly tested and in good condition
- Ensure employees are trained on electrical hazards, the proper inspection methodology when inspecting electrical issues, the safe use of field testing equipment and the use, care and cleaning of PPE
- Maintain records of training and electrical field testing equipment and PPE supplied
- Ensure the Electrical Safety Program is followed;
- Ensure defective or damaged equipment is immediately removed from service
- Ensure that appropriate assistance is provided to employees where questions or concerns arise regarding inspection situations where the OSHA employee has a question about their qualifications or proper equipment for the inspection.
Employees are responsible for following the requirements of this chapter.
- Attend electrical safe work practices training;
- Know how to determine the nature and extent of the potential electrical hazard
- Be familiar with appropriate PPE and safe approach distances
- Be familiar with the use and hazards of appropriate electrical test equipment. Unless authorized by the responsible OSHA Manager(s) employees will only use the following electrical test equipment:
- Santronics AC Sensor
- Sure test circuit analyzer
- Tic tracer
- 120 Volt outlet circuit tester
- Report to the responsible OSHA Manager(s) any inspection situation where the employee has a question about their qualifications or proper equipment for the inspection.
General Precautions
- Inspect portable cord-and-plug connected equipment, extension cords, power bars, and electrical fittings for damage or wear before each use. Repair or replace damaged equipment immediately.
- Always tape extension cords to walls or floors when necessary. Nails and staples can damage extension cords causing fire and shock hazards.
- Use extension cords or equipment that is rated for the level of amperage or wattage that you are using.
- Always use the correct size fuse. Replacing a fuse with one of a larger size can cause excessive currents in the wiring and possibly start a fire.
- Be aware that unusually warm or hot outlets may be a sign that unsafe wiring conditions exists. Unplug any cords or extension cords to these outlets and do not use until a qualified electrician has checked the wiring.
- Always use ladders made with non-conductive side rails (e.g., fibreglass) when working with or near electricity or power lines.
- Place halogen lights away from combustible materials such as cloths or curtains. Halogen lamps can become very hot and may be a fire hazard.
- Risk of electric shock is greater in areas that are wet or damp. Install Ground Fault Circuit Interrupters (GFCIs) as they will interrupt the electrical circuit before a current sufficient to cause death or serious injury occurs.
- Use a portable in-line Ground Fault Circuit Interrupter (GFCI) if you are not certain that the receptacle you are plugging your extension cord into is GFCI protected.
- Make sure that exposed receptacle boxes are made of non-conductive materials.
- Know where the panel and circuit breakers are located in case of an emergency.
- Label all circuit breakers and fuse boxes clearly. Each switch should be positively identified as to which outlet or appliance it is for.
- Do not use outlets or cords that have exposed wiring.
- Do not use portable cord-and-plug connected power tools with the guards removed.
- Do not block access to panels and circuit breakers or fuse boxes.
- Do not touch a person or electrical apparatus in the event of an electrical accident. Always disconnect the power source first
Lightning
Direct Protection
By installing a lightning strike installation on building
- The Franklin system
- Faraday Cage System
- Static Electrical System
Indirect Protection
By equipping voltage equalizing equipment on the network of electrical installations (Arrester)
Lift
The function of lift is to transport persons and goods in private and commercial buildings. Hydraulic lift are frequently used for low lifting height, otherwise counterbalanced cable lifts are used
When dangerous thing happens and the passengers can do nothing, the aspects of reliability and safety of passengers are the basic factors in the consideration of the design of lift
What is the feature incorporated in the high rise building to cater for lightning strike?
ReplyDelete1. Grounding
DeleteBen Franklin was an early user of grounding. While the principle is still the same we have multiple methods to keep the power of lightning out of your building. Lightning Rods are the most familiar grounding protection. Ben Franklin understood the theory of making a lightning target and directing the resultant strike harmlessly to the ground. Different designs work in different environments and meet different requirements. The wires over utility substations act as lightning rods, although we call them air terminals today. Other applications are definitely not suited for air terminals like the munitions dump in New Jersey or where electronics need to be protected within structures. A Faraday Cage is a good choice for those buildings. Downconductors, like lightning rods, direct current to ground to prevent lightning damage. Building steel may be used in place of downconductors where practical as a beneficial part of the earth electrode subsystem.
2. Transients and Surges
To a lightning bolt building wiring, fuses and circuit breakers are all the same. They’re all conductors. They’re also not capable of dealing with the extreme flow of current suddenly added to the system by lightning. These lightning-induced transients are controlled with Transient Voltage Surge Suppressor (TVSS) equipment. They’re our high tech answer to a switch that shuts off power as soon as any rise is identified. A TVSS shunts, filters, clamps or blocks energy from traveling down the wire. Getting the right combination of methods
requires a partner who understands the equipment, codes and standards, the types of equipment in and around your campus and, of course, your application.
3. Detection
There is a lot of controversy about being able to detect lightning and then being able to detect it in time to avoid damage. One aim of detection is to be able to switch from AC line power to standby power. This way the system is not interrupted and the main AC power is not subject to lightning damage. We recommend a plan on what is to be protected, what is the cost and what is the level of confidence you need.
4. Remain Vigilant
Lightning is out there. Weather, time, changes to the building and maintenance can all have an effect on the resistance to lightning. An inspection of your lightning protection and a review of what’s now available could save you a lot of headaches, and perhaps save you from seeing stars.