Protection from electric shock

Protection from electric shocks (grounding system)... 

Grounding. Grounding is another way to provide protection from electric shock however, it is nonnally a secondary protective measure. By grounding a tool or electrical system, a low-resistance patlr to tire earth Uirough a ground coimection or comiections is intentionally created. Wlien properly done, tliis patli offers sufficiently low resistance and lias sufficient current-cariy ing capacity to prevent the buildup of voltages that may result... 

In similar studies, the reduction potentials of 1,2-benzothiazole derivatives in DMF were correlated to antimycotic activity [166], and those of 1,3,5,7-substituted-1,3-dihydro-2H-l, 4-benzodiazepin-2-ones and benzodiazepine-2-thiones in dimethylformamide (DMF)-water solutions were correlated to inhibition of orientation reactions and to protection from electric shock [167]. 

Biopotential amplifiers have to provide sufficient protection from electrical shock to both user and patient. Electrical-safety codes and standards specify the minimum safety requirements for the equipment, especially the maximum leakage currents for chassis and patient leads, and the power distribution system (Webster, 1992 AAMI, 1993). 

Protection from electric shock is provided by basic protection and fault protection. Protective bonding is bonding for the purpose of safety. 

Protection from electric shock is provided by basic protection and fault protection. 

When it is required to provide the very hest protection from electric shock and fire risk, earth fault protection devices are incorporated in the installation. The object of the Regulations concerning these devices, 411.3.2.1 to 411.3.2.6, is to remove an earth fault current very quickly, less than 0.4 s for all final circuits not exceeding 32A and limit the voltage which might appear on any exposed metal parts imder fault conditions to not more than 50 V They will continue to provide adequate protection throughout the life of the installation even if the earthing conditions deteriorate. This is in direct contrast to the protection provided hy overcurrent devices, which require a low resistance earth loop impedance path. 

We have seen that fuses and circuit breakers are not effective as protection from electrical shock. Equipment fuses, generally rated at one ampere or greater, are also useless for personal protection. These devices are designed solely... 

When it is required to provide the very best protection from electric shock and fire risk, earth fault protection devices are incorporated into the installation. The object of the regulations concerning these devices (411.3.2 to 411.3.3) is... 

It has become standard practice in recent years to use sensitive earth leakage current detectors in circuit breakers to further protect against electric shock. The current sensitivity can be chosen from a range of standard current values, e.g. 30, 100, 500 and 1000 mA. The 30 mA sensitivity is used at individual consumer sub-circuits, e.g. feeders to domestic and small power socket outlets, feeders to luminairs. The higher sensitivities are used in the upstream circuit breakers so that protection discrimination is achieved. 

Install ground-fault circuit intermpters (GCFls) as required by code to protect users from electric shock, particularly if an electrical device is hand-held during a laboratory operation. 

It should be noted that GFCI devices are not foolproof, nor are they absolute protection against electric shock from an instrument. They only are effective with fault currents that follow a path to ground. It is still possible to receive a shock from an appliance fault where a person s body is across the hot-to-neutral circuit, requiring a simultaneous contact with two conductors. This is a more unusual situation and implies exposed wiring from the appliance. 

The primary standard covering minimum requirements for the manufacturing and testing of rubber insulating gloves for the protection of workers from electrical shock. ASTM F 1818, Specification for Foot Protection for Chainsaw Users... 

A fast-acting circuit breaker that is sensitive to very low levels of current leakage to ground. They are designed to provide protection against electrical shock from ground... 

Workers exposed to electrical hazards face a risk of death or serious injury from electric shock. According to the Bru eau of Labor Statistics, there were 192 and 170 fatalities involving contact with electric crurent in 2008 and 2009, respectively. About half of these fatalities (89 in both years) occrured in construction. OSHA explains that the use of properly designed, manufactured, and cared-for electrical protective equipment helps protect employees from this risk. 

Cover the general requirements for head protection. Head injuries are caused by falling or flying objects or by bumping your head against a fixed object. Other head injuries are from electrical shock and burns. Hard hats are designed to do two things resist penetration and absorb the shock of a blow. 

Employees working in areas where there is possible danger of head injury from impact, or falling of flying objects, or from electrical shock and burns, must be protected by protective helmets. 

Leather gloves will not protect you from electrical shock They are cowhide, typically, and have inherent moisture in them. 

Mention has already been made of the need to ensure that electrical conductors etc. are adequately insulated. Insulating material has extremely high resistance values such as virtually to prevent electric current flow through it. The principle of insulation is used when work has necessarily to be carried out at or near uninsulated live parts. Obviously such parts should always be made dead if at all possible. If this cannot be done then properly trained people, competent to do the work, can make use of insulating stands, mats or screens, or rubber insulating gloves to protect them from electric shock. Periodic examination of all such insulating devices is necessary. 

Employers may use the IEEE Std 1048-2003 equation to determine safe body current limits only if the employer protects workers from hazards associated with involuntary muscle reactions from electric shock (for example, the hazard to a worker from falling as a result of an electric shock). Moreover, the equation applies only when the duration of the electric shock is limited. If the precautions the employer takes, including those required by applicable standards, do not adequately protect employees from hazards associated with involuntary reactions from electric shock, a hazard exists if the induced voltage is sufficient to pass a current of 1 milliampere through a 500-ohm resistor. (The 500-ohm resistor represents the resistance... 

The electricity supply company has one of its conductors solidly connected to the earth and every circuit supplied by the company must have one of its conductors connected to earth. This means that if there is a fault, such as a break in the circuit, the current, known as the earth fault current, will return directly to earth, which forms the circuit of least resistance, thus maintaining the supply circuit. This process is known as earthing. Other devices, such as fuses and residual currertt devices, which will be described later, will also be needed within the circuit to interrupt the current flow to earth so as to protect people from electric shock and equipment from overheating. Good and effective earthing is absolutely essential and must be connected and checked by a competent person. Where a direct contact with earth is not possible, for example, in a motor car, a common voltage reference point is used, such as the vehicle chassis. 

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