Electric shock protection

Selection and Erection Isolation and Switching Inspection and Testing Protection against Fire Protection against Electric Shock Protection against Overcurrent Special Locations Earthing and Bonding... 

Protection against Electric Shock. Protection against Overcurrent... 

Electric-powered vehicles Electrolyte spillage and electric shock protection... 

Electric shock protection.Personal protective equipment-35... 

For protection against both direct and indirect electric shock, the specified supply system is SELV, but the limit of 25 V a.c. or 60 V d.c. has been dropped. Where a functional earth is needed, for certain instruments for example, it may be utihsed provided all exposed and extraneous conductive parts are bonded together and to the protective conductor. Where there is no need for direct electric shock protection and only indirect is required, section 606-04-0 l(iii) allows mains voltage supplies to fixed equipment within the equipotential zone provided the exposed conductive parts are coimected to the extraneous conductive parts in the location. Alternatively, Class ff equipment may be used provided its enclosure is suitable for the location and it has sensitive RCD protection to trip the circuit at a residual current of 150 mA within 40 ms (or in a time of five times the residual operating current when the current is less than 30 mA). For hand-held equipment, portable tools and hand lamps, for example, there is no relaxation and they have to be supplied at SELV. 

Protection against overcurrent and electric shock is in section 3. It compares the performances of semi-enclosed and cartridge fuses and MCBs for both overcurrent and short circuit protection. It deals with RCDs for earth leakage and electric shock protection. It concludes with Tables 10 and 11 for the sizes of main earthing, main bonding and supplementary bonding conductors. 

As a vessel is loaded, it moves downward because of deflection of the load cells and support stmcture. Pipes rigidly attached to a vessel restrict its free movement and assume some portion of the load that cannot be measured by the load cells. This is very detrimental to scale accuracy. Deflection of the load cell is unavoidable deflection of the vessel support stmcture should be minimized. Anything which increases vessel deflection, eg, mbber pads used for shock protection, must be avoided. The total number of pipes should be minimized and be of the smallest diameter, thinnest wall possible. Pipe mns to weigh vessels must be horizontal and the first pipe support should be as far as possible from the vessel. Alternatively, a section of mbber hose or flexible bellows should be used to make the final connection to the vessel. The scale should be caUbrated using weights, not by means of an electrical simulation method, which cannot account for the effects of the piping or test the correct functioning of the scale. 

Protection from electric shocks (grounding system)... 

The purpose of this test is to check for proper insulation of all the insulated live parts and components and to ensure protection of a human body against electrical shocks while the eqtiipment is energized and is in operation. The test detects weak insulation, if any, and this must be rectified before putting the equipment into service. 

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... 

Protection against electrical shocks (device and or connections)... 

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]. 

After the sample is applied to the dampened piece of paper, the paper is placed in the electrophoresis chamber so that both ends are in contact with reservoirs of the electrophoresis buffer at the electrodes (Fig. 4-4). If the origin line is not in the center of the paper, the paper must be positioned to allow maximum migration toward the correct electrode. After the chamber is covered or closed to protect against electric shock, an electric field is applied to the system. 

The shock protection by these sources can be implemented in the following ways enhanced insulation of wires and equipment, and insulation of a person who is working on a power line. Electrical equipment can be isolated. These should be properly marked by warning signs of high voltage and electrical shock. 

The unit shall be designed to protect the operator against electrical shock or excessive radiation. 

The SWGR and MCC eqnipment are invariably housed in a building or enclosed module, or at least effectively protected against bad weather and aggressive environmental conditions. The constrnction is therefore of the metal clad type, in which all the live parts are housed in a mild-steel sheet metal enclosure. The enclosure is sub-divided so that personnel may work safely on some compartments without danger or the risk of electric shock. 

When an earth fault occurs at the far end of a cable it is possible that the armouring, cable gland and the frame of the consumer equipment can be raised to a dangerous potential with respect to electric shock exposure to human operators. This subject has been given considerable attention over the last 20 years, and is well documented in for example IEC60364. The international documentation concentrates on low voltage fixed and portable equipment protected by fuses and miniature circuit breakers. See also Chapter 13. 

Hence an earth leakage circuit breaker should be used in the MCC to protect the circuit against electric shock hazard. 

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