How to be protected from defeat by electric current?
In this article examples of those ways and methods of protection thanks to which perhaps considerably to secure themselves will be given and others when performing electrotechnical works, thereby having reduced probability of accident to the minimum.
Application of protective barriers
The touch of the person to the uninsulated current carrying part which is energized is dangerous is the fact. Even knowing about availability of tension in these or those places, there is the probability of accidental touch.
In order to avoid similar cases for ensuring electrical safety of working personnel it is accepted to do protective barriers around dangerous zones (systems, the equipment, parts, etc.).
Use of protective blocking
Blocking, perhaps, belong to electrotechnical protection against accidental defeat of the person electric current or from sudden turning on of the equipment more that can also cause accident.
At their installation those cases which can occur in case of wrong and wrong behavior of the people working or servicing electric systems and devices are considered.
At operation of blocking there is the forced shutdown and de-energization of electric equipment for the purpose of prevention of the emergency.
Figurative grounding conductors
Figurative grounding conductors represent temporary means of protection. They are applied to ensuring additional safety (protection of working personnel against defeat by electric current) during the works on the disconnected sites of electric systems, the equipment, devices, etc. In that case when suddenly there is tension on these sites where people still work, these figurative grounding conductors (the conductors concerning the earth) will send the electric power to the earth.
Use of protective isolation
One more important way of technical protection against defeat by electric current is uses of protective isolation in the workplace.
Isolation of the workplace assumes the certain organization of events directed to prevention of emergence of the electric circuit of "people earth".
Primal problem of this method is increase in resistance (transitional) on this electrochain.
This option assumes use of rubber carpets, isolation of current carrying parts of electric equipment in most electrically dangerous places, etc.
Technical measures for protection against defeat by electric current
Technical measures for protection can be separated into 2 main groups.
It is possible to refer division of power supply networks, use of low tension, timely control over isolation, protective grounding, reinforced insulation (use of double isolation) to the first and other. Use of similar measures of protection gives to the person the maximum protection against defeat by electric current.
We will refer protective shutdown and nulling to the second group:
- Division of power supply networks. For division of the power supply network use transformers. They allow to break the general chain into separate chains and sites (electrically not connected among themselves). In power supply networks where the isolated neutral is applied, it increases insulating resistance and lowers ground capacitance, comparing to the power supply network in general. At division of power supply networks use of autotransformers is inadmissible.
- Use of low tension of power supply. According to state standard specification low tension can be considered tension up to 42 Century. It is used for the purpose of increase in safety from defeat by electricity. Low tension usually receives by means of the transformers (lowering).
- Isolation, its control, detection of damages, prevention.
- Control over the condition of insulating covering is exercised by periodic measurement of its resistance. The purpose of this procedure is detection of defective places and timely prevention of short circuits on the earth.
- Protective grounding. Protective grounding is called deliberate electrical connection with the earth (or its equivalent). The problem of grounding is lowering of values of tension concerning the earth. It is used in power supply networks with tension till 1000 in (with the isolated neutral). Protective grounding assumes redistribution of voltage drops on sites of the electric circuit: "the body – the earth" and "the phase – the earth".
- Use of double isolation. Double isolation is understood as association of working and additional isolation together. It considerably increases the general reliability of protection against defeat by current. The electric equipment done with such isolation, as a rule, is marked by special signs. Effectively double isolation in the different electric tool proves.
- Application of protective shutdown. Protective shutdown is quite effective measure of protection against defeat by electric current. It represents high-speed protection that provides premature automatic operation and switches-off electric equipment.
- Nulling. Protective grounding is the deliberate (special) electrical connection with the zero conductor of not current carrying metal parts which potentially can be energized (at malfunctions, insulation breakdowns, etc.). It is used in power supply networks with tension to 1000 V (with deafly grounded neutral). The primal problem of such nulling is decrease in probability of defeat by electric current of the person at emergency breakdown of electric equipment on the body on one of power supply network phases.