2. Classification of methods of safe operation of electroinstallation

Safe operation of electroinstallation is carried out by application of protective actions, use of electroprotective means and observance of electroprotective actions.

Protective actions - the circuit or constructive decisions directed on safe operation of electroinstallations.

Electroprotective means are tools which are applied at performance of works in electroinstallations, and also overalls and спецобувь.

Protective actions are the legalized positions which adhere at the organization of works on electroinstallations.

3. Protective actions in electroinstallations

Protective actions which provide safe work on electroinstallations, are subdivided into three groups.

1. Protective actions which provide safety at a normal operating mode of electroinstallation, i.e. during all time when electroinstallation is energized, to them concern:

Isolation of current carrying parts (isolation has the big resistance to an electric current, through it proceeds small currents safe for the person);

o Inaccessibility of current carrying parts - the person cannot touch to current carrying parts is is provided with an arrangement of current carrying parts at height and in an accessible place;

o Blocking safety - the devices warning working from erroneous actions:

- Which are locked;

- Disconnecting;

o Orientation in electroinstallation, as methods of orientation serve:

- Marks of parts of the equipment;

- Drawing signs on safety;

- Corresponding arrangements and colouring of phases (a phase A - yellow, B - red, C - green);

o Protective short circuit - artificial short circuit on the ground of a phase of a network in which there was a source of a current of short circuit on the ground;

o Isolating platforms - platforms, a floor and which fences it is isolated from the ground.

2. Actions which provide safety at an emergency condition of installations when there is a damage of working isolation and a pressure appears on metal cases, to them concern:

o Protective grounding - connection of the metal case of electroinstallation with the device which is connected to the ground, reduction of a pressure of a touch is effectual measures of protection in electroinstallation which eats from networks with the isolated neutral of any class of a pressure, and with the isolated neutral - only above 1 кВ.

o зануление - connection of the case of electroinstallation with a zero wire of a power line, is applied in networks less than 1 кВ; short circuit of a phase on the case turns to single-phase short circuit, from this current works МТЗ, disconnecting the damaged electroinstallation.

o Protective switching-off - devices of automatics which disconnect electroinstallation at occurrence in it dangers of defeat of the person an electric current;

o Double isolation - performance of cases of electroinstallation from the isolated materials (impossibility of transition of a pressure on the case);

o Protective isolation of a workplace - the covering of a floor and building designs near electroinstallation by an isolating material, is carried out, when impossible application of grounding or зануления cases of electroinstallation.

3. Protective actions of the combined action which remove danger both at normal, and at an emergency condition of installation, to them concern:

o Performance of electric networks isolated from the ground;

Iч = Uф / (Rч + Z/3)

Iз = Uф / (Z/3)

o Electric division of networks is a division of the lingering or branched out electric networks into separate sites, электрично not connected among themselves, is applied seldom in the form of a feed of separate consumers through dividing transformers;

o Indemnification of making spaciousness of currents of short circuit on the ground - the cable line has rather greater spaciousness, to reduce it it is possible either division of a network or indemnification, for what нейтрале the transformer заземляют through дугогасящий a reactor;

o Alignment of potentials is an increase of potential of a basic surface of legs of the person to potential of current carrying parts or cases of electroinstallatio n which are mentioned by the person;

o Application of small pressure:

- For an alternating current it is no more 42 In;

- For a direct current - 110 Century there are more