Electrical safety of premises: protection against electric current, classification of hazardous and highly hazardous premises

Electrical equipment in industrial plants is used everywhere. It boosts production and reduces manual labor. But such devices are dangerous to human health due to the possibility of electric shock. One of the norms of protection against the influence of damaging factors is the classification of premises for electrical safety.

Types of premises

They are classified according to the way they are used:

• special areas where electrical appliances are located;
• space for other needs (production, trade, household and utility units).

Rooms with power plants are areas or their isolated fragments with working electrical devices, admission is only allowed by trained specialists for maintenance. For them characterized by increased temperature and dampness, a lot of grounded iron parts. These factors increase the potential for stress.

Electrical Installation Rules (PUE) allow the existence of such spaces:

• dry;
• wet;
• raw;
• especially raw;
• hot;
• dusty.

Dry areas have sixty percent relative humidity. If the air is 60 percent damp and water vapor appears periodically, then such a space qualifies as humid.

Long-term moisture saturation of more than seventy-five percent makes the premises damp. 100% moisture content means that on all surfaces and thingslocated in a certain area, liquid accumulates. This space is called especially damp.

Water conducts electricity well. Therefore, the impressive moisture content in industrial buildings, contributing to the formation of sediment, is taken into account when determining the category of premises for electrical safety. A hot place is exposed to heat radiation continuously or at intervals of 24 hours. The ambient air warms up more than 35 degrees above zero. An increase in temperature conditions weakens the insulating capabilities of dielectrics, and the aging process accelerates. This leads to an increase in the frequency of accidents.

If the production conditions allow the formation of technological dust masses, followed by sedimentation on surfaces and penetration into the equipment housings, the space will be called dusty. Settled in thick layers on an electrical appliance the dusty mass can create a conductive environment, which leads to emergency situations. The danger also lies in obstructing the ventilation of the equipment, resulting in overheating and fire. Dust deposits can conduct electricity, and maybe dielectric.

And also there are territories subject to aggressive chemical activity or under the influence of organic reactions. The influence of vapors, gases contributes to the destruction of insulating layers and conductive parts. The current-carrying strips appearing during oxidation create an additional hazard for employees who come into contact with electrical machines.

Increasing the level of safe work performance and reducing the negative impact of these points requires additional measures:

• installation of additional fire protection on cable ducts and live parts;
• modernization of supply and exhaust ventilation;
• laying on floor elements of dielectric coatings.

Classification of premises by hazard

Long-term use in extreme industrial environments reduces the protective performance of the insulating elements. When you are in workshops with conductive coatings or touching devices, located close to earthed parts, the likelihood of getting under voltage is dramatically increases. Paragraph 1. 1. 13 of the Rules for Electrical Installations (PUE) subdivides industrial buildings, branches for trade and utility rooms in three separate categories, characterizing the level of threat to health and life.

Safe premises

The reduced moisture content (less than 75 percent) and the presence of efficient exhaust and heating systems rank a particular space as safe.

The flooring must not be electrically conductive. Conductive floors include iron, concrete, earth, etc.. To qualify industrial units as safe floors, dielectric mats must be installed.

In rooms without an increased threat to life, there is no humidity, high temperature conditions, live floors and dust, chemically aggressive environment.

Typical examples of non-hazardous objects are ordinary apartments and offices, tool storage rooms, laboratory installations, industrial structures of instrument-making factories, the design of which immediately involved the installation of insulating coatings, impressive air filters for sucking out dust accumulations and a complex for correcting the temperature balance.

Premises with increased danger

Modern systematization of structures, due to the likelihood of falling under the influence of electricity, classifies the building into a group of premises with increased danger electric shock if one of the following requirements is met:

1. dampness (with a moisture content over seventy-five percent);
2. conductive dust structure (regular formation of conductive dust masses);
3. departments with conductive sex components (the existence of concrete, iron, stone and other types of floors with conductive characteristics);
4. buildings with a constant temperature inside over thirty-five degrees above zero;
5. contact conditions for electrical appliance components and steel parts of factory buildings that are connected to a protective earth, for example, a water pipe and a protective casing of the equipment.

Parameters related to structures presenting an increased risk of electrical injury are regulated by provisions 1. 1. 8 and 1. 1. 10 PUE. These include electromechanical shops with heating and ventilation.

Particularly dangerous premises

Spaces with the highest moisture content, particles chemical elements in a closed atmosphere, in combination with two or more criteria of increased danger, characterize premises with increased danger:

1. spaces with a humidity of about one hundred percent;
2. chemical and organic effects leading to the destruction of the insulating coating of electrical appliances.

Particularly dangerous rooms for electrical safety can be found at machine-building enterprises. These are electrical erosion areas, as well as those located in the open space and under the canopies of the industrial site.

The latest techniques allow the design of effective protection of work collectives from electrical injuries. This is facilitated by progress in the use of new insulating materials and technologies. Despite the differences in the security of the premises, using the best possible techniques to improve working conditions, you can reduce the number of accidents when using electrical equipment.