Selection of devices for the protection of aircraft electrical networks. Qualification groups for electrical safety Selection of protection devices for medium voltage electrical networks

Analysis of failures and non-nominal operating modes of electrical machines makes it possible to distinguish the following types of accidents that are often encountered in practice:

Short circuit (SC) at the terminals of the machine or in the stator winding;

Locked rotor when starting the engine (short circuit mode of the engine, especially often found when starting it directly);

Loss of phase of the stator winding (often found when protecting windings with fuses);

Technological overloads arising from a load surge during engine operation;

Disturbance of cooling caused by a malfunction of the forced ventilation system of the engine;

Decrease in insulation resistance resulting from aging of the insulation due to cyclic temperature overloads.

Emergency modes in the asynchronous motor circuit can cause either a short-term increase in current by 12 ... 17 times compared to the nominal, or a long-term current flow 5 ... 7 times higher than its nominal value.

To protect electrical circuits from the short circuit mode, automatic switches, current relays and fuses are widely used. Overcurrent events require other protective equipment. So, in case of breakage of one of the phases of an induction motor, the most effective are the minimum current and temperature protection; less effective, but efficient - thermal protection (thermal relays). With a locked rotor, overcurrent relays and temperature protection are very effective, thermal protection is less effective. In case of overload, thermal protection gives the best results. Thermal relays are also effective. In the event of engine cooling failure, only temperature protection can prevent an accident.

A decrease in the insulation resistance of the stator winding of the motor can provoke both an overload in the circuit and a short circuit.

Protection in such an accident is carried out by special devices for monitoring the insulation resistance of the motor winding.

The main emergency mode in lighting installations is short circuit. Overload protection is required only for lighting installations operated indoors and in explosive and fire hazardous environments. The most common protection device for lighting installations is a circuit breaker. When incandescent lamps are turned on, a short-term current surge appears, 10 ... 20 times higher than the rated current. In about 0.06 s, the current decreases to the nominal. The inrush current value is determined by the lamp wattage. When choosing the type of protection for incandescent lamps, it is necessary to take into account the peculiarities of their starting characteristics.

Due to the widespread use of power semiconductor technology, its protection requires the use of effective devices. One of the main disadvantages of power semiconductor devices is their low current overload capacity, which imposes severe conditions on the protection equipment (in terms of speed, selectivity and reliability of operation). Currently, to protect power semiconductor devices from short-circuit (both external and internal), high-speed circuit breakers, semiconductor switches, vacuum switches, pulse arc switches, high-speed fuses, etc. are used. The feasibility of using one or another protection of power semiconductor devices is determined by specific conditions of their operation.

Protection of electrical circuits takes a special place. At present, networks with a voltage of 0.4 to 750 kV are widely used. The main, most dangerous and frequent types of faults in networks are short-circuit between phases and a phase-to-earth fault.

The bulk of consumers receive power from distribution networks with a voltage of 0.4; 6 and 10 kV (recently, 0.66 kV networks have been widely used). To supply stationary power consumers and general-purpose lighting installations, three-phase four-wire networks with a voltage of 380/220 V with a dead-grounded neutral are used. Power consumers are connected to line voltages of the network, and lighting devices are connected to phase voltages. Powerful power consumers, for example, electric motors with a capacity of 160 kW and above, have a voltage of 0.66; 6 and 10 kV.

The main emergency modes in such networks are: single-phase short-circuit (up to 60% of accidents), three-phase short-circuit (up to 10%), two-phase short-circuit to earth (up to 20%), two-phase short-circuit (up to 10%).

Protection of electrical networks with voltages up to 1000 V is carried out, as a rule, by protection devices, and networks with voltages above 1000 V have relay protection.

The most common network protection devices are circuit breakers and fuses. If it is required to have protection with high speed, sensitivity or selectivity, then relay protection based on relays and circuit breakers is used.

Indoor electrical networks with voltages up to 1000 V must also have overload protection, as a rule, based on circuit breakers with thermal or combined releases.

The main task facing the selection of equipment for protecting consumers and electrical networks is to match the characteristics of protection devices with the maximum load characteristics (dependences of the permissible current on the duration of its flow) of various consumers and networks (wires and cables). For each specific type of consumer, the most complete agreement can be achieved using a specific type of protection devices. In the case of full agreement, the current-voltage and time characteristics of the protection device on the graph go above and as close as possible to the load characteristic of the consumer.

The personnel servicing electrical installations, as far as they are concerned, must know:

· Rules of technical operation of electrical installations of consumers (PTEEP);

· Rules for electrical installations (PUE);

· Manuals for the design and operation of the assigned electrical installations;

· Job and operational instructions in relation to the position held and the work performed;

· Rules for freeing a person from the action of electric current;

· Rules of rendering first aid to the victim from the action of electric current.

2. Qualification groups for electrical safety.

Group	The amount of knowledge required.
	For group 1, persons who do not have special electrical training, but who have a clear idea of the danger of electric current and safety measures when working on the serviced area, electrical equipment, and electrical installation, are certified. Must have practical knowledge of first aid procedures. Training for 1 group is carried out in the form of briefing followed by a control survey by a specially appointed person with an electrical safety group of at least 3.
	Persons with group 2 must have: 1. elementary acquaintance with the electrical installation device; 2. a clear idea of the danger of electric current and the approach to live parts; 3. knowledge of basic safety precautions when working on electrical installations; 4. practical acquaintance with the rules of first aid.
	Persons with group 3 must have: 1. elementary knowledge of electrical engineering; 2. a clear understanding of the hazards when working in electrical installations; 3. knowledge of PTE, PTEEP and MPOT in terms of organizational and technical measures to ensure the safety of work; 4. knowledge of the rules for using protective equipment; 5. knowledge of the structure of the serviced equipment and the rules of its operation; 6. knowledge of the rules of first aid and the ability to practically provide first aid to the victim.
	Persons with group 4 must have: 1. a clear knowledge of the basics of electrical engineering; 2. knowledge of PTE, PTEEP, MPOT and PUE in terms of fixed electrical installations; 3. a complete understanding of the dangers when working in electrical installations; 4. knowledge of the rules of use and testing of protective equipment; 5. knowledge of the installation so that it is free to understand exactly which elements must be disconnected for the production of work, to find all these elements in nature and to check the implementation of the necessary safety measures; 6. the ability to organize the safe conduct of work and to supervise them in electrical installations with a voltage of up to 1000 volts; 7. knowledge of the rules of first aid and the ability to practically provide first aid to the victim.

2.1 Verification of knowledge of PTE by personnel.

Subdivided into:

1. primary;

2. periodic;

3. extraordinary.

Periodic subject to verification:

· Personnel involved in the operation of electrical installations, as well as management and engineering staff, organizing their operation - once a year;

· Management staff and engineering and technical staff, not related to the previous group, but in charge of electrical installations - once every three years.

Primary called the first of the periodic checks.

Extraordinary knowledge is tested:

· Persons who have committed violations of PTE, PTEEP, MPOT, official or operational instructions;

· Persons having a break in work at this electrical installation for more than 6 months;

· Persons transferred to a new electrical installation;

· Persons on the instructions of the management of the enterprise or on the instructions of the energy supervision inspector.

3. Electrical safety in existing electrical installations up to 1000 Volts. Manufacturing jobs.

Electrical installations such installations are called in which electricity is produced, converted and consumed. Electrical installations include mobile and stationary sources of electricity, electrical networks, switchgear and connected pantographs.

Operating electrical installations Installations are considered to be fully or partially energized or to which voltage can be applied at any time by switching on the switching equipment.

According to the degree of danger of injury to personnel by electric current, electrical installations are subdivided into electrical installations up to 1000 Volts and above 1000 Volts .

According to the safety regulations, the operation of electrical installations is divided into two parts:

· Operative maintenance of electrical installations;

· Performance of work in electrical installations.

Prompt service includes:

· Watch in the existing electrical installations;

· Bypasses and inspections of electrical installations;

· Operational switching;

· Work performed in the order of current operation.

An employee of management personnel who has an electrical safety group of at least the 4th has the right to give an order to perform work in existing electrical installations up to 1000 Volts.

Work in electrical installations with regard to safety measures is divided into those performed:

1.with stress relief;

2. without removing the voltage on live parts and near them.

TO stress relief work includes work performed in an electrical installation (or part of it), in which voltage is removed from live parts.

TO work without removing voltage on live parts, and near them includes work performed directly on these parts or near them. In installations with voltages above 1000 Volts, as well as on overhead lines up to 1000 Volts, the same work includes those that are performed at distances from live parts that are less than permissible. Such work must be performed by at least two persons: the manufacturer of work with a group of at least IV, the rest - below III.

3.1 Technical measures to ensure the safety of work with stress relief.

When preparing the workplace for work with stress relief, the operating personnel must perform the following technical measures in the specified order:

1.the necessary disconnections were made and measures were taken to prevent the supply of voltage to the place of work due to erroneous or spontaneous switching on of the switching equipment;

2. prohibiting posters ("Do not turn on, people are working", "Do not turn on, work on the line") are displayed on the manual drives and keys for remote control of switching equipment and, if necessary, barriers are installed;

3. portable grounding is connected to the "Earth", the absence of voltage on live parts, on which grounding must be applied to protect people from electric shock, has been checked;

4. Immediately after checking the absence of voltage, grounding must be applied (grounding knives are included, and where they are absent, portable grounding is installed);

5. warning and prescriptive posters are posted, workplaces and live parts remaining under voltage are fenced, if necessary. Depending on local conditions, live parts are shielded before or after grounding.

The technical measures specified in clause 3.1 can be performed by an admitting person with a qualification group of at least 3.

Work with stress relief can be carried out either with the imposition of grounding, or without the imposition of grounding, but with the adoption of technical measures to prevent the erroneous supply of voltage to the place of work.

3.1.1 Making outages.

At the place of work, the live parts on which the work is performed, as well as those that may be accessible to touch during the work, must be disconnected.

Non-insulated live parts accessible to touch need not be disconnected if they are securely shielded with insulating linings made of dry insulating materials.

Disconnection should be made in such a way that parts of the electrical installation or electrical equipment allocated for work are separated from all sides from live parts that are energized by switching devices or by removing fuses, as well as by disconnecting the ends of cables (wires) through which voltage can be applied to place of work.

Disconnection can be done:

1. manual switching devices, the position of the contacts of which is visible from the front side or can be established by examining the panels from the rear side, opening the shields, removing the covers. These operations must be carried out in compliance with safety measures. If there is complete confidence that in switching devices with closed contacts, the position of the handle or pointer corresponds to the position of the contacts, then it is allowed not to remove the covers to check the disconnection;

2. contactors or other switching devices with an automatic drive and remote control with contacts accessible to inspection after taking measures to eliminate the possibility of erroneous switching on (removing the operating current fuses, disconnecting the ends of the closing coil).

The procedure for checking the disconnected state of switching devices is established by the person issuing the order or giving the order.

To prevent the supply of voltage to the place of work due to transformation, all power, measuring and various special transformers connected with the electrical equipment being prepared for repair should be disconnected from the side of both high and low voltage.

In cases where work is performed without the use of portable grounding, additional measures must be taken to prevent the erroneous supply of voltage to the place of work: mechanical locking of the drives of disconnected devices, additional removal of fuses connected in series with switching devices, the use of insulating linings in circuit breakers, automatic machines, etc. p. These technical measures must be indicated when issuing a work order. If it is impossible to take these additional measures, the ends of the supply or outgoing lines on the board, assembly or directly at the place of work must be disconnected; when disconnecting the cable from the fourth (zero) core, this core must be disconnected from the zero bus.

3.1.2 Hanging warning posters, fencing of the place of work.

On the handles, keys and control buttons of all switching devices, as well as on the contact racks (bases) of the fuses, with the help of which voltage can be applied to the place of work, posters should be posted "Do not turn on - people work", "Do not turn on - work on lines ".

Non-disconnected live parts adjacent to the workplace, accessible to accidental touch, must be fenced during operation.

Temporary fences can be dry, well-reinforced screens, overlays made of wood, mikanite, getinax, textolite, rubber, etc. Temporary fences should contain posters "Stop - it is dangerous to life."

Before installing the fences, they must be thoroughly dust-wiped off.

The installation of fences applied directly to live parts should be done with caution, with dielectric gloves and goggles, in the presence of a second person with IV qualification group.

At all prepared places of work, after the grounding has been applied, the poster “Work here” is displayed.

During work, the staff of the brigade FORBIDDEN rearrange or remove posters and installed temporary fences and enter fenced areas.

3.1.3 Checking the absence of voltage.

Before starting all work on electrical installations with voltage removal, it is necessary to check the absence of voltage in the work area. The absence of voltage is checked by a voltage indicator with a neon lamp.

Immediately before checking the absence of voltage, it is necessary to make sure that the indicator used is in good working order by checking it on live parts located nearby and knowingly energized.

FORBIDDEN use indicators with low input impedance (test lamps, LED voltage indicators, sound "controls", etc.) to check the absence of voltage, since they do not indicate induced voltage that is dangerous to human life .

The absence of voltage must be checked:

· Between three pairs of phases;

· Between each phase and PE-conductor ("earth");

· Between zero working (N) and zero protective conductor (PE).

Stationary devices signaling the disconnected state of the installation are only an auxiliary means, based on the readings of which it is not allowed to make a conclusion about the absence of voltage.

3.1.4 Applying grounding.

3.1.4.1 Grounding locations.

Grounding must be applied to the live parts of all phases of the electrical installation section disconnected for the production of work from all sides, from where voltage can be applied, including due to reverse transformation.

It is sufficient to overlay one ground on each side. These grounds can be separated from live parts or equipment on which work is performed by disconnected disconnectors, switches, circuit breakers or removed fuses.

The imposition of grounding directly on live parts on which work is performed is required when these parts can be under induced voltage (potential) or they can be energized from an extraneous source of dangerous magnitude. Places of overlapping grounding must be selected so that the grounding is separated by a visible break from live parts. When using portable groundings, the places of their installation should be located at such a distance from live parts that remain energized so that the imposition of groundings is safe.

When working on busbars, at least one grounding must be applied to them.

In closed switchgears, portable earthing must be applied to live parts in the designated places. These areas should be free of paint and surrounded by black stripes.

In all electrical installations, the points of connection of portable grounding to the grounding wiring must be cleaned of paint and adapted to fix the portable grounding clamp, or there should be clamps (thumbs) on this wiring.

In electrical installations, the design of which is such that the imposition of grounding is dangerous or impossible (for example, in some distribution cubicles, switchgear of certain types, etc.), when preparing the workplace, additional safety measures must be taken to prevent accidental voltage supply to the place of work. These measures include: locking the disconnector drive with a lock, protecting the blades or the upper contacts of these devices with rubber caps or rigid pads made of insulating material.

The list of such electrical installations must be determined and approved by the chief power engineer (the person responsible for the electrical equipment).

Grounding is not required when working on equipment if busbars, wires and cables are disconnected from it on all sides, through which voltage can be applied, if it cannot be energized by reverse transformation or from an external source, and provided that no voltage is applied to this equipment. The ends of the disconnected cable must be short-circuited and grounded.

3.1.4.2 The procedure for applying and removing grounding.

Grounding should be done immediately after checking the absence of voltage. The application and removal of portable grounding must be done by two persons.

Portable earthing must be connected to the earth terminal before checking the absence of voltage. Portable grounding clamps are applied to grounded live parts using a rod made of insulating material using dielectric gloves. The clamps are fastened with the same rod or directly with your hands in dielectric gloves.

It is forbidden to use any conductors for grounding that are not intended for this purpose, as well as to connect the grounding by twisting them.

Portable grounding must be made of bare copper stranded wires and have a cross-section of at least 25 mm 2.

The grounding should be removed in the reverse order using a rod and dielectric gloves, that is, first remove it from live parts, and
then disconnect from grounding devices.

If the nature of work in electrical circuits requires grounding removal (for example, when checking transformers, when testing equipment from an external current source, when checking insulation with megohm meters, etc.), temporary removal of groundings that interfere with the work is allowed. In this case, the place of work must be prepared in full compliance with the above requirements, and only during the production of work can those groundings be removed, in the presence of which the work cannot be performed.

Switching on and off the grounding knives, the imposition and removal of portable groundings should be accounted for according to the operational scheme, in the operational log and in the order.

3.2 Organizational measures to ensure the safety of work.

Organizational measures to ensure the safety of work in stationary electrical installations are:

1. registration of work by order or order;

2. admission to work;

3. supervision during work;

4. registration of a break in work, transfers to another workplace, completion of work.

3.2.1 Attire, order, routine maintenance.

Work in electrical installations is carried out:

· Alongside;

· By order;

· In the order of current operation.

Outfit - this is a written task for work in electrical installations, drawn up on a form of the established form and determining the place, time of the beginning and end of work, the conditions for its safe conduct, the composition of the calculation and persons responsible for the safety of work. As a rule, planned work should be carried out alongside.

Order - this is a task for work in electrical installations, drawn up in the operational log by the person who gave the order, or by the person of the operational staff who received the order orally directly or by means of communication from the person who gave the order.

Current operation - this is the performance of the operational (operational-repair) staff on a fixed electrical installation during one shift of work according to the list approved in accordance with the established procedure, while determining the need and scope of work, as well as preparing the workplace for the safe performance of work, are carried out directly by the manufacturer of the work.

3.3 Measures to ensure the safety of work without removing voltage near and on live parts that are energized.

When working without removing the voltage near and on live parts that are energized, measures must be taken to prevent workers from approaching these live parts at a distance less than permissible in electrical installations with voltages above 1000 Volts, and in electrical installations with voltages up to 1000 Volts - measures that exclude touching live parts. These works should be done together along the side.

These activities include:

1.safe location of working persons in relation to live current-carrying parts;

2. organization of continuous supervision of workers;

3. the use of basic and additional insulating means that allow work to be carried out directly on live parts.

A person working near live parts that are energized must:

· To work with the sleeves of clothes and a headdress lowered and buttoned at the hands;

· Be located so that these live parts are in front of him and only on one side.

FORBIDDEN perform work if live parts under voltage are located at the back or on both sides.

FORBIDDEN work in a bent position, if during straightening it is possible to touch live parts that are energized.

On electrical installations located in especially damp rooms with conductive dust, corrosive vapors, as well as in rooms that are dangerous in relation to fire
or explosion, performance of work on non-disconnected live parts FORBIDDEN .

In rooms with increased danger, if necessary, work can be carried out on non-disconnected live parts with the use of additional safety measures determined by the persons issuing the outfit or giving the order.

Work on live parts that are energized must be carried out using basic and additional insulating protective equipment.

4. Production of certain types of work.

4.1 Measurement of insulation resistance with portable megohmmeters.

Measurement of insulation resistance in electrical installations is carried out:

· After repair;

· During technical maintenance (routine maintenance);

· During conservation;

· At technical examination.

Insulation resistance of the electric unit is checked by persons with qualification group III or higher using a megohmmeter of the appropriate voltage.

The insulation resistance of individual elements of an electrical installation with a solidly grounded neutral must be at least 0.5 megohm (500 kOhm).

It is necessary to measure the insulation resistance for individual elements of the installation after this element is disconnected from all sides. Insulation resistance measurements are carried out with complete removal of voltage from the electrical installation and with the implementation of safety measures to prevent accidental voltage supply to the place of work. Before starting measurements, it is necessary to make sure that there are no people on the tested electrical installation, and take measures to exclude the possibility of accidental touching live parts.

The wires used to connect the megohmmeter must have good insulation and be terminated with reliable ferrules. The cross-section of copper wires must be at least 1.5 mm 2.

4.2 PTE when performing work with power tools and portable lamps.

Hereinafter, under the power tool, according to PTE 3.5.1., We mean portable and mobile electrical receivers, the design of which provides for the possibility of manually moving them to the place of use for their intended purpose (without the use of vehicles), as well as auxiliary equipment for them. These include: portable lamps; hand power tools; "Extension cords" of all voltages; vibrators and vibrating scaffolds; portable transformers for powering power tools; portable electric pumps; welding machines used outside equipped welding stations.

Persons with the 2nd qualification group for electrical safety are allowed to work with a power tool, which is not related to the maintenance of its electrical part, in JSC DSMU.

4.2.1 Selection of the protection class of the power tool depending on the working conditions.

Use in especially hazardous rooms and especially unfavorable conditions of a power tool of protection class (against electric shock) 0, 01 , 1- ABSOLUTELY FORBIDDEN.

The use of portable luminaires with voltages above 42 Volts AC without the use of electrical protection in any conditions - ABSOLUTELY FORBIDDEN.

Using portable luminaires with voltages above 12 Volts AC in particularly adverse conditions - ABSOLUTELY FORBIDDEN;

According to MPOT 10.3, it is allowed to use an electric tool of protection class (against electric shock) 2 without the use of means of protection against electric shock in any conditions, except especially unfavorable ones.

According to MPOT 10.3, it is allowed to use a power tool of protection class (against electric shock) 3 without the use of protective equipment against electric shock in any conditions.

4.2.2 Connection and rules for performing work with a power tool.

The connection of the power tool to the mains must be carried out by means of flexible hose wires or cables. One end of the hose wire must be inserted into the electrical receiver, and the other into the half-plug of the plug connection.

FORBIDDEN connection of a power tool and portable lamps to the mains with a wire or cable without a half-plug.

Plug connections (plugs, sockets) used for a voltage of 42 Volts of alternating current and below, in their design, must differ from the plug connections used at voltages of 220 and 380 Volts; the possibility of connecting plugs up to 42 volts to 220/380 sockets should be technically excluded.

Plug connections (plugs, sockets) used for a voltage of 42 Volts AC and below must have a color that is sharply different from the color of 220/380 Volt plug connections.

FORBIDDEN power tool power from autotransformers.

FORBIDDEN turn on and off the electric lamps of the lamps by screwing them in and out. Replace burnt-out lamps after the luminaire is disconnected from the mains.

Working with a power tool from ladders with a height of more than 2.5 meters FORBIDDEN... Use a portable metal ladder for working with power tools of protection class lower than 2 FORBIDDEN .

4.2.3 Obligations of the employee issuing an order (order) to perform work with a power tool.

An employee issuing an outfit (order) for performing work with an electric tool must pass a test of knowledge of the rules and regulations of work in electrical installations for a group of at least 3, have a valid certificate and belong to management personnel.

4.2.3.1 In the order (order), the employee is obliged to indicate:

1. the nature of the work;

2. the exact location of the work;

3. a list of protective equipment used in the performance of this work;

4. an exhaustive list of organizational and technical measures to ensure the safety of the prescribed work.

4.2.3.2 The issuing outfit (order) employee is obliged to ensure:

1.checking with the contractor for the presence of a valid electrical safety group required for this type of work;

2. checking the performer's admission to work with a power tool according to age and medical criteria;

3. issuance of serviceable protective equipment to the contractor in the amount prescribed by the PTE and PTB during the work;

4. issuance of a serviceable tool to the contractor, corresponding to the conditions and type of work prescribed by the order (order);

5. compliance of the used (specified in the order) power tool and protective equipment with the conditions of the place of work according to the requirements of electrical safety;

6. fulfillment of all organizational and technical measures prescribed in the order (order) to ensure the safety of work;

7. control over compliance by the contractor with PTB, PPB, PTE in the course of work;

8. storage of protective equipment and power tools.

5. Rules for the use of protective equipment used in electrical installations.

5.1 General.

Protective equipment refers to devices, apparatus, portable and transported devices and devices, as well as individual parts of devices, devices and apparatus that serve to protect personnel working on electrical installations from electric shock, from the effects of an electric arc, products of its combustion, etc. ...

Protective equipment used in electrical installations includes:

· Insulating operational rods, insulating strippers for operations with fuses, voltage indicators to determine the presence of voltage;

· Insulating ladders, insulating platforms, insulating rods, grips and tools with insulated handles;

· Rubber dielectric gloves, boots, galoshes, rugs, insulating supports;

· Portable grounding;

· Temporary fences, warning posters, insulating caps and linings;

· Goggles, canvas gloves, filtering and insulating gas masks, safety belts, safety ropes.

Insulating protective equipment serves to isolate a person from live parts of electrical equipment that are energized, as well as to isolate a person from the ground. Insulating protective equipment is divided into:

· For basic protective equipment;

· For additional protective equipment.

The main such protective means are called, the insulation of which reliably withstands the operating voltage of electrical installations and with which it is allowed to touch live parts that are energized.

The test voltage for the main protective equipment depends on the operating voltage of the installation and must be at least three times the line voltage in electrical installations with an insulated neutral or with a neutral grounded through a compensating device, and at least three times the phase voltage in electrical installations with a solidly grounded neutral.

Additional such protective means are called, which by themselves cannot provide safety against electric shock at a given voltage and are only an additional measure of protection to the main means. They also serve as protection against touch voltages, step voltages and as an additional protection against the effects of electric arcs and products.

Additional insulating protective equipment is tested with a voltage independent of the voltage of the electrical installation in which they are to be used.

The main insulating protective equipment used in electrical installations with voltages up to 1000 Volts include:

· Dielectric gloves;

· Tools with insulated handles;

· Voltage indicators.

Additional insulating protective equipment used in electrical installations with voltages up to 1000 Volts include:

· Dielectric bots;

· Dielectric rubber mats;

· Insulating supports.

The choice of certain insulating protective equipment for use during operational switching or repair work is regulated by safety rules for the operation of electrical installations and power lines and special instructions for performing individual work.

Portable fences, insulating pads, insulating caps, temporary portable grounding and warning posters are intended for temporary protection of live parts, as well as to prevent erroneous operations with switching devices.

Auxiliary protective equipment is intended for individual protection of the worker from light, thermal and mechanical influences. These include goggles, gas masks, gloves, etc.

5.2 General rules for the use of protective equipment.

The use of insulating protective equipment should be carried out only for their intended purpose in electrical installations with a voltage not higher than that for which the protective equipment is designed. All basic insulating protective equipment is designed for use in open or closed electrical installations only in dry weather. Therefore, the use of these protective equipment outdoors in wet weather (rain, snow, fog) is prohibited.

Before each use of the protective equipment, the electrician must:

Check its serviceability and the absence of external damage, clean and wipe off dust; check rubber gloves, boots, galoshes for punctures, cracks, bubbles and other foreign inclusions. If a malfunction is detected, the protective equipment must be immediately withdrawn from use.

Check the stamp for which voltage the use of this tool is permissible and whether its last check has expired. It is prohibited to use protective equipment, the test period of which has expired, since such equipment is considered to be faulty.

5.3 Requirements for certain types of protective equipment and rules for using them.

5.3.1 Dielectric gloves.

For work in electrical installations, it is allowed to use only dielectric gloves made in accordance with the requirements of GOST or technical conditions. Gloves intended for other purposes (chemical and others) must not be used as a protective agent when working in electrical installations.

Dielectric gloves issued for the maintenance of electrical installations must be of several sizes. The length of the glove must be at least 350 mm. Gloves should be worn on hands to their full depth. It is not allowed to wrap the edges of the gloves or lower the sleeves of clothing over them. When working outdoors in winter, dielectric gloves are worn over woolen gloves. Each time before use, the gloves must be checked for leaks by filling them with air.

5.3.2 Dielectric boots and galoshes.

Dielectric boots and galoshes, in addition to performing the function of an additional protective device, are a protective device against step voltage in electrical installations of any voltage.

For use in electrical installations, only dielectric boots and galoshes made in accordance with the requirements of GOST are allowed. They should be different in appearance from bots and galoshes intended for other purposes. Each bot, each halo must have the following inscriptions: manufacturer, date of issue, OTK mark, test voltage and test date.

Boots and galoshes issued for the maintenance of electrical installations must be of several sizes.

5.3.3 Dielectric mats.

Dielectric mats are allowed as an additional protective device in closed electrical installations of any voltage during operations with disconnector drives, switches and ballasts. Dielectric mats are only insulating when dry. In damp and dusty rooms, insulating pads should be used instead of mats.

Dielectric rugs must be made in accordance with the requirements of GOSTs with a size of at least 50 × 50 cm. The upper surface of the rug must be corrugated.

5.3.4 Tool with insulated handles.

Tools with insulated handles are allowed to be used in electrical installations with voltages up to 1000 volts.

Tool handles should be coated with moisture resistant, non-brittle insulating material. All insulating parts of the tool must have a smooth surface, free from cracks, breaks, and burrs. The insulating cover of the handles must adhere tightly to the metal parts of the tool and completely isolate that part of it that is in the hand of the worker during operation. Insulated handles must be provided with stops and have a length of at least 10 cm. For screwdrivers, not only the handle must be insulated, but also the metal rod along its entire length up to the working point.

When working with a tool with insulated handles on live parts that are energized, the worker must have dielectric galoshes on his feet or stand on an insulating base, in addition, he must be wearing a headdress with the sleeves of the clothes down and buttoned. Dielectric gloves are not required.

5.3.5 Voltage indicators up to 500 Volts, operating on the principle of active current flow.

Voltage indicators can be of three types:

1. voltage indicators with a neon lamp (current detectors) - used in electrical installations with voltages up to 500 volts;

2. control lamp - allowed in electrical installations with voltages up to 220 volts;

3. other voltage indicators.

5.3.5.1 Voltage indicators with neon lamp.

The voltage indicator (current detector) is a portable device operating on the principle of active current flow, and is used to check the presence or absence of voltage only in electrical circuits of 110 - 500 Volt alternating current with a frequency of 50 Hz. The locator is a two-pole device equipped with insulating handles with palm rests.

The resistance of the current-limiting resistor used in the current detector must be at least 500 kOhm when checked with a megohmmeter for a voltage of 500 volts.

5.3.5.2 Control lamps.

The test lamp must be enclosed in a case made of insulating material with a slot for a light signal. Conductors should have a length of no more than 0.5 m and go out of the reinforcement into different holes in order to exclude the possibility of short circuiting when passing them in a common lead-through. Conductors must be reliably insulated, flexible and have rigid electrodes at their free ends, protected by insulated handles. The length of the bare end of the electrode should not exceed 1 - 2 cm.

5.3.5.3 Other voltage indicators.

These include portable voltmeters and two-pole voltage indicators, in which LEDs, liquid crystal indicators, and sound alarms are used for indication. To be used as a voltage indicator, they must be encased in a dielectric material. The conductors of the device must be reliably insulated, flexible and have rigid electrodes at their free ends, protected by insulated handles. The length of the bare end of the electrode should not exceed 1 - 2 cm.

5.3.5.4 Use of voltage indicators.

To check the presence of voltage, you need to touch two opposite phases or poles with the contacts of the voltage indicator. FORBIDDEN touch the electrodes of the voltage indicator while at least one of the electrodes is connected to parts that may be energized.

The threshold of the clear glow of the current detector lamp should be no higher than 90 Volts, and for the control lamp - no more than 50% of the operating voltage. The current detector is designed for intermittent operation. The use of the current detector is carried out without the use of other protective equipment.

Use single-pole devices (various "indicator screwdrivers") as a voltage indicator, in which the operating current of the device flows through the human body, FORBIDDEN... If such devices are used in 220/380 Volt electrical installations for other purposes, for example, as an indicator of the electromagnetic field (EMF), as a "dial tone", etc., then the resistance of the current-limiting resistor of the device must be checked. The check is carried out with a 500 Volt megohmmeter, the resistance of the resistor must be at least 500 kOhm.

5.3.6 Portable earthing.

Portable grounding in the absence of stationary grounding knives is the most reliable means of protection when working on disconnected sections of equipment or a line in case of erroneous voltage supply to the disconnected section or the appearance of induced voltage on it.

Portable grounding consists of the following parts:

· Wires for grounding and for short-circuiting between themselves the current-carrying parts of all three phases of the installation. It is allowed to use a separate portable grounding for each phase;

· Clamps for connecting grounding wires to the grounding bus and shorting wires to live parts.

Portable earthing must meet the following conditions:

Wires for shorting and for grounding must be made of flexible non-insulated copper conductors and have a cross-section that meets the requirements of thermal stability in case of short circuits, but not less than 25 mm 2 in electrical installations with voltages above 1000 Volts and at least 16 mm 2 in electrical installations up to 1000 Volts ; in networks with a grounded neutral, the cross-section of the wires must meet the requirements of thermal stability in case of a single-phase short circuit;

· The clamps for connecting short-circuit wires to the busbars must be of such a design that when the short-circuit current passes, the portable grounding cannot be torn off from its place by electrodynamic forces. Clamps must have a device that allows them to be applied, secured and removed from the busbars using a rod to apply grounding. Flexible copper wire must be connected directly to the terminal without an adapter lug;

· The lug on the grounding wire must be made in the form of a clamp or correspond to the design of the clamp (wing), which is used to connect to the grounding wiring or structure;

· All connections of portable grounding elements must be made firmly and reliably by pressing, welding or bolting, followed by soldering. Soldering alone is prohibited.

Portable earthing connections must be inspected prior to each installation. Upon detection of the destruction of contact connections, violation of the mechanical strength of conductors, melting, breakage of conductors, etc., portable grounding should be withdrawn from use.

When applying grounding, first connect the grounding wire to the "ground", then check the absence of voltage on the grounded live parts, after which the clamps of the shorting wires are applied to the live parts using a rod and fixed there with the same rod or with hands in dielectric gloves. Removal of grounding is carried out in the reverse order. All operations for the application and removal of portable grounding must be carried out with the use of dielectric gloves.

5.3.7 Warning posters.

Warning posters should be used to warn of the danger of approaching live parts, to prohibit the operation of switching devices that can energize the place designated for work, to indicate to the working personnel the place prepared for work and to remind about the safety measures taken ...

Posters are divided into four groups:

1. cautionary;

3. permissive;

4. reminiscent.

By the nature of the application, posters can be permanent and portable.

Portable warning signs are made of insulating or poorly conductive material (cardboard, plywood, plastics).

Permanent posters should be made of tin or plastic materials.

5.3.8 Safety glasses.

Safety glasses are used for:

1. work without removing the voltage near and on live parts that are energized, including when changing fuses;

2. cutting cables and opening couplings on cable lines in operation;

3. soldering, welding (on wires, tires, cables, etc.), cooking and heating mastic and pouring it into cable sleeves, bushings, etc .;

4. grooving and grinding of rings and collectors;

5. work with electrolyte and battery maintenance;

6. tool sharpening and other work involving the risk of eye damage.

It is allowed to use only glasses made in accordance with the requirements of GOST.

5.3.9 Safety belts, fixer claws, safety ropes and ladders.

Safety belts are designed to protect against falling from a height when working on poles or wires of power transmission lines and on structures or equipment of switchgear.

A durable, non-stretching material is used for the belts. The width of the belts should be at least 100 mm, the length - from 900 to 1000 mm. Three rings are attached to the belt: one is for fastening the belt sling, the other is for fastening the carabiner of the sling, and the third is for fastening the safety rope.

A belt sling, intended for gripping by supports or structures, is made of a belt, chain or nylon halyard in accordance with the requirements of GOSTs and is attached tightly to the right ring, and a carbine is tightly attached to the other end of the sling.

The carabiner, in addition to the lock with a spring, must have an additional latch to prevent spontaneous opening.

When works performed near live parts that are energized, on power lines or in switchgears, a belt with a sling made of a belt, nylon halyard or cotton rope should be used. For work performed on disconnected power lines or switchgears, as well as far from voltage, it is allowed to use belts with a chain.

If, during operation, the safety belt is subjected to a dynamic load (during a jerk in the event of a fall of the worker), the belt must be taken out of service and, prior to the static load test, in order to check its integrity, it must not be used. A belt, parts of which have received any damage from dynamic loading, must be destroyed.

The safety rope is used as an additional safety measure. It is mandatory to use it when the place of work is at a distance that does not allow the safety belt to be attached to a support or structure with a sling.

Monter's claws are designed for lifting and lowering on smooth wooden poles and power lines. The monter's claws should be inspected before use, and attention should be paid to the serviceability of belts, buckles, spikes, to the absence of cracks, etc.

When servicing electrical equipment located at a height of up to 5 m, fixer ladders and stepladders are used. The height of the ladders should not exceed 4.5 m. When working at a height of more than 5 m, scaffolding and scaffolding should be used.

6. Application.

6.1 Classification of premises (working conditions) according to the degree of danger of electric shock.

The environment of industrial premises has a significant impact on electrical safety. With regard to the danger of injury to personnel by electric current, PUE are distinguished:

Premises without increased danger in which there are no conditions that create an increased or special danger;

Premises with increased danger characterized by the presence of one of the following signs that create an increased danger:

· Dampness (relative humidity of the air for a long time exceeds 75%) or the presence of conductive dust (deposited on wires, penetrating into machines, devices, etc.);

conductive floors (metal, earth, reinforced concrete, brick, etc.);
high temperature (for a long time exceeds +35 ◦С);
the ability of a person to simultaneously touch the metal structures of buildings, technological devices, etc., which have a connection to the ground, on the one hand, and to the metal cases of electrical equipment, on the other;

Particularly dangerous premises characterized by the presence of the following conditions that create a particular hazard:

· Special dampness (relative humidity is close to 100% - ceiling, walls, floor, objects covered with moisture);

· Chemically active or organic environment (corrosive vapors, gases, liquids are contained for a long time, deposits or mold are formed, destroying insulation and live parts);

· Simultaneously two or more conditions of increased danger.

Areas for the location of outdoor electrical installations (in the open air, under a canopy, behind mesh fences) are equated to especially dangerous premises.

In a number of normative documents, they are allocated in a separate group of work in particularly unfavorable conditions (in vessels, apparatus, boilers and other metal containers with a limited ability to move and exit the operator). The danger of electric shock, and hence the safety requirements in these conditions, are higher than in especially hazardous premises.

The conditions for the production of work impose certain requirements on the power supply of such consumers as power tools, local lighting fixtures, portable lamps.

In rooms with increased danger and especially dangerous, they must be powered from a voltage of no more than 42 Volts of alternating current, in especially unfavorable conditions - no more than 12 Volts.

6.2 Classification of electrical products.

According to the method of protecting a person from electric shock, electrical products are divided into 5 classes of protection:

Protection class.	Characteristics of the protection method.
	Products that have working insulation and do not have elements for grounding.
0 I	Products with working insulation, a grounding element and a wire without a grounding conductor for connection to a power source.
	Products that are provided with working insulation, a grounding element and a grounding conductor and a grounding plug.
	Products with double or reinforced insulation, without earthing elements.
	Products in which there are no internal and external electrical circuits with a voltage exceeding 42 Volts. Products powered by an external source can only be classified as Class 3 if they are intended to be directly connected to a 42 Volt or less power source. When a transformer is used as a power source, its input and output windings must not be electrically connected and there must be double or reinforced insulation between them.

6.3 List of examination questions for the 3rd group on electrical safety.

6.3.1 Topic:"Knowledge of the device of the serviced equipment and the rules of its operation - RCD".

Question number 30. Explain the principle of the RCD. What types of RCDs do you know?

Question number 31. What is the most common reason for the RCD trip in your electrical installation? How do you fight her?

Question number 32. What is the difference between electromechanical and electronic RCDs? How can you tell them apart without supporting documentation?

Question number 33. For what purpose are RCDs used? In what parts of electrical installations is the use of an RCD required?

Question number 34. What checks should electromechanical RCDs be subjected to? How often?

Question number 35. Draw a typical diagram for turning on a three-phase electric motor through an RCD. Sign the conductors according to the PUE.

6.3.2 Topic: "Knowledge of the rules for using protective equipment."

Literature: “Electrical safety. Methodical materials ... for the 3rd group ”, PTE.

Question number 40. Outline the general rules for using protective equipment.

Question number 41. State the rules and requirements for the use of tools with insulated handles (“electrician's tools”).

Question number 42. State the rules of use and requirements for voltage indicators.

Question number 43. Why is it forbidden to use control lamps if the voltage of the electrical installation exceeds 220 volts? What are the advantages of control lamps over other voltage indicators, what are the disadvantages?

Question number 44. State the rules for use and requirements for dielectric gloves.

Question number 45. State the rules of use and requirements for dielectric bots and galoshes.

Question number 46. State the rules for use and requirements for dielectric rugs.

Question number 47. State the rules for use and requirements for the warning signs.

Question number 48. State the rules of use and requirements for protective glasses.

Question number 49. State the rules for use and requirements for harnesses, fixer claws, safety ropes and ladders.

6.3.3 Topic: "Knowledge of PTE, PTEEP and MPOT in terms of organizational and technical measures to ensure the safety of work."

Literature: “Electrical safety. Methodical materials ... for the 3rd group ”, PTE, PTEEP, MPOT.

Question number 50. Outline the requirements for personnel serving electrical installations.

Question number 51. List what a skill group 3 electrician should know (amount of knowledge required).

Question number 52. What types of tests of knowledge of PTE do you know? Who is subjected to each type of PTE knowledge test?

Question number 53. How is the operation of electrical installations divided under the terms of safety? What is included in the operational maintenance, how is work in electrical installations divided?

Question number 54. What safety measures should be applied if work with voltage removal is carried out without the use of portable grounding?

Question number 55. How exactly should warning posters be posted, temporary barriers should be applied when working with complete stress relief?

Question number 56. List the organizational measures to ensure the safety of work in electrical installations.

Question number 57. Explain the difference between work alongside, by order and in the order of current operation.

Question number 58. List the measures to ensure the safety of work without relieving stress. What rules must be observed by an employee directly performing work under voltage?

Question number 59. Describe the classification of the premises according to the degree of danger of electric shock to personnel.

Question number 60. Outline the classification of electrical products according to the method of protecting a person from electric shock.

6.3.4 Topic: "Certain types of work - power tools, meggers".

Literature: “Electrical safety. Methodological materials ... for the 3rd group ”, PTE, PTEEP.

Question number 61. How is the protection class of the power tool carried out depending on the working conditions?

Question number 62. Outline the rules for connecting the power tool to the mains.

Question number 63. List what must be indicated in the order (order) for performing work with a power tool. Who has the right to issue such an outfit (order)?

Question number 64. What is the responsibility of the employee who gives the order to work with the power tool?

Question number 65. List the PTB when working with portable megohm meters? What is the smallest insulation resistance value at which you can continue to operate the electrical equipment of stationary electrical installations?

6.3.5 Topic: "Basic knowledge of electrical engineering."

Literature: "Methodology for the selection of conductors and protection equipment when connecting electrical receivers", TOE.

Question number 70. Calculate what current is consumed by 100-watt lamps at network voltages of 36 and 220 volts. What power will be released on each lamp if two 220 V 100 W lamps are connected in series to a 220 Volt network? Draw a diagram.

Question number 71. Calculate the current consumed by a three-phase electric motor, if the data is indicated on its nameplate: U = 380 V, P = 3 kW, cos j = 0.85, h = 0.95. What is h?

Question number 72. When you turn on a piece of wire PNSV-1´1.2 with a length of 28 meters and a resistance of 3.7 Ohm per line voltage TP, the current in the wire is 15 Amperes. What should be the length of the wire segments so that you can connect them to a star (three) and the current in the wire remains the same (15 Amperes)?

Question number 73. At a voltage of U = 80 Volts in a piece of PNSV-1´1.2 wire with a length of 28 meters and a resistance of 3.7 Ohm, the current is 15 Amperes. How long should the wire be so that the current in it remains the same at a voltage of 36 volts?

Question number 74. Three lamps are connected to a star, a common point is connected to zero. The current in the phases is 3 Amperes. How will the current in the phases change if one of the lamps burns out? How will the current in the neutral wire change?

Question number 75. To what value should the insulation resistance of the 220 Volt extension cord fall so that a single-phase 30 mA RCD is guaranteed to disconnect the line?

Question number 76. Determine how much power is dissipated in an active symmetrical three-phase load with a line voltage of 42 Volts and a line current of 24 Amperes.

The document is provided by the site http://note-s.narod.ru

Rules for the technical operation of electrical installations of consumers.

Electrical safety regulations.

Cross-industry rules on labor protection.

PTB - Safety regulations.

Current limiting , in relation to voltage indicators, is called a resistor that limits (limiting) the maximum current through the device.

Dielectric - non-conductive (poorly conductive) electric current.

1.1 Introduction. 3

5.1 General. 18

5.3.8 Safety glasses. 25

6. Application. 27

Introduction.

Group	The amount of knowledge required.
I	For group 1, persons who do not have special electrical training, but who have a clear idea of the danger of electric current and safety measures when working on the serviced area, electrical equipment, and electrical installation, are certified. Must have practical knowledge of first aid procedures. Training for 1 group is carried out in the form of briefing followed by a control survey by a specially appointed person with an electrical safety group of at least 3.
II	Persons with group 2 should have: 1. basic familiarity with the electrical installation; 2. a clear idea of the danger of electric current and the approach to live parts; 3. knowledge of basic safety precautions when working on electrical installations; 4. practical acquaintance with the rules of first aid.
III	Persons with group 3 must have: 1. basic knowledge of electrical engineering; 2. a clear understanding of the hazards when working in electrical installations; 3. knowledge of PTE, PTEEP and MPOT in terms of organizational and technical measures to ensure the safety of work; 4. knowledge of the rules for using protective equipment; 5. knowledge of the structure of the serviced equipment and the rules of its operation; 6. knowledge of the rules of first aid and the ability to practically provide first aid to the victim.
IV	Persons with group 4 must have: 1. clear knowledge of the basics of electrical engineering; 2. knowledge of PTE, PTEEP, MPOT and PUE in terms of fixed electrical installations; 3. a complete understanding of the dangers when working in electrical installations; 4. knowledge of the rules of use and testing of protective equipment; 5. knowledge of the installation so that it is free to understand exactly which elements must be disconnected for the production of work, to find all these elements in nature and to check the implementation of the necessary safety measures; 6. the ability to organize the safe conduct of work and to supervise them in electrical installations with a voltage of up to 1000 volts; 7. knowledge of the rules of first aid and the ability to practically provide first aid to the victim.

Testing knowledge of PTE by personnel.

Subdivided into:

1. primary;

2. periodic;

3. extraordinary.

Periodic subject to verification:

· Personnel involved in the operation of electrical installations, as well as management and engineering staff, organizing their operation - once a year;

· Management staff and engineering and technical staff, not related to the previous group, but in charge of electrical installations - once every three years.

Primary called the first of the periodic checks.

Extraordinary knowledge is tested:

· Persons who have committed violations of PTE, PTEEP, MPOT, official or operational instructions;

· Persons having a break in work at this electrical installation for more than 6 months;

· Persons transferred to a new electrical installation;

· Persons on the instructions of the management of the enterprise or on the instructions of the energy supervision inspector.

Production of outages.

At the place of work, the live parts on which the work is performed, as well as those that may be accessible to touch during the work, must be disconnected.

Non-insulated live parts accessible to touch need not be disconnected if they are securely shielded with insulating linings made of dry insulating materials.

Disconnection can be done:

The procedure for checking the disconnected state of switching devices is established by the person issuing the order or giving the order.

Overlay grounding.

Places of overlapping grounding.

When working on busbars, at least one grounding must be applied to them.

In closed switchgears, portable earthing must be applied to live parts in the designated places. These areas should be free of paint and surrounded by black stripes.

The list of such electrical installations must be determined and approved by the chief power engineer (the person responsible for the electrical equipment).

General Provisions.

Protective equipment used in electrical installations includes:

· Insulating operational rods, insulating strippers for operations with fuses, voltage indicators to determine the presence of voltage;

· Insulating ladders, insulating platforms, insulating rods, grips and tools with insulated handles;

· Rubber dielectric gloves, boots, galoshes, rugs, insulating supports;

· Portable grounding;

· Temporary fences, warning posters, insulating caps and linings;

· Goggles, canvas gloves, filtering and insulating gas masks, safety belts, safety ropes.

· For basic protective equipment;

· For additional protective equipment.

The main such protective means are called, the insulation of which reliably withstands the operating voltage of electrical installations and with which it is allowed to touch live parts that are energized.

Additional such protective means are called, which by themselves cannot provide safety against electric shock at a given voltage and are only an additional measure of protection to the main means. They also serve as protection against touch voltages, step voltages and as an additional protection against the effects of electric arcs and products.

Additional insulating protective equipment is tested with a voltage independent of the voltage of the electrical installation in which they are to be used.

The main insulating protective equipment used in electrical installations with voltages up to 1000 Volts include:

· Dielectric gloves;

· Tools with insulated handles;

· Voltage indicators.

Additional insulating protective equipment used in electrical installations with voltages up to 1000 Volts include:

· Dielectric bots;

· Dielectric rubber mats;

· Insulating supports.

Auxiliary protective equipment is intended for individual protection of the worker from light, thermal and mechanical influences. These include goggles, gas masks, gloves, etc.

Requirements for certain types of protective equipment and rules for using them.

Dielectric gloves.

Dielectric rugs.

Dielectric rugs must be made in accordance with the requirements of GOSTs with a size of at least 50 × 50 cm. The upper surface of the rug must be corrugated.

Control lamps.

Portable grounding.

Portable grounding consists of the following parts:

· Clamps for connecting grounding wires to the grounding bus and shorting wires to live parts.

Portable earthing must meet the following conditions:

· The lug on the grounding wire must be made in the form of a clamp or correspond to the design of the clamp (wing), which is used to connect to the grounding wiring or structure;

· All connections of portable grounding elements must be made firmly and reliably by pressing, welding or bolting, followed by soldering. Soldering alone is prohibited.

Warning posters.

Posters are divided into four groups:

1. cautionary;

3. permissive;

4. reminiscent.

By the nature of the application, posters can be permanent and portable.

Portable warning signs are made of insulating or poorly conductive material (cardboard, plywood, plastics).

Permanent posters should be made of tin or plastic materials.

Protective glasses.

Safety glasses are used for:

1. work without removing the voltage near and on live parts that are energized, including when changing fuses;

2. cutting cables and opening couplings on cable lines in operation;

3. soldering, welding (on wires, tires, cables, etc.), cooking and heating mastic and pouring it into cable sleeves, bushings, etc .;

4. grooving and grinding of rings and collectors;

5. work with electrolyte and battery maintenance;

6. tool sharpening and other work involving the risk of eye damage.

It is allowed to use only glasses made in accordance with the requirements of GOST.

Application.

Literature: "Methodology for the selection of conductors and protection equipment when connecting electrical receivers", TOE.

Question number 70. Calculate what current is consumed by 100-watt lamps at mains voltages of 36 and 220 volts. What power will be released on each lamp if two 220 V 100 W lamps are connected in series to a 220 Volt network? Draw a diagram.

Question number 71. Calculate the current consumed by a three-phase electric motor, if the data is indicated on its nameplate: U = 380 V, P = 3 kW, cos j = 0.85, h = 0.95. What is h?

Question number 72. When you turn on a piece of wire PNSV-1´1.2 28 meters long and with a resistance of 3.7 Ohm per line voltage TP, the current in the wire is 15 Amperes. What should be the length of the wire segments so that you can connect them to a star (three) and the current in the wire remains the same (15 Amperes)?

Question number 73. At a voltage of U = 80 Volts in a piece of wire PNSV-1´1.2 with a length of 28 meters and a resistance of 3.7 Ohm, the current is 15 Amperes. How long should the wire be so that the current in it remains the same at a voltage of 36 volts?

Question number 75. To what value should the insulation resistance of the 220 Volt extension cord fall so that a single-phase 30 mA RCD is guaranteed to disconnect the line?

Question number 76. Determine how much power is dissipated in an active symmetrical three-phase load with a line voltage of 42 Volts and a line current of 24 Amperes.

The document is provided by the site http://note-s.narod.ru

Rules for the technical operation of electrical installations of consumers.

Electrical safety regulations.

Cross-industry rules on labor protection.

PTB - Safety regulations.

Current limiting , in relation to voltage indicators, is called a resistor that limits (limiting) the maximum current through the device.

Dielectric - non-conductive (poorly conductive) electrical current.

1. Basic requirements for the organization of safe operation of electrical installations. 3

1.1 Introduction. 3

1.2 Requirements for personnel serving electrical installations. 3

2. Qualification groups for electrical safety. 4

2.1 Verification of knowledge of PTE by personnel. five

3. Electrical safety in existing electrical installations up to 1000 Volts. Manufacturing jobs. 6

3.1 Technical measures to ensure the safety of work with stress relief. 7

3.1.1 Making outages. eight

3.1.2 Hanging warning posters, fencing of the place of work. nine

3.1.3 Checking the absence of voltage. nine

3.1.4 Applying grounding. 10

3.2 Organizational measures to ensure the safety of work. 12

3.2.1 Attire, order, routine maintenance. 12

3.3 Measures to ensure the safety of work without removing voltage near and on live parts that are energized. 13

4. Production of certain types of work. fourteen

4.1 Measurement of insulation resistance with portable megohmmeters. fourteen

4.2 PTE when performing work with power tools and portable lamps. fifteen

4.2.1 Selection of the protection class of the power tool depending on the working conditions. fifteen

4.2.2 Connection and rules for performing work with a power tool. fifteen

4.2.3 Obligations of the employee issuing an order (order) to perform work with a power tool. sixteen

5. Rules for the use of protective equipment used in electrical installations. 18

5.1 General. 18

5.2 General rules for the use of protective equipment. nineteen

5.3 Requirements for certain types of protective equipment and rules for using them. twenty

5.3.1 Dielectric gloves. twenty

5.3.2 Dielectric boots and galoshes. twenty

5.3.3 Dielectric mats. 21

5.3.4 Tool with insulated handles. 21

5.3.5 Voltage indicators up to 500 Volts, operating on the principle of active current flow. 22

5.3.6 Portable earthing. 24

5.3.7 Warning posters. 25

5.3.8 Safety glasses. 25

5.3.9 Safety belts, fixer claws, safety ropes and ladders. 26

6. Application. 27

6.1 Classification of premises (working conditions) according to the degree of danger of electric shock. 27

6.2 Classification of electrical products. 28

6.3 List of examination questions for the 3rd group on electrical safety. 29

6.3.1 Topic: "Knowledge of the device of the serviced equipment and the rules of its operation - RCD". 29

6.3.2 Topic: "Knowledge of the rules for using protective equipment." 29

6.3.3 Topic: "Knowledge of PTE, PTEEP and MPOT in terms of organizational and technical measures to ensure the safety of work." thirty

6.3.4 Topic: "Certain types of work - power tools, megohmmeters". thirty

6.3.5 Topic: "Basic knowledge of electrical engineering." 31

1. Basic requirements for the organization of safe operation of electrical installations.

Introduction.

This methodological manual was compiled for the training of electrical personnel for the 3rd group on electrical safety (with a tolerance of up to 1000 Volts) on the basis of the current PTEEP, PTE and MPOT.

Requirements for personnel serving electrical installations.

The personnel servicing electrical installations, as far as they are concerned, must know:

· Rules of technical operation of electrical installations of consumers (PTEEP);

· Rules for electrical installations (PUE);

· Manuals for the design and operation of the assigned electrical installations;

· Job and operational instructions in relation to the position held and the work performed;

· Rules for freeing a person from the action of electric current;

· Rules of rendering first aid to the victim from the action of electric current.

Electrical safety qualification groups.

drilling machine electric drive automation

Control devices are designed to turn on, turn off and switch electrical circuits and electrical receivers, control the speed and reversal of motors, control the parameters of power, lighting, heating and other electrical installations.

Protective devices are designed to disconnect electrical circuits in the event of abnormal conditions (short circuits, significant overloads, sudden voltage drops, etc.)

Reliability of operation and safety of equipment as a whole, numerical, qualitative and economic indicators of the production mechanism and electrical safety of people largely depend on the correct choice of protection and automation equipment.

Calculation and selection of switching equipment

We use magnetic starters to control asynchronous motors. Overload protection of motors is carried out by thermal relays.

a) Calculation and selection of the KM1 magnetic starter and the KK1 thermal relay.

These devices are located in the power circuit of the M1 engine with a power

12 kW.
1) Determine the continuous current in the motor line according to the formula

where I dl - continuous current, A;

Р д - engine power, kW;

U n - rated voltage of the electric motor, V;

h d - engine efficiency;

costs - power factor.

2) Select the KK1 thermal relay.

The thermal relay is installed in 3 phases of the motor circuit independently of the magnetic starter. The thermal relay is selected according to the condition

I tr? 1.25 I nd, (10)

where I tr is the current of the thermal relay, A;

I nd - rated motor current, A.

According to the reference book, we select a thermal relay, which is installed independently of the TRN-40 magnetic starter I nom = 40A, I N. tep.el. = 40A

3) Choose a wire for the line.

Because line with a thermal relay, then the choice of the wire is made taking into account the compliance with this protection device, i.e. the condition must be met

I add? K zsch I tr, (11)

where I add - permissible current, A;

K ssh - protection factor.

According to the reference book, we select a wire of the PV brand with copper conductors. The wire is laid open S = 2.5 mm 2; I dp = 40A

We check the selected wire taking into account the long-term load current, i.e. the condition must be met

I dp? I add, (12)

where I dp is the permissible wire current, A.

4) Select the KM1 magnetic starters.

P dv = 12 kW

According to the reference book, we select the closest in power magnetic starter brand PME-3

b) Calculation and selection of magnetic starters KM2-KM3

These devices are located in the power circuit of the M2 engine with a power

1.5 kW.

2) Choose a wire for the line.

I add? 1.25 3.5

S = 0.5 mm 2 I dp = 11A

Since the condition is met, the wire is selected correctly.

3) We choose magnetic starters KM2-KM3.

Because magnetic starters KM4-KM5 are designed to control this

motor, then the calculation is reduced to only one, for example, we calculate the magnetic starter KM2, and the other we take the same brand.

P dv = 1.5 kW

c) Calculation and selection of the KM4 magnetic starter

These devices are located in the power circuit of the M3 engine with a power

0.12 kW.
1) Determine the continuous current in the motor line according to the formula (9)

2) Choose a wire for the line.

Because line without a thermal relay, then the choice of the wire is made taking into account the compliance with this protection device, i.e. condition (11) must be satisfied

I add? 1.25 0.47

According to the reference book, we select a wire of the VRG brand in a polyvinyl chloride sheath with copper conductors. The wire is laid openly.

S = 0.5 mm 2 I dp = 11A

We check the selected wire taking into account the long-term load current, i.e. condition (12) must be satisfied

Since the condition is met, the wire is selected correctly.

3) Select the KM4 magnetic starter.

P dv = 1.5 kW

According to the reference book, we select the closest in power magnetic starter brand PME-0

The choice of switching devices and protection devices for electrical receivers is made based on the nominal data of the latter and the parameters of their supply network, requirements for the protection of receivers and the network from abnormal modes, operational requirements, in particular the frequency of switching on and environmental conditions at the place of installation of the devices.

Selection of devices by type of current, number of poles, voltage and power

The design of all electrical devices is calculated and marked by the manufacturers for voltage, current and power values determined for each device, as well as for a specific operating mode. Thus, the choice of equipment for all these features is essentially reduced to finding, on the basis of the catalog data, the corresponding types and sizes of apparatuses.

Selection of devices according to the conditions of electrical protection

When choosing protection devices, one should keep in mind the possibility of the following abnormal modes:

a) phase-to-phase short circuits,

b) phase closure to the case,

c) an increase in current caused by overloading of technological equipment, and sometimes by incomplete short circuit,

d) the disappearance or excessive decrease in voltage.

must be carried out for all electrical consumers. It must operate with a minimum trip time and must be detuned from inrush currents.

Overload protection is required for all power consumers with continuous operation, except for the following cases:

a) when the overload of electrical receivers for technological reasons cannot take place or is unlikely (centrifugal pumps, fans, etc.),

b) for electric motors with power less than 1 kW.

Overload protection is optional for electric motors operating in short-term or intermittent modes. In hazardous areas, overload protection of electrical receivers is mandatory in all cases. Undervoltage protection must be installed in the following cases:

a) for electric motors that cannot be connected to the network at full voltage,

b) for electric motors, the self-starting of which is unacceptable for technological reasons or poses a danger to the operating personnel,

c) for other electric motors, the disconnection of which when the power is cut off is necessary in order to reduce the total starting power of the electrical consumers connected to the network to the permissible value, and possibly from the point of view of the operating conditions of the mechanisms.

In addition to the above, DC, parallel and mixed excitation motors must be protected against excessive speed increase in cases where such an increase can lead to danger to human life or to significant losses.

Protection against excessive increase in the number of revolutions can be carried out by various special relays (centrifugal, induction, etc.).

Since in power networks protection against overload and against short circuits is of particular importance, we will dwell in somewhat more detail on the fundamental side of this issue.

Short circuit current should turn off instantly or almost instantly. Its value in different sections of the network can be very different, but almost always it can be assumed that the protection devices must confidently and quickly disconnect any current that is significantly greater than the starting one, and at the same time, in no case should it be triggered during normal start-up.

Overload current is any current in excess of the rated current of the motor, but there is no reason to require the motor to be switched off whenever an overload occurs.

It is known that a certain overload of both electric motors and their supply networks is permissible, and that the more short-term the overload, the greater its value. Hence, the advantages for overload protection of such devices that have a "dependent characteristic", ie, the response time of which decreases with an increase in the overload multiplicity, are clear.

Since, with very rare exceptions, the protection device remains in the motor circuit even during start-up, it should not trip with a starting current of normal duration.

From the above considerations, it is clear that, in principle, for protection against short-circuit currents, an inertialess device should be used, tuned to a current significantly higher than the starting one, and for overload protection, on the contrary, an inertial device with a dependent characteristic, selected so that it does not operate in a time start-up. To the greatest extent, these conditions are met by a combined release, which combines thermal overload protection and instantaneous electromagnetic tripping at short-circuit current.

Taking into account the above and the totality of requirements for control and protection devices, the following recommendations can be made.

1. For manual control of electrical receivers with low inrush currents can beused and fuses built into various electrical structures or distribution and. JARV boxes without fuses are used as disconnecting devices for highways, etc.

2. For manual control of electric motors up to 3 - 4 kW, which do not require overload protection, are used.

3. For electric motors up to 55 kW, requiring overload protection, the most common devices are magnetic starters in combination with fuses or air breakers.

With an electric motor power of more than 55 kW, they are used in combination with protective relays or air breakers. It should be remembered that contactors do not allow the circuit to break in the event of short circuits.

4. For remote control of electrical receivers, the use of magnetic starters or contactors becomes necessary.

5. For manual control of electrical receivers with a small number of starts per hour, it is possible to use automatic switches.