Electrical installations. General requirements

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Section 7. Electrical equipment of special installations

Electrical installations. General requirements

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Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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7.6.10. Type design, degree of protection and composition of equipment (elements) of electric welding installations should be selected taking into account the technology and type of welding, the parameters of the parts (workpieces) to be welded and welds, taking into account the specific environmental conditions when performing welding work (indoors or outdoors, in confined and hard-to-reach spaces).

7.6.11. Electrical receivers of the main equipment and auxiliary mechanisms of electric welding installations in relation to ensuring the reliability of power supply, as a rule, should be classified as category III or II electrical receivers (see Chapter 1.2).

Category III should include electrical receivers of all mobile and portable electric welding installations, stationary electric welding installations listed in 7.5.8, workshops and sections, as well as other workshops and sections, if a break in the power supply of the electric welding equipment used in them does not lead to mass undersupply of products, downtime of workers and mechanisms.

7.6.12. The electrical load of electric welding installations should not decrease below the values of power quality indicators for electrical receivers connected to general-purpose networks, which are normalized by the current standard.

Where necessary, measures should be taken to reduce the impact of electric welding installations on the electrical network.

7.6.13. The design and arrangement of the equipment of electric welding installations, fences and interlocks should exclude the possibility of its mechanical damage, as well as accidental contact with rotating or energized parts. An exception is allowed for electrode holders of manual arc welding, cutting and surfacing installations, as well as for mouthpieces, arc welding torches, plasma torch nozzles, electrodes of contact machines and other parts under voltage, at which welding, spraying, cutting, etc. are carried out.

7.6.14. The placement of equipment for electric welding installations, its components and mechanisms, as well as controls should provide free, convenient and safe access to them. In addition, the location of the controls should provide the ability to quickly turn off the equipment and stop all its mechanisms.

For electric welding installations, the equipment of which requires operational maintenance at a height of 2 m or more, work platforms must be made, fenced with railings, with permanent stairs. Platforms, fences and stairs must be made of non-combustible materials. The flooring of the working platform must be coated with a dielectric material that does not spread combustion.

7.6.15. It is recommended that control devices for electric welding installations be equipped with guards that prevent them from being accidentally turned on or off.

7.6.16. As welding power sources, only welding transformers or static or motor-generator converters with electric motors or internal combustion engines specially designed for this purpose and meeting the requirements of current standards should be used. Power supply of the welding arc of the electroslag pool and the resistance of contact welding directly from the power, lighting or contact electrical network is not allowed.

7.6.17. The circuit for switching on several welding current sources when they are working on one welding arc, electroslag pool or contact welding resistance should exclude the possibility of a voltage occurring between the product and the electrode that exceeds the highest open-circuit voltage of one of the welding current sources.

7.6.18. The electrical load of several single-phase welding current sources should be distributed as evenly as possible between the phases of a three-phase network.

7.6.19. A single-station welding current source, as a rule, should be located at a distance of no more than 15 m from the welding station.

7.6.20. The primary circuit of the electric welding installation must contain a switching (switching off) and protective electrical apparatus (device), its rated voltage must not exceed 660 V.

Welding circuits must not have connections with electrical circuits connected to the network (including with electrical circuits fed from the network of excitation windings of converter generators).

7.6.21. Electric welding installations with a multi-station welding current source must have a device (circuit breaker, fuses) to protect the source from overload, as well as switching and protective electrical devices (apparatus) on each line that goes to the welding station. These lines should be done radially; application in installations with multi-station welding rectifiers of main circuits is allowed only with a feasibility study.

7.6.22. To determine the value of the welding current, the electric welding installation must have a measuring device. On electric welding installations with a single-station welding current source, it may not have a measuring device if there is a scale on the current regulator in the welding current source.

7.6.23. Portable and mobile electric welding installations (except autonomous ones) should be connected to electrical networks directly by cable or cable through trolleys. The length of the trolley conductors is not standardized, their cross section must be selected taking into account the power of the welding current source.

7.6.24. The connection of a portable or mobile electric welding installation directly to a stationary electrical network should be carried out using switching and protective devices (apparatus) with collapsible or detachable contact connections. It is mandatory to have a lock that excludes the possibility of opening and closing these connections, connecting (disconnecting) the cores of the cable line (wires) when the switching device is on.

7.6.25. The cable line of the primary circuit of a portable (mobile) electric welding installation from the switching device to the welding power source must be carried out by a portable flexible hose cable with aluminum or copper conductors, with insulation and a sheath (hose) made of flame retardant rubber or plastic. The welding power source must be located at such a distance from the switching device that the length of the flexible cable connecting them does not exceed 15 m.

7.6.26. Welding machines or semi-automatic machines with remote control of the mode of operation of the welding power source are recommended to be equipped with two sets of controls for regulating devices (handles, buttons, etc.), one installed at the welding power source and the second on the control panel or control panel of the welding machine or semi-automatic. To select the type of controller control (local or remote), a switch must be installed that provides blocking¹⁾, excluding erroneous inclusion. It is allowed not to provide for the possibility of blocking, but to use a mechanical lock with special keys.

7.6.27. Cabinets of complete devices and housings of welding equipment (machines) with uninsulated current-carrying parts that are energized above 50 V AC or above 110 V DC must be equipped with a lock²⁾, providing, when opening the doors (doors), disconnection from the electrical network of devices located inside the cabinet (case). In this case, the inputs (outputs) that remain energized must be protected from accidental touches.

Instead of locking, it is allowed to use locks with special keys if it is not required to open doors (doors) during operation.

1. Blocking - a term according to GOST 18311-80.

2. Blocking - a term according to GOST 18311-80.

7.6.28. In electric welding installations, in addition to protective grounding of open conductive parts and connection to the potential equalization system of third-party conductive parts (according to the requirements of Ch. 1.7), grounding of one of the outputs of the secondary circuit of welding current sources must be provided: welding transformers, static converters and those motor-generator converters, in which the excitation windings of the generators are connected to the electrical network without isolating transformers (see also 7.6.30).

In electric welding installations in which the arc burns between the electrode and the electrically conductive product, the output of the secondary circuit of the welding current source connected by a conductor (return wire) to the product should be grounded.

7.6.29. Welding electrical equipment for connecting a protective PE conductor must have a bolt (screw, stud) with a contact pad located in an accessible place, with the inscription "Earth" (or with a conventional grounding sign in accordance with GOST 2.721-74 *). Bolt and contact pad diameters must be at least standardized by GOST 12.2.007.0-75.

Plug-in contact connectors of wires for inclusion in an electric circuit with a voltage above 50 V AC and above 110 V DC of portable control panels for welding machines or semi-automatic machines must have protective contacts.

7.6.30. Electric welding installations in which, due to the conditions of the electrical process, grounding in accordance with 7.6.28 cannot be performed, as well as portable and mobile electric welding installations, the equipment grounding of which presents significant difficulties, must be equipped with protective shutdown devices or continuous insulation monitoring.

7.6.31. Capacitors used in electric welding installations for the purpose of storing energy for welding pulses must have a device for automatic discharge when the protective cover is removed or when the doors of the cabinets in which the capacitors are installed are opened.

7.6.32. With water cooling of elements of electric welding installations, it should be possible to control the state of the cooling system using funnels for draining water or jet relays. In water cooling systems of automatic machines (semiautomatic devices), it is recommended to use pressure, jet or temperature switches (the last two are used at the outlet of water from cooling devices) with their operation on a signal. If interruption of flow or overheating of the cooling water could lead to accidental damage to the equipment, automatic shutdown of the unit must be provided.

In water-cooling systems where potential dangerous to operating personnel can be transferred through pipelines, insulating hoses shall be provided (the length of the hoses is selected according to 7.5.39).

Detachable connections and hoses of the water cooling system are recommended to be arranged in such a way as to exclude the possibility of water jet hitting electrical equipment (welding power source, etc.) when the hoses are removed or damaged.

The quality of the water used in the water cooling system must meet the requirements given in Table. 7.5.13, unless other standard values are given in the standards or specifications for the relevant equipment.

See other articles Section Rules for the installation of electrical installations (PUE).

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