RU2240633C1 - Method and device for grounding power consumers - Google Patents

Abstract

FIELD: installation of plug sockets in newly commissioned houses or those reconstructed.

SUBSTANCE: installation of three-jack sockets in newly commissioned buildings or those subjected to reconstruction or overhaul involves insertion of 5-Ohm resistor into plug socket. One lead of resistor is connected to ground contact of socket and other one, to socket metal box. The latter is set in concrete or brick wall on non-insulating mortar. Power is supplied to socket from protective gear responding to differential leakage current. Proposed method provides for grounding power consumers in supply mains having no neutral conductor.

EFFECT: enhanced efficiency of phase-to-neutral fault protection.

2 cl, 1 dwg

Description

The invention relates to electrical engineering, in particular to the operation of power receivers, including household electrical appliances and computers, and is closely related to the installation of three-pin European-type sockets in newly constructed, reconstructed and overhaul residential, public and industrial buildings of all types, and it is also associated with the replacement two-pin outlets to three-pin outlets in already operating residential apartments and other premises (schools, kindergartens, hospitals and clinics, institutes, editorial offices and newspapers, ministries and departments, etc.), ie, wherever outdated two-pin sockets, not intended for grounding electrical receivers, still continue to take place and function.

There are various ways of grounding an electrical receiver, for example, described in the reference R.N. Karjakina “Grounding devices of electrical installations”, Moscow, ZAO “Energoservice”, 2000. All of them consist in connecting the grounded part of the electrical receiver to the grounding of a transformer substation (TP) or power station (ES) through a protective earth conductor (so-called PE conductor) in electrical networks with grounding systems of types TN-S and TN-CS or through the combined zero protective and zero working conductors (the so-called PEN conductor) in electrical networks with a grounding system of type TN-C. All these methods are aimed at achieving two main goals - to eliminate the emission of an electromagnetic field harmful to human health by an electric receiver and to reduce the likelihood of a person being struck by electric currents in the event of a violation of electrical insulation in the electric receiver.

The main disadvantages of all known methods of grounding are, firstly, the high consumption of wires for their implementation and, secondly, a sharp increase in the risk of fires from short circuits.

Closest to the claimed one is a method of grounding the power receiver, including attaching its body to a ground protective conductor (PE conductor) grounded on a TP or ES by means of a plug connection with a ground contact connected to said PE conductor, and a device is known for implementing this method , which is a three-pin socket of the European type, the grounding contact of which is connected to the PE conductor of the electrical network, and the socket itself receives residual current protection device (RN Karyakin's Handbook “Grounding Devices for Electrical Installations”, Moscow, CJSC Energoservice, 2000).

This grounding method and device for its implementation are selected as a prototype.

The prototype has three significant drawbacks. Firstly, it requires for its implementation not two, but three conductors, laid in the walls of the room to each outlet, which increases the consumption of wires by a third. In addition, if a two-pin socket is changed to a three-pin socket in an apartment in which people already live, then for laying a third conductor, it is necessary to hollow the strobes (grooves) in the walls, followed by terminating them after laying the conductor, which additionally requires a lot of work and money, and most importantly, it is associated with considerable inconvenience to residents. Secondly, when the grounding contacts of several outlets are connected to the same PE conductor, the probability of electric shock in case of a dangerous voltage on the PE conductor increases sharply. So, in the event of a breakdown of the electrical insulation between the phase and PE conductors, for example, at the entrance to the building, with the formation of an electric arc at the site of a short circuit and burning off the neutral wire of the network from the power source, a life-threatening PE conductor will appear voltage close to 220 V. In this case, the PE conductor from the protective turns into its opposite and thereby creates a special danger of electric shock, since on all cases connected to it by electric Ikov, and with perfectly good insulation, there is a danger to human life stress. Such emergency conditions can last indefinitely, sometimes for months, and manifest themselves only after people begin to die. The more outlets connected to the indicated PE conductor with their grounding contacts, the naturally higher the likelihood of electric shock to people. Indeed, suppose that only one socket is connected to the indicated PE conductor by its grounding contact. A person will be defeated if an electric receiver is connected to this outlet and a person standing on the electrically conductive floor touches the body of this electric receiver. Let us denote the probability of a person being struck by electric current in the case under consideration by p. With ten outlets, it is easy to calculate that the probability P ^{(10) of} electric shock will become equal to P ⁽¹⁰⁾ = 10p, i.e. increases by an order of magnitude. With a hundred outlets - two orders of magnitude, etc. At the same time, the danger of group electrocution increases. The above emergency conditions, in which voltages of the order of 220 V appear on the PE conductor from the phase wire on which the short circuit occurred, lead to the fact that for the vast majority of power receivers powered by two other phase wires, the voltage on the live parts in relation to to the body will increase from phase to linear, i.e. up to 380 V, which inevitably leads to a sharp increase in the probability of breakdown of insulation of live parts on the chassis in these power consumers, and they, in turn, lead to new short circuits. It is well known that it is a short circuit that causes many fires. In addition, when the specified emergency mode occurs, all absolutely functional and grounded to the PE-conductor power receivers begin to irradiate the surrounding electromagnetic field.

The objective of the invention is to eliminate all of the above disadvantages, namely: reducing wire consumption, reducing the complexity and eliminating inconvenience to apartment residents when replacing obsolete two-pin outlets with three-pin European types, reducing the likelihood of electric shock, completely eliminating the possibility of short circuits of live parts on the housing grounded electrical receivers, elimination of exposure to the surrounding electromagnetic field.

As a result of using the claimed technical solution, all of the listed disadvantages are eliminated. So, to reduce the consumption of wires (almost to zero), it is proposed to use a metal sub-socket box made of metal and unpainted outside, fixed in the wall with a concrete, alabaster or other solution that is not insulating, walled into the concrete (or brick) wall of the room as a ground electrode. At normal humidity of the concrete, the resistance to spreading of the subgrid box is about 1-2 kOhm, which is quite enough, and with a huge, almost ten-fold margin, for the box to perform all the functions of the ground electrode when using protection against differential leakage current. In wet rooms, the above margin increases even more, thereby increasing the reliability of protection. In very dry rooms, the margin of response current, of course, decreases, but the resistance to current spreading from the feet of a person standing on the floor increases sharply, which in itself dramatically increases electrical safety. To eliminate the dangerous electrical potential on the box in case of insulation failure in the power receiver, it is proposed to connect to the box through a resistor, the resistance of which, together with the resistance to current spreading from the box to the ground, would provide protection for differential current, for example, 5 kOhm. The proposed technical solution does not require laying an additional conductor on the walls, and therefore, reduces the complexity and does not create inconvenience to residents when replacing outlets. The probability of a person being struck by electric shock when using the indicated technical solution is minimal, since there is no connection between the grounding contacts of the outlets among themselves. And the presence of a resistor and high resistance to current spreading from the socket boxes to the ground completely exclude short circuits that are dangerous from the point of view of fires.

The technical result is achieved by the fact that in the method of grounding the power receiver, including connecting its body (or other grounded part) to the ground electrode, a metal socket box fixed to the concrete (or brick) wall of the room is used as the ground electrode, and connection to it is carried out through a resistor with a large electrical resistance.

In a device for grounding an electrical receiver containing a three-pin plug outlet, one contact of which is grounding, attached to a wall-mounted subgrid box, powered by a differential leakage current protection device, the grounding contact of the outlet is connected through a resistor to an outlet box made of metal and unpainted outside fixed in the wall with concrete, alabaster or other solution that is not insulating.

The drawing shows a diagram of the device, which depicts a socket 1 with working contacts 2 and a grounding contact 3 connected through a resistor 4 to the socket box 5 located in the concrete wall 6.

The device operates as follows. In an apartment (office, office, etc.), a conventional two-pin socket is replaced with a three-pin one, one of the contacts of which the ground is connected to a metal socket box through a resistor located in the socket. When the three-pin plug of the power receiver is inserted into the outlet, it will immediately be grounded.

Specific example.

A 5-kΩ resistor is placed in a three-pin socket, one end of which is connected to the grounding pin of the socket, and the other end to the undergrid metal box. The specified outlet is replaced by a remote bipolar. If there was a plastic subgrid box in the wall, it is changed to a metal box and fixed in the wall on a concrete mortar.

Claims (2)

1. The method of grounding the power receiver, including attaching its body (or other grounded part) to the ground electrode, characterized in that a metal receptacle mounted in a concrete (or brick) wall of the room is used as the ground electrode, and connection to it is carried out through a resistor with a large electric resistance. 2. A device for grounding an electrical receptacle, comprising a three-pin receptacle, one contact of which is a ground receptacle, attached to a wall-mounted subgrid box, powered by a differential leakage current protection device, characterized in that the grounding contact of the receptacle is connected through a resistor to a receptacle box made from metal and unpainted outside, fixed in the wall with a solution that is not insulated.