EP1480243B1

EP1480243B1 - An electrical device for protection against residual currents

Info

Publication number: EP1480243B1
Application number: EP04076453A
Authority: EP
Inventors: Gabriele Colombo
Original assignee: ABB Service SRL
Current assignee: ABB Service SRL
Priority date: 2003-05-20
Filing date: 2004-05-18
Publication date: 2007-09-26
Anticipated expiration: 2024-05-18
Also published as: ATE374430T1; DE602004009130T2; ITBG20030033A1; DE602004009130D1; EP1480243A1

Abstract

An electrical device for protection against residual currents, which comprises an insulating casing having a rear wall, a front wall, a bottom wall, a top wall, and two side walls. Inside said casing there are: a residual-current sensor, which comprises a toroidal core, a primary winding and a secondary winding; and a tripping relay, having a containment box, from a wall of which there protrude a first pin and a second pin designed to enable operative connection of the relay with the current sensor via circuit-connection means positioned between them. Said connection means comprise a first substantially rigid body, on which there are defined two distinct electrically conductive paths; the first conductive path has a first end connected to the secondary winding and a second free end designed to be connected operatively to said first pin, and the second path has a third end connected to the secondary winding and a fourth free end designed to be connected to said second pin, said first and second pins and said second and fourth free ends being located in a spatial position that is pre-defined with respect to one of said walls of the casing. <IMAGE>

Description

The present invention relates to an electrical device for protection against residual currents, in particular for low-voltage applications, i.e., with operating voltages of up to one kilovolt.
It is known that in electric-power distribution systems different types of electrical devices are widely used, the basic task of which is to protect against faults, failures and malfunctioning, both in order to guarantee proper operation of the system and of the loads connected thereto and, above all, in order to protect the safety of persons, who, for various reasons, interact with the system.
An electrical device according to the preamble of claim 1 is known from the document WO 0145128 .
In this perspective, of particular importance is the adoption of systems of protection against residual currents, i.e., in case of leakage currents to ground higher than a preset limit. Such protection systems have the main purpose of guaranteeing persons from direct contacts, i.e., accidental contacts with a normally live phase conductor, and from indirect contacts, i.e., for example, with a metal body that is normally insulated, which, on account of a failure, happens to be in contact with a phase. In addition, said systems enable protection of the distribution system from risks of failure or fire due to the deterioration of the distribution system caused by conditions of continuous current-dispersion.
The above type of protection from residual currents is normally obtained by using two types of electrical devices, namely, the so-called pure "residual-current circuit breakers" and the "residual-current units". Both of these types of devices are equipped with a sensor part, which enables detection of any possible presence of residual currents and tripping of a purposely designed tripping unit. In turn, the tripping unit actuates an appropriate mechanism, operatively connected to the electrical contacts. In the case of a pure residual-current circuit breaker, said mechanism and the contacts are located inside the same casing hosting the sensor part and the tripping unit, whilst, in the case of a residual-current unit, they form part of a separate interruption unit, typically a magnetothermal circuit breaker, which is coupled to the block itself by the fact that the two components are mounted alongside one another.
From the constructional point of view, the part in common to residual-current units and pure residual-current circuit breakers comprises a transformer assembly and a tripping relay, which are assembled and operatively connected to one another by means of an appropriate connection circuit.
In particular, the transformer assembly consists essentially of a residual-current sensor, which, according to widely used embodiments, is made up of a ferro-magnetic toroidal core with the respective primary and secondary windings. In turn, the relay, which is generally of the demagnetization-polarized type, comprises a containment box, inside which there is provided the electromagnetic equipment and a tripping pin, which protrudes from said box and, when it is actuated by the electromagnetic equipment, triggers the tripping part. A pair of pins also protrude from the box for electrical connection of the relay to the transformer assembly and, more precisely, for connection to the terminals of the secondary winding of the current sensor.
According to the current state of the art, the modalities with which the protection devices are built, in particular as regards, in the manufacturing phase, assembly and operative connection of the transformer assembly with the tripping relay, present certain critical aspects that are not altogether satisfactory.
In the solutions of a known type, after the transformer assembly and the relay have been arranged inside the casing of the device, the relative positions of the connection elements of the relay and of the outputs of the transformer are undefined and may vary from one device to another. It follows that, in order to make the operative connections between the relay, the transformer assembly, and the circuit means to be set between them, manual intervention by an operator who brings the various parts into the positions suitable for connection is necessary. Alternatively, it is necessary to resort to a manipulating member, which picks up and positions said elements in the right positions.
It is clear that such operations involve a slowing-down of the assembly operations or even prevent a complete automation, possibly creating delays, possible errors, or imprecisions in the process.
The primary task of the present invention is to provide an electrical device for protection against residual currents which will enable the drawbacks mentioned above to be overcome and, in particular, is suited for being implemented in an optimized way as compared to the devices of the known art, enabling faster assembly operations and minimizing the possibility of errors and imprecisions.
The above task is achieved by an electrical device for protection against residual currents, which comprises an insulating casing having a rear wall, a front wall, a bottom wall, a top wall, and two side walls, there being positioned inside said casing: a residual-current sensor, which comprises a toroidal core, a primary winding and a secondary winding; and a tripping relay, having a containment box, from a wall of which there protrude a first pin and a second pin designed to enable operative connection of the relay with the current sensor via circuit-connection means interposed between them, said electrical device being characterized in that said connection means comprise a first substantially rigid body, on which there are defined two distinct electrically conductive cables, the first of said conductive cables having a first end connected to the secondary winding and a second free end designed to be connected operatively to said first pin, and the second of said cables having a third end connected to the secondary winding and a fourth free end designed to be connected to said second pin, said first and second pins and said second and fourth free ends being located in a spatial position that is pre-defined with respect to one of said walls of the casing.
In this way, in the device according to the invention, when the various components are mounted, the points of connection between the relay and the part for connection with the current sensor are located in a pre-defined desired spatial position, which thus enables a complete automation of the process of assembly, enabling elimination of any manual intervention and consequent optimization of the operations, with a resulting benefit in terms of overall production costs and times.
Further characteristics and advantages of the invention will emerge more clearly from the description of preferred but non-exclusive embodiments of the protection device according to the invention, illustrated by way of indicative and non-limiting example, with the aid of the attached drawings, in which:

Figure 1 is a perspective view illustrating an embodiment of a connection means used in the protection device according to the invention;
Figure 2 is a lateral plan view of the connection means illustrated in Figure 1, in accordance to a second embodiment;
Figure 3 is a perspective view illustrating the means of Figure 2 mounted on the transformer assembly and electrically connected to the secondary winding of the current sensor in the device according to the invention; and
Figures 4 to 6 are perspective views illustrating in sequence successive phases of assembly of the device according to the invention.

In the aforesaid figures and in the ensuing description, reference is made to a pure residual-current circuit breaker, i.e., to a protection device complete with a sensor part, a tripping relay, and the tripping mechanism, without in any way implying a limitation of the scope of possible application, the device according to the present invention being likewise usable just as residual-current unit.
With reference to the aforesaid figures, the protection device according to the invention, designated, as a whole, comprises an insulating casing (of which in Figures 4 to 6 only the base part is illustrated), having a rear wall 1, a bottom wall 2, a top wall 3, two side walls 4, and a front wall; said front wall is normally made up of a cover or lid which closes the device at the front, and which is not illustrated in the figures with the only purpose of enabling a clearer illustration of the internal components. In the case of a residual-current unit, the internal side wall may be defined only partially, or else may coincide with the wall of the interruption unit positioned alongside, according to the desired s. The walls of the casing delimit an internal space, inside which the various components of the device are positioned, said components comprising in particular: a tripping relay 5; a kinematic mechanism 6 for opening the contacts associated thereto, according to known constructional and functional embodiments; a transformer assembly 7 for detection of possible residual currents; and circuit-connection means positioned between and designed to connect operatively the tripping relay 5 and the transformer assembly 7, according to modalities which will be described below more in details.
According to embodiments widely known to the art and for this reason not illustrated in detail, the transformer assembly 7 comprises a residual-current sensor, constituted in its essential parts by a toroidal core generally made of ferro-magnetic material, a primary winding, and a secondary winding. As is illustrated in Figures 3 to 6, in the embodiment of the device according to the invention, the transformer assembly 7 comprises a containment or protective structure 8, housed within which is the toroidal core, with the terminals 9 of the primary winding as well as the terminals 10 of the secondary winding (partially visible in Figure 3) which come out therefrom; on the outer surface of the container 8 there is preferably defined an assembly seat 11 for the purposes that will emerge in greater detail in what follows.
In turn, the tripping relay 5, comprises a containment box, inside which there is provided the active equipment of the relay. Typically, the relay 5 is of the demagnetization-polarized type, in which the equipment comprises an armature equipped with a mobile anchor, on which a coil is wound. From a wall 12 of the casing there protrude a first pin 13 and a second pin 14, designed to enable, via the circuit-connection means previously mentioned, operative connection of the relay itself with the transformer assembly 7 and, more precisely, electrical connection with the secondary winding of the current sensor.
Advantageously, in the protection device 100 according to the invention, the operative-connection means between the relay and the transformer assembly comprise at least one substantially rigid body, designated as a whole in the figures by the reference number 20, upon which are defined two distinct electrically conductive paths, a first path designated by 30 and a second path designated by 40. The first conductive path 30 has a first end 31 connected to the secondary winding and a second free end 32 designed to be connected operatively to the first pin 13. The second path 40 has a third end 41 connected to the secondary winding of the sensor and a fourth free end 42 designed to be connected to the second pin 14 of the relay. In particular, as illustrated in Figures 5 and 6, the relay 5 and the body 20 are arranged inside the casing, with the two pins 13 and 14 and the two free ends 32 and 42 which are arranged in a spatial position that is pre-defined with respect to any one of the walls of the casing.
In particular, the rigid body 20 is made of insulating material, and the two conductive cables 30 and 40 are made using two corresponding metal inserts having at least the end portions that come out therefrom on opposite sides. According to a simple and functionally effective embodiment, the two metal inserts are advantageously formed by two substantially rigid filiform conductive cables, which are arranged parallel to one another and are partially embedded inside the body 20 with at least the ends 31, 32, 41, 42 that exit therefrom.
In particular, as may be seen from Figure 3, the first cable 30 has the first end 31 that is electrically connected to the first terminal of the secondary winding, preferably by welding, and the second free end 32 that comes out of the body and that, in practice, constitutes a substantially rigid pin, designed to be operatively connected to the first pin 13 of the relay. Likewise, the second cable 40 has a third end 41 preferably welded to the second terminal of the secondary winding and a fourth free end 42 designed to be connected to the second pin 14, which also comes out of the rigid body and forms a rigid connection pin.
Possibly, other modes of connection between the terminals of the secondary winding and the two conductive cables 30 and 40 may be used, for example, a pressure-connection system.
In a preferred embodiment, the rigid body 20 has an area shaped so as to have surfaces for coupling with a geometrically conjugated assembly seat set inside the casing, preferably the assembly seat 11 defined on the container 8 of the transformer assembly 7, so as to simplify the connections with the terminals of the secondary winding. Alternatively, the body 20 can be set in the casing by being coupled to a seat defined in another position, for example, on the internal surface of one of the walls of the casing, such as a side wall, or else on other components or walls, for example an internal divisory diaphragm.
As illustrated in greater detail in Figures 1 and 2, the rigid body 20 comprises a first portion 21 of a substantially parallelepipedal shape, and a second portion 22, on which there is made said shaped coupling area, said portions being made in two pieces spaced apart along the longitudinal development of the conductive cables 30 and 40, with the first end 31 and the third end 41 coming out from the second portion 22 and the second end 32 and the fourth end 42 coming out from the first portion 21.
Preferably, the second portion 22 is shaped in such a way that, viewed laterally (see Figure 2), has a substantially L-shaped cross section, in which a first branch 23 of the L-shaped portion has, in the proximity of the internal corner in common with the second branch 24, a groove 25, positioned substantially perpendicular to the longitudinal development of the two conductive cables. In particular, the first branch 23 of the L with the lowered groove 25 enables a simple and precise coupling with the assembly seat, whilst the second branch 24 of the L, thanks to its geometrical configuration prevents the possibility of performing incorrect installation of the body 20 in the seat, for example, the wrong way round.
In the embodiment illustrated, the rigid body 20 further comprises a third portion 26, once again made of the same insulating material, which interconnects the two portions 21 and 22 and has a smaller cross section than these. Said portion 26 is positioned between two conductive cables 30 and 40, the portion of these two conductive cables comprised between the first portion 21 and the second portion 22 being not coated with the insulating material of the rigid body.
In this way, the part of the body 20 corresponding to the portions of conductive cables 30 and 40 has a smaller structural stiffness than the remaining part, and this fact makes it possible to bend it and thus obtain the configuration illustrated in Figures 2 and 3. This makes it possible to use the rigid body 20 inside the casing with two different configurations, namely, with the second portion 22 inserted in the assembly seat 11 with the free portions that extend aligned with respect to one another (Figures 4 to 6), or, alternatively, with the second portion 22 again inserted in the assembly seat, with the third portion 26 curved to form an elbow, and the first portion 21 and the second portion 22 set crosswise with respect to one another.
In this way, it is not only advantageously possible to effect positioning of the body 20 on assembly seats arranged in different angular positions, but above all it is possible to avoid the effects of dimensional variations due to the fact that the components, for example the relay and the transformer assembly, can be very different depending on the features of the device in which they are used. For example, if the transformer is larger, in the case of installation of the body 20 on a seat defined on the container 8, the ends 32 and 42 come to occupy, owing to the bending, always the desired position with respect to the pins of the relay, thus eliminating said dimensional variation.
Advantageously, in the device according to the invention, the circuit-connection means further comprise a second body 50 of a substantially planar shape made of a substantially flexible material, arranged on which is an electronic circuit which operatively connects the relay 5 to the transformer assembly 7 and, more precisely, the two pins 13 and 14 to the two free ends 32 and 42 of the metal inserts 30 and 40. For this purpose, on the second body 50, four through seats 51 are preferably defined, in each of which there are inserted and electrically connected to the electronic circuit, for example by welding, the two pins 13 and 14, and the third and fourth free ends 32 and 42, respectively.
In practice, in the assembly stage, the transformer assembly 7 is inserted inside the casing of the device, so that it rests on the rear wall 1. The rigid body 20 is then positioned, with the portion 22, which is inserted inside the assembly seat 11, preferably defined on the container 8, with the ends 31 and 41 that are connected to the terminals of the secondary winding. In particular, the rigid body 20 is positioned, both in the configuration of Figure 1 and in the configuration of Figure 2, with the second portion 22 connected to the assembly seat 11 and with the first parallelepipedal portion 21 that extends towards the front wall, parallel to one of the side walls of the casing 4, or to the bottom wall 2 or the top wall 3. The relay 5 is then positioned, together (in the case of the circuit breaker illustrated in Figures 4 to 6) with the kinematic tripping mechanism 6. In particular, the relay 5 is positioned with a side wall 15 of the box that is set parallel to and alongside the first portion 21 so that the third and fourth free ends 32 and 42 and the two pins 13 and 14 are located in a pre-defined relative position, basically at a desired height with respect to the rear wall of the casing, preferably at one and the same height, i.e., on one and the same imaginary plane. Finally, the body 50 is positioned so that it rests on the wall 12 of the box of the relay, inserting the two pins 13 and 14 and the two free ends 32 and 42 each inside a corresponding seat 51 and then welding for making the connections. In particular, the flexibility of the body 50 enables the imprecisions due to the inevitable constructional tolerances to be eliminated. Furthermore, the fact that the two pins 13 and 14 and the two ends 32 and 42 are in one and the same plane further facilitates the operations of positioning and connection.
It has, in practice, been noted how the protection device according to the invention fully performs the intended task, thanks to the particular configuration of the connection means described previously, it can be assembled in a completely automatic way with a fast and simple process which enables minimization of the possible errors due to manual intervention. Moreover, all the innovative functions and inventive aspects of the device may be achieved using elements and materials that are readily available on the market, with extremely contained costs and according to a simple and at the same time effective structure of implementation. In addition, the device according to the invention can advantageously be used both as a pure residual-current circuit breaker and as a simple residual-current unit to be connected, then, to an associated tripping unit.

Claims

An electrical device for protection against residual currents, which comprises an insulating casing having a rear wall (1), a front wall, a bottom wall (2), a top wall (3), and two side walls (4), there being positioned inside said casing: a residual-current sensor, which comprises a toroidal core, a primary winding and a secondary winding; and a tripping relay (5), having a containment box, from one wall of which there protrude a first pin (13) and a second (14) pin designed to enable operative connection of the relay (5) to the current sensor via circuit-connection means interposed between them, said electrical device being characterized in that said connection means comprise a first substantially rigid body (20), on which there are defined two distinct electrically conductive cables (30,40), the first of said conductive cables having a first end (31) connected to the secondary winding and a second free end (32) designed to be connected operatively to said first pin (13), and the second (40) of said conductive cables having a third end (41) connected to the secondary winding and a fourth free end (42) designed to be connected to said second pin (14), said first (13) and second (14) pins and said second (32) and fourth (42) free ends being located in a spatial position that is pre-defined with respect to one of said walls (1,2,3,4) the casing.
The electrical device according to Claim 1, characterized in that said rigid body is made of insulating material, and in that said first (30) and second (40) conductive cables are made using a first metal insert and a second metal insert having at least said first (31) and third (41) ends and said second (32) and fourth (42) ends that protrude therefrom on opposite sides.
The electrical device according to Claim 2, characterized in that said first and second metal inserts are formed by a first filiform conductive cable and a second filiform conductive cable, which are arranged parallel to one another and are partially embedded inside the insulating body and with the ends exiting therefrom.
The electrical device according to Claim 2 or Claim 3, characterized in that said rigid body has an area shaped so as to have surfaces for coupling with a geometrically conjugated assembly seat set (11) inside the casing.
The electrical device according to one or more of the preceding claims, characterized in that said rigid body comprises a first portion (21) of a substantially parallelepipedal shape, and a second portion (22), on which there is made said shaped area, said first and second portions being made of two pieces spaced apart along the longitudinal development of the conductive cables (30,40), with said first end (31) and said third end (41) corning out from said second portion (22) and said second end (32) and said fourth end (42) coming out from said first portion (21).
The electrical device according to Claim 5, characterized in that said second portion (22), viewed laterally, has a substantially L-shaped cross section, in which a first branch (23) of the L-shaped portion has, in the proximity of the internal corner in common with the second branch (24), a groove (25) positioned substantially perpendicular to the two conductive cables (30,40), said first branch (23) being designed to be connected to said assembly seat (11).
The electrical device according to Claim 4, characterized in that said rigid body (20) has a third portion (26), which interconnects said first (21) and second portions (22), has a smaller cross section than these, and is positioned between the two conductive cables (30, 40); the portion of these two conductive cables (30, 40) comprised between the first portion (21) and the second portion (22) being exposed.
The electrical device according to one or more of Claims 4 to 7, characterized in that said rigid body (20) is located inside said casing with the second portion (22) inserted in said assembly seat (11), with said first (21) portion, said second (22) portion, and said third portion (26) extending aligned with one another.
The electrical device according to one or more of Claims 4 to 7, characterized in that said rigid body (20) is located inside said casing with the second portion (22) inserted in said assembly seat (11), with said third portion (26) curved to form an elbow, and said first (21) and second (22) portions positioned crosswise with respect to one another.
The electrical device according to Claim 1, characterized in that said circuit-connection means further comprise a second body (50) of a substantially planar shape, provided on which is an electronic circuit which operatively connects said first (13) and second (14) pins to said second (32) and fourth (42) free ends.
The electrical device according to Claim 10, characterized in that on said second body (50) there are a first through seat (51) and a second through seat (51), said first (13) and second (14) pins being inserted in said first and second through seat (51) and electrically connected to the electronic circuit, and a third seat and a fourth seat (51), said third (32) and fourth (42) free ends being inserted in said third and fourth seats (51) and electrically connected to the electronic circuit.
The electrical device according to Claim 10, characterized in that said second body (50) on which the electronic circuit is positioned is made of a substantially flexible material and rests on the wall of the box of the relay (5) from which there project said first (13) and second (14) pins.
The electrical device according to one or more of the preceding claims, characterized in that said current sensor is inserted inside a container, which rests on the rear wall (1) of the casing and on which there is defined said assembly seat (11) of the rigid body (20), the rigid body (20) being positioned with the second portion (22) connected to said assembly seat (11) and the first parallelepipedal portion (21) that extends towards the front wall of the casing, substantially parallel to and interposed between a side wall (4) of the casing and a side wall of the box of the relay (5), the relay (5) being positioned between the current sensor and the front wall of the casing in such a way that said third (31) and fourth (41) free ends and said first (13) and second (14) pins are located substantially at the same height with respect to the rear wall (1) of the casing.
The electrical device according to one or more of the preceding claims, characterized in that it is a pure residual-current circuit breaker or a residual-current unit.