AU601490B2

AU601490B2 - Modular assembly multipole earth leakage circuit breaker

Info

Publication number: AU601490B2
Application number: AU78825/87A
Authority: AU
Inventors: Rene Challande; Michel Charbonneau; Marc Paupert
Original assignee: Merlin Gerin SA
Current assignee: Schneider Electric SE
Priority date: 1986-09-23
Filing date: 1987-09-22
Publication date: 1990-09-13
Anticipated expiration: 2007-09-22
Also published as: EP0264314A1; YU173687A; DE3783704T2; DE3783704D1; AU7882587A; CN1021388C; ES2040270T3; FR2604294A1; EP0264314B1; FR2604294B1; PT85770A; CN87106499A; PT85770B; JPS6388729A; ATE84915T1; IN170069B; TNSN87104A1

Abstract

Differential circuit-breaker formed by the modular assembling of a circuit-breaker unit (11) with separable contacts, and with control mechanism (18) with handle, and of a differential trigger unit (20) having a triggering relay (26), a first mechanical link (27) for triggering the mechanism (18), a second mechanical link (45) for automatic resetting of the relay (26), a test circuit (28) with test button (44), and a control for remote opening by remotely-controlled contact (46). One of the faces of the casing of the trigger unit (20) engaging with the circuit-breaker unit (11) contains openings for transverse passage of the first and second mechanical links (27, 45). The other opposite face of the casing serves alternately as support, either to a detector unit (150) enclosing a totalising transformer (21), or to an auxiliary unit (202) containing an electronic circuit (204) driven by triggering and supply signals coming from the separate detector unit (150). <IMAGE>

Description

I

Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-69 COMPLETE

SPECIFICATION

(ORIGINAL)

Class I t. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: A Related Art: 60 14 This docU M; nt cc)fIl~aSte amIfldr n i1t ade tne 'ctiofl 49 and i, correct foT

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0 N~itme of Applicant: MERLIN

GERIN

'Aderessof Applicant: Rue Henri Tarze F 38050 Grenoble Gedex, France ,Actual Inventor: Address for Service: RENE CHALLANDE, MICHEL CHARBONNEAU and MARC PAUFERT EDWD. WATERS

SONS,

50 QUEEN STREET, MELBOURNE, AUSTRALIA, 3000.

N

Complete Specification for the invention entitled: MODULAR ASSEMBLY MULTIPOLE EARTH LEAKAGE CIRCUIT

BREAKER

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Th fllwig taI emntita ul dscipio o tisinetininluin te es mthd f ejrmngitknwnt us-u t I I 11 4Lg

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la The invention relates to a multipole electrical earth leakage protection circuit breaker having a modular side by side assembly comprising: a circuit breaker unit having first opposite parallel side walls and a multipole breaking device with separable contacts actuated by a toggle operating mechanism equipped with a handle which can be moved between an ON position and an OFF position, an earth leakage trip unit having a trip unit housing with second opposite parallel side walls, the units being stacked with side walls thereof in face to face engagement, said trip unit comprising a trip relay, a first mechanical link capable of transmitting a tripping order from the relay to the toggle operating mechanism when an earth leakage fault occurs, a second mechanical link to derive from the toggle opening movement between the ON and OFF positions, an automatic resetting movement of the relay, a test circuit having at least one test resistor in a leakage branching circuit, a test button closing of which creates an artificial earth leakage current, a protective switch designed to disconnect the r test resistor and to break the artificial earth leakage f f current in the test circuit after opening of the circuit breaker by earth leakage tripping.

4: 4 The earth leakage trip unit of a miniature circuit 4414 breaker generally houses the earth leakage current detector including a transformer in the form of a toroid passing around the active conductors of the system to be protected.

In the electromechanical version of the earth leakage circuit breaker, the secondary winding is directly connected to the trip relay, and it is then indispensable that a trip unit be fitted for each tripping sensitivity. In the electronic version of the earth leakage circuit breaker, an electronic circuit is fitted between the secondary winding ;pK~' -6 ii I ii i 4A4 W<4-P and the relay to obtain a high-sensitivity earth leakage protective device. A special trip unit is also required.

The number of different trip units gives rise to storage and cost price problems for a range of miniature circuit breakers.

The object of the invention is to achieve a modular earth leakage circuit breaker using as many common parts as possible for each of the electromechanical or electronic versions.

The circuit breaker according to the invention is characterized in that one of the second side walls of the trip unit housing coming into engagement with the circuit breaker unit comprises transverse openings for the first and second mechanical links to pass through, and wherein the other of the second side walls of the trip unit housing acts as a support member: either in an electromechanical version for a detector unit containing a summation transformer for residual earth leakage current detection, said detector unit being then stacked side by side with the trip unit, or in an electronic version for an auxiliary unit containing an electronic circuit controlled by tripping and power supply signals delivered by said detector unit, said auxiliary unit being then stacked side by side with the trip unit, and the detector unit being mechanically separated from the trip unit.

c(e The relay of the earth leakage trip unit is connected by an internal electrical connection, either to the measurement winding of the transformer incorporated in 30 the detector unit for the electromechanical version, or to f the auxiliary unit electronic circuit board for the electronic version. It can be noted that the structures of the circuit breaker unit, the trip unit and the detector *unit are identical for each version, the i: Z U(D Iz os :Vi% -2aonly modification being the presence or not of the auxiliary unit with an appropriate wiring.

The front panel of the auxiliary unit is equipped with an earth leakage tripping sensitivity setting selector, and with a time delay button to set the earth leakage tripping delay. The trip unit comprises a built-in remote opening control by artificial earth leakage tripping, and an earth leakage tripping visualization window, located in the vicinity of the test button.

f 4 t i 10 The detector unit is electrically connected by a strap to a connector of the auxiliary unit electronic circuit in such a way t Ott t 4 i OtrStt I 4 4 Rr7$j" iii Iii~

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1 I 3 S as to transmit the power supply and the earth leakage current measurement signal to the electronic circuit board, and to provide the connection of the test circuit with the system upstream and downstream from the transformer.

According to an alternative embodiment of the invention, the electronic circuit comprises transformer secondary winding load resistors, cooperating with the setting selector to select the earth leakage tripping sensitivity, said selector being in connection with an auxiliary switch designed to be actuated by the test button to impose automatic switching of the selector to the highest sensitivity when the test circuit is closed.

4 0 4 0 aa 0 00 0 0 r 00 t Ca ii CC j c Brief description of the drawings C r.

VC C t C C CC Other advantages and features will become more clearly apparent from the following description of an illustrative embodiment of the invention, given as a non-restrictive example only and represented in the accompanying drawings, in which Figure 1 represents the wiring diagram of a circuit breaker with an electromechanical earth leakage trip unit; Figure 2 is an elevational view of the earth leakage trip unit capable of being associated with the breaking unit of the circuit'breaker, represented in the closed-loaded position Figures 3 to 5 respectively show sectional views of the earth leakage trip unit along the lines III-III, IV-IV, and V-V of figure 2; Figure 6 shows a schematic view of the modular assembly of the circuit breaker according to figure 1, comprising a breaking unit, an earth leakage trip unit, and a detector unit with a summation transformer;

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h.Y; U T ;4 Figure 7 is a plan view of figure 6, with the detector unit cover removed Figure 8 is the wiring diagram of an alternative embodiment of a circuit breaker equipped with an electronic earth leakage trip unit Figure 9 represents the diagram of the auxiliary unit electronic circuit Figure 10 shows a schematic view of the modular assembly of the earth leakage circuit breaker according to figure 8.

tr Detailed description It Figure 1 shows the wiring diagram of a two-pole earth leakage circuit breaker inserted in a single-phase alternating current system having a phase conductor L and a neutral conductor N. The earth leakage circuit breaker 10 comprises a two-pole or singlepole plus neutral breaking device 12 with separable contacts 14, 16 actuated by an operating mechanism with a handle 19, which operates in conjunction with a thermomagnetic trip unit (not shown) sensitive to overload and short-circuit currents, and an earth leakage trip unit 20 sensitive to earth leakage current.

The earth leakage trip unit 20 comprises a residual earth leakage current detector formed by a summation transformer 21 r Ct detecting a zero sequence current, having a ring core 22 passing around the active conductors L and N, and a measurement winding S24 wound on the core 22. The measurement winding 24 is electrically connected to a polarized electromagnetic trip relay 26 operating in conjunction with the mechanism 18 via a first mechanical tripping link 27 so as to bring about automatic Il -opening of the contacts 14, 16, when an earth leakage fault S9 occurs in the conductors L and N. A test circuit 28 is associated with the earth leakage trip unit 20 being electrically connected by a conductor 29 to a first connection point 30 of the phase conductor L, and by a conductor 31 to a second connection point 32 of the neutral conductor N, respectively upstream and downstream from the summation transformer 21. The test circuit 29 constitutes a leakage branching circuit comprising a pair of test resistors 34, 36, a breaking or protection device 38 with twin protective contacts 42, and a push-type test button 44. Manual closing of the test button 44 simulates an earth leakage current by inserting the resistors 34, 36 in the test circuit 28, enabling satisfactory operation of the earth leakage trip unit 20 to be checked. The artificial earth leakage current flows in the test circuit 28 from the first connection point 30 of the phase conductor L via the resistor 36, the protective contact 40, the test button 44, the protective contact 42, the resistor 34, and returns to the second connection point 32 of the neutral conductor N.

During the earth leakage phase controlled by the relay 26, opening of the protective contacts 40, 42 of the breaking device 38 takes place automatically by means of a second mechanical link 45 of the mechanism 18, causing the two resistors 34, 36 to be switched out of the circuit, even if the test button 44 is kept depressed. The breaking device 38 of the test circuit 28 is located between the test button 44 and the resistors 34, 36.

A remote tripping control can be associated with the mechanism 18 of the circuit breaker 10, and comprises a single remote control contact 46 inserted in a link circuit 48 capable of Sbeing electrically connected in parallel to the terminals 50, 52 of the test button 44. Actuating the remote control contact 46 |j 30 has the same effect as local closing of the test button 44, i.e.

opening of the contacts 14, 16 of the circuit breaker 10 by earth leakage tripplhg.

I 6 The presence in the test circuit 28 of the two protective contacts 40, 42 of the breaking device 38 enables the test button 44 and the remote control contact 46 to be fully isolated from the system after earth leakage tripping has occurred.

De-energizing by complete disconnection of the two buttons 44, 46 is achieved by simultaneous breaking of the two conductors 29, 31, regardless of the connertion mode of the circuit breaker i.e. in the case of a upstream power supply (terminals 51, 53) or in the case of an opposite downstream power supply (terminals 54, 56).

The presence of a test resistor 34, 36 in each conductor 31, 29 .of the test circuit 28 enables full user safety to be achieved, even in the case of accidental bindifig of the protective K~contacts 40, 42.

t S Referring now to figures 2 to 5, the mechanism 60 of the earth t c leakage trip unit 20 is housed in an insulated casing 62 capable of being juxtaposed and coupled to the circuit breaker unit 11 containing the breaking device 12, the mechanism 18 and the thermomagnetic trip unit. The tr~.p relay 26 of the mechanism 2b' comprises a movable blade (not shown) capable of cooperating with an arm 63 actuating a drive lever 64 pivotally mounted on a spindle 66 between a loaded position and a released position.

The drive lever 64 bears a finger 68 providing the first mechanical tripping link 27 designed to release the latch of the cianism 18 of the circuit breaker 10 when the blade of the relay 26 is. actuated towards the tripped position following an earth leakage fault.

The second mechanical link 45 of the earth leakage mechanism connects the handle 19 of the mechanism 18 of the circuit breaker 10 to a transmission cam 70 pivotally mounted on a spindle 72 in such a way as to follow the opening and closing movements of the handle 19.. The transmission cam 70. cooperates on the one hand with an arm 74 of a resetting lever 76, and on In I hLli~_-. l-W1-;t 7 the other hand with an indicator lever 78, both pivotally mounted on the same spindle A latch 82 (figs. 2 and 4) is pivotally mounted on a spindle 84 and comprises a retaining catch 86 capable of locking the indicator lever 78 in an inactive position in which a flag 88 is removed from a visualization window 90 disposed in the front panel of the housing 62.

Operation of the earth leakage mechanism 60 is the same as that described in French Patent n 2,437,692 which should be referred to for further details.

A spring 92 of the torsion type, made of electrically conducting metallic material, is fitted on the insulating spindle of the levers 76, 78. One of the ends 94 of the spring 92 bears on an edge of the resetting lever 76 in such a way as to urge it clockwise, bearing on the cam 70. The end 94 of the spring 92 can in addition cooperate with a first fixed conducting tongue S 96 to constitute the protective contact 40 of the breaking device 38 of the test circuit 28. The other end 97 of the spring 92 is in engagement against a stop 98 of the casing 62, and is 29' connected to the resistor 36 electrically connected by the conductor 29 to the first connection point 30 of the phase conductor L.

C C.

The other protective contact 42 of the breaking device 38 C cS Sj

A

rl:1! comprises a second fixed conducting tongue 100 capable of 25 cooperating with an elastic contact part 102. The opposite end of this blade 102 is secured to a fixed attachment 104 of the casing 62 surrounding the pivoting spindle 66 of the drive lever 64, and is electrically connected to the resistor 34 inserted in the conductor 31 of the test circuit 28. The contact blade 102 30 is actuated by a finger 103 of the resetting lever 76.

f r

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ii ii~ ~r i i The two fixed tongues 96, 100 are connected respectively to two connectors 106, 108 of the link circuit 48 of the remote control contact 46, the two connectors 106, 108 being in electrical connection with the terminals 50, 52 of the test button 44. A plug 110 can blank off the access opening to the connectors 106, 108 when the remote tripping mechanism is not connected to the earth leakage trip unit The test button 44 is equipped with a deformable elastic blade 112 described in detail in French Patent n 0 2,526,995. The blade 112 comes into contact with the first fixed tongue 96 of the protective contact 40 in the depressed position of the test t~ button 44.

Operation of the mechanism 60 of the earth leakage trip unit according to figures 2 to 5 is as follows: V -1 -1 when the circuit breaker 10 is closed corresponding to the position in f igure 2 of tne mechanism 60 of the earth leakage trip unit 20, the occurrence of an earth leakage fault causes tripping of the relay 26 bringing about clockwise pivoting of the drive lever 64 around the spindle 66, from the loaded 2Q', position to the tripped position. The finger 68 of the first mechanical link 27 transmits the tripping order to the latch of the mechanism 18 of the circuit breaker 10 which opens the C contacts 14, 16 of the breaking device 12 and releases the latch C C t 82 of the indicator lever 78. opening of the circuit breaker is accompanied by a counterclockwise pivoting movement of the handle 19 and of the transmission cam 70. The second mechanical link 45 with the mechanism 18 derives, from the circuit breaker opening movement, an automatic resetting movement of the relay 26 by means of the drive lever 64 urged by the resetting lever 76. The indicator lever 78 in addition moves the flag to an active position lined up with the visualization window 90 to indicate tripping on! an earth leakage" fault. After the relay 26 has been reset, the second mechanical link 45 moves the p r I 9 resetting lever 76 and the, indicator lever 78 back to their original positions when the handle 19 is moved maiually from the open position to the closed position of the circuit breaker.

Simulation of an earth leakage fault is achieved by depressing the push-button 44 causing the resistors 34, 36 to be inserted in the test circuit 28. The elastic contact blade 112 comes into contact with the terminal 50 of the first tongue 96. After the circuit breaker 10 has opened, the two protective contacts 42 open automatically by the clockwise pivoting movement of the resetting lever 76. The end 94 of the' spring 92 and the contact blade 102 move respectively away from the first and second fixed t tongues 96, 100, and switch the two resistors 34, 36 out of the .J circuit. The test circuit 28 is thus kept fleetingly energized during the response time of the circuit breaker mechanism 18.

The terminals 50, 52 and the connectors 106, 108 are deenergized when the circuit breaker is opened.

When the handle 19 of the circuit breaker 10 is then actuated towards the closed position after the relay 26 of the earth leakage trip unit 20 has been reset, the resetting lever 76 urges the protective contacts 40, 42 to the closed position. A fresh test can then be carried out.

It can be noted that the actuating arm 63 of the lever 64 is common to the first and second mechanical links 27, 45, and acts t both as a tripping means, when a trip signal is sent to the coil of the relay 26, and as resetting means of the relay 26, when the circuit breaker 10 has opened. The arm 63 has associated ,with it an elastic tongue 120 (fig. 2) made of insulating material, designed to maintain a preset clearance 122 between 30r the arm 63 and the blade after the relay 26 has been reset, and 1 0 when the handle 19 of the circuit breaker 10 is moved from the Jk open position to the closed position. The presence of this clearance enables a good transmission of the tripping order from the relay 26.

s i r Figures 6 and 7 show the modular assembly of the earth leakage circuit breaker 10 according to figure 1, with the electromechanical earth leakage trip unit 20 fitted between the twopole circuit breaker unit 11 and the detector unit 150 with summation transformer 21 for residual earth leakage current detection. The secondary winding 24 of the transformer 21 incorporated in the detector unit 150 is connected to the coil of the relay 26 of the earth leakage trip unit 20 by an internal electrical connection 152. Each pole of the circuit breaker unit 11 is for example of the type described in French Patent application n 0 86 00111 filed on January 3rd 1986 by the applicant, but any other miniature multipole circuit breaker may r' be used. The handle 19 is mechanically coupled to the second mechanical link 45 of the earth leakage trip unit 20, whereas 5" the first mechanical tripping link 27 controls the latch of the r v mechanism 18.

te r C, "C The earth leakage circuit breaker 10 comprises a pair of intermediate connectors 154, 156 connected between the lower terminals 158, 160 of the two-pole circuit breaker unit 11 and r 20 the upper terminals 162, 164 of the detector unit 150. The earth leakage circuit breaker 10 is system powered, and the system S conductors L, N are connected to the upstream terminals 51, 53 of the circuit breaker unit 11, and to the downstream terminals 54, 56 of the detector unit 150. The toroid 22 of the summation 25 transformer 21 comprises two primary coils 166, 168, whose rC S opposing ends are connected to the corresponding upper 162, 164 and downstream 54, 56 terminals of the detector unit 150. The intermediate conductors 154, 156 are input to the detector unit 150 by means of openings 170, 172 arranged unaer the downstream terminals 54, 56.

Figures 8 to 10 deal with an alternative embodiment of an electronic earth leakage circut breaker 200 with an auxiliary power supply. The same reference numbers will be used to designate identical or similar parts to those of the circuit

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b ri g i f II1 breaer 0 4nfigres to7. Te erth eakge crcut brake breake 10 ajinefgred to .he earth leakage circuuit bread oae auxiliary unit 202 housing an electronic processing circuit 204 of the signals from the separate detector unit 150.

A five-wire connecting strap 206'connects the detector unit 150 to an input connector 208 of the electronic circuit 204 to ensure on the one hand emission of a first measurement signal from the secondary winding 24, and of a second signal for the D.C. voltage power supply, and on the'other hand connection of the test circuit 28 of the earth leakage trip unit 20 with pushbutton 44.

The electronic circuit 204 of the auxiliary unit 202 is connected to the relay 26, to the test circuit 28 Lind to the test 44 and remote control 46 buttons of the trip unit 20 by an internal eight-wire connection 210.

The front face of the auxiliary electronic unit 202 is provided with an earth leakage trip sensitivity setting selector 212 (for example 30 mA, 300 mA, 1 A, 3 and with a time delay button 214 for setting the earth leakage tripping time delay.

The electronic circuit 204 (fig. 9) of the 'auxiliary unit 202 Scomprises a set of resistors RO, Ri, R2, R3, adjusting the Ssensitivity, and the secondary winding 24 of the summation transformer 21 is loaded by one or more of these resistors RO to R3 depending on the position of the selector 212. The highest sensitivity of 30 mA corresponds to insertion of the resistor Rwhereas the 300 MA, 1 A, and 3 A sensitivities correspond to *connection of Rl, R2, R3 in parallel with the 'resistor RO. The Output of the set of resistors RO to R3 is connected to an operational amplifier 216, arranged as a comparator which controls a processing circuit 218 of, the earth leakage tripping signal. The remote control contact 46 is directly Connected to 12 the processing circuit 218 by resistors 220, 222. The output of the processing circuit 218 is connected to one of the inputs of a logic OR gate 224 which controls excitation of the coil of the trip relay 26.

The output terminal 226 of the secondary winding 24 of the transformer 21 is connected by a resistor 228 to the D.C.

voltage supply, and by a capacitor 230 to the set of rescistors RO to R3. The other input of the logic OR gate 224 is connected by a conductor 232 to the terminal 226 of the winding 24. A poor continuity of the secondary circuit of the detector unit 150 causes the potential of the terminal 226 to rise, delayed by the V time constant RC of the resistor 228 and of the capacitor 230.

The logic OR gate 224 can thus receive two tripping orders comprising -r first tripping signal on an earth leakage fault generated by the processing circuit 218, and a second tripping signal on a secondar-y circuit continuity fault. Discrimination of the two tripping signals is performed by the opening time delays of the earth leakage circuit breaker 200.

The sensitivity setting selector 212 is connected to the ground by means of an auxiliary switch 232 (figs. 8 and The latter is housed in the trip unit 20 and is actuated when the test button 44 is depressed (see figs. 2 and causing automatic breaking of the connection of the selector 212 with the ground when the test circuit 28 is closed. This results in forced "2S switching to the highest sensitivity, i.e. 30 mA~ (resistor RO), It regardless of the position of the selector 212. In operation without test of the circuit breaker 200, damage to the selector .212 or auxiliary switch 232 leads to an increased sensitivity of the electronic circuit 204.

In the electromechanical version of the earth leakage circuit breaker 10 in f igure 7, the detector unit 150 is part of the modular assembly and it must be adjoined, to the trip unit 20. In the electronic version of the'earth leakage circuit breaker 200 I T aa-; i ilcu- 13 in figure 10, the auxiliary unit 202 of the electronic circuit 204 is disposed side by side with the trip unit 20, whereas the detector unit 150 is physically separate from the modular assembly, with simple electrical connections with the circuit breaker unit 11 (conductors 154, 156), and the electronic circuit 204 (connecting strap 206).

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Claims

1. A multipole electrical earth leakage protection circuit breaker having a modular side by side avmembly comprising: a circuit breaker unit having first opposite parallel side walls and a multipole breaking device with separable contacts actuated by a toggle operating mechanism equipped with a handle which can be moved between an ON position and an OFF position, an earth leakage trip unit having a trip unit housing with second opposite parallel side walls, the units being stacked with side walls thereof in face to face engagement, said trip unit comprising a trip relay, -a first mechanical link capable of transmitting a tripping order from the relay to the toggle operating mechanism when an earth leakage fault occurs, a second mechanical link to derive from the toggle opening movement between the ON and OFF positions, an automatic resetting movement of the relay, a test circuit having at least one test resistor in a leakage branching circuit, a test button closing of which creates an artificial earth leakage current, a protective switch designed to disconnect the test resistor and to break the artificial earth leakage current in the test circuit after opening of the circuit breaker by earth leakage tripping, wherein one of the second side walls of the trip unit housing coming into engagement with the circuit breaker unit comprises transverse openings for the first and second mechanical links to pass through, and wherein the other of the second side walls of the trip unit housing acts as a support member: VA: 2 i <V -either in an electromechanical version for a detector unit containing a summation transformer for residual earth leakage current detection, said detector unit being then stacked side by side with the trip unit, or in an electronic version for an auxiliary unit containing an electronic circuit controlled by tripping and power supply signals delivered by sa\detector unit, said auxiliary unit being then stacked side by side with the trip unit, and the detector unit being mechanically separated from the trip unit.

2. An electrical circuit breaker according to claim 1, wherein the relay of the earth leakage trip unit is connected by an internal electrical connection, either to the measurement winding of the transformer incorporated in the detector unit for the electromechanical version, or to the auxiliary unit electronic circuit board for the electronic version.

3. An electrical circuit breaker according to claim 2, wherein the front face of the auixiliary unit is equipped with an earth leakage tripping sensitivity setting selector, and with a time delay button to set the earth leakage tripping delay and wherein the trip unit comprises a built-in remote opening mechanism by artificial earth leakage tripping, and an earth leakage tripping visualization window, located near to the test button. An electrical circuit breaker according to claim 1, wherein the detector unit is electrically connected by a connecting strap to a connector of the auxiliary unit electronic circuit in such a way as to transmit th:' power supply and the earth leakage current measurement signal to the electronic circuit board, and to provide the connection of the test circuit with the system upstream and downstream from the transformer. I? 16 16 An electronical circuit breaker according to claim 4, wherein the electronic circuit comprises load resistors of the transformer secondary winding, operating in conjunction with the setting selector to select the earth leakage tripping sensitivity, said selector being in connection with an auxiliary switch designed to be actuated by the test button to impose automatic switching of the selector to the highest sensitivity when the test circuit is closed. t tr

6. An electrical circuit breaker according to claim wherein the electronic circuit comprises, in addition: Ct c an earth leakage signal processing circuit, controlled by an operational amplifier comparator connected to the o secondary winding by means of the sensitivity adjustment resistors, a secondary circuit continuity monitoring circuit, and a logic gate capable of taking account of any of the tripping signals on an earth leakage or secondary circuit continuity fault, to trigger the trip relay.

7. A circuit breaker as claimed in claim 1, substantially as herein described with reference to the accompanying drawings. DATED this 24th day of May, 1990. MERLIN GERIN WATERMARK, P PATENT TRADEMARK ATTORNEYS, 290 BURWOOD ROAD, i HAWTHORN, VIC. 3122. AUSTRALIA. ~T AL i z