Description:
TECHNICAL FIELD OF THE INVENTION
The present subject matter described herein, relates to the technical field of integrated tripping unit for short circuit and residual current fault along with separate fault indication means for RCBO.

BACKGROUND OF THE INVENTION
With the increase of industry size and automation, the requirement of protection devices has also increased and become mandatory. Along with the competitive criterions such as compactness, cost-effectiveness and reliability, advance safety features continue to be of utmost attraction in protection. Therefore, any enhancement in safety and compactness will always be welcome in electrical industry.

The residual current circuit breakers with overload protection (RCBO) can detect residual current, short-circuit and overload faults. A pair of contacts and suitable mechanical linkages are used to make and break the circuit where it is installed. In healthy circuit condition, contacts can carry a specified amount of current and can be opened or closed by manual or automatic means. In abnormal condition such as an overload condition or a relatively high-level short circuit or residual current fault condition, a detection device senses abnormality (over current or short circuit or residual current fault) and gives the trip command to mechanism in order to separate / open contacts to isolate the faulty circuit from system.

In an electromagnetic circuit breaker, the detection units and tripping units are different for different types of faults. In case of a compact modular device, it is very difficult to accommodate all three types of protection for all the poles. For example, in case of a 2 Pole RCBO, manufacturers offer short circuit and overload protection in only one pole due to space constraint. The overall product size increases in order to accommodate fault detection and tripping units in all poles.

In this regard, reference is made to AU2003214138B2 (Prior art A) which relates to a circuit breaker for automatically interrupting an electrical flow of current (I), comprising a trip element (4), which has a tappet (26) for actuating a switching mechanism (3) and a coil (10) for generating an electromagnetic tripping force that moves the tappet (26) out of a first position and into a tripping position. The invention is characterized in that a second coil (12) is arranged coaxial to the first coil (10), whereby the second coil (12) is flown through by a current (i) that is controlled according to a signal output by a summation current transformer (42) as a response to the detection of fault-currents.

Reference is made to CN201421812Y (Prior art B) disclosing a combined electromagnetic tripper, wherein a coil framework is installed in a magnet yoke; a static iron core and a movable iron core are installed in a holding cavity ofthe coil framework; current coils and voltage coils are installed on the coil framework or the magnet yoke, the current coils and the voltage coils are in a same magnetic loop, and the different tap positions of the current coils and the voltage coils are connected into the magnetic loop. In the utility model, the functions of an electromagnetic tripper for short circuit current and an electromagnetic tripper for residual current can be achieved on one electromagnetic tripper, thereby not only saving the space, reducing the parts and lowering the cost, but also being favor for the modularization of a small-sized breaker.

Both the inventions of Prior art A and Prior art B disclose an integrated tripping device for magnetic and residual current fault. It has accommodated tripping devices in a single sub-assembly to reduce overall space requirement. Two coils are placed coaxially on a single bobbin/tube. In case of “A”, coils are displaced radially and in case of “B” Coils are displaced axially. Both the coils use same flux path of Armature, Core and Magnet yoke. Plunger is placed through Core and moves with the movement of Armature. In case of magnetic fault or residual current fault Armature moves towards right and pushes the Plunger to actuate circuit breaker mechanism.

Limitations of prior art A and B:
i. Circuit breaker mechanism cannot differentiate between Magnetic, residual and overload fault as the mechanism is actuated by same component (Plunger) for all three types of faults. So different mechanical indications for different types of faults are not possible for this arrangement.
ii. Another drawback of this arrangement is that the coils must produce similar MMF to actuate armature as the armature cannot be biased with two different springs for two different faults. In general, a magnetic fault produces a very high MMF and it is difficult to produce such a high amount of MMF from an electronically operated solenoid. So, this type of arrangement is not practically feasible for high rating circuit breaker.

Further, reference is made to CN103337423A (Prior art C) disclosing a double-action electromagnetic trip. The head of an ejector rod is glidingly mounted in a first bearing hole of a static iron core and stretches out of the hole; a first framework is sleeved with a current coil and arranged in a magnetic yoke, and accommodates a first reaction spring and a first movable iron core; two ends of the first reaction spring abut against a first spring accommodating hole of the first movable iron core and a support of the first framework respectively; the first movable iron core is contacted and matched with an association operation end of the tail part of the ejector rod; and under the action of short circuit of the current coil, a current magnetic field drives to prevent the elastic force of the first reaction spring from pushing the ejector rod to move. A second framework is sleeved with a voltage coil and accommodates a second reaction spring and a static iron core; two ends of the second reaction spring are connected with a limit step of the ejector rod and the static iron core respectively; a second movable iron core is mounted in an accommodating area formed through butt joint of the two frameworks through a linear sliding pair structure and is contacted and matched with a limit step of the ejector rod, and under the action of short circuit of the voltage coil, a current magnetic field drives to push the ejector rod to prevent the second reaction spring from moving.

Yet another reference is made to CN102064058A (Prior art D) an electric protection device. The electric protection device comprises a first control device and a second control device, wherein the first control device comprises a first electromagnetic coil, a fixed iron core, a first movable iron core and an actuating rod; the first electromagnetic coil is arranged around a first sheath; the fixed iron core is fixed at one end of the first sheath; the first movable iron core is slidably accommodated in the first sheath; the actuating rod is slidably arranged in the fixed iron core and coordinately acts with the first movable iron core to start a tripping mechanism of a circuit breaker; the second control device comprises a second electromagnetic coil and a second movable iron core; the second electromagnetic coil is arranged around a second sheath; the second movable iron core is slidably accommodated in the second sheath; when the first or second control device sends out a tripping command, the first or second movable iron core drives the actuating rod to reach a position for actuating the tripping mechanism; a second shell is arranged around the periphery of the second electromagnetic coil; and the second shell is approximately a semicircular cylinder with a closed end.

The inventions of Prior art C and Prior art D disclose an integrated tripping device for magnetic and residual current fault. The coils (Magnetic and residual current) are placed co-axially and displaced axially. Flux for the current coil-1 completes path through moving core-1 and moving core-2. When coil-1 is energised, moving core-1 moves towards right and pushes Plunger towards right. Coil-2 completes its flux path through moving core-2 and Static core. When coil-2 is energised, moving core-2 moves towards right and pushes Plunger towards right.

Limitations of prior art C and D:
i. When coil-1 (in case of prior art “C”)/ coil-2 (in case of prior art “D”) is energised, moving core-1 (in case of prior art “C”)/ moving core-2 (in case of prior art “D”) respectively has to overcome both spring-1 and spring-2.
ii. Another disadvantage for this invention is that, circuit breaker mechanism will not be able to differentiate between magnetic and residual current fault as it actuates same Plunger for both types of faults in same direction.

Another shortfall of a prior art compact RCBO is that, it does not provide different fault indication for different faults. Most of the compact RCBOs with all protected poles provides fault indication only for residual current fault and not for short circuit fault.

Therefore, there is a dire need for fault detection units and tripping units to be arranged in such a way that all the types of protection (short circuit, overload and residual current) are offered for all the poles. Further, there remains a need for a fault indication arrangement which will have different fault indication for short circuit and residual current fault.

SUMMARY OF THE INVENTION
The following disclosure presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

The main object of present invention is to address and remove all the above limitations.

The first aspect of present invention residual current circuit breaker with overload protection, RCBO, comprising: a contact system (1) for carrying current; a mechanism (2) to close or open contacts; a fault indication arrangement adapted for different fault indication for short circuit and residual current fault; at least one fault detection unit adapted to detect fault in a circuit; and at least one tripping unit adapted to trip/disengage the mechanism in the event of a fault, wherein the at least one fault detection unit and the at least one tripping unit arranged in a way to provide short circuit, overload current and residual current protection for a plurality of poles, where the solenoids of the poles are integrated into one.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The above and other aspects, features and advantages of the embodiments of the present disclosure will be more apparent in the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 illustrates an external structure of the RCBO, according to an embodiment of the present invention.

Figure 2 illustrates an internal structure of a 2nd pole of the RCBO, according to an embodiment of the present invention.

Figure 3 illustrates an internal structure of a 1st pole of the RCBO, according to an embodiment of the present invention.

Figure 4 illustrates interaction of short circuit tripping units and leakage tripping unit, according to an embodiment of the present invention.

Figures 5-6 illustrate corresponding tripping devices of Prior art A, B, C and D, as disclosed in the background.

Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may not have been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding, but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to “a component surface” includes a reference to one or more of such surfaces.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure.

The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising” used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof. Also, Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.

The present disclosure will now be described more fully with reference to the accompanying drawings, in which various embodiments of the present disclosure are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the various embodiments set forth herein, rather, these various embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the present disclosure. Furthermore, a detailed description of other parts will not be provided not to make the present disclosure unclear. Like reference numerals in the drawings refer to like elements throughout.

According to an embodiment, residual current circuit breaker with overload protection, RCBO, comprising: a contact system (1) for carrying current; a mechanism (2) to close or open contacts; a fault indication arrangement adapted for different fault indication for short circuit and residual current fault; at least one fault detection unit adapted to detect fault in a circuit; and at least one tripping unit adapted to trip/disengage the mechanism in the event of a fault, wherein the at least one fault detection unit and the at least one tripping unit arranged in a way to provide short circuit, overload current and residual current protection for a plurality of poles, where the solenoids of the poles are integrated into one.

Figs. 1 to 4 represent different operating positions of a circuit breaker and are used to explain present invention. Residual current circuit breakers with overload protection, RCBO, comprises of a contact system to carry current, a mechanism to close or open contacts, fault detection units to detect fault in circuit and tripping units to trip/disengage the mechanism in the event of fault.

The contact system (1) consists a Fixed contact and a Moving contact. Fixed contact is mounted on Housing and Moving contact is assembled with Mechanism (2). Moving contact is rotated/actuated by Mechanism (2) to make or break contact with Fixed contact. In healthy condition when Moving contact is in closed condition, contact system carries current. Contact system (1) gets separated with the help of Mechanism (2) in the event of any fault or if the RCBO is opened manually.

The Mechanism (2) is used to drive the Moving contact to make and break contact with Fixed contact to close and open the circuit respectively. Mechanism (2) primarily consists of Mechanism plates, Latches, Springs and an Operating means (Knob / Handle). Moving contact and Latches are mounted on support to form contact actuation mechanism. Single or multiple springs are used to bias the contact actuation mechanism. An operating means (knob) which is connected through a pin to contact actuation mechanism is used to drive the contact actuation mechanism manually. The biasing spring gets charged when the operating means rotates the contact actuation mechanism to close the circuit. The latches get engaged with each other to form a single body during closing operation. In detection of a fault-by-fault detection units, latches are disengaged from each other by tripping units and contact actuation mechanism along with moving contact comes to its open position with the help of mechanism spring to open the circuit.

Primarily RCBOs have three types of different fault detection units – a short circuit fault detection unit (3) for detection of high current fault, an overload fault detection unit (4) for detection of overload fault and a residual current fault detection unit (5) for detection of leakage/residual current fault. A short circuit fault detection and trip unit consists of a Coil (7) [with single or multiple number of turns of current carrying conductor], a Moving core (11), a Fixed core (8), a Frame (9a and 9b) and a biasing Spring (10). The Moving core (11), Fixed core (8) and Frame (9) is made of soft magnetic material to increase flux density in magnetic circuit. Current through the Coil (7) generates a flux path through Fixed frame (9), Moving core (11), air gap and Fixed core (8). The operating flux in the magnetic circuit creates attraction force between Moving core (11) and Fix core (8) in order to close the air gap. However, the moving core (11) cannot move in normal or healthy condition as the spring (10) opposes the moving core (11) movement. Coil (7) is designed in such a way that in case of a short circuit fault, the force on Moving core (11) overcomes the Spring (10) opposition force and tries to close the airgap. An additional component Hammer (13 and 14) which is made of non-magnetic material is used to transfer the force from Moving core (11) to mechanism. The Hammer (13 and 14) pushes the Latch (15) and disengages the latches to collapse the mechanism (2) and open the circuit. In case of overload fault, a bimetallic strip is used as fault detection and trip unit (4). When the current flowing through circuit is higher than specified value (higher than nominal current), more heat is generated in bimetal which results in deflection of bimetallic strip. This deflection is used to disengage the latches and collapse the mechanism linkages to open the contacts. For a residual current fault, a Core balance current transformer (5) is used to detect residual / leakage current and a printed circuit board is used to send trip signal to Residual current fault tripping unit (6).

According to an embodiment, the present invention describes RCBO having short-circuit and overload protection in both poles. One pole of the RCBO have detection and tripping unit for residual current, short-circuit and overload fault where as other pole has only short-circuit and overload fault detection and tripping unit. Figure -1 represents the 2 Pole RCBO described in present invention. The 1st Pole of RCBO is consist of short-circuit (3) and overload fault tripping (4) units as shown in Figure – 2. The 2nd Pole of RCBO is consist of residual current (6), short-circuit (3) and overload fault tripping (4) units as shown in Figure - 3. Here in represented figures, 1st pole consists leakage fault tripping unit (6) along with short circuit (3) and overload fault tripping (4) units as shown in Fig. 2. The present invention discloses a unique arrangement of the short circuit and leakage tripping units where both the solenoids are integrated one unit. A single moving core (11) and hammer (13) is used for both short circuit tripping unit (3) and leakage tripping unit (6) as shown in Fig. 4. This arrangement reduces space requirement and helps in designing a product with less space. In case of a leakage fault, moving core (11) moves towards right and disengages the latches (15) of 1st pole to trip the RCBO as shown in Fig. 4. During disengaging the latches (15), it disengages the fault indication assembly of 1st pole by pushing the fault indication slider (14) towards right. Similarly, in case of a short circuit fault in 2nd pole, moving core (11) moves towards right and disengage the latches (15) of 2nd pole. While disengaging the latches (15), it disengages the fault indication assembly of 2nd pole by pushing the fault indication slider (14) towards right. However, in case of a short circuit fault in 1st pole, unlike 2nd pole, moving core (11) moves towards left instead of right due to its airgap position. While moving towards left, it rotates the trip lever (16) in anticlockwise direction with respect to pivot 17. Due to rotation of trip lever (16) in anticlockwise direction, tip (16B) of trip lever (16) disengages the latches (15) of 2nd pole. While disengaging the latches (15), it disengages the fault indication assembly of 2nd pole by pushing the fault indication slider (14) towards right. So, with this arrangement, short circuit fault indication is displayed in 2nd pole for short circuit fault in any one pole or in both the pole and leakage fault indication is displayed in 1st pole. Here the moving core (11) is common to leakage fault detection unit (6) as well as short circuit fault detection unit (3). However, the moving core (11) is subjected to different opposition spring force by means of different opposition spring. The unit is designed in such a way that the springs applies forces independently on moving core (11). Short circuit detection unit spring (10) acts on moving core (11) when the moving core (11) tries to move towards left under the influence of short circuit fault in 1st pole. During moving core movement towards left, leakage detection unit spring (12) does not apply any force. Similarly, leakage detection unit spring (12) acts on moving core (11) when moving core (11) moves towards right under the influence of leakage fault. During moving core movement towards right, short circuit detection unit spring (10) does not apply any force on moving core (11).

Some of the non-limiting advantages of the Integrated tripping unit for short circuit and residual current fault along with separate fault indication means for RCBO are:

1. Integrated tripping unit for short circuit tripping and leakage tripping
2. Compact/space saving tripping unit arrangement
3. Separate fault indication for leakage and short circuit fault
4. Short circuit fault indication even for an individual pole fault
5. Independent mechanism for contact actuation and fault indication

Although an integrated tripping unit for short circuit and residual current fault along with separate fault indication means for RCBO and a RCBO thereof has been described in language specific to structural features, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific methods or devices described herein. Rather, the specific features are disclosed as examples of implementations of an integrated tripping unit for short circuit and residual current fault along with separate fault indication means for RCBO and a RCBO thereof.

List of components:
1. Contact system
2. Mechanism
3. Short circuit detection and tripping unit
4. Overload detection and tripping unit
5. Leakage fault detection unit
6. Leakage fault tripping unit
7. Short circuit detection unit coil
8. Fixed core
9.
a. Frame 1st pole
b. Frame 2nd pole
10. Spring – Short circuit detection unit
11. Moving core
12. Spring – Leakage tripping unit
13. Hammer
14. Slider – Fault indicator assembly
15. Latch – mechanism assembly
16. Trip lever
17. Trip lever pivot
, Claims:
1. A residual current circuit breaker with overload protection, RCBO, comprising:
a contact system (1) for carrying current;
a mechanism (2) to close or open contacts;
a fault indication arrangement adapted for different fault indication for short circuit and residual current fault;
at least one fault detection unit adapted to detect fault in a circuit; and
at least one tripping unit adapted to trip/disengage the mechanism in the event of a fault,
wherein the at least one fault detection unit and the at least one tripping unit arranged in a way to provide short circuit, overload current and residual current protection for a plurality of poles, where the solenoids of the poles are integrated into one.

2. The RCBO as claimed in claim 1, wherein the contact system (1) comprises:
a fixed contact mounted on a housing; and
a moving contact operably coupled with the mechanism (2), wherein the moving contact is rotated/actuated by the mechanism (2) to make or break contact with the fixed contact to close or open the circuit, wherein in healthy condition when the moving contact is in closed condition, the contact system (1) carries current, and the contact system (1) gets separated with the help of mechanism (2) in the event of any fault or if the RCBO is opened manually,
wherein the mechanism (2) comprises: a plurality of mechanism plates, latches, at least one spring and an operating means (Knob / Handle), wherein the moving contact and latches of the mechanism (2) are mounted on a support to form a contact actuation mechanism, and the at least one spring is operably coupled to bias the contact actuation mechanism,
wherein the operating means (knob) of the mechanism (2) is connected through a pin to the contact actuation mechanism to drive the contact actuation mechanism manually,
the at least one spring operably coupled to bias the contact actuation mechanism gets charged when the operating means rotates the contact actuation mechanism to close the circuit,
the latches get engaged with each other to form a single body during closing operation, and in detection of a fault by the fault detection unit, latches are disengaged from each other by the tripping unit, and the contact actuation mechanism along with the moving contact is adapted to return to its open position with the help of the spring of the mechanism to open the circuit.

3. The RCBO as claimed in claim 1, wherein the RCBO comprises different fault detection units – a short circuit fault detection unit (3) for detection of high current fault, an overload fault detection unit (4) for detection of overload fault and a residual current fault detection unit (5) for detection of leakage/residual current fault.

4. The RCBO as claimed in claim 3, wherein the short circuit fault detection and trip unit consists of a coil (7) (with single or multiple number of turns of current carrying conductor), a movable core (11), a fixed core (8), a frame (9a and 9b) and a biasing spring (10), wherein the moving core (11), fixed core (8) and frame (9) is made of soft magnetic material to increase flux density in magnetic circuit, and the current through the coil (7) generates a flux path through fixed frame (9), moving core (11), air gap and fix core (8), such that the operating flux in the magnetic circuit creates an attraction force between the moving core (11) and the fixed core (8) in order to close the air gap.

5. The RCBO as claimed in claim 4, wherein the moving core (11) does not move in normal or healthy condition as the spring (10) opposes the moving core (11) movement, and the coil (7) is designed in such a way that in case of a short circuit fault, the force on the moving core (11) overcomes the spring (10) opposition force and tries to close the airgap.

6. The RCBO as claimed in claim 4, wherein the RCBO comprises:
a hammer (13 and 14) made of non-magnetic material is adapted to transfer the force from the moving core (11) to the mechanism (2), wherein the hammer (13 and 14) pushes the latch (15) and disengages the latches to collapse the mechanism (2) and open the circuit;
a bimetallic strip used as fault detection and trip unit (4) in case of overload fault, and when the current flowing through circuit is higher than specified value (higher than nominal current), more heat is generated in the bimetal resulting in a deflection of the bimetallic strip, so as to disengage the latches and collapse the mechanism linkages to open the contacts.

7. The RCBO as claimed in claim 1, wherein the RCBO comprises a core balance current transformer (5) adapted to detect residual / leakage current for a residual current fault; and a printed circuit board adapted to send a trip signal to a residual current fault tripping unit (6).

8. The RCBO as claimed in claim 1, wherein one pole of the RCBO have a detection and tripping unit for residual current, short-circuit and overload fault whereas the other pole has a detection and tripping unit for short-circuit and overload fault detection and tripping unit, wherein the 1st pole of the RCBO consists a leakage fault tripping unit (6) along with a short circuit (3) and an overload fault tripping (4) unit.

9. The RCBO as claimed in claim 7, wherein a single moving core (11) and hammer (13) is used for both short circuit tripping unit (3) and leakage tripping unit (6),
wherein in case of a leakage fault, the moving core (11) moves towards right and disengages the latches (15) of 1st pole to trip the RCBO, wherein during disengaging the latches (15), it disengages the fault indication assembly of 1st pole by pushing a fault indication slider (14) towards right,
wherein in case of a short circuit fault in 2nd pole, the moving core (11) is adapted to move towards right and disengage the latches (15) of the 2nd pole, and while disengaging the latches (15), it disengages the fault indication assembly of 2nd pole by pushing the fault indication slider (14) towards right,
wherein, in case of a short circuit fault in 1st pole, the moving core (11) moves towards left instead of right due to its airgap position, and is adapted to rotate a trip lever (16) in anticlockwise direction with respect to a pivot (17), such that a tip (16B) of the trip lever (16) is adapted to disengage the latches (15) of the 2nd pole, and while disengaging the latches (15), it is adapted to disengage the fault indication assembly of the 2nd pole by pushing the fault indication slider (14) towards right,
wherein short circuit fault indication is displayed in 2nd pole for short circuit fault in any one pole or in both the poles and leakage fault indication is displayed in 1st pole.

10. The RCBO as claimed in claim 8, wherein the moving core (11) is common to leakage fault detection unit (6) as well as short circuit fault detection unit (3),
wherein the moving core (11) is subjected to different opposition spring force by means of different opposition springs,
wherein the springs apply forces independently on the moving core (11), wherein the short circuit detection unit spring (10) acts on the moving core (11) when the moving core (11) tries to move towards left under the influence of short circuit fault in 1st pole, and during moving core movement towards left, leakage detection unit spring (12) does not apply any force,
wherein leakage detection unit spring (12) acts on the moving core (11) when the moving core (11) moves towards right under the influence of leakage fault, and when the moving core movement towards right, short circuit detection unit spring (10) does not apply any force on the moving core (11).