IE20150433A1

IE20150433A1 - Safety breaker

Info

Publication number: IE20150433A1
Application number: IE20150433A
Authority: IE
Inventors: Kostanjsek Mark
Original assignee: Kostanjsek Mark
Priority date: 2015-01-05
Filing date: 2015-12-14
Publication date: 2016-08-24
Also published as: GB2533821A; GB2533821B; IE86800B1

Abstract

A ring circuit safety breaker for providing over current protection to an electrical ring circuit connected to a mains power supply. The electrical ring circuit comprises a neutral ring and a live ring and a current that flows in two opposite directions about the live ring. The ring circuit safety breaker also comprises a means for current differential detection and a means for disconnecting the electrical ring circuit from the mains power supply. The means for current differential detection detects a current differential between the live ring and the neutral ring when a disconnection is present in either the neutral ring or the live ring and; when the disconnection is detected the means for disconnecting the electrical ring circuit from the mains power supply, disconnects the electrical ring circuit from the mains power supply. <Figure 1>

Description

Field of the invention

[0001] The present invention relates to ring circuit safety breakers.

Background of the invention

[0002] Electrical installations may comprise ring main circuits. Such ring circuits consists of cables which run from a consumer unit (the interface between the site and the electricity supply), through to socket outlet points for connecting to loads and then back to the consumer unit. This configuration forms a ring where two paths exist for current to flow to a connected device from the electrical supply unit. Users of ring circuits are protected from residual current by the use of Residual current devices (RCD) and miniature circuit breakers (MCB).

[0003] RCD’s detect and activate when a current leakage to earth is present. Such faults occur when there is a short circuit between the live cable and earth or neutral cables.

[0004] The RCD achieves this by monitoring the balance of current between the live and neutral conductors. When an imbalance is detected (such as current draining to earth) the breaker trips, shutting off the current supply to the circuit.

[0005] MCB monitor for current overload and provide short circuit protection.

[0006] The MCBs and RCDs are located within a consumer unit.

[0007] Due to domestic and industrial supplies utilising ring circuits, current flowing in the system has two potential paths to travel, both clockwise and anticlockwise about the ring. This system was introduced to reduce the cross sectional area of copper cable required for a ring main supplying sockets (2.5mm<2>rather than 4mm<2>), but still allow a current of up to 32A to flow safely.

[0008] One disadvantage of using a 32A ring main to supply sockets is when a break occurs in the live or neutral cables of the ring. The circuit continues to operate as current is supplied or returned through the connected ends. Effectively the circuit is reduced to two 32A radials (or a partial 32A radial) using 2.5mm<2>cable. This can present a safety risk as 2.5mm<2>copper cable is rated to safely accept a current up to 27A (under ideal conditions) but the trip switch will only function at a current greater than 32A. This would be in excess of the safe limit for the cable.

Summary of the Invention

[0009] A system is disclosed herein for continuously monitoring the continuity of a ring circuit and which incorporates principles of a standard residual current device protection system in order to determine if the ring is not continuous.

[0010] According to a first aspect there of the present invention, there is provided a ring circuit safety breaker for providing over current protection to an electrical ring circuit connected to a mains power supply; wherein the electrical ring circuit comprises a neutral ring and a live ring; and a current flows in two opposite directions about the live ring; the ring circuit safety breaker comprising; means for current differential detection; means for disconnecting the electrical ring circuit from the mains power supply, characterised in that; the means for current differential detection detects a current differential between the live ring and the neutral ring when a disconnection is present in either the neutral ring or the live ring and; when the disconnection is detected the means for disconnecting the electrical ring circuit from the mains power supply disconnects the electrical ring circuit from the mains power supply.

[0011] Suitably the ring circuit safety breaker also incorporates a residual current device.

[0012] Advantageously, the ring circuit safety beaker further comprises a two-stage contactor wherein; the two-stage-contactor is configured such that once the disconnection means has operated, a reconnection cannot proceed until an initial condition has been fulfilled. This means an average consumer cannot ignore a fault, and the system must be made safe before it can be used again. The two-stage contactor preferably comprises a first non-latching position and a second latching position wherein; the initial condition must be fulfilled in order for the two-stage contactor to enter the second latching position from the first nonlatching position.

[0013] Preferably, a current differential of 0.5 Amps or less is required for the initial condition to be fulfilled preventing reconnection until the fault causing the current differential has been rectified.

[0014] Suitably, the means for current differential detection samples current from one point on the neutral ring and the live ring. As such only one sensing means is required to confer protection to the consumer.

[0015] Alternatively, the means for current differential detection samples current from two or more points on the neutral ring and the live ring.

[0016] Preferably, the ring circuit safety breaker further comprises a test mechanism, wherein the correct functioning of the ring circuit safety breaker may be determined. This allows the system to be periodically checked and establishes that the system still operates as it should.

[0017] According to a second aspect of the present invention there is provided a test socket, for testing the functioning of a ring circuit safety breaker as hereinbefore described wherein; the test socket comprises means for engaging and disengaging the neutral ring or the live ring from a connected position to a disconnected position, wherein; when the neutral ring or live ring are in the disconnected position a current differential is created and; the means for current differential detection detects the current differential between the live ring and the neutral ring and; the means for disconnecting the electrical ring circuit from the mains power supply disconnects the electrical ring circuit from the mains power supply; wherein; the correct functioning of the ring circuit safety breaker may be determined.

[0018] Suitably, the test socket functions as an electrical connection socket for connection to an electrical load.

[0019] Preferably, the means for engaging and disengaging the neutral ring and the live ring comprises; a lock and key.

[0020] Suitably, the key is irremovable from the lock when the means for engaging and disengaging the neutral ring and the live ring is positioned such that the neutral ring and the live ring are in the disconnected positon.

[0021] The invention is substantially, a ring circuit safety breaker as depicted by the figures.

[0022] The invention substantially comprises a test socket, for testing the functioning of a ring circuit safety breaker as depicted by the figures.

[0023] Other aspects are as set out in the claims herein.

Brief Description of the Drawings

[0024] For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which: Figure 1 details a basic overview of the present safety breaker invention. Figure 1 details a basic overview of the present safety breaker invention.

Figure 2 presents a schematic of the ring circuit breaker device without RCD or MCB protection devices incorporated into the design.

Figure 3 is a representation of a test switch that may be used in combination with the present invention.

Figure 4 is a schematic of the test switch of Figure 3.

Detailed Description of the Embodiments

[0025] There will now be described by way of example a specific mode contemplated by the inventor. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description.

[0026] The examples given below are pertinent to domestic electrical installations. However, it will be obvious to a person skilled in the art that the below teachings are applicable to any electrical installation involving ring circuits including but not limited to, industrial sites, and lighting circuits.

[0027] Figure 1 shows a simplified wiring diagram of the present invention, wherein an imbalance safety breaker (101) is connected to the external supply (102) and the ring main circuit (103) that requires protection. The ring main circuit consists of two live cables (104, 105), two neutral cables (106, 107), wherein the first live cable (104) forms the first half of the ring, the first neutral cable (106) runs parallel to the first live wire (104), the second live wire (105) forms the second half of the ring and the second neutral cable runs parallel to the second live wire (105).

[0028] The first live wire (104) is connected to the second live wire (105) at a point about the ring, and the first neutral wire (106) is connected to the second neutral wire (107) at a point about the ring. Upon connection of the wires the ring main is formed.

[0029] First and second earth wires (not shown) may also run parallel to the respective first and second live/neutral pairs.

[0030] In a 32A socket ring main (103) the cables are typically twin and earth cables as used in the United Kingdom, wherein the twin cables are typically made of copper wire with a cross section of 2.5mm<2>. The earth cable is also typically made from copper and has a cross sectional area of 1.5mm<2>. However, it will be apparent to one skilled in the art that any suitable conductor may be used to form the live, neutral and earth conductors. As such the conductor need not be wire, cable, made of copper, and may be of any suitable required or appropriate dimension.

[0031] It will be apparent to one skilled in the art that the pair of live cables (104, 105) and pair of neutral conductors (106, 107) form rings which are independent to each other and may be referred to as the neutral ring and the live ring.

[0032] Electrical loads (108, 109, 110) may be connected in parallel along the neutral and live rings, whereby electrical energy may be provided from the ring main to any appropriate device an end user may wish to connect to the ring main.

[0033] It will be apparent to one skilled in the art that such loads may be connected using any appropriate connection means, such as a plug and socket, or directly connected to the ring by means of a fused spur.

[0034] The imbalance safety breaker consists of a current differential sensing means (111). Whereby the currents flowing in the neutral and live legs of the ring main may be continuously monitored.

[0035] Such a sensing means may typically comprise a soft iron toroidal core (112), wherein the live and neutral legs have respective windings (113, 114) about the toroidal ring.

[0036] It will be apparent to one skilled in the art that when an abnormal current flows through a leg of the ring (either the neutral leg or the live leg) a current may be induced in a third winding (115) about the ring. Such an induced current may then be utilised to disconnect the ring main circuit from the electrical supply, whereby the system is made safe and an end user, and the conductors that form the ring, are protected from the abnormal current flow.

[0037] One method of disconnecting the ring main (103) from the power circuit (102) is demonstrated in figure 1, a relay (116) is connected to the third winding (115) about the core (112). The relay being provided with switching means (117) that switches the live legs (104, 105) and neutral legs (106, 107) of the ring from a connected position to a disconnected position.

[0038] In the connected position current may flow from the mains supply and through the live legs and return through the neutral legs of the ring.

[0039] It will be apparent to one skilled in the art that any suitable current differential sensing means may be used to monitor the current flowing about a ring.

[0040] Furthermore, the current sensing means may be provided with any suitable means to disconnect the ring main from the electrical supply (102).

[0041] In the present invention, the current sensing means is able to determine the presence of a current imbalance about a component of the ring. For example, if there is a disconnection in the live ring, hence the sockets are supplied by just one of the two legs that form the live circuit.

[0042] By way of illustrated example, referring to figure 1, the live feed from the mains supply (102) feeds into the imbalance safety breaker and then connects to both legs (104, 105) of the live ring.

[0043] Both legs of the live ring feed into the circuit breaker (101). One leg of the live ring (104) then connects to the differential current sensing means (111) wherein the current flowing through that wire is compared to the current flowing in a leg of the neutral component of the ring (106). The live leg (104) then connects from the differential current sensing means (111) to the rest of the ring (103), end user sockets (108, 109, 110), and supplies any load a user may connect.

[0044] Should a disconnection occur prior to the differential current sensing means (111) in the first live leg (104), then the sockets are supplied current only from the second live leg (105) which is not connected to the current sensing means (111).

[0045] The current passes through the partial ring and is then shared between and returns through the two neutral legs. The division of current between the two legs may be unequal. One of the two neutral legs is monitored by the differential current sensing means.

[0046] As the first live leg (104) is disconnected, but the neutral leg (106) is connected to the differential current sensing means (111) and has a current flowing through it, the differential current sensing means (111) detects an imbalance between the first live leg (104) and the neutral leg (106), and the circuit is disconnected via a disconnection means (117).

[0047] It will be apparent to one skilled in the art that such disconnection means (117) may comprise a relay (116) with a winding on the toroidal ring (115), wherein when a current imbalance occurs, the relay winding (115) has a current induced within it which triggers the relay (116) and switches (117) connected to the at least first and second live legs (104, 105) and the first and second neutral legs (106, 107).

[0048] It will also be apparent to one skilled in the art that other disconnection means are available.

[0049] Should a disconnection occur in the second live leg (105) anywhere between the mains supply (102) and the end user sockets (108, 109, 110), then the end user sockets are supplied current only from the first live leg (104) connected to the current differential connecting means (111).

[0050] Instead of the current being shared between the two live legs (104, 105) of the ring (103), as would happen should a disconnection not be present, all the current passes through the leg (104) being monitored by the current differential detecting means.

[0051] As the neutral legs (106, 107) are intact, the current upon return from the ring (103), is shared between the two neutral legs (106, 107). This creates a current differential which the differential current sensing means (111) then detects, and the circuit is disconnected via a disconnection means (117).

[0052] Should a disconnection occur in the live legs (104, 105) of the ring at a point between the end user sockets (108, 109, 110) such that the sockets are distributed unequally between the live legs then, as described above, a current imbalance will be created. The differential current sensing means (111) then detects this imbalance, and the circuit is disconnected via a disconnection means (117).

[0053] It will be apparent to one skilled in the art that the legs of the neutral component (106, 107) of the ring may also be monitored by the differential current sensing means (111) such that a current imbalance between the legs may be detected.

[0054] The neutral legs (106, 107) are connected to the mains supply (102) prior to one of the legs (106) being connected to the differential current sensing means (111).

[0055] It will be apparent to one skilled in the art that a winding (114) on the above referenced toroidal ring (112) may be used or any other suitable differential current sensing means (111).

[0056] When a disconnection is present in a first neutral leg (106) connected to the differential current sensing device (111), the current sensing device will detect a current drop in the neutral leg (106) relative to the still correctly functioning live leg (104) also connected to the current sensing device (111). As such the differential current sensing means detects an imbalance, and the circuit is disconnected via a disconnection means (117).

[0057] When a disconnection is present in a second neutral leg (107) which is not connected to the differential current sensing device (111), the current may only flow through the first leg (106), through the current sensing device (111). As such the differential current sensing device will observe an increased current flowing through the first neutral leg (106) compared to the live leg (104) that is also connected to the current differential device. As such the differential current sensing means detects an imbalance, and the circuit is disconnected via a disconnection means (117).

[0058] It will be apparent to one skilled in the art that a disconnection may occur at any point along the neutral or live components of a ring main circuit, and that the current differential detecting means (111) will be capable of detecting any significant difference between the respective neutral and live legs, and that any of a spectrum of current differentials may trigger the circuit disconnection means.

[0059] The circuit disconnection means may be one way, such that the circuit cannot be reconnected until the aberration that resulted in the disconnection is corrected.

[0060] It will be apparent to one skilled in the art that the disconnection means may be arranged such that it may only be reset by a suitably skilled and trained person.

[0061] It will be obvious to one skilled in the art that the circuit as depicted in figure 1 will also provide over current and RCD protection as well as the above outlined features such that the in balance safety breaker substantially fulfills the same function as prior art safety breakers, protecting end users from earth leakages and over current protection, but additionally protects the users from live ring and neutral ring disconnections and irregularities.

[0062] Suitably, if a current imbalance differential of more than 0.5 Amps occurs the safety breaker will operate such that it may not be reset until the fault has been remedied. However, the size of the differential required to cause the safety breaker to operate could be made adjustable and an appropriate differential selected upon installation of the safety breaker.

[0063] Referring to figure 2, the imbalance safety breaker may additionally be provided with a test mechanism (201) whereupon a competent person, service engineer, or other suitable professional, or an end user may test the function of the in balance safety breaker (101).

[0064] The breaker is provided with a second disconnection means (202). The second disconnection means is preferably, but not exclusively, a relay (203). The second disconnection means is connected to the first disconnection means or test circuit (116), such that upon a successful test result the safety breaker (101) trips and the ring main circuit is isolated from the mains supply (102).

[0065] The second disconnection means (203) is coupled to the first disconnection means (116) such that action of the second disconnection means (203) results in action of, or prevents the action of, the first connection means (116).

[0066] It will be apparent to one skilled in the art that the first and second disconnection means may be a single unit, functioning as a single disconnection means.

[0067] Furthermore, it will be apparent that the second disconnection means may be independent of the first disconnection means, wherein the first and second disconnection means are not linked together, but that action of the second disconnection means by itself results in the isolation of the mains ring circuit from the mains power supply.

[0068] The second disconnection means is triggered by means of a test device (201), which, upon suitable fulfilment of preset conditions, creates an imbalance.

[0069] Such a test, by way of non-limitative example, can consist of creating a connection between a live leg (104) and the neutral legs (106, 107) of the ring, wherein the connection passes through a resistance (204) such that an imbalance is created. Under such conditions the imbalance safety breaker (101) will trip if it is functioning correctly.

[0070] Furthermore, the test will identify if both a live and a neutral cable are disconnected in the ring main circuit. In such a scenario it would not be obvious to an end user that a problem was present. For example, referring to figures 1 and 2, should the first live cable (104) and the first neutral cable (106) be severed prior to any loads (108, 109, 110) on the ring main circuit, the loads may still function by receiving power from the second live cable (105) and the second neutral cable (107).

[0071] Such faults are identified by the test circuit (201) as when the test is initiated a current flows from the first live wire (104) to the first neutral wire (106). The connection to the first neutral wire bypasses the coil (101), as such an imbalance is created and the safety breaker disconnects the circuit.

[0072] In order to reconnect the circuit a relay (203) must become energized to allow a user to reengage a trip switch. In order for the relay (203) to become energized it must receive power from a connection to a live supply.

[0073] By way of non-limitative example, a three position relay engagement means may be used. The three positions consist of a first, off position, a second non-latching momentarily on position, and a third operational “on” position.

[0074] In order to energize the relay a user must navigate the three position relay engagement means from the first off position, through the second momentarily non-latching position and then to the third “on” position. The circuit will only receive power once the three position engagement means is locked in the third “on” position.

[0075] When a user adjusts the three position relay engagement means such that the second momentarily latching position is engaged a test is performed. Only on successful fulfilment of preset test criteria may a user proceed to engage the third “on" position.

[0076] When the second momentarily latching position is engaged current flows through the first live leg and along the length of the live ring and to the neutral leg. The current is prevented from returning to the consumer unit through the connection from the consumer unit to the second live leg and second neutral leg.

[0077] As such, the continuity of the live cable of the ring is tested. Should a break occur anywhere along the length of the live cable of the ring the current will fail to return to the test device. As such the relay (203) cannot become energized and prevents the user proceeding to re-engage the trip switch.

[0078] As such there is provided means for detecting if the live cable is severed and means for indicating a potential break on the neutral ring.

[0079] It will be apparent to one skilled in the art that any suitable means may be used to achieve the intended outcome of ensuring continuity about a ring circuit before allowing a user to fully engage a safety means.

[0080] A timed relay may be used in order to ensure adequate time is allowed for the test to be performed. This may be appropriate for particularly large ring circuits.

[0081] A two-stage contactor (116) is used such that when a user attempts to reconnect the circuit, the circuit must fulfil an initial condition in order for the switch to enter the second position and latch into place.

[0082] The initial condition is tested when the switch is thrown to the first non-latching position, whereby if the condition is not fulfilled the switch returns to a disconnected position.

[0083] When the switch is in the first position, and the ring is complete, a current flows from the live supply to the relay (203). Only when the relay (203) receives power is the user allowed to progress the switch to the second, latched position, reconnecting the circuit.

[0084] This arrangement forces current to flow all the way around the ring, as such should a live cable be severed, current cannot flow all the way around the ring, hence the relay (203) cannot become energized and the circuit not reconnected until the ring is repaired.

[0085] Further to the incorporation of a test circuit, with reference to figure 3, a test socket (301) may be incorporated at a location about the ring connected to the safety breaker.

[0086] The test socket, while employed to test the ring main, functions as a normal prior art device, allowing a user to connect devices which that user is desirous of powering.

[0087] Suitably, the socket comprises of switches (302, 303) and plug sockets (304, 305) appropriate for connecting to a device the end user wishes to power.

[0088] It will be apparent to one skilled in the art the socket may take any suitable form, such as but not exclusively, a single socket, double socket, triple socket, shaving socket, or any other suitable arrangement.

[0089] It will also be apparent that the device need not be a socket, but may comprise a dedicated panel specifically for the purpose of providing ring main testing.

[0090] The test socket comprises of engagement means (306) (suitably but not exclusively, a lock and key), wherein when disengaged the socket performs as any other socket.

[0091] When a person suitably skilled in the art engages the engagement means, the socket allows the testing of the ring main or begins testing the ring main circuit.

[0092] The engagement means may suitably comprise a lock and key, when the engagement means is initiated the key may not be removable from the lock (however it will be apparent to one skilled in the art that this is not essential, embodiments may allow for key removal).

[0093] With reference to figure 4, the engagement means (301), connects to and operates switches (401, 402) connected to the live and neutral legs that pass through the socket.

[0094] When the engagement means is operated the switches are operated and suitably the live cable is disconnected or the neutral and live cables are disconnected.

[0095] When the engagement means is not in use the switches are positioned such that normal operation of the circuit can recommence.

[0096] It will be obvious to one skilled in the art that the circuit may be alternatively arranged such that when the engagement means is initiated the normal operation of the circuit commences, and then when the engagement means is not in use, the switches may operate disconnecting the live and neutral cables.

[0097] When the switches are operated, the live cable or the live and neutral cables are severed. As such, an imbalance can be created. This creates a safe testing condition in order to determine the correct functioning of the imbalance safety breaker.

[0098] When no load is applied to the circuit the live and neutral cables are disconnected. The circuit cannot be reconnected at the safety breaker until the live and neutral cables are reconnected.

Claims

1. A ring circuit safety breaker for providing over current protection to an electrical ring circuit connected to a mains power supply; wherein the electrical ring circuit comprises a neutral ring and a live ring; and a current flows in two opposite directions about the live ring; the ring circuit safety breaker comprising; means for current differential detection; means for disconnecting the electrical ring circuit from the mains power supply, characterised in that the means for current differential detection detects a current differential between the live ring and the neutral ring when a disconnection is present in either the neutral ring or the live ring and; when the disconnection is detected the means for disconnecting the electrical ring circuit from the mains power supply disconnects the electrical ring circuit from the mains power supply.

2. A ring circuit safety breaker as claimed in claim 1 wherein; the ring circuit safety breaker incorporates a residual current device.

3. A ring circuit safety breaker as claimed in any preceding claim wherein the ring circuit safety beaker further comprises a two-stage contactor wherein; the two-stage contactor is configured such that once the disconnection means has operated, a reconnection cannot proceed until an initial condition has been fulfilled.

4. A ring circuit safety breaker as claimed in claim 3 wherein the twostage contactor comprises; a first non-latching position and a second latching position wherein; the initial condition must be fulfilled in order for the two-stage contactor to enter the second latching position from the first non-latching position.

5. A ring circuit safety breaker as claimed in claim 3 or 4 wherein a current differential of 0.5 Amps or less is required for the initial condition to be fulfilled.

6. A ring circuit safety breaker as claimed in any preceding claim wherein; the means for current differential detection samples current from one point on the neutral ring and the live ring.

7. A ring circuit safety breaker as claimed in any of claims 1 to 5 wherein; the means for current differential detection samples current from two or more points on the neutral ring and the live ring.

8. A ring circuit safety breaker as claimed in any preceding claim wherein the ring circuit safety breaker further comprises a test mechanism, wherein the correct functioning of the ring circuit safety breaker may be determined.

9. A test socket, for testing the functioning of a ring circuit safety breaker as claimed in claim 1 wherein; the test socket comprises means for engaging and disengaging the neutral ring or the live ring from a connected position to a disconnected position, wherein; when the neutral ring or live ring are in the disconnected position a current differential is created and; the means for current differential detection detects the current differential between the live ring and the neutral ring and; the means for disconnecting the electrical ring circuit from the mains power supply disconnects the electrical ring circuit from the mains power supply; wherein; the correct functioning of the ring circuit safety breaker may be determined.

10. The test socket as claimed in claim 9 wherein, when the test socket functions as an electrical connection socket for connection to an electrical load.

11. The test socket as claimed in claim 9 or claim 10 wherein the means for engaging and disengaging the neutral ring and the live ring comprises; a lock and key.

12. The test socket as claimed in claim 11 wherein the key is irremovable from the lock when the means for engaging and disengaging the neutral ring and the live ring is positioned such that the neutral ring and the live ring are in the disconnected positon.