AU2013100479A4

AU2013100479A4 - Device and method for providing electrical protection

Info

Publication number: AU2013100479A4
Application number: AU2013100479A
Authority: AU
Inventors: Baldamero Gato; Richard Ian Martin
Original assignee: SAFELEC TECHNOLOGY HOLDINGS PTY Ltd
Current assignee: SAFELEC TECHNOLOGY HOLDINGS PTY Ltd
Priority date: 2010-11-17
Filing date: 2013-04-12
Publication date: 2013-05-16
Anticipated expiration: 2019-11-17
Also published as: AU2013100479B4

Abstract

An electrical protection device and apparatus. The electrical protection device includes: at least two input terminals for connection with conductors of a power source; 5 at least two output terminals for connection with a load; a protection unit for operating in a first state to allow the power source to be in electrical connection with the load, and a second state to prevent the power source being in electrical connection with the load; a first detection for sensing an imbalance in current flowing through the 10 conductors, wherein in response, the protection unit operates in the second state; and a second detection unit including a sensor line for electrical connection to a reference which should be electrically isolated from the conductors, wherein the second detection unit senses a current flowing through the sensor line which meets or exceeds a threshold current, and in response, the protection unit operates in the second state. / No Ct) ---- C:q' Ct" ........... OIC) Coj LOT N *"\ ' 'L' t ', CYC) Ct) CMj :C

Description

- 1 DEVICE AND METHOD FOR PROVIDING ELECTRICAL PROTECTION Technical Field The present invention relates to a device and method for providing electrical protection. 5 Background The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived 10 from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. It is known to provide protection to electrical loads used in a multiple earth neutral (MEN) electrical distribution system (EDS) on the one hand, and in a floating earth EDS on the 15 other. One common form of such protection is a residual current device (RCD) that most typically monitors the differential in the current between the active and neutral to selectively isolate the load. To operate effectively, there is a need for a reliable and effective earth connection. In an MEN EDS it is possible to often have a good earth connection for a given electrical load. However, there are many instances where the earth 20 connection is compromised, lost, or simply not available. A floating earth EDS does not include an earth connection and, as such, does not allow proper operation of the RCD. Notwithstanding the operational limitations of RCD, it is often mandatory to have such devices installed in an EDS. This not only exposes personnel to danger, it also provides a 25 false sense of security to those personnel. Summary In a first aspect there is provided an electrical protection device including: at least two input terminals for connection with an active and neutral conductor of 30 an electrical power source; at least two output terminals for connection with an electrical load; a protection unit for operating in a first state to allow the electrical power source to -2 be in electrical connection with the load, and a second state to prevent the electrical power source being in electrical connection with the load; a first detection unit configured to sense an imbalance in current flowing through active and neutral conductor, wherein in response to detecting the imbalanced current, the 5 protection unit operates in the second state; and a second detection unit including a sensor line for electrical connection to a reference which should be electrically isolated from at least the active conductor, wherein the second detection unit is configured to sense a current flowing through the sensor line which meets or exceeds a threshold current, and in response actuates the protection unit to 10 operate in the second state. In certain embodiments, the first and the second detection units operate contemporaneously. 15 In certain embodiments, the first detection unit is disposed within a first housing and the second detection unit is disposed within a second housing. In certain embodiments, the first and second housings are adjacent to each other. 20 In certain embodiments, the first and second housings are abutted with each other. In certain embodiments, the first housing includes a first detection unit switch and the second housing includes a second detection unit switch which are operable by a user. 25 In certain embodiments, the electrical protection device is housed within a device housing. In certain embodiments, the device housing includes a first device housing portion and one or more second device housing portions releasably attached to the first housing portion. 30 In certain embodiments, the first device housing portion is an open faced container which the protection unit is mounted therein, and wherein the device housing includes a plurality of second device housing portions which cover respective portions of the open face of the -3 container. In certain embodiments, the one or more second device housing portions include one or more electrical socket covers, wherein each electrical socket cover includes an electrical 5 socket for receiving an electrical plug of the load, wherein the electrical socket is in electrical connection with the protection unit. In certain embodiments, the plurality of covers includes: an access cover including an opening which exposes the first detection unit switch 10 and the second detection unit switch; and an activation cover including an activation switch operable in a first mode to prevent electrical power being provided to each electrical socket, and a second mode which allows electrical power to be provided at each electrical socket in the event that the protection unit is operating in the first state. 15 In certain embodiments, the access cover includes a hinged lid which covers the first detection unit switch and the second detection unit switch, wherein the hinged lid is openable to gain access to the first detection unit switch and the second detection unit switch. 20 In certain embodiments, the hinged lid is substantially transparent. In certain embodiments, the lid is biased by a biasing element toward a closed position. 25 In certain embodiments, the first detection unit is a differential current transformer. In certain embodiments, the protection unit is a residual current device including a switching system in electrical connection with the first detection unit, wherein in the event that the first detection unit detects the unbalanced current, a fault signal is generated to 30 cause the switching system to open thereby disconnecting the input terminals from the output terminals.

-4 In certain embodiments, the residual current device and the first detection unit are contained in a common housing. In certain embodiments, the second detection unit is operably connected to the protection 5 unit via a electro-mechanical assembly, wherein in response to the current flowing in the sensor line, a fault signal is generated to cause the electro-mechanical assembly to actuate the protection unit such that the protection unit operates in the second state. In certain embodiments, the first detection unit includes a first mechanical actuator which 10 is mechanically actuated by a second mechanical actuator of the second detection unit to cause the protection unit to operate in the second state. In certain embodiments, second detection unit includes a solenoid which is actuated in response to the current threshold being met or exceeded, which in turn causes the first 15 mechanical actuator to actuate such that the protection unit operates in the second state. In certain embodiments, the solenoid includes a piston which is operably connected to a pin extending outwardly from the housing of the second detection unit, wherein the first housing includes a slot housing the first mechanical actuator for receiving the pin, wherein 20 in response to the second detection unit detecting the current flowing in the sensor line causes the solenoid to move the piston, wherein the pin slides within the slot to actuate the first mechanical actuator, such that the protection unit operates in the second state. In certain embodiments, the second detection unit includes: 25 a first relay in electrical connection with the reference; and a second relay in electrical connection with the first relay and the solenoid; wherein the detection of the current flow in the sensor line results in the first relay being actuated, thereby resulting in actuation of the second relay, thereby resulting in the first relay being disconnected from the reference and the solenoid being actuated such that 30 the protection unit operates in the second state. In certain embodiments, the first relay is a low voltage relay and the second relay is a -5 mains rated relay. In certain embodiments, the second detection unit includes an energy storage device in electrical connection with the first relay, wherein the energy storage device stores energy 5 in response to the current flowing through the sensor line, and wherein when the second relay is actuated to disconnect the first relay from the reference, the energy storage device discharges energy to maintain the first relay device in the actuated state until after the first relay has been disconnected from the reference. 10 In certain embodiments, the energy storage device is a capacitor. In certain embodiments, the electrical protection device is configured to detect an electrical fault within a multiple earth neutral (MEN) electrical distribution system (EDS) and a floating earth EDS. 15 In a second aspect there is provided an apparatus including: a frame having a ground conveyance assembly; and an electrical protection device according to the first aspect, wherein the electrical protection device is supported upon the frame; 20 wherein, in use, the electrical power source can be placed in electrical connection with the electrical protection device via the input terminals and the electrical load can be placed in electrical connection with the output terminals of the electrical protection device. In certain embodiments, the apparatus includes an electrical transformer which is 25 supported upon the frame, wherein the electrical power source is in electrical connection with the electrical protection device via the electrical transformer. In certain embodiments, the ground conveyance assembly includes a wheel arrangement for allowing the apparatus to be transported over a ground surface. 30 In certain embodiments, the frame and the ground conveyance assembly form a trolley.

-6 In certain embodiments, the frame supports a receptacle for transporting objects with the apparatus. In certain embodiments, the receptacle is a basket. 5 Brief Description of the Figures A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing in which: 10 Figure 1 is a schematic representation of an example of an electrical protection device according to one embodiment in an MEN EDS; Figure 2 is a schematic representation of the electrical protection device of Figure 1 in a floating earth EDS; 15 Figure 3 is a schematic representation of another example of an electrical protection device; Figure 4 is a schematic representation of another example of an electrical protection 20 device; Figure 5 is a schematic representation of a mechanical linkage between the first and second detection unit; 25 Figure 6 is a front perspective view of an example of the first device housing portion which has mounted therein the electrical protection device; Figure 7A is a front perspective view of a device housing including the first device housing portion and a plurality of second device housing portions; 30 Figure 7B is a front perspective view of another embodiment of the device housing including the first device housing portion and a plurality of second device housing -7 portions; Figure 7C is a side view of the device housing of Figure 7B; 5 Figure 7D is a front view of an insert for the opening of the access cover of the device housing of Figure 7B; Figure 8 is a front perspective view of an example of an apparatus including the electrical protection device housed within the device housing; and 10 Figure 9 is a side perspective view of the apparatus of Figure 8. Detailed Description Referring to Figure 1 there is illustrated a schematic representing an electrical protection 15 device 1. In particular, the electrical protection device 1 includes at least two input terminals 9, 10, two output terminals 13, 14, a protection unit 17, and a first and second detection unit 21, 22. In particular, the input terminals 9, 10 are configured for connection with active conductor 20 100 and the neutral conductor 110 of an electrical power source 11. The at least two output terminals 13, 14 are configured for connection with an electrical load 15. The protection unit 17 is configured to operate in a first state to allow the electrical power source 11 to be in electrical communication with the electrical load 15, and a second state to prevent the electrical power source 11 being in electrical communication with the electrical load 15. 25 The first detection unit 21 is configured to sense an imbalance in current flowing through the active and neutral conductors, wherein in response to detecting the imbalanced current, the protection unit operates in the second state. The second detection unit 22 includes a sensor line 40 which is electrically connected to a reference point which should be electrically isolated from the conductors 100, 110. The second detection unit is configured 30 to sense a current flowing through the sensor line 40 which meets or exceeds a threshold current, and in response actuates the protection unit 17 to operate in the second state.

-8 Referring more specifically to Figure 1, the electrical protection device is configured for use in a 240 V, 50 Hz MEN electrical distribution system (EDS) 2. However, referring to Figure 2, the electrical protection device 1 is shown suited for and in use in a floating earth EDS 3. EDS 2 includes an earth conductor 5 and EDS 3 includes a floating conductor 6. 5 Thus, the electrical protection device is suitable for electrically disconnecting the electrical power supply 11 from the electrical load 15 in instances of an electrical fault in both an earthed or floating earth electrical distribution system 2, 3 which a typical residual current device is unable to achieve. 10 As illustrated in Figures 1 and 2, the two input terminals 9 and 10 of the electrical protection device 1 are connected to an active conductor 100 and a neutral conductor 100 of the electrical power source 11. The two output terminals 13 and 14 are connected with active and neutral terminals of the electrical load 15. 15 The protection unit 17 of the electrical protection device 1 is generally provided in the form of a residual current device circuit breaker (RCD C/B) 17, which operates in a first state to allow terminals 9 and 10 to be in electrical communication with the terminals 13 and 14 respectively, and a second state when an electrical fault is detected, such that terminals 9 and 10 are electrically disconnected from terminals 13 and 14 respectively. 20 The RCD C/B 17 includes a switching system 30 which is in electrical communication with a first detection unit 21. The first detection unit 21 is responsive to an unbalanced current condition in respect of the active conductor and the neutral conductor. In particular, the first detection unit 21 detects a differential between the current flowing in the active 25 phase conductor and that current flowing through the neutral phase conductor. Specifically, the first detection unit 21 is a differential current transformer. Upon the current differential exceeding a current differential threshold, the first detection unit 21 selectively generates a fault signal 35 which electrically actuates the switching system 30 of the protection unit 17, wherein the switching system 30 is actuated to open contacts 31 and 32, thereby 30 electrically disconnecting the input terminals 9, 10 from the output terminals 13, 14. The second detection unit 22 is operably connected to the protection unit 17. As will be -9 explained in further detail below in relation to Figure 5, the second detection unit 22 is operably connected to the protection unit 17 to mechanically actuate the protection unit 17 to change from operating in the first state to the second state when an electrical fault in detected. 5 In response to the second detection unit 22 sensing the current flowing through the sensor line which exceeds the current threshold, the second detection unit operably causes the protection unit 17 to operate to change operation from the first state to the second state. Specifically, the second detection unit 22 includes an electro-mechanical device provided 10 in the form of a trip solenoid 60 which is actuated to cause a mechanical actuator of the switching system 30 of the protection device 17 to actuate, thus electrically disconnecting the input terminals 9, 10 from the output terminals 13, 14 respectively. As will be appreciated, the first detection unit 21 and the second detection unit 22 are configured to operate contemporaneously. 15 As will be appreciated from Figures 1 and 2, the electrical protection device 1 is able to be used selectively in either an MEN EDS 2 or a floating earth EDS 3 without any modification. This is particularly advantageous for electrical loads that are at times connected to an MEN EDS 2 and at other times connected to a floating earth EDS 3. 20 However, it is also applicable to providing superior protection for electrical loads that are only ever connected to one type of EDS. The first detection unit can be configured such that the current threshold is set to approximately 30mA. The second detection unit can be configured to set the threshold 25 current flowing through the sensor line as 15mA. The sensor line 40 of the second detection unit 22 is in electrical communication with the reference point such as an object 200 which should be electrically isolated from the conductors 100, 110. The sensor line 40 is also in electrical communication with the earth 30 conductor 5 or floating conductor 6 depending upon the respective EDS 2, 3. The reference object 200 may be a housing of the electrical protection device 1, a chassis of another device, or the like which should be electrically isolated from the conductors 100, 110. The -10 sensor line 40 is in electrical communication with a resistor 42 which is a 470 ohm, 1 Watt resistor. The sensor line 40 is also in electrical communication, via the resistor 42, with a diode 44 which is a 1N4007 type diode. The diode 44 is in electrical communication with a low voltage trip relay 46. Whilst the protection device 1 is operating in the first state (i.e. 5 no electrical fault), a contact 47 of the relay 46 is in an open state as shown in Figures 1 and 2. The first relay is in electrical communication with a zener diode 48 which is a 1N5349B zener diode type, and a capacitor 50 which is a 0.01 micro farad capacitor rated for 630V. The zener diode 48 and the capacitor 50 are in parallel with the relay 46. 10 The relay 46 is in electrical communication with a trip solenoid 60. The trip solenoid 60 is actuated once the contact 47 of the relay 46 is closed due to the current flowing through the sensor line meeting or exceeding the threshold current. Upon the solenoid 60 energizing and actuating, the solenoid in turn actuates a mechanical actuator of the protection unit 17 to disconnect the input terminals 9, 10 from output terminals 13, 14. 15 The relay 46 is in electrical communication with a first diode 52 which is a 1N4007 type diode, wherein the first diode 52 is in electrical communication with the neutral output terminal 14 of the electrical protection device 1. The relay is also in electrical communication with a second diode 54 which is a 1N4007 type diode, wherein the second 20 diode 54 is in electrical communication with the active output terminal 13 of the electrical protection device 1. As will be discussed in relation to Figure 3, diode 54 is optional. In the event that the active conductor comes into electrical contact with the reference object (i.e. an equipment fault, a person touching the active conductor with one hand and 25 the housing of the electrical protection device with the other hand), a current flows through the sensor line which exceeds the threshold current. This causes the current flowing through the sensor line to flow through diode 52 due to being connected with the neutral conductor 110. Due to the current in the sensor line exceeding the current threshold, the trip relay trips, resulting in the solenoid energizing and actuating the protection unit such 30 that the contacts 31, 32 are opened, thereby electrically disconnecting the load from the power source. As such, the reference object which the sensor line is electrically connected with also is electrically disconnected from the power source 11. This situation is applicable - 11 to both the configuration illustrated in Figure 1 and Figure 2. Considering the configuration in Figure 2, in the event that the neutral conductor (i.e. an equipment fault, a person touching the neutral conductor with one hand and the housing of 5 the electrical protection device with the other hand) which is provided within a floating earth EDS and thus is likely not be earth as in Figure 1, a current flows through the sensor line which can exceed the threshold current. This causes the current flowing through the sensor line to flow through diode 54 due to being connected with the active conductor 100. In the event the current threshold is exceeded, the contact 47 of the low voltage trip relay 10 closes, thereby causing the trip solenoid to enegerise and actuate, thereby actuating the switching system 30 of the protection unit 17 so that the contacts 31, 32 are opened, thereby electrically disconnecting the load from the power source. As such, the reference object which the sensor line is electrically connected with also is electrically disconnected from the power source 11. 15 As shown in Figures 1 and 2, the electrical protection unit 1 includes a test switch arrangement which a user can actuate to the second detection unit 22 to sense the threshold current such that the protection unit 17 operates in the second state. In particular, the test switch arrangement includes a test switch 54 which is electrically connected to the sensor 20 line at a first terminal, and a second terminal is electrically connected to a resistor 56 which is a 4.7 K ohm resistor which is in turn electrically connected to the active conductor 110. When the switch is manually actuated via a depressing action by the user, a current flows from the active conductor 100, through the sensor line via resistor 42, diode 44, relay 46 and diode 52 to the neutral conductor 110. Due to this current exceeding the 25 current threshold, the relay 46 closes causing the protection unit 17 to disconnect the terminals 9 and 10 from the terminals 13, 14 respectively. Referring to Figure 3 there is shown another schematic of an example of the electrical protection device 301. For clarity purposes, the electrical power source 11 and electrical 30 load 15 have been omitted. The second detection unit has a number of common components as illustrated by like reference numbers. As can be seen from Figure 3, diode 54 is not provided such that an electrical fault caused by the active conductor 100 coming - 12 into electrical contact with the reference object 40 is sensed. However, referring to Figure 4 there is shown a further example of the electrical protection unit 401 which includes diode 54 and therefore senses if the neutral 110 or active conductor 100 comes into contact with the reference object 40. 5 Referring back to Figure 3, the electrical protection unit 301 includes a mains rated relay 310 which includes a first relay contact 312 and a second relay contact 314. The mains relay is electrically connected in parallel across the solenoid such that a first terminal is electrically connected to the active conductor 100 and the second terminal is electrically 10 connected to the relay contact 47 of relay 46. The first relay contact 312 of the mains rated relay 310 is illustrated in a first position such that the sensor line is in electrical contact with resistor 42 when the protection unit 17 is operating is the first state. As will be explained in further detail below, when the mains 15 rated relay 310 actuates to cause the first relay contact 312 to move to a second position, the first relay contact 312 is in contact with the neutral conductor 110 and remains in contact with sensor 40. The second relay contact 314 of the mains rated relay 310 is illustrated in Figure 3 and 4 in 20 a first position such that it is in an open position. As will be explained in further detail below when the mains rated relay 310 is actuated, the second relay contact 314 toggles and closes to a second position. The second relay contact 314 in the closed position electrically connects the neutral conductor 110 with one of the terminals of the solenoid 60. 25 Referring specifically to Figure 3, the electrical protection device 301 illustrated is able to be used where the supply neutral conductor 110 is connected to an earth point in an MEN environment. The RCD C/B 17 is configured to sense, via the first detection unit 21, the unbalanced current condition such that the switching system 30 disconnects the electrical power supply 11 from being provided to the electrical load 15. However, the second 30 detection unit 22 which is mechanically connected to the RCD C/B 17 is configured to sense situations where the RCD does not detect a fault current between the load side active conductor 100 and earth or the equipment frame. The second detection unit 22 provides a - 13 backup to the RCD C/B 17, as the second detection unit 22 is configured to detect a current of approximately l5mA or greater that flows from the load side active conductor 100 through to the sensor line 40 which is in connection with the reference point, such as the electrical protection device frame, chassis, or earth to the neutral conductor 110 of the load 5 15. Therefore, in the event that the load side active conductor 120 is electrically connected with a frame of an electrical load 15 being powered by the electrical power source 11, due to for example a device fault or a person touching the load side active conductor 120 with 10 one hand and the device frame or earth with the other, the second detection unit 22 detects the electrical fault such that the mechanical linkage 70 is actuated causing the RCD C/B 17 to trip, thereby electrically disconnecting the electrical power source 11 from the electrical load 15. As such, in the event that the electrical fault was caused by a person, the person can be saved from electrocution. In the event that the electrical fault was caused by an 15 equipment fault, the electrical disconnection can restrict the equipment from damage such as burn out. Referring more specifically to the second detection unit in Figure 3, when the electrical fault occurs as described above in relation to Figure 3, a current (approximately 15mA at 20 240VAC) flows through the sensor line 40 to the load side neutral conductor 130 via the a first relay contact 314 of the mains rated relay 310, resistor 42, and diodes 44 and 53, such that the low voltage trip relay 46 energizes, thereby closing the respective relay contact 47. The closing of the low voltage trip relay contact 47 results in the supply voltage from the 25 load side active and neutral conductors 120, 130 being applied to the mains rated relay 310 and the solenoid 60. Once the mains rated relay 310 energizes, the first relay contact 314 and a second relay contact 314 are toggled from the respective first positions as illustrated in Figure 3 to the respective second positions as previously discussed such that the low voltage relay 46 is electrically disconnected from the sensor line 40. The changing of the 30 position of the second relay contact 314 to the second position causes the mains rated relay 310 and the trip coil solenoid 60 to stay energised, as the load side active and neutral conductors are placed across both components via the second relay contact 314 of the - 14 mains rated relay 310. The toggling of the first relay contact 312 removes the fault current from the sensor line 40 to the load side neutral conductor, thereby protecting components 42, 44, 48, 51 and the low voltage trip relay 47 from a continuous fault condition. This arrangement of quickly actuating and then de-actuating the low voltage trip relay 47 once 5 the sensor line 40 has been electrically connected with the load side neutral conductor is advantageous such as to extend the safe use of the low voltage trip relay 47. Once the solenoid (TC) has energized, the mechanical linkage is actuated, causing the switching system to electrically disconnect the electrical power supply from the electrical 10 load. The mechanical linkage includes a mechanical button which retains the mechanical trip mechanism in a latched state until the user presses a mechanical reset pushbutton releasing the latch. This then allows the RCD C/B 17 to be closed again (i.e. move to the first operating state) once the electrical fault has been removed. Due to the switching system 30 electrically disconnecting the electrical power supply 11 from the load 15, the 15 solenoid 60 and the mains rated relay 310 de-energize. The zener diode 48 is configured to ensure that the voltage across the low voltage trip relay does not exceed approximately 12V during fault current detection. The combination of 48 and capacitor 50 convert the AC supply voltage to DC voltage and the capacitor 50 also 20 holds the trip relay energized for a few milliseconds after the mains rated relay 310 has energized, thereby eliminating any race condition between the mains rated relay 310 and low voltage relay 47. Referring to Figure 4, the electrical protection unit 401 includes substantially the same 25 components as discussed in relation to Figure 3. However, the electrical protection device 401 can be used in an environment where the supply neutral conductor 110 is not connected to the earth (i.e. a floating earth system). In the event that the load side active conductor comes into electrical contact with the 30 reference object, such as the housing of the electrical protection device, a chassis of a vehicle, or the like, the electrical protection device 401 operates the same as the electrical protection device 301 as described above.

- 15 However, in the event that the load side neutral conductor, which is a floating conductor, comes into electrical contact with the reference object, such as the housing of the electrical protection device, a chassis or a vehicle, or the like, a current flows through the sensor line 5 40 via diode 54 due to diode 54 being in electrical contact with the load side active conductor 120. In the event that the current that flows through the sensor line 40 in this fault situation meeting or exceeding the threshold current, the low voltage relay 46 actuates. The operation of the second detection unit 22 carries on as described in relation to Figure 3 once the low voltage relay 46 actuates. 10 Referring to Figure 5 there is shown a schematic of the mechanical linkage 70 between the housing of the protection unit 17 and the housing of the second detection unit 22. In particular, for clarity purposes, only the mechanical components of the arrangement have been shown in Figure 5. Additionally, for clarity purposes, the housings of the protection 15 unit 17 and second detection unit 22 are separated, however in a preferred embodiment the houses are butted against each other. As already discussed, the second detection unit 22 includes a second mechanical actuator 520 which is mechanically connected to a first mechanical actuator 510 provided by the switching system 30 of the protection unit 17. In particular, the solenoid 60 which is actuated in response to the sensed current flowing 20 through the sensor line, which in turn causes the switching system 30 to actuate such that the protection unit 17 operates in the second state. More specifically, the solenoid 60 includes a piston 61 which is operably connected to a pin 62 extending outwardly from the housing 530 of the second detection unit 22, wherein the housing 540 of the protection unit 17 includes a slot 570 which houses the first mechanical actuator for receiving a portion of 25 the pin 62, wherein in response to the second detection unit 22 detecting the current flowing in the sensor line, the solenoid 60 moves the piston 62 as shown by arrow 550, wherein the pin slides (as illustrated by arrow 560 and reference numbers 62A and 62B) within the slot 570 to actuate the switching system 30, thereby disconnecting the contacts 31 and 32 discussed in relation to Figures 1 to 4. The reference number 62B to the broken 30 line represents the position of the pin upon the solenoid 60 having been actuated. As discussed in Figure 5 and now discussed in relation to Figure 6, the first detection unit - 16 is disposed within the first housing 540 and the second detection unit is disposed within a second housing 530. In particular, the first and second housings 530, 540 are adjacent to each other such that the housings 530, 540 are abutted with each other. In a particular form, the first and second housings 530, 540 can be integrally formed although it will be 5 appreciated that the housings can be alternatively separate housings. Still referring to Figure 6, the electrical protection device includes a device housing 600 which includes a first device housing portion 610 provided in the form of an open faced container, and a plurality of second device housing portions 710, 720, 730, 740 (see Figure 10 7) which are releasably attached to the first housing portion 610. Referring to Figure 7A, the second device housing portions 710, 720, 730, 740 are provided in the form of a plurality of covers which are releasably attachable to the open faced container 610. Another version of the plurality of covers attached to the first device housing portion 610 is shown in Figure 7B. 15 Referring to Figures 7A, 7B, and 7C the releasably attachable covers 710, 720, 730, 740 include one or more electrical socket covers 710, 720. Each electrical socket cover 710, 720 includes an electrical socket 715, 725 for receiving an electrical plug of an electrical load 15. In the event that a plurality of electrical socket covers is provided, as illustrated in 20 Figures 7A and 7B by the electrical protection device, a plurality of electrical loads 15 can be powered by the electrical protection device via the plurality of electrical socket sockets 715, 725. Still referring to Figure 7, the plurality of covers includes an access cover 730 which 25 includes an opening 732 which exposes a first detection unit switch 734 and a second detection unit switch 736 of the first and second detection unit (see Figure 7A) respectively. In particular, the first housing 540 includes the first detection unit switch 734 and the second housing 530 includes the second detection unit switch 736 which is operable by a user. The first and second detection unit switches 734, 736 are located 30 externally to the first and second housings 540, 530 to allow user operation. The first detection unit switch 734 is a manually operable switch which indicates the state of the protection unit, in particular the first and second state. When the protection unit operates in - 17 the second state, the first detection unit switch 734 is actuated to indicate that the electrical power source 11 has been isolated from the electrical load 15 due to an electrical fault. A user can then manually toggle the first detection unit switch 734 such that electrical power source 11 is once again placed in electrical connection with the electrical load 15. The 5 second detection unit switch 736 is a reset switch which resets the relays within the second detection unit 22 such that the protection unit 1 is operating in the first state. In a particular form, the second detection unit switch 736 is actuated prior to actuation of the first detection unit switch 734 in order to return the protection unit 1 to the first operating state. 10 As shown in Figure 7A, the access cover includes a hinged lid 739 which covers the first detection unit switch 734 and the second detection unit switch 736. The hinged lid 739 is can be opened by a user to gain access to the first detection unit switch 734 and the second detection unit switch 736 such that the user can manually operate the switches 734, 736 if required. The hinged lid 739 can be substantially transparent to allow the user to view the 15 state of the first detection unit switch 734 through the transparent lid 739 without having to open the lid. As shown in Figure 7, the lid is biased by a biasing element 738 toward a closed position. Still referring to Figures 7A and 7B, the plurality of covers can include an activation cover 20 740 which includes an activation switch 742 operable in a first mode to prevent electrical power being provided to each electrical socket 710, 720, and a second mode which allows electrical power to be provided at each electrical socket 710, 720 in the event that the protection unit 1 is operating in the first state. Figure 7D illustrates a front view of an insert which can be attached to circumference of the access cover 730 illustrated in Figure 7B. 25 Referring to Figure 8 and 9 there is illustrated an apparatus 800 including a frame 810 having a ground conveyance assembly 820, and the electrical protection device 1 which is supported upon the frame 810. In use, the electrical power source 11 can be placed in electrical connection with the electrical protection device 1 via the input terminals and the 30 electrical load 15 can be placed in electrical connection with the output terminals of the electrical protection device 1.

- 18 Referring to Figure 9, the apparatus 800 includes an electrical transformer 840 which is supported upon the frame 810, wherein the electrical power source 11 is in electrical connection with the electrical protection device 1 via the electrical transformer 840. In this configuration, the transformer 840 includes an electrical socket 842 which an electrical 5 plug of the electrical power source 11 can be received within, thereby placing the electrical power source 11 in electrical connection with the transformer 840. The transformer 840 is in electrical connection with the input terminals of the electrical protection unit 1 such that the electrical output of the transformer 840 is provided to the input terminals of the electrical protection unit 1. 10 As illustrated in Figure 9, the ground conveyance assembly 820 includes a wheel arrangement for allowing the apparatus 800 to be transported over a ground surface. The frame and the ground conveyance assembly form a trolley. As also illustrated in Figures 8 and 9, the frame 810 supports a receptacle 830, provided in the form of a bucket, for 15 transporting objects with the apparatus. In particular applications, tools can be transported within the bucket to a specific site. The bucket can include a material structure located on the external surface of the bucket including a plurality of pockets which can be used for retaining a number of various tools. 20 In the embodiments described, in the event that the RCD C/B 17 is wired incorrectly such that the supply power active and neutral 100, 110 is swapped on the RCD C/B supply side, the RCD C/B 17 will automatically trip. Embodiments of the invention have been particularly developed for protecting electrical 25 loads that are use in either or both of a multiple earth neutral (MEN) electrical distribution system (EDS) or a floating earth EDS. While some embodiments have been described with particular reference to that application, it will be appreciated that the invention is not limited to such a field of use, and is applicable in broader contexts, for example, in a DC voltage EDS. 30 It will be appreciated that as the second detection unit has been described to sense a current flowing through the sensor line. However, it will be appreciated that due to a voltage - 19 difference causing the current flow, the second detection unit can be described as sensing a voltage. It will be appreciated that the sensor line can be permanently connected to the reference 5 object such as the housing of the electrical protection device. Alternatively, the sensor line can be attached and detached to various reference points according to the circumstances. This application claims priority from Australian Provisional Application No. 2010905097, the disclosure of which is incorporated herein by way of cross reference. 10 Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described. 15 Similarly, it is to be noticed that the term connected, when used in the claims, should not be interpreted as being limited to direct connections only. The terms "coupled" and "connected," along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Thus, the scope of the expression a 20 device A connected to a device B should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and an input of B which may be a path including other devices or means. "Connected" may mean that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with 25 each other but yet still co-operate or interact with each other.

Claims

1. An electrical protection device including: at least two input terminals for connection with an active and neutral conductor of 5 an electrical power source; at least two output terminals for connection with an electrical load; a switching system for operating in a first state to allow the electrical power source to be in electrical connection with the load, and a second state to prevent the electrical power source being in electrical connection with the load; 10 a first detection unit configured to sense an imbalance in current flowing through active and neutral conductor, wherein in response to detecting the imbalanced current, the first detection unit actuates the switching system to operate in the second state, wherein the first detection unit includes a first mechanical actuator which when mechanically actuated causes the switching system to operate in the second state; and 15 a second detection unit including a sensor line for electrical connection to a reference which should be electrically isolated from at least the active conductor, wherein the second detection unit includes a second mechanical actuator operably connected to the first mechanical actuator, wherein the second detection unit is configured to sense a current flowing through the sensor line which meets or exceeds a threshold current, and in 20 response actuates the second mechanical actuator, thereby actuating the first mechanical actuator such that the switching system operates in the second state.

2. The electrical protection device according to claim 1, wherein the second detection unit includes a solenoid which is operably connected to the second mechanical actuator, 25 wherein in response to the second detection unit sensing that the current flowing through the sensor line meets or exceeds the threshold current, the solenoid is electrically actuated to mechanically actuate the second mechanical actuator.

3. The electrical protection device according to claim 1 or 2, wherein the first 30 detection unit is disposed within a first housing and the second detection unit is disposed within a second housing, wherein the first and second housings are abutted in a side-by side relationship with each other. -21

4. The electrical protection device according to claim 3, wherein the second mechanical actuator includes an arm which projects from the second housing and into the first housing to actuate the first mechanical actuator. 5

5. The electrical protection device according to any one of claims 1 to 4, wherein the electrical protection device includes a test switch, wherein user actuation of the test switch causes the second detection unit to actuate the second mechanical actuator, thereby causing the switching system to operate in the second state.