AU2006202668B2 - Portable electrical monitoring device - Google Patents

Description

Regulation 3.2 -1 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT APPLICANT: Safe T Smart Plug Pty. Limited NUMBER: FILING DATE: Invention Title: PORTABLE ELECTRICAL MONITORING DEVICE The following statement is a full description of this invention, including the best method of performing it known to me: 2 PORTABLE ELECTRICAL MONITORING DEVICE Technical Area This invention relates to a portable monitoring device which can be connected between a source of electrical power and an apparatus which uses power and which can give continuous monitoring of the status of the equipment on the down-stream side of the device. Background to the Invention It is desirable, and in some areas essential, under regulations, for the status of earth leakage in equipment and extension cords, which give an indication as to the status of the insulation, to be monitored. For example, on all building sites, all power tools and extension cords to be used by tradesmen, must be tested, and must be tagged, and these tests must be carried out, either at predetermined intervals, if the tradesman is to be on a site some time, or when he moves from site to site. It is also desirable to monitor other parameters, such as earth continuity (resistance to earth). Safe T Smart Plug Complete 200606.wpd June 21, 2006 3 Outline of the Invention It is the object of the invention to provide means whereby certain parameters in an electrical circuit can be monitored whilst in service, and preferably continuously monitored, and the result of this monitoring used to maintain a check on the status of the equipment concerned. The invention provides a portable electrical monitoring device Which is adapted to be connected to a mains electrical power supply and which has at least one power outlet receptacle and means to monitor parameters of any item connected to the receptacle and, on such items providing a possible fault parameter, to automatically provide an audible and/or visible alarm and including means to isolate the item connected to the receptacle on the alarm being tripped. Preferably, the monitoring device includes means connected to or associated with each receptacle whereby earth leakage current can be monitored and means whereby, on the leakage current exceeding a predetermined value, the alarm is initiated. The invention can also provide a monitoring device having means provided so that where there is a substantial increase in leakage current, the alarm will be initiated and the power to the associated circuit will be cut off. In a further aspect of the invention, the device includes means to monitor earth Safe T Smart Plug Complete 200606.rtf October 5, 2010 4 continuity by applying a test current to earth and ascertaining the voltage drop at the earth wire. In a still further aspect, the monitoring device is arranged so that the or each receptacle includes or is associated with means to isolate the receptacle if the current flow becomes greater than the permitted maximum. It may be preferred to provide means to prevent the use of the equipment on the alarm being tripped. Wherever there is an earth leakage current of 30mA, the equipment should be isolated from the power mains and it is know to use RCD's (Residual current devices) which trip when the earth leakage current reaches this value- RCD's are fitted in many commercial and domestic applications, basically to provide protection against catastrophic failure of a piece of equipment, and the 30MA value is selected to permit normal operation of devices but to be far under the level of current against which RCDs are designed to give protection. In certain applications, where there is an earth leakage current of 1 or 5mA (under Australian Standards), the equipment should be reviewed but there may be no necessity that use be stopped immediately so it may be preferred that under these conditions, the warning be provided without preventing further use. Where there is current of 30mA, the circuit should be isolated Safe T Smart Plug Complete 200606.wpd June 21, 2006 5 immediately and the device can effect this. RCDs are normally provided with a test button which indicates that the RCD is operating correctly Further, it may be desirable if one or some outlets draw too much current in normal operation, that means be provided, by way of a circuit breaker, to isolate the outlet(s). Earth leakage current is ascertained by the use of an RCD, and it is necessary that the operation of this can also be checked and means are provided whereby this can be done at specified intervals. In a preferred form, the invention may act as a power-board, having a number of outlets from which power can be taken, each of which receptacles is provided with the test means of the invention. Description of an Embodiment of the Invention In order that the invention may be more readily understood, we shall describe one particular device made in accordance with the invetnion in relation to its application, the device being described with reference to the accompanying drawings, in which: Fig 1 is a perspective view of the device; and Fig 2 is a view of one side thereof. Safe T Smart Plug Complete 200606.wpd June 21, 2006 6 The device 10 may be in the form of a hollow body 11 and in the illustrated embodiment, the end 12 is triangular and the device has a length which depends upon what is to be provided by the device, as will be described hereinafter. The triangle defined by the end 11 is either equilateral or isosceles and one of the sides 13 constitutes a base. The body made be made of pressed metal or could be a plastics moulding and meets normal dust and moisture electrical enclosure standards. As illustrated, there is a handle 20 extending upwardly from the apex of the triangle 12 whereby the device can readily be transported. On one face of the device, there can be a number of electrical output receptacles and in the particular form these are shown to be Australian three pin 230 volt plug sockets, although they can be of any required type, and there are four of these mounted in each of two rows along the length of the device. The number and the orientation may vary with the requirements of the user and the types of receptacles used. The sockets 21 are shown with associated switches 22 but ,alternatively, the sockets may be of the form which automatically switch when a three-pin plug is connected thereto. Safe T Smart Plug Complete 200606.wpd June 21, 2006 7 Also mounted on the face, in this particular embodiment, to one side of the receptacles 22, there can be a warning light 25, preferably a strobe light, and a warning horn 26. There is also provided an LCD indicator 27 which can provide specific information about any fault condition and its location. Whilst there has been described an embodiment of the device as having all of the components on one of the upwardly-directed faces of the triangle, it is possible to vary this orientation. For example, it would be possible to have receptacles on each side and thus, restrict the length of the device or, alternatively, it would be possible to have the receptacles on one side and the warning devices, the light, the LCD display, if any, and the siren on the other side. Other shapes and orientations can also be used. For example outlets could be provided on both sides and the ends and the shape could be a solid rectangle or cube if required. Mounted on one end of the device there can be a power inlet which would normally be conductive prongs adapted to be received in a plug, and this may be either a normal three-pin arrangement, used in Australia for 230 volts, or could be some other form of receptacle, depending upon the requirements and the demands of the appropriate supply authority. Safe T Smart Plug Complete 200606.wpd June 21, 2006 8 From this receptacle each of the sockets are connected by way of a device designed in accordance with the invention which is adapted to check earth leakage and earth-continuity of electrical equipment. The earth leakage can be determined by the use of a current transformer, which is conventional in the art. For example, in Australia, there is permissible earth leakage of up to 1 mA if the equipment is double insulated and 5 mA if the equipment is earthed. This means that in this, and possibly other jurisdictions, there may have to be two forms of device, one for each type of equipment, although it will be understood that this is necessitated by the vagaries of the relevant Authority, and has rio effect on the concept of the invention. Each circuit is provided with an RCD switch which is designed to trip out and cut-off power at 30 milliamps so that should there be any earth conductivity which leads to a signal greater than this, the RCD switch will trip, this will cut off power to the particular circuit. Thus there are two conditions which are monitored by the invention. The first is the low amperage leakage current and if this is detected, as will be described later, normally the warning devices will be activated but the outlet can continue to be used until a suitable time when it is checked. The other is where there is a substantial current when the RCD switch will immediately open the circuit. Safe T Smart Plug Complete 200606.wpd June 21, 2006 9 In each case, power will be applied to the light 25 which may be a strobe light which will demand attention rapidly and to the warning siren 26. If there is an LCD, this can indicate which of the sockets has the faulty equipment attached to it. The check of each outlet is controlled by a micro-processor which steps through each of the outlets every few seconds and, on any fault being fourd, the alarm will operate and, if there is a substantial fault the RCD associated with the faulty circuit will be caused to trip, cutting off the power to the circuit, and the warning signals will be initiated. The microprocessor can also effect a check to ensure that the RCD continues to operate correctly but there is also a manual check, which can be used before the device is connected to the normal power source whereby a current can be passed through the RCD to ensure both that it operates if the current is greater than 3OmA and also that it operates within a prescribed time period. The device can also ascertain earth continuity and this is ascertained by applying a test current and measuring the voltage drop across the earth wire. The test current may be transmitted along the neutral wire and the voltage drop measured between this and earth. If there is no earth, there will be a zero volts reading, a high voltage drop, if a bad earth a relatively low voltage reading again a substantial voltage drop and a satisfactory earth only a small voltage drop. The differences are of a substantial order so it is obvious if the product is not earthed. test. Safe T Smart Plug Complete 200606.wpd June 21, 2006 10 The polarity of the system (that is if the active is wrongly connected to neutral) can also be ascertained when this test is being done. It will be seen that by the use of the device of the invention, a tradesman could go onto a building site and connect an untagged piece of equipment, say, a power drill on the end of an extension cord, the device will automatically check the status of the combination and if there is excessive earth-leakage will cause the RCD associated with the particular socket to operate and this will immediately prevent further operation of the equipment, will sound an alarm and will provide an indication that there is a fault situation. Normally after connecting the device to the power source and before any equipment is attached thereto, the check of the RCD mentioned above would be effected and, if the device is to be used at the same site for several days, or longer, the check should be effected at regular intervals. The tradesman or a safety officer can then, if required, check, say, the extension cord to see whether it is causing the alarm situation or the tool concerned, so that unsafe equipment can immediately be removed from the work-site. Of course, a similar device would be equally useful for individuals and in the home. They could use equipment, confident that there was no electrical fault in the equipment or the extension cords associated therewith. Safe T Smart Plug Complete 200606.wpd June 21, 2006 Whilst there has been described the particular device in association with standard sockets, there can also be provided devices with, say, higher amperage circuits, if this is required. There can also be provided a device which can be used with three-phase power with 10 or 20 amp outlets. In each case, the features of the device are provided generally as discussed herein. Whilst there has been described the device in its simplest form for use in monitoring earth-continuity and earth-leakage, it is preferred to provide with the device means whereby the total current drawn can be monitored by providing a circuit breaker associated with each circuit or even each outlet and if excess current is drawn through any particular outlet, the circuit breaker associated with this outlet or its circuit will trip. There could also be provided means whereby reverse polarity upstream of the device could be checked automatically when the device is first connected to any particular power source. Any such variations and modifications can be deemed to be within the scope of the invention, as can modifications in the tests effected and the number and type of outlets and the size and shape of the container of the unit. Safe T Smart Plug Complete 200606.wpd June 21, 2006

Claims (12)

1. A portable electrical monitoring device which is adapted to be connected to a mains electrical power supply and which has at least one power outlet receptacle and means to monitor parameters of any item connected to the receptacle and, on such items providing a possible fault parameter, tO automatically provide an aUdible and/or visible alarm and including means to isolate the item dnnected to the receptacle on the alarm bding tripped.

2. A monitoring device as claimed in claim 1 which includes connected to or associated with each re6eptacle, means whereby ath leakage current can be monitored and means whereby, on the )eakage current exceeding a predetermined value, the alarm is initiated.

3. A monitoring device as claimed in claim 2 wherein the current which initiates the alarm is of the order of 5 milliamps or less.

4. A monitoring device as claimed in claim 2 or claim 3 Wherein earth leakage current is monitored by a current transformer

5. A monitoring device as claimed in any preceding clair wherein means are provided so that where there is a substantial increase in leakage current, the alarm will be initiated and the power to the associated circuit will be cut off.

6. A monitoring device as claimed in claim 5 wherein the current which will initiate the alarm and cut off the power to the circuit is heater than 30 milliamps.

7. A monitoring device as claimed in claim 5 or claim 6 Wherein the means Safe T Smart Plug Complete 200606.rtf October 5, 2010 ^ 13 to ascertain the presence of the high earth leakage current is a Residual Current Device (RCD).

8. A monitoring device as claimed in any preceding clairh Wherein there are means to monitor earth continuity by applying a test current to earth and by ascertaining the voltage drop at the earth wire, receive an indication as to whether there is earth continuity..

9. A monitoring device as claimed in any preceding claim Wherein the or each receptacle includes or is associated with means to isolate the receptacle if the current flow becomes greater than the permitted maximum.

10. A monitoring device as claimed in claim 9 wherein the rrieans to isolate the receptacle is a circuit breaker.

11. A monitoring device as claimed in any preceding clairh Wherein there are a plurality of receptacles which are monitored singly or as a group each of which groups comprises a circuit with which is associated with the testing devices of the invention.

12. A portable electrical monitoring device substantially as herein described with reference to the accompanying drawings. DATED this 5th day of October 2010 SAFE T SMART PLUG PTY. LIMITED By Its Patent Attorneys A TATLOCK & ASSOCIATES Safe T Smart Plug Complete 200606.rtf October 5, 2010 EDITORIAL CASE NOTE: "2006202668" This specification does not contains page numbered 14.