WO2005091002A1

WO2005091002A1 - Electrical monitoring device

Info

Publication number: WO2005091002A1
Application number: PCT/AU2005/000370
Authority: WO
Inventors: Robert Watson
Original assignee: Global Spill Control Pty. Limited
Priority date: 2004-03-19
Filing date: 2005-03-17
Publication date: 2005-09-29

Abstract

A means for ascertaining a parameter which comprises a device associated with electrical apparatus to be monitored which device is provided with circuitry whereby the parameter can be monitored and means whereby the results of the monitoring can be transmitted to an indicator. The parameter is normally earth leakage but can include earth continuity, operational parameters of the apparatus, smoke temperature and gas detection. The means also includes means whereby on a fault condition an alarm is initiated and can also maintain records of the operation of the various devices.

Description

ELECTRICAL MONITORING DEVICE

Area of the Invention

This invention relates to a means for monitoring the status of an electrical apparatus and in particular for continuous monitoring of such apparatus. The invention is particularly suitable for continuously monitoring changes in earth leakage and therefore insulation integrity for connected equipment and earth continuity for earthed equipment.

Background to the Invention

It is a requirement in many industrial areas for the status of the earth leakage in equipment, which gives an indication as to the status of the insulation, to be monitored regularly, say every six or twelve months to ensure that the equipment does not constitute a likely hazard for its operator and such monitoring is both very expensive, in that an authorised person must come to each piece of equipment, cause it to cease operating, place a monitoring device in line with the equipment and then ascertain the parameter being checked. It is also disruptive if the equipment is being used in a production process and must be

shut down. It is also desirable to monitor other parameters such as earth continuity,

operating time, voltage and current, and/or power use, which can be ascertained from the two previous parameters, and we wish to provide a means whereby this can be effected.

Applicant has identified several prior art references in the U.S. patent art. U.S. Patent No 4,652,139 by Sulcer describes a non-volatile elapsed-time meter. U.S. Patent No 4,920,549 by Dinovo describes a means for collecting data about the accumulated run-time and average cycle-time of a switched circuit, typically for tracing equipment run-time. These devices do not record spikes, surges, brief dropouts or other perturbations of the supply line. These devices only record the accumulated time that a supply of power was detected as being present. In addition, Dinovo's invention also calculates and stores the average on-time of a piece of equipment.

U.S. Patent No 5,315,236 by Lee is a monitor that measures the instantaneous power and total accumulated energy consumed by a device. It is a device that plugs into an electric socket and has a separate receptacle for an appliance plug.

It is the object of the invention to provide means whereby certain parameters can be monitored, and preferably continuously monitored, and the result of this monitoring used to maintain a check on the status of the equipment concerned. Outline of the Invention

The invention includes a means for ascertaining a parameter which comprises a device associated with electrical equipment to be monitored which device is provided with circuitry whereby the parameter can be monitored and means whereby the results of the monitoring can be transmitted to an indicator.

The device may be in a power outlet providing power to a particular piece of equipment, it may be connected between a power outlet and the equipment or it could be built into the equipment.

The device may be used with 415, 230 or 110 volt supplies, or other supplies and can be used with single phase or three phase equipment.

It is preferred that the means for transmitting details of the parameter being monitored can permit transmission along the power line to which the device is connected but an alternative form of connection, such as an independent conductor or RF, IR or other transmission system can be provided.

The indicator can be a computer, which can be used to monitor and display the parameters being measured for a number of devices and which can have memory whereby the results of the monitoring can be maintained and also can include a warning function if the parameter being measured varies from a preset

value.

It is preferred that each device is coded so that the source of a signal can be readily identified or, alternatively, the signals from the various devices can be monitored serially.

Alternatively, the indicator can be associated with each device and be an audible and/or visual alarm or it could be an audible and/or visual alarm which can be operated by any one of a number of devices.

In a still further application, the indicator could be a data logger, which can provide the alarm and from which the output can be used later to download details of the operating parameters of the equipment to a computer.

In order that the invention may be more readily understood we will describe by way of non limiting example a specific embodiment of it.

Description of an embodiment of the Invention

In order to generally describe the invention, reference will be made to the Figure of drawings which show various arrangements of the invention. The invention, in its most usual form, is adapted to check earth leakage and

earth continuity of electrical equipment and cables and to provide a continuous monitoring arrangement and an alarm function if the earth leakage rises to a level greater than that regarded as representing a safe operating value or that permitted by the authorities in the place where the equipment is located or if there is a break in earth continuity.

The earth leakage can be determined by the use of a current transformer, which is conventional in the art. Earth continuity is ascertained by sending a test current to the equipment body and measuring the current returning along the earth wire. For checking earth continuity of the building as a whole a test current is sent through the neutral wire which is connected at the test area to the earth and the existence of current flow indicates that the earth is continuous. This can also be used to check polarity as if the system is wrongly wired, this will be indicated.

For example, in Australia, an 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 no effect on the concept of the invention. The general concept of the invention is well illustrated in the Figure. There is a computer 10 which has two functions, the first of which is to continually and sequentially monitor all pieces of equipment associated with the system to ensure that they meet the particular requirements of that equipment and the second is to receive any fault indication from any piece of equipment and not only log this but also provide and audible/visual fault signal, as by indicator light 20, to alert an operator, supervisor, maintenance electrician or any other person of the fault.

The figure shows five different types of provision of the monitoring of the invention. The black line around part of the drawing indicated the location of the power lines throughout the building.

In three of the cases, there is a conventional power point 25 and in the other two there is a power point 25¹ which is a conventional power point which shares its box with the device 11 of the invention, as will be described.

In the first of these, the monitoring device 11 is shown as being built into a switch/socket power point 25¹ and in this case, the device has a double insulated power drill 12 connected thereto. This can be the preferred arrangement in new premises and, where the Authorities are the same as those in Australia, there can be two adjacent power points one of which is designed for tools which is double insulated and the other for tools which are earthed. We will not, in later discussions refer to the alternative.

The second, shown associated with a drill press 14 has the device 13 physically located on the equipment. As this tool is earthed rather than double insulated, we incorporate a fault signal line 21 between the tool and the device 13.

The third, shown associated with a power saw 16 has the device 15 associated with the power lead of the saw. In this case the device can be built into the saw's three pin plug or can be located on the lead upstream of the plug.

The fourth, shown in association with a power hack saw 18 has the device attached to an extension power lead. This can be associated with the socket of the lead or the plug or can be located in the lead cable. In this case, as the saw is earthed, there is a test lead 19, to check earth continuity, passing from the body of the saw to the device.

The fifth, shown in association with a docking saw 21 shows a combined power point 25² and monitoring device 11 similar to the first arrangement. As in this case the saw is earthed there is a test lead 22 passing from the body of the saw to the device 11. The device can be used with equipment connected to a 415V, 240V, 110 V or

other, AC power supply by flexible cable. Where the device is for use with a three phase supply, it will inherently be larger than where used with a lower voltage supply and would preferably be located in a box which is physically mounted adjacent the outlet. It is also quite feasible to locate the device in a separate box which is physically located close to a switch socket combination and to which the conductors from the switch pass before being connected to the socket. In these cases, a device of the invention will normally be associated with each phase of the supply.

Similarly, depending on miniaturisation, the device can be fitted into the same box as a switch socket combination or also within the bounds of a normal three pin plug or socket.

The basic function of the device is to play a supervisory role with respect to the electrical safety of the appliance.

The device can be extended to provide an appliance specific computer record of hours of operation and load.

Each device is coded and can be designed to periodically transmit data to a central computer facility, identifying the apparatus or lead, or, and preferably, a sequential arrangement can be used in the computer software, to select the individual apparatus or lead to be examined. The results of these transmissions or interrogations can be maintained in a data base in the computer 10 and any Inspector can examine the history of each individual device. This should remove the necessity of anything other than a visual inspection of each piece of equipment and remove the necessity of having to turn these off and thus compromise production, to carry out an electrical inspection.

The parameters to be considered can be any of the following:-

• earth leakage current.

• resistance to earth, for earthed equipment (a separate device attached to an appliance but fault information sent via the plug)

• its operating status

• the current drawn

• reversed polarity. This would normally only occur on original installation or after maintenance when the wiring to the equipment is reversed.

• additional functions such as smoke detection, temperature detection, gas concentration detection. The data measured can be sent to the computer 10 by the use of a power line modem or can be transmitted by a dedicated line to which a number of plugs can be connected, the signals being ascertained atthe computer by the coding of the plug. Alternatively an RF or IR signal could be used to transmit the data.

Computer software enables this data to be interpreted to provide -

• A Differential Earth Leakage failure alarm, indicating an insulation fault, detected by excessive earth leakage, when and if current differential measured between active and neutral is, say, greater than 1 mA or 5 mA depending on the type of equipment being used.

• Insulation breakdown is most often a progressive matter, due to aging or normal wear, and will be detected at a level well in advance of that regarded as a safety hazard. The monitor can readily indicate any deterioration in the insulation and can be adapted to provide a warning display or an audible alarm if there is deterioration beyond an acceptable level.

• This alarm may be manifested by an audio and/or visual alarm which can be located in the area of the devices, or elsewhere and an alarm indication which can appear on the computer screen and indicate the source of the alarm and if several parameters are being monitored, the cause of the alarm.

• A historical record of all alarms can be maintained by the computer. • Where required, an historical record for each power tool, with respect to usage, time of day and date, period on load, maximum current drawn (load), and maximum daily values for the earth leakage test.

• By adaptation the system of the invention can also provide an Earth Continuity failure alarm, by which an earth connection fault is detected, by excessive resistance to earth, in excess of 1 ohm. This is required only for appliances that are provided with an earth connection and are not double insulated, that is, equipment having an exposed and earthed metal component.

This recording and alarm system is designed to provide the required level of protection for personnel and equipment, as may be achieved by the periodic testing in accordance with AS/NZS 3760:2001 , required by state workplace safety authorities. Also, to satisfy the requirements of Work Cover NSW, in place of their Code of Practice "Electrical practices for construction work", or any other appropriate Standard or Code.

It is further proposed that this on-line testing process will provide better personnel protection than periodic (annual or semi-annual) inspection because it offers continuous recording of equipment and connection usage and performance, and an instantaneous alarm if there is any breach of electrical

safety issues. The only further requirement, to meet or exceed the requirements of the Standard and the requirements of the authorities, will be periodic visual inspection of the equipment and connection. A place will also be provided for reporting of these observations within the computer log, together with witness verification. This will provide industry with a valuable management tool. Also an electronic or paper copy of the log can be filed and made available for inspection authorities.

It is to be understood that variations can be made in the system of the invention without departing from the spirit and scope thereof.

Claims

We claim:

1. A means for ascertaining a parameter which comprises a device associated with electrical apparatus to be monitored which device is provided with circuitry whereby the parameter can be monitored and means whereby the results of the monitoring can be transmitted to an indicator.

2. A means as claimed in claim 1 wherein the device is located in a power outlet to which the apparatus is connected.

3. A means as claimed in claim 1 wherein the device is located on the apparatus.

4. A means as claimed in claim 1 wherein the device is located in the power lead by which the apparatus is connected to the power supply.

5. A means as claimed in claim 1 wherein the device is located in a power extension cord to which the apparatus is connected.

6. A means as claimed in any one of the preceding claims wherein the device is adapted to measure earth leakage current.

7. A means as claimed in claim 6 wherein the apparatus is earthed and the device is adapted to measure earth continuity.

8. A means as claimed in any one of claims 1 to 5 wherein the device is adapted to monitor functions included in the group of operating status of the apparatus, reversed polarity, smoke detection, temperature, gas.

9. A means as claimed in any preceding claim wherein the means to transmit results are selected from a group including a modem to send results along a power line, a dedicated conductor to transmit the results, and infra red transmitter or a radio frequency transmitter.

10. A means as claimed in any preceding claim where the indicator is a computer.

11. A means as claimed in claim 10 wherein the computer sequentially polls a number of devices which are each key coded.

12. A means as claimed in claim 10 wherein each of a number of devices, each of which are key coded, send information to the computer at intervals.

13. A means as claimed in any one of claims 10 to 12 on receipt of a fault signal from any device the computer initiates an alarm.

14. A means as claimed in claim 13 wherein the alarm includes a notification on the computer screen and an indication of the position of the fault.

15. A means as claimed in claim 13 or claim 14 wherein the alarm is an audible and/or visual alarm.

16. A means as claimed in any one of claims 10 to 15 wherein the computer retains a log of the monitoring of the devices and any alarms sent from them.

17. A means as claimed in any one of claims 1 to 9 wherein the indicator is an audible and/or visible alarm connected to the device.

18. A means as claimed in claim 17 wherein the alarm is connected to a plurality of devices.

19. A means as claimed in any one of claims 1 to 9 wherein the alarm includes a data logger whereby information can be stored for later downloading.