GB2164756A

GB2164756A - Multi-purpose earth-leakage current detector and recorder

Info

Publication number: GB2164756A
Application number: GB08523238A
Authority: GB
Inventors: John Slevin
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-09-20
Filing date: 1985-09-20
Publication date: 1986-03-26
Also published as: GB8423845D0; GB2164756B; GB8523238D0

Abstract

An earth-leakage current detector and recorder 10 comprising a housing 11, a plug socket 19 for the earth-leakage current testing of plug-in portable electrical appliances, a socket 21 enabling the connection of a current detector 22 for the earth-leakage current testing of permanently installed electrical appliances and installations, and an outlet socket 27 for connection of a chart recorder 28 for the recording of such tests over a given period of time. <IMAGE>

Description

SPECIFICATION Multipurpose earth-leakage current detector and recorder This invention concerns earth-leakage current detectors and recorders.

Presently known earth-leakage current detectors can only be used for checking for any earth-leakage current on electrical equipment/ appliances which plug and unplug from the mains circuit where the current they measure is in the order of milliamps. Such detectors have an electrical socket (usually a three pin socket) into which the plug of the appliance is plugged, the detector in turn being plugged by its lead into a mains socket. This type of detector cannot be used for detecting earthleakage current on appliances which are permanently fixed to the mains circuit.

For detecting earth-leakage current (in the order of amps) on fixed (i.e. permanently connected) electrical equipment and installations it is common practice to use a clamp meter the jaws of which are clamped around the earth lead or the phase(s) and neutral leads of the equipment usually at the junction box to which the leads are connected. The clamp meter is quite an expensive piece of equipment.

If one is checking, for example, a factory which has a number of electrical machines in order to see which machine or machines is faulty but where each machine is switched on at a different time during the day, it is time consuming for someone using a clamp meter to spend the whole day waiting for each machine to be switched on so that it can be checked. It would be far more convenient if the operation of the machines in the factory during the day could be recorded, without the constant attendance of some person, to give an indication as to when and in which machine or machines the earth-current leakage occure.

An object of the invention is to provide an earth-leakage current detector which can be used for testing both plug-in type electrical equipment and permanently fixed or installed electrical equipment, and the installation itself, and which has a facility for recording the test.

With this object in view the present invention provides an earth-leakage current detector and recorder comprising at least one plug socket, at least one inlet socket for a clamp and at least one outlet socket for connection thereto of recording means for recording data as to any detected earth-leakage current.

The invention will be described further, by way of example, with reference to the accompanying drawing in which the single figure is a perspective view of a preferred embodiment of the multipurpose earth-leakage current detector and recorder of the present invention, it being understood that the following is illustrative and not limitative of the scope of the invention.

Referring in detail to the drawing, the preferred detector and recorder 10 comprises a standard box-like housing 11, incorporating electronic circuitry well known in the art, which for ease of use and convenience is disposed in one compartment 12 or a two compartment case 13 made, for example, of leather. The other compartment 14 of the case 13 is ideally useful as a storage compartment for ancillary equipment. The compartments 12 and 14 have respective studfastening lids 15 and 16. The lid 15 is provided on its inside with an operating instructions panel 17.

The housing 11 has an instrumentation panel 18, coverable by the lid 15, provided with various input and output means as will be described in detail hereinafter.

To enable the detector and recorder 10 to measure any earth-leakage current on portable electrical appliances, such as a typewriter, electric kettle, fridge, toaster, vacuum cleaner, electric drill, computer, etc., which use current in the order of milliamps and which are plugged into the mains circuit, a three pin plug socket 19 which is provided on the instrumentation panel 18. The plug (not shown) of the appliance is plugged into the socket 19 and the detector and recorder lead (not shown) is plugged into the mains. Any imbalance in the current flowing along the live lead and back down the neutral lead of the appliance is indicative of earth-leakage current. A digital display meter 20 is also provided on the panel 18 so as to indicate digitally said imbalance.Of course said digital display meter 20 could easily be replaced by an analogue display meter or a lamp or series of lamps.

To enable the detector and recorder 10 to measure earth-leakage current on permanently installed electrical appliances its panel 18 is provided with a clamp socket 21 for reception of a clamp, indicated generally by the reference numeral 22. The clamp 22 does not need to have its own built in meter as the digital display meter 20 of the recorder and detector 10 will suffice. This means that a much less expensive clamp can be employed comprising simply a main body 23, jaws 24, lead 25 and jack-plug 26, for socket 21, as shown in the drawing.

The instrumentation panel 18 is also provided with a monitoring or recording outlet socket 27 for the connection of recording means such as chart recorder 28. The socket 27 is a useful facility in that it enables the detector and recorder 10 to be used for the detection of earth-leakage current in an installation consisting of a number of electrical machines which each come into operation at a different time during a particular time span, for example over a twenty-four hour period, and one or more of which may be faulty. With the jack-plug 26 of the clamp 22 plugged into the clamp socket 21 of the detector and recorder 10 and the jaws 24 clamped to an appropriate part of the installation, the chart recorder 28 can be plugged into the socket 27 by its jack-plug 29 and allowed to operate for say twenty-four hours.At the end of this time, chart 30 of the recorder 28 can be checked to ascertain in which part of the installation has there been earth-leakage current. Therefore, with the detector and recorder of the present invention there is no need for the presence of personnel during all of the test period.

Also on the panel 18 an outlet socket 31 for connect of an oscilloscope (not shown); an earth-healty indicator 32, in the form of a lowvoltage filement indicator, to indicate earth continuity of the appliance under test; and a power-on indicator 33, for example a 240 volt red neon indicator, to indicate that power is available at the socket 19.

The panel 18 is additionally provided with a function select switch 34 so that the mode of operation of the detector and recorder 10 can be selected with ease.

When the detector and recorder 10 is being used to test plug-in appliances it is connected to the mains supply by its lead plug.

When the detector and recorder 10 is being used in conjunction with the clamp 22 it can be powered by means of internal re-chargeable batteries.

The current ranges for the socket 21 for the clamp 22 may be 0-200 MA, 0-2 A and 0-20 A and for the outlet socket 27 for the chart recorder 28 0-200 MA. The charge time for the batteries of the recorder 10 is approximately seven hours.

Claims

1. An earth-leakage current detector and recorder comprising at least one plug socket, at least one inlet socket for a clamp and at least one outlet socket for connection thereto of recording means for recording data as to any detected earth-leakage current.

2. A detector and recorder as claimed in claim 1 wherein it also comprises a box-like housing having an instrumentation panel mounting the or each plug socket, inlet socket and outlet socket.

3. A detector and recorder as claimed in claims 1 and 2 wherein the plug socket is a three-pin socket enabling the testing of portable electrical appliances such as a fridge, toaster, etc.

4. A detector and recorder as claimed in claim 1 and 2 wherein the inlet socket for the clamp enables the detection of earth-leakage current in fixed electrical appliances and installations.

5. A detector and recorder as claimed in claim 1 wherein the recording means is a chart recorder.

6. An earth-leakage current detector and recorder substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.