GB2072860A - Appliance earth leakage tester - Google Patents

Appliance earth leakage tester Download PDF

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Publication number
GB2072860A
GB2072860A GB8006193A GB8006193A GB2072860A GB 2072860 A GB2072860 A GB 2072860A GB 8006193 A GB8006193 A GB 8006193A GB 8006193 A GB8006193 A GB 8006193A GB 2072860 A GB2072860 A GB 2072860A
Authority
GB
United Kingdom
Prior art keywords
earth
transformer
testing
electrical appliances
leakages
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB8006193A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
REDSURE ELP Ltd
Original Assignee
REDSURE ELP Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by REDSURE ELP Ltd filed Critical REDSURE ELP Ltd
Priority to GB8006193A priority Critical patent/GB2072860A/en
Publication of GB2072860A publication Critical patent/GB2072860A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/16—Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
    • G01R27/18—Measuring resistance to earth, i.e. line to ground
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

A portable device for testing earth leakage in electrical appliances comprises a housing having a socket 2 and a complementary plug 1. The socket and plug terminals are connected by lines extending in the housing. The live and neutral lines extend through a core balance current transformer 3 connected to a precision amplifier and rectifier unit 4 which is connected to a display meter 5. An earth probe 11 is connected to the secondary of an auxiliary transformer 6. Earth leakage currents in an appliance connected through the device to a supply are reflected in the current transformer and displayed on the meter. <IMAGE>

Description

SPECIFICATION Appliance earth leakage tester The present invention relates to apparatus for testing the earth leakage currents in electrical appliances.
It is the common practice in domestic, commercial and industrial premises, to protect both personnel and equipment against the effects of excessive earth leakage currents. This is generally done by including an earth leakage circuit breaker which disconnects the supply in the event of the arithmetic sum of the earth leakage currents in all equipment fed from the earth leakage circuit breaker exceeding the current necessary to operate the circuit breaker mechanism. It is, therefore, useful to be able to check the earth leakage current on individual electrical appliances.
According to the present invention, there is provided apparatus for testing for earth leakages in electrical appliances comprising a core balance current transformer having a core adapted to be disposed around supply lines to the appliance under test, a rectifier and amplifier unit adapted to receive signals from the transformer at its input and to provide a rectified and amplified signal at its output and a display means adapted to display the output signal so produced.
In order that the present invention may be more clearly understood, one embodiment thereof will now be described by way of example with reference to the accompanying drawings, in which Figure 1 shows a circuit diagram in partial block form of testing apparatus, and Figure 2 shows a detailed circuit diagram of a block forming part of the circuit of Figure 1.
Referring to Figure 1 , the testing apparatus is a portable hand-held unit comprising circuitry disposed in a housing (diagrammatically indicated by dotted line H). A supply cable terminating in a three pin plug 1 leads out of the housing and a complementary three pin socket 2 is disposed in the housing. Live, neutral and earth conductors extend between the plug 1 and the socket 2. The earth conductor is earthed to the unit and the live and neutral conductors extend through the centre of a toroidal transformer forming the primary of a core balance current transformer 3. This transformer 3 has two secondary windings 30 and 31. Secondary winding 30 is connected to the input side of a precision amplifier and rectifier unit 4. Secondary winding 31 forms part of a test link 10 which also comprises a resistor 9 and pushbutton 8.This test link 10 is supplied from the secondary winding of an auxiliary supply transformer 6. The primary winding of this transformer 6 is connected through a fuse 7 across the live and neutral conductors. A probe 11 is also connected to the secondary winding of the transformer 6 through an indicator lamp 12. The purpose of the probe 11 will be described later.
Referring now to Figure 2, the amplifier/rectifier 4 comprises three operational amplifiers 50, 51 and 52. Amplifier 50 has two inputs 53 and 54.
The secondary winding 30 of the transformer 3 acts as a detection coil which is connected across the inputs 53 and 54. A potential representing the earth leakage current on the balance core current transformer 3 which is detected by the winding 30 is therefore fed to the amplifier 50. This potential is amplified by the amplifiers 50, 51 and 52 and the amplified signal is displayed by the meter 5.
Variable resistors 56 and 57 are connected to the operational amplifier 52 to enable the amplifier/rectifier to be calibrated and zero adjusted.
In operation of the apparatus, an appliance to be tested is plugged into the socket 2 and the plug 1 is plugged into the mains supply. The probe 11 is placed in contact with any earth part of the appliance in order to ensure that the earth connection in the plug of the appliance under test is correctly connected to the earth on the appliance itself. If the earth connection is correct, the lamp 12 will illuminate but not otherwise. Any earth leakage current flowing in the appliance will also flow through the conductors extending through the toroidal core of the transformer 3. Any earth leakage present will be indicated by a reading on the meter 5.
It will be appreciated that the above embodiment has been described by way of example only and that many variations are possible without departing from the scope of the invention.
1. Apparatus for testing for earth leakages in electrical appliances comprising a core balance current transformer having a core adapted to be disposed around supply lines to the appliance under test, a rectifier and amplifier unit adapted to receive signals from the transformer at its input and to provide a rectified and amplified signal at its output and a display means adapted to display the output signal so produced.
2. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 1, in which the rectifier and amplifier unit comprises operational amplifier means.
3. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 2, in which the secondary of the transformer is connected to the input of the operational amplifier means.
4. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 2 or 3, in which variable resistors are connected to the operational amplifier means to provide for zero adjustment and calibration.
5. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 4, in which an auxiliary supply transformer is provided.
6. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 5 in which a test link is connected to the secondary of the auxiliary transformer linking the core of the
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Appliance earth leakage tester The present invention relates to apparatus for testing the earth leakage currents in electrical appliances. It is the common practice in domestic, commercial and industrial premises, to protect both personnel and equipment against the effects of excessive earth leakage currents. This is generally done by including an earth leakage circuit breaker which disconnects the supply in the event of the arithmetic sum of the earth leakage currents in all equipment fed from the earth leakage circuit breaker exceeding the current necessary to operate the circuit breaker mechanism. It is, therefore, useful to be able to check the earth leakage current on individual electrical appliances. According to the present invention, there is provided apparatus for testing for earth leakages in electrical appliances comprising a core balance current transformer having a core adapted to be disposed around supply lines to the appliance under test, a rectifier and amplifier unit adapted to receive signals from the transformer at its input and to provide a rectified and amplified signal at its output and a display means adapted to display the output signal so produced. In order that the present invention may be more clearly understood, one embodiment thereof will now be described by way of example with reference to the accompanying drawings, in which Figure 1 shows a circuit diagram in partial block form of testing apparatus, and Figure 2 shows a detailed circuit diagram of a block forming part of the circuit of Figure 1. Referring to Figure 1 , the testing apparatus is a portable hand-held unit comprising circuitry disposed in a housing (diagrammatically indicated by dotted line H). A supply cable terminating in a three pin plug 1 leads out of the housing and a complementary three pin socket 2 is disposed in the housing. Live, neutral and earth conductors extend between the plug 1 and the socket 2. The earth conductor is earthed to the unit and the live and neutral conductors extend through the centre of a toroidal transformer forming the primary of a core balance current transformer 3. This transformer 3 has two secondary windings 30 and 31. Secondary winding 30 is connected to the input side of a precision amplifier and rectifier unit 4. Secondary winding 31 forms part of a test link 10 which also comprises a resistor 9 and pushbutton 8.This test link 10 is supplied from the secondary winding of an auxiliary supply transformer 6. The primary winding of this transformer 6 is connected through a fuse 7 across the live and neutral conductors. A probe 11 is also connected to the secondary winding of the transformer 6 through an indicator lamp 12. The purpose of the probe 11 will be described later. Referring now to Figure 2, the amplifier/rectifier 4 comprises three operational amplifiers 50, 51 and 52. Amplifier 50 has two inputs 53 and 54. The secondary winding 30 of the transformer 3 acts as a detection coil which is connected across the inputs 53 and 54. A potential representing the earth leakage current on the balance core current transformer 3 which is detected by the winding 30 is therefore fed to the amplifier 50. This potential is amplified by the amplifiers 50, 51 and 52 and the amplified signal is displayed by the meter 5. Variable resistors 56 and 57 are connected to the operational amplifier 52 to enable the amplifier/rectifier to be calibrated and zero adjusted. In operation of the apparatus, an appliance to be tested is plugged into the socket 2 and the plug 1 is plugged into the mains supply. The probe 11 is placed in contact with any earth part of the appliance in order to ensure that the earth connection in the plug of the appliance under test is correctly connected to the earth on the appliance itself. If the earth connection is correct, the lamp 12 will illuminate but not otherwise. Any earth leakage current flowing in the appliance will also flow through the conductors extending through the toroidal core of the transformer 3. Any earth leakage present will be indicated by a reading on the meter 5. It will be appreciated that the above embodiment has been described by way of example only and that many variations are possible without departing from the scope of the invention. CLAIMS
1. Apparatus for testing for earth leakages in electrical appliances comprising a core balance current transformer having a core adapted to be disposed around supply lines to the appliance under test, a rectifier and amplifier unit adapted to receive signals from the transformer at its input and to provide a rectified and amplified signal at its output and a display means adapted to display the output signal so produced.
2. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 1, in which the rectifier and amplifier unit comprises operational amplifier means.
3. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 2, in which the secondary of the transformer is connected to the input of the operational amplifier means.
4. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 2 or 3, in which variable resistors are connected to the operational amplifier means to provide for zero adjustment and calibration.
5. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 4, in which an auxiliary supply transformer is provided.
6. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 5 in which a test link is connected to the secondary of the auxiliary transformer linking the core of the balance current transformer and incorporating a switch and lamp whereby to create on closure of the switch out of balance conditions in the current transformer.
7. Apparatus for testing for earth leakages in electrical appliances as claimed in Claim 5 or 6, in which an earth probe is connected through a lamp to the secondary of the auxiliary supply transformer.
8. Apparatus for testing for earth leakages in electrical appliances as claimed in any preceding claim comprising a housing incorporating a socket for connection to the appliance under test, a plug input for connection to the supply and lines electrically connecting the plug and socket extending through the core the earth connection of the plug and socket being electrically connected to the housing.
9. Apparatus for testing for earth leakages in electrical appliances as claimed in any preceding claim, in which the display means comprises a meter.
10. Apparatus for testing for earth leakages in electrical appliances substantially as hereinbefore described with reference to the accompanying drawings.
GB8006193A 1980-02-23 1980-02-23 Appliance earth leakage tester Withdrawn GB2072860A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8006193A GB2072860A (en) 1980-02-23 1980-02-23 Appliance earth leakage tester

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8006193A GB2072860A (en) 1980-02-23 1980-02-23 Appliance earth leakage tester

Publications (1)

Publication Number Publication Date
GB2072860A true GB2072860A (en) 1981-10-07

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB8006193A Withdrawn GB2072860A (en) 1980-02-23 1980-02-23 Appliance earth leakage tester

Country Status (1)

Country Link
GB (1) GB2072860A (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2164756A (en) * 1984-09-20 1986-03-26 John Slevin Multi-purpose earth-leakage current detector and recorder
GB2242278A (en) * 1990-03-21 1991-09-25 John Slevin Fuse-rating tester
GB2277381A (en) * 1993-04-20 1994-10-26 Jekyll Electronic Technology L Portable appliance testers
EP0636893A2 (en) * 1993-07-30 1995-02-01 Cesare Gallone Circuit device for visually signalling leakage currents from an electric system to earth
WO2005091002A1 (en) * 2004-03-19 2005-09-29 Global Spill Control Pty. Limited Electrical monitoring device
CN108828371A (en) * 2018-07-23 2018-11-16 山东省计量科学研究院 Household electric appliance safety is test bed

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2164756A (en) * 1984-09-20 1986-03-26 John Slevin Multi-purpose earth-leakage current detector and recorder
GB2242278A (en) * 1990-03-21 1991-09-25 John Slevin Fuse-rating tester
GB2277381A (en) * 1993-04-20 1994-10-26 Jekyll Electronic Technology L Portable appliance testers
EP0636893A2 (en) * 1993-07-30 1995-02-01 Cesare Gallone Circuit device for visually signalling leakage currents from an electric system to earth
EP0636893A3 (en) * 1993-07-30 1995-03-29 Cesare Gallone Circuit device for visually signalling leakage currents from an electric system to earth.
WO2005091002A1 (en) * 2004-03-19 2005-09-29 Global Spill Control Pty. Limited Electrical monitoring device
CN108828371A (en) * 2018-07-23 2018-11-16 山东省计量科学研究院 Household electric appliance safety is test bed

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)