GB2072441A - Apparatus for monitoring electrical earth leakage currents - Google Patents
Apparatus for monitoring electrical earth leakage currents Download PDFInfo
- Publication number
- GB2072441A GB2072441A GB8006195A GB8006195A GB2072441A GB 2072441 A GB2072441 A GB 2072441A GB 8006195 A GB8006195 A GB 8006195A GB 8006195 A GB8006195 A GB 8006195A GB 2072441 A GB2072441 A GB 2072441A
- Authority
- GB
- United Kingdom
- Prior art keywords
- earth leakage
- leakage current
- monitoring
- electrical earth
- circuit
- 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- Withdrawn
Links
- 238000012544 monitoring process Methods 0.000 title claims abstract description 19
- 238000004804 winding Methods 0.000 claims description 7
- 230000000007 visual effect Effects 0.000 claims description 4
- 230000006866 deterioration Effects 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 4
- 238000009413 insulation Methods 0.000 description 3
- 230000007935 neutral effect Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 239000004020 conductor Substances 0.000 description 2
- 230000002542 deteriorative effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 206010014405 Electrocution Diseases 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 235000013611 frozen food Nutrition 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/04—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
- H02H3/33—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
- H02H3/33—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
- H02H3/334—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers with means to produce an artificial imbalance for other protection or monitoring reasons or remote control
- H02H3/335—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers with means to produce an artificial imbalance for other protection or monitoring reasons or remote control the main function being self testing of the device
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Emergency Protection Circuit Devices (AREA)
Abstract
A supply protected by an earth leakage circuit breaker 2 is provided with a further current transformer-based earth leakage detector 3 downstream of the breaker 2 which feeds a monitoring circuit comprising an amplifier and rectifier circuit 9 which is connected to a meter drive circuit. A meter M measures the earth leakage current and alarm circuitry 16, 17 is activated by a relay R connected to the meter drive circuit when a preset leakage current level is reached. In this way early warning of deterioration leading eventually to circuit breaker operation can be given. <IMAGE>
Description
SPECIFICATION
Apparatus for monitoring electrical earth leakage currents
The present invention relates to apparatus for monitoring electrical earth leakage currents.
Earth leakage currents exist due to the imperfections of electrical insulation between live connections and earth. They are normally of very small magnitude and do no harm.
However, should insulation deteriorate, due to age, dampness or other causes, the leakage currents to earth may rise to high magnitudes.
This is an undesirable condition since, when such leakage currents exist, considerable heat may be generated thus causing a fire hazard.
In addition, if the insulation is allowed to deteriorate seriously it may break down completely in the form of a flash over thus considerably increasing the risk of fire and damage to property and apparatus. Also, should the leakage occur to exposed metalwork that is only or mainly earthed by means of an earth conductor and this earth conductor becomes damaged or broken the metalwork will become live and this may give rise to electrocution of any person touching it. For these reasons it is common practice to make use of an earth leakage circuit breaker (E.L.C.B.) in the supply of electrical power to electrical apparatus. This device will monitor the magnitude of earth leakage currents and will rapidly disconnect the supply should the leakage current exceed a certain pre-set level.
Unfortunately it is not always desirable to suddenly remove the electrical supply to a piece of apparatus. For example, in the case of a large frozen room such as one used for the storage of foodstuffs or a lift used for transporting people, the sudden removal of the supply may cause great problems. In the first case it may result in the loss of many thousand pounds worth of frozen food and in the second case people may be left stranded in the lift.
According to the present invention, there is provided apparatus for monitoring an electrical earth leakage current flowing in the supply line to a piece of AC electrical equipment comprising an earth leakage circuit breaker adapted to be connected in the supply iine, detector means disposed downstream of the circuit breaker, a relay responsive to certain signals produced by the detector means, means for pre-setting the responsive signal level of the relay and means for indicating that the pre-set signal level has been reached.
In order that the 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 is a circuit diagram, partly in block form, of apparatus for monitoring an earth leakage current and
Figure 2 is a detailed circuit diagram of a block forming part of the circuit of Fig. 1.
Referring to the drawings, the apparatus is inserted in the single phase electrical current supply system to electrical equipment (not shown). The input terminals to the apparatus are referenced 1 and the output terminals from the apparatus are referenced 6. The apparatus comprises an earth leakage circuit breaker 2 (to BS 4293 or better), a core balanced current transformer 3 and an electronic amplifer and rectifier circuit 9. This circuit 9 is adapted to receive signals from the transformer 3 via its secondary windings 5.
The circuit breaker 2, which is of course a commonly used device for protecting against the effects of excessive earth leakage current and which may also be used as an isolating switch, comprises a double pole switch 23 and a combined balanced core current transformer 24 and relay 25. An integral test circuit consisting of a push button 26 and resistor 27 is also provided. When the button 26 is pushed the live and neutral of the supply are bridged via the resistor 27 and the circuit breaker should trip out if it is working correctly as an out of balance current will then flow in the neutral.
Referring to Fig. 2, the electronic amplifier and rectifier 9 comprises four operational amplifiers 50, 51, 52 and 53. Amplifier 50 has two inputs respectively referenced 54 and 55.
A potential representing the earth leakage current on the core balanced current transformer secondary winding 5 is received across input 54 and 55. This potential is amplified and rectified by operational amplifiers 50 and 51 and fed to a meter drive circuit comprising operational amplifiers 52 and 53. The meter driven by this circuit is referenced 11. This meter 11, which may give a digital or analogue representation of the magnitude of the leakage current, may be calibrated and zero adjusted by means of two variable resistors 57 and 58. Circuit 9 feeds an alarm relay 12 and the level of earth leakage current detected by the transformer 3 necessary to operate the relay 12 may be set by a variable resistor 21.
A further variable resistor 59 enables the range of earth leakage currents covered to be adjusted. The relay 1 2 has two sets of contacts 1 3 and 14. Contacts 1 3 may be used to switch alarms disposed either locally or remote from the relay 1 2. Contacts 14 control an audible indicator 1 6 and a visual indicator 17. These indicators 16 and 1 7 are fed from the mains supply circuit via an auxiliary supply voltage transformer 1 8. A fuse 1 9 is employed to protect the supply from the effects of a short circuit in the transformer 1 8 and a fuse 20 is used to protect the transformer 1 8 from the effects of short circuits or overloading.A switch 1 5 is provided to enable the audible indicator 1 6 to be isolated should this be required.
A further secondary winding 4 of the transformer 3, a switch 7 and a resistor 8 are provided for a purpose which will be described later. A reset switch 10 is also provided.
The operation of the circuit is as follows.
The value of the earth leakage current which it is felt attention of the monitoring staff should be drawn to is set by means of the variable resistor 21. When this pre-set earth leakage current is reached, an appropriate signal is generated in the secondary winding 5 of the transformer 3 and is used to operate through the electronic amplifier and rectifier 9 the relay 12. On operation of the relay 12, contacts 1 3 and 14 close to operate the audible indicator 1 6 (assuming switch 1 5 is closed), the visual indicator 1 7 and whatever other local and remote alarms are provided.
The relay 1 2 remains in the actuated condition, even if the earth leakage current is subsequently removed, until such time as the reset switch 10 is operated. The reset switch 10 will not reset the relay until the earth leakage current is less than the preset level.
The alarm circuitry may be tested by means of the switch 7 and resistor 8. The test circuit is designed to pass a fixed current having a value set by the values of the output voltage of supply transformer 18, resistor 8 and voltage in secondary winding 4. If switch 7 is closed current flows through the secondary winding 4 and simulates the effect an earth leakage current would have on the core balance transformer 3. If this current is of sufficient magnitude, the alarms will be operated and the meter 11 will indicate a fault thus effectively testing the operation of the circuit.
Thus, by means of the above described circuit earth leakage currents exceeding a certain preset level can be used to actuate an audible and/or visual alarm to draw attention to the deteriorating condition resulting in the earth leakage current. In normal operation, the preset level of earth leakage current will be somewhat lower than the level of current required to operate the earth leakage circuit breaker 2. In this way, advance warning of, for example, slowly deteriorating insulation giving rise to the slowly increasing earth leakage current can be given prior to the circuit breaker operating to discontinue the supply.
Of course, should a serious fault occur resulting in rapid rise of an earth leakage current, the circuit breaker 2 will operate in the normal way. Although a single phase two wire system has been described the invention is equally applicable to three phase three wire or three phase and neutral four wire systems.
Claims (11)
1. Apparatus for monitoring an electrical earth leakage current flowing in the supply line to a piece of AC electrical equipment comprising an earth leakage circuit breaker adapted to be connected in the supply line, detector means disposed downstream of the circuit breaker, a relay responsive to certain signals produced by the detector means, means for pre-setting the responsive signal level of the relay and means for indicating that the pre-set signal level has been reached.
2. Apparatus for monitoring an electrical earth leakage current as claimed in Claim 1, in which the detector means comprises a core balanced current transformer feeding an amplifier and rectifier circuit.
3. Apparatus for monitoring an electrical earth leakage current as claimed in Claim 2, in which the amplifier and rectifier circuit comprises an operational amplifier means whose input is connected to the secondary winding of the current transformer.
4. Apparatus for monitoring an electrical earth leakage current as claimed in Claim 3, in which the amplifier and rectifier circuit is connected to a meter through a meter drive circuit.
5. Apparatus for monitoring an electrical earth leakage current as claimed in Claim 4, in which the meter drive circuit also comprises operational amplifier means.
6. Apparatus for monitoring an electrical earth leakage current as claimed in Claim 5, in which variable resistors are provided connected to the operational amplifier means of the meter drive circuit for calibration and zero adjustment.
7. Apparatus for monitoring an electrical earth leakage current as claimed in Claim 4, 5 or 6, in which the coil of the relay is connected to the meter drive circuit and the relay contacts are disposed in an alarm circuit.
8. Apparatus for monitoring an electrical earth leakage current as claimed in Claim 7, in which there are two sets of relay contacts one to operate alarms in either a local or a remote location and the other to operate both audible and visual alarms.
9. Apparatus for monitoring an electrical earth leakage current as claimed in Claim 7 or 8, in which the relay is provided with a reset switch.
10. Apparatus for monitoring an electrical earth leakage current as claimed in any of claims 2 to 9, in which means are provided for adjusting the earth leakage current that the amplifier and rectifier circuit and the meter drive circuit respond to.
11. Apparatus for monitoring an electrical earth leakage current as claimed in Claim 10, in which the means for adjusting comprises a variable resistor connected to the meter drive circuit.
1 2. Apparatus for monitoring an electrical earth leakage current substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8006195A GB2072441A (en) | 1980-02-23 | 1980-02-23 | Apparatus for monitoring electrical earth leakage currents |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8006195A GB2072441A (en) | 1980-02-23 | 1980-02-23 | Apparatus for monitoring electrical earth leakage currents |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2072441A true GB2072441A (en) | 1981-09-30 |
Family
ID=10511629
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8006195A Withdrawn GB2072441A (en) | 1980-02-23 | 1980-02-23 | Apparatus for monitoring electrical earth leakage currents |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2072441A (en) |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3819529A1 (en) * | 1987-06-09 | 1989-01-05 | Bassani Spa | ELECTRICAL THERMOMAGNET AND DIFFERENTIAL PROTECTIVE DEVICE |
| WO1990007214A1 (en) * | 1988-12-16 | 1990-06-28 | Solar Wide Industrial Ltd | Method and apparatus for protecting electrical systems |
| DE4322845A1 (en) * | 1993-07-08 | 1995-01-12 | Kopp Heinrich Ag | Arrangement for measuring fault currents in load circuits or the like |
| EP0636893A2 (en) * | 1993-07-30 | 1995-02-01 | Cesare Gallone | Circuit device for visually signalling leakage currents from an electric system to earth |
| WO2001050565A1 (en) * | 1999-12-30 | 2001-07-12 | Abb Service S.R.L | An improved electronic earth leakage current device |
| US6882511B1 (en) * | 1999-12-30 | 2005-04-19 | Abb Service S.R.L. | Electronic earth leakage current device |
| AU2005202544B2 (en) * | 1999-12-30 | 2007-05-31 | Abb Schweiz Ag | An improved electronic earth leakage current device |
| CN101860007A (en) * | 2010-04-20 | 2010-10-13 | 山东卓尔电气有限公司 | Remote intelligent residual current monitoring and protection system |
| EP0936716B2 (en) † | 1998-02-11 | 2015-12-30 | Schneider Electric Industries SAS | Differential protection device |
| CN108241103A (en) * | 2018-01-19 | 2018-07-03 | 广东电网有限责任公司茂名供电局 | A kind of low pressure becomes platform electric leakage monitor and alarm system and its alarming method by monitoring |
| EP1734632B1 (en) * | 2005-05-17 | 2018-12-19 | Bticino S.P.A. | Safety device for a circuit breaker |
-
1980
- 1980-02-23 GB GB8006195A patent/GB2072441A/en not_active Withdrawn
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3819529C2 (en) * | 1987-06-09 | 2003-03-13 | Bassani Spa | Electrical thermomagnetic and differential protection device |
| DE3819529A1 (en) * | 1987-06-09 | 1989-01-05 | Bassani Spa | ELECTRICAL THERMOMAGNET AND DIFFERENTIAL PROTECTIVE DEVICE |
| WO1990007214A1 (en) * | 1988-12-16 | 1990-06-28 | Solar Wide Industrial Ltd | Method and apparatus for protecting electrical systems |
| DE4322845A1 (en) * | 1993-07-08 | 1995-01-12 | Kopp Heinrich Ag | Arrangement for measuring fault currents in load circuits or the like |
| 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. |
| EP0936716B2 (en) † | 1998-02-11 | 2015-12-30 | Schneider Electric Industries SAS | Differential protection device |
| WO2001050565A1 (en) * | 1999-12-30 | 2001-07-12 | Abb Service S.R.L | An improved electronic earth leakage current device |
| US6882511B1 (en) * | 1999-12-30 | 2005-04-19 | Abb Service S.R.L. | Electronic earth leakage current device |
| AU2005202544B2 (en) * | 1999-12-30 | 2007-05-31 | Abb Schweiz Ag | An improved electronic earth leakage current device |
| EP1734632B1 (en) * | 2005-05-17 | 2018-12-19 | Bticino S.P.A. | Safety device for a circuit breaker |
| CN101860007A (en) * | 2010-04-20 | 2010-10-13 | 山东卓尔电气有限公司 | Remote intelligent residual current monitoring and protection system |
| CN101860007B (en) * | 2010-04-20 | 2012-08-15 | 山东卓尔电气有限公司 | Remote intelligent residual current monitoring and protection system |
| CN108241103A (en) * | 2018-01-19 | 2018-07-03 | 广东电网有限责任公司茂名供电局 | A kind of low pressure becomes platform electric leakage monitor and alarm system and its alarming method by monitoring |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |