GB2128047A - Earth leakage monitor and earth proving apparatus - Google Patents
Earth leakage monitor and earth proving apparatus Download PDFInfo
- Publication number
- GB2128047A GB2128047A GB08326399A GB8326399A GB2128047A GB 2128047 A GB2128047 A GB 2128047A GB 08326399 A GB08326399 A GB 08326399A GB 8326399 A GB8326399 A GB 8326399A GB 2128047 A GB2128047 A GB 2128047A
- Authority
- GB
- United Kingdom
- Prior art keywords
- earth
- transformer
- input
- circuit
- winding
- 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.)
- Granted
Links
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
- H02H3/26—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
- H02H3/338—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 also responsive to wiring error, e.g. loss of neutral, break
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
- H02H5/10—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to mechanical injury, e.g. rupture of line, breakage of earth connection
- H02H5/105—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to mechanical injury, e.g. rupture of line, breakage of earth connection responsive to deterioration or interruption of earth connection
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Emergency Protection Circuit Devices (AREA)
- Breakers (AREA)
Abstract
Earth leakage and earth continuity monitoring apparatus comprises a transformer 48 responsive to current imbalance in supply conductors owing to earth leakage fault current and operable to trip a circuit-breaker 42 when the earth leakage current exceeds a predetermined value. The circuit-breaker is also trippable in response to magnetic flux imbalance in reference 52 and monitor 54 windings of the same or an additional transformer owing to increase above a predetermined value in the impedance of an earth loop including the earth loop conductors 28, 30 connecting the apparatus to an appliance. Risk to personnel is minimised under a very wide range of electrical fault conditions. <IMAGE>
Description
SPECIFICATION
Earth leakage monitor & earth proving apparatus
Earth leakage monitor & earth proving apparatus
The invention relates to earth leakage monitor and earth proving apparatus.
Earth proving is widely used and examples of apparatus for that purpose are described and claimed in British patent specifications Nos. 727966 and 923308. In those examples, the impedance of the earth circuit directly determines the magnitude of a current which circulates through the earth circuit and through the trip coil of the circuit-breaker, which is operable to open the main circuit contacts.
It is the object of the present invention to provide earth proving apparatus in which magnetic fluxes dependent respectively on current flowing through an earth loop and a reference current are mutually opposed, a difference between the fluxes due to increase of the earth loop impedance causing the circuit-breaker to open.
Earth leakage monitor and earth proving apparatus, according to the invention, comprises earth loop terminals, a circuit-breaker having input and output terminals and operable to connect and disconnect the input and output terminals, a first transformer means comprising an output winding in a circuit energisable to operate the circuit-breaker and comprising an input reference winding and an input monitor winding arranged to produce opposed fluxes and comprising further input windings in series with the outlet terminals, second transformer means having input winding means connected to input terminals of the circuit-breaker and having output winding means which is isolated from the input winding means and which is arranged to supply currents to the input windings of the first transformer means, the earth loop terminals being in series with the input monitor winding of the first transformer means and with the output winding means of the second transformer means, the apparatus being operable to supply electric current to an electrical appliance having input terminals connected by supply conductors in a cable means to said output terminals of the apparatus and having a conductive casing at least part of which is connected by earth loop conductors in said cable means between said earth loop terminals, and said first transformer means being responsive to current imbalance in said further input windings thereof owing to the occurrence of earth leakage fault current at said appliance or cable means above a predetermined level to energise said output winding to operate said circuitbreaker and said apparatus comprising two circuit loops formed each partly by said output winding means and respectively including said input reference winding and said input monitor winding and said loops having effective impedance values such that said circuitbreaker is also energised in response to imbalance in the fluxes produced by an increase above a predetermined value in the impedance of the earth loop comprising said earth loop conductors and at least said part of said appliance casing.
The first transformer means is preferably a single core-balance transformer.
Alternatively, the first transformer means comprises a first transformer having the output winding and the input reference and monitor windings and a second transformer is provided which has said further input windings and which has an output winding which is in a circuit energisable to operate the circuit-breaker.
Earth leakage monitor and proving apparatus will now be described by way of example to illustrate the invention with reference to the accompanying drawing, which is a schematic circuit diagram of the apparatus.
The drawing shows earth leakage monitor and earth proving apparatus 10 connected to an appliance 12 which, for example, may be a portable tool such as an electric drill.
The apparatus 10 includes a conductive metal casing 14 and the appliance 12 includes a conductive metal housing 16.
The casing 14 has an electrical socket outlet engaged by a plug both being indicated schematically at 20, including respective socket contacts for three phases and a neutral and two socket contacts 24 for an earth loop.
The appliance 12 is connected to a cable 22 which includes three phase conductors and a neutral conductor and two earth loop conductors 28,30. The conductors 28, 30 are connected to the appliance housing 16 at respective points 27,29 which are spaced apart so that part of the housing 16 is included in the earth loop.
The cable 22 is connected to the plug mentioned above and the plug includes respective plug contacts connected to the phase and neutral conductors and two plug contacts 26 connected to the earth loop conductors 28, 30 and engaged with the socket contacts 24.
The apparatus 10 is supplied from a source (not shown) of threephase alternating voltage which is connected to input terminals 18 of a circuit-breaker described below. In addition, a main earth 31 at the source is connected by a main earth conductor 32, which passes into the casing 14, to one of the socket contacts 24. The main earth conductor 32 is connected to the casing 14 at 34. The source main earth 31 is also connected by an auxiliary earth conductor 36, which passes into the casing 14, to the other socket contact 24 via further circuitry described below, the auxiliary earth conductor 36 also being connected to the main earth conductor 32 within the casing by a removable link 38.
The circuit-breaker includes output terminals 40 connected to respective socket contacts of the socket outlet indicated at 20 and movable contacts 42 connected to the input terminals 18. The contacts 42 are manually operable and the circuit-breaker includes a trip coil 44 which, when energised, releases toggle mechanism (not shown) to ailow springs (not shown) to open the contacts 42.
The trip coil 44 is in series with an output winding 46 on a toroidal core of a first transformer 48. The transformer 48 is a corebalance current transformer having phase and neutral input windings 50 interconnecting fixed contacts engageable by the movable contacts 42 and the respective output terminals 40. The windings 50 are arranged to produce equal, opposed fluxes so long as the vector sum of the currents in the phase and neutral lines is zero.
The transformer 48 also has two further input windings 52 and 54 arranged to produce opposed fluxes, the winding 52 being an input reference winding and the winding 54 being an input monitor winding.
The casing 14 also contains a second transformer 56, which has a high-voltage input winding 58 connected between two phases at the input terminals 18 of the circuit-breaker (or alternatively between one such phase terminal and the neutral terminal). The input winding 58 is isolated from the low-voltage output winding 60 by screening and insulation 62 and the output winding 60 is arranged to supply separate currents to the input windings 52 and 54 of the first transformer 48. The windings 52 and 54 are supplied via respective resistors 64 and 66 and the latter resistor is in series with the link 38, one socket contact 24 and one plug contact 26, the earth loop made up of the conductor 30, the appliance housing 16 and the conductor 28, the other plug contact 26 and the other socket contact 24, the input winding 54 and the output winding 60.
A varistor 70 is connected within the casing 14 across the earth loop circuit between one socket contact 24 and the resistor 66 and the other socket contact 24 and the link 38.
Operation
Provided that earth leakage is below a predetermined level and the earth loop including the conductors 28 and 30 is completely intact (that is its impedance is below a predetermined value) and assuming the main earth is intact, the currents in the windings 52 and 54 produce equal, opposite fluxes, the resitors 64 and 66 being chosen to give suitable values for those currents. The current circulating through the winding 46 and the trip coil 44 is zero or is insufficient to energisethe latterto initiate operation of the circuit-breaker to open the contacts 42.
So long as those conditions appertain the contacts 42 may be manually opened and closed.
An increase in earth leakage current above the predetermined level causes an unbalance in the currents flowing through the input windings 50 of the transformer 48. If the unbalance is greater than a predetermined amount, the resulting flux in the core of the transformer 48 produces current in the coil 46 to energise the trip coil 44 and causes the contacts 42 to open, disconnecting the appliance 12 from the voltage source.
Should a real or apparent increase above a predetermined value occur in the impedance of the earth loop, including the conductors 28,30, the current in the winding 54 is reduced relative to the current in the reference winding 52 thus upsetting the normal balance between the opposed fluxes produced by the two windings. The resultant flux induces current in the winding 46 and in the coil 44 so that the circuit-breaker is tripped and the contacts 42 open. As the circuit-breaker trip coil is energised directly by the windings 52, 54, the response time is limited only by the circuit-breaker operating time.
The circuit-breaker operating times are generally less than 30 milliseconds and are typically of the order of 10 milliseconds.
Should similar conditions arise while the contacts 42 are open, the apparatus will prevent closure of the contacts 42.
An apparant increase in the impedance of the earth loop can be caused by an increase in the potential of the appliance casing 16 above the potential of the main earth conductor 32 at 34 resulting from earth leakage.
If the link 38 is removed, the impedance of the main earth conductor 32 is connected in series with the resistor 66 by the auxiliary earth conductor 36 so that an increase in the impedance of the main earth conductor 32 above a pre-determined value causes the circuit-breaker to open the contacts 42.
Where the normal impedance of the loop formed by the main earth conductor 32 and the auxiliary earth conductor 36 is relatively high, an impedance-conversion transformer (not shown) may be connected in place of the link 38. That transformer may be an auto-transformer or a double-wound transformer so that an increase in the impedance of the loop formed by the main earth conductor 32 and the auxiliary earth conductor 36 is converted to a similar percentage increase in the lower apparent impedance presented by the transformer in series with the resistor 66.
The varistor 70 has parameters which ensure that if a fault in the connection between the appliance casing 16 and the main earth conductor 32 at 34 should result in a high impedance or open circuit condition in the connections, a low impedance earth connection will be maintained via the conductor 28 and the varistor 70 which limits the potential appearing at the appliance casing 16 under severe earth fault conditions.
Under normal fault-free conditions, the varistor 70 does not conduct significant current and does not affect the earth proving function.
A particular advantage provided by the invention is that earth proving can be readily combined with earth leakage monitoring in a way which was not possible with the known earth proving apparatus referred to above.
The current circulating through the winding 46 and the trip coil 44 is the resultant current generated by the vectorial summation of the fluxes produced by any phase-to-earth leakage currents present and the monitor and reference currents.
Where a single phase source only is supplied to the appliance via the apparatus, the phasing of the connections may be arranged so that the flux produced by any earth leakage currents and the resultant flux produced by any unbalance in the currents in windings 52 and 54 owing to the earth loop impedance are cumulative. Therefore, there will be an interaction between the level of earth leakage current and the value of earth loop impedance at which operation of the circuit-breaker will be initiated. As earth leakage current rises, the value of earth loop impedance which will cause operation of the circuit-breaker will fall linearly, and vice-versa.If the phasing of the connections (either by connection or by phase shift components, typically capacitance connected in series with the second transformer input winding) is arranged so that the fluxes are substractive, the resultant interaction will be modified. In that instance, the interaction is such that, as the earth loop impedance increases, the level of earth leakage current necessary to operate the circuit-breaker will also increase. However, owing to the effect of the varistor 70, the level of earth leakage current necessary to operate the circuit-breaker does not increase in a linear manner but reaches a threshold value at which any further increase results in operation of the circuit-breaker.Similarly, as earth leakage current increases, the value of earth loop impedance at which operation of the circuit-breaker occurs will rise but again a threshold value will be reached beyond which any further increase operates the circuit-breaker. When three phase leakage currents are present similar intermediate characteristics result. However, in all instances, operation of the circuit-breaker will always be initiated before unsafe conditions develop.
The preferred forms of apparatus such as shown in the drawing, for example, in which earth leakage and earth integrity are both monitored are of especial value in reducing the danger from earth leakage to which personnel using appliances are exposed. The advantages afforded by those forms of the invention as compared with known apparatus are discussed below.
A low-level shock may not cause injury or death, but reaction and its consequences can endanger personnel, especially in industrial environments, for example in proximity to moving machinery or at a height.
The degree of protection from shock given to personnel by earth leakage circuit-breakers under fault conditions depends on the extent to which exposed metalwork of fixed installations or appliances is solidly bonded either to a local earth or to an earth supplied by the electricity supply authority. In either case, if the earth connection is defective owing either to a broken connection or to earth loop impedance above a safe value, then the degree of protection will be reduced and the level of shock experienced by personnel will be increased.
This is of particular importance where flexible cables are used to supply electric power to portable hand tools, tranportable appliances, caravans and cabins.
Such cables are vulnerable to damage and/orfailure.
Where damage to a cable connecting an earth leakage circuit-breaker to any appliance causes earthing of the neutral conductor, another return path to the supply source of similar or lower impedance than the return ground path is created.
This parallel path allows a portion of any earth leakage current to flow back to the source via the neutral conductor through the current balance transformer. That portion is therefor not detected as earth leakage current. The result is that a large earth leakage current could flow without tripping the circuit-breaker, so increasing the danger of shock to personnel.
Earth-proving units used as the sole form of protection give a high degree of protection to personnel by ensuring that power is only supplied to an appliance which is well earthed. If, however, the energising or tripping supply used in the unit is lost, the degree of protection is reduced to zero. This can occur if the neutral conductor in a single-phase system sustains an open-circuit. Also, since such units rely on a closed loop for the detection circuit, it is possible that cable damage could occur which breaks the earth connnection to the appliance yet leaves the loop intact. Where removable inspection or maintenance covers are fitted to appliances, it is possible that access by personnel to live conductors could be made with the consequent danger of electrical shock.In all these cases the degree of protection given to personnel from electrical shock will be zero as the assocated circuit-breaker will not be operated to open the isolating contacts. The provision of both earth monitoring and earth leakage protection ensures that the duration of any such shocks occurring in those circumstances will be minimised.
In a modification (not shown) the core 48 is not threaded by the windings 50 and a second core balance transformer having a toroidal core is provided having those windings and having also a detector winding, similar to the winding 46, in series with another trip coil similar to the coil 44 arranged to trip the contacts 42 in the event of earth leakage above a predetermined value.
Other modifications (not shown) are possible within the scope of the invention. For example, the windings 52 and 54 can be parts of the same winding, which has a centre tap, instead of being separate windings. Instead of a single transformer 56, the second transformer means can comprise two similar transformers, one supplying the input reference winding 52 and the other supplying the input monitor winding 54. In that instance, in a multi-phase system the respective input windings of the two transformers are preferably connected to the input terminals across different phase combinations whereby the loss of a phase causes imbalance of the windings 52 and 54 and consequent tripping of the circuit-breaker. The casing 14 may be of plastics material instead of metal. The cable 22 may be in a metal conduit, in which instance the conduit can act as one of the earth loop conductors 28,30. The socket outlet and plug can be omitted, the phase conductors and the earth loop conductors being connected to the terminals 40 and to corresponding earth loop terminals within the casing 14, respectively.
Claims (9)
1. Earth leakage monitor and earth proving apparatus comprising earth loop terminals, a circuit-breaker having input and output terminals and operable to connect and disconnect the input and output terminals, a first transformer means comprising an output winding in a circuit energisable to operate the circuit-breaker and comprising an input reference winding and an input monitor winding arranged to produced opposed fluxes, and comprising further input windings in series with the outlet terminals, second transformer means having input winding means connected to the input terminals of the circuit-breaker and output winding means which is isolated from the input winding means and which is arranged to supply currents to the input windings of the first transformer means, the earth loop terminals being in series with the input monitor winding ofthefirst transformer means and with the output winding means of the second transformer means the apparatus being operable to supply electric current to an electrical appliance having input terminals connected by supply conductors in a cable means to said output terminals of the apparatus and having a conductive casing at least part of which is connected by earth loop conductors in said cable means between said earth loop terminals, and said first transformer means being responsive to current imbalance in said further input windings thereof owing to the occurrence of earth leakage fault current at said appliance or cable means above a predetermined level to energise said output winding to operate said circuit-breaker, and said apparatus comprising two circuit loops formed each partly by said output winding means and respectively including said input reference winding and said input monitor winding and said loops having effective impedance values such that said circuit-breaker is also energised in response to imbalance in the fluxes produced by an increase above a predetermined value in the impedance of the earth loop comprising said earth loop conductors and at least said part of said appliance casing.
2. Apparatus according to claim 1, in which said first transformer means is a core-balance transformer.
3. Apparatus according to claim 1, in which said first transformer means comprises a first transformer having said output winding and said input reference and monitorwindings and a second transformer which has said further input windings and which has an output winding which is in a circuit energisable to operate the circuit-breaker.
4. Apparatus according to any preceding claim, in which a varistor is connected across the earth loop terminals.
5. Apparatus according to any preceding claim, in which a main earth conductor is connected to one of the earth loop terminals and in which an auxiliary earth conductor is connected to said output winding means and a removable link connects the two earth conductors.
6. Apparatus according to claim 5, in which the removable link is removed and replaced by an impedance conversion transformer.
7. Apparatus according to claim 6, in which the impedance conversion transformer is an auto-transformer.
8. Apparatus according to claim 6, in which the impedance conversion transformer is a double-wound transformer.
9. Apparatus according to claim 1 substantially as herein described with reference to the accompanying drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08326399A GB2128047B (en) | 1982-10-05 | 1983-10-03 | Earth leakage monitor & earth proving apparatus |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8228452 | 1982-10-05 | ||
| GB08326399A GB2128047B (en) | 1982-10-05 | 1983-10-03 | Earth leakage monitor & earth proving apparatus |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8326399D0 GB8326399D0 (en) | 1983-11-02 |
| GB2128047A true GB2128047A (en) | 1984-04-18 |
| GB2128047B GB2128047B (en) | 1986-10-08 |
Family
ID=26284043
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08326399A Expired GB2128047B (en) | 1982-10-05 | 1983-10-03 | Earth leakage monitor & earth proving apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2128047B (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2150374A (en) * | 1983-12-08 | 1985-06-26 | Ashley Accessories Ltd | Fault detection circuitry |
| FR2568425A1 (en) * | 1984-07-30 | 1986-01-31 | Technology Res Corp | CURRENT CIRCUIT IN THE EVENT OF A GROUND FAULT, WITH PROTECTION AGAINST INTERRUPTION OF NEUTRAL AND EARTH CONDUCTORS. |
| EP0210060A2 (en) * | 1985-07-19 | 1987-01-28 | Mk Electric Limited | Power supply apparatus |
| FR2669159A1 (en) * | 1990-11-09 | 1992-05-15 | Barthelemy Louis | SECURITY DEVICE PROCESSING INFORMATION, GIVEN BY THE CONTACT POTENTIAL, ASSOCIATED WITH A SWITCHING OFFICE. |
| GB2251992A (en) * | 1991-01-17 | 1992-07-22 | Shakira Ltd | Missing earth or neutral mains monitor |
| WO1999001773A1 (en) * | 1997-07-04 | 1999-01-14 | Liaisons Electroniques-Mecaniques Lem S.A. | Electric current pick-up shoe |
| WO2011083029A1 (en) | 2009-12-17 | 2011-07-14 | Prüftech GmbH | Self-monitoring connection line and operating equipment |
| DE102017004018A1 (en) | 2017-04-26 | 2018-10-31 | Dirk Lehrling | Electrical connector |
Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB240574A (en) * | 1924-07-14 | 1925-10-08 | Ehret Ernest Grover | A safety device for use with portable electrically operated machines |
| GB246893A (en) * | 1924-10-03 | 1926-02-03 | Reyrolle A & Co Ltd | Improvements in or relating to protective arrangements for alternating current electric circuits |
| GB343667A (en) * | 1929-12-28 | 1931-02-26 | Reginald William Mann | Improvements in or relating to control systems for electrical apparatus such as motors |
| GB391290A (en) * | 1932-02-27 | 1933-04-27 | Electrical Apparatus Co Ltd | Improvements relating to electrical switch gear |
| GB549679A (en) * | 1941-05-26 | 1942-12-02 | Reyrolle A & Co Ltd | Improvements in or relating to control and protective systems for electrical apparatus |
| GB551090A (en) * | 1941-09-19 | 1943-02-08 | Robert Ironside Bagnall | Improvements in electric cut-out or protective systems with automatic circuit breakers |
| GB649929A (en) * | 1947-03-14 | 1951-02-07 | Merlin Gerin | Improvements in remote control electric circuits |
| GB747696A (en) * | 1952-11-12 | 1956-04-11 | Merlin And Gerin Ets | Improvements in and relating to the protection of high-tension cables |
| GB830018A (en) * | 1957-03-13 | 1960-03-09 | Michael Cornelius Gerrard | Protective device for electrical circuits and apparatus |
| GB2072443A (en) * | 1980-02-23 | 1981-09-30 | Redsure Elp Ltd | An earth fault detector |
-
1983
- 1983-10-03 GB GB08326399A patent/GB2128047B/en not_active Expired
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB240574A (en) * | 1924-07-14 | 1925-10-08 | Ehret Ernest Grover | A safety device for use with portable electrically operated machines |
| GB246893A (en) * | 1924-10-03 | 1926-02-03 | Reyrolle A & Co Ltd | Improvements in or relating to protective arrangements for alternating current electric circuits |
| GB343667A (en) * | 1929-12-28 | 1931-02-26 | Reginald William Mann | Improvements in or relating to control systems for electrical apparatus such as motors |
| GB391290A (en) * | 1932-02-27 | 1933-04-27 | Electrical Apparatus Co Ltd | Improvements relating to electrical switch gear |
| GB549679A (en) * | 1941-05-26 | 1942-12-02 | Reyrolle A & Co Ltd | Improvements in or relating to control and protective systems for electrical apparatus |
| GB551090A (en) * | 1941-09-19 | 1943-02-08 | Robert Ironside Bagnall | Improvements in electric cut-out or protective systems with automatic circuit breakers |
| GB649929A (en) * | 1947-03-14 | 1951-02-07 | Merlin Gerin | Improvements in remote control electric circuits |
| GB747696A (en) * | 1952-11-12 | 1956-04-11 | Merlin And Gerin Ets | Improvements in and relating to the protection of high-tension cables |
| GB830018A (en) * | 1957-03-13 | 1960-03-09 | Michael Cornelius Gerrard | Protective device for electrical circuits and apparatus |
| GB2072443A (en) * | 1980-02-23 | 1981-09-30 | Redsure Elp Ltd | An earth fault detector |
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2150374A (en) * | 1983-12-08 | 1985-06-26 | Ashley Accessories Ltd | Fault detection circuitry |
| FR2568425A1 (en) * | 1984-07-30 | 1986-01-31 | Technology Res Corp | CURRENT CIRCUIT IN THE EVENT OF A GROUND FAULT, WITH PROTECTION AGAINST INTERRUPTION OF NEUTRAL AND EARTH CONDUCTORS. |
| EP0210060A2 (en) * | 1985-07-19 | 1987-01-28 | Mk Electric Limited | Power supply apparatus |
| GB2177859A (en) * | 1985-07-19 | 1987-01-28 | Mk Electric Ltd | Power supply apparatus |
| EP0210060A3 (en) * | 1985-07-19 | 1988-09-28 | Mk Electric Limited | Power supply apparatus |
| GB2177859B (en) * | 1985-07-19 | 1989-07-26 | Mk Electric Ltd | Protection apparatus for use in a power supply circuit |
| FR2669159A1 (en) * | 1990-11-09 | 1992-05-15 | Barthelemy Louis | SECURITY DEVICE PROCESSING INFORMATION, GIVEN BY THE CONTACT POTENTIAL, ASSOCIATED WITH A SWITCHING OFFICE. |
| WO1992009129A1 (en) * | 1990-11-09 | 1992-05-29 | Louis Barthelemy | Device for processing data provided by the contact potential, and cutoff device linked thereto |
| GB2251992A (en) * | 1991-01-17 | 1992-07-22 | Shakira Ltd | Missing earth or neutral mains monitor |
| GB2251992B (en) * | 1991-01-17 | 1994-04-06 | Shakira Ltd | A C mains monitoring circuit |
| WO1999001773A1 (en) * | 1997-07-04 | 1999-01-14 | Liaisons Electroniques-Mecaniques Lem S.A. | Electric current pick-up shoe |
| US6323636B1 (en) | 1997-07-04 | 2001-11-27 | Liaisons Electroniques-Mecaniques Lem S.A. | Electric current pick-up shoe |
| WO2011083029A1 (en) | 2009-12-17 | 2011-07-14 | Prüftech GmbH | Self-monitoring connection line and operating equipment |
| US9470730B2 (en) | 2009-12-17 | 2016-10-18 | Pruftech Gmbh | Self-monitoring power supply cord and operating equipment |
| DE102017004018A1 (en) | 2017-04-26 | 2018-10-31 | Dirk Lehrling | Electrical connector |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2128047B (en) | 1986-10-08 |
| GB8326399D0 (en) | 1983-11-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2623718C (en) | A ground-fault circuit-interrupter system for three-phase electrical power systems | |
| EP0762591B1 (en) | Electrical system with arc protection | |
| Bridger | High-resistance grounding | |
| US3558980A (en) | Automatic ground fault circuit interrupter | |
| EP0890210B1 (en) | Safety adapter for ungrounded electrical socket | |
| Paul et al. | Low-voltage shore connection power systems: Optional designs and a safety loop circuit | |
| US4634981A (en) | Method for testing a circuit breaker using a three terminal current transformer | |
| GB2128047A (en) | Earth leakage monitor and earth proving apparatus | |
| Shipp et al. | Characteristics of different power systems grounding techniques: Fact and fiction | |
| US3612951A (en) | Safety device for use with electric installations | |
| US3492533A (en) | Ground fault detection for power distribution system | |
| US3308346A (en) | Ground cable continuity check circuit | |
| Fulchiron | Protection of MV/LV substation transformers | |
| US2162516A (en) | Automatic network protector | |
| US3005932A (en) | Protective circuits | |
| US11705713B1 (en) | Network primary feeder self protected transient limiting device | |
| US3544985A (en) | Voltage-indicating device for a switch bushing stud | |
| Cook et al. | SDG&E Relay Standards–Updating Tertiary Bus and Reactor Protection | |
| Sattari et al. | High-Resistance Grounding Design for Industrial Facilities: Providing Continuity of Service in Complex Distribution Systems | |
| US2027189A (en) | Control and protection of electric circuits | |
| Love | Ground fault protection for electric utility generating station medium voltage auxiliary power systems | |
| Love | Ground fault protection for electric utility generating station 480-volt auxiliary power systems | |
| SU1473000A1 (en) | Ground fault current limiter in ship power system | |
| RU2007006C1 (en) | Device for protection of transformer connected to power line via isolating switch | |
| US1969542A (en) | Electrical distribution system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19961003 |