EP0101172B2 - Short circuit fault isolation means for electrical circuit arrangements - Google Patents

Short circuit fault isolation means for electrical circuit arrangements Download PDF

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Publication number
EP0101172B2
EP0101172B2 EP83303841A EP83303841A EP0101172B2 EP 0101172 B2 EP0101172 B2 EP 0101172B2 EP 83303841 A EP83303841 A EP 83303841A EP 83303841 A EP83303841 A EP 83303841A EP 0101172 B2 EP0101172 B2 EP 0101172B2
Authority
EP
European Patent Office
Prior art keywords
isolators
circuit
short circuit
circuit elements
detectors
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.)
Expired - Lifetime
Application number
EP83303841A
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German (de)
English (en)
French (fr)
Other versions
EP0101172A1 (en
EP0101172B1 (en
Inventor
Roger Dennis Payne
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.)
Apollo Fire Detectors Ltd
Original Assignee
Apollo Fire Detectors Ltd
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Filing date
Publication date
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First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=10531742&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=EP0101172(B2) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Application filed by Apollo Fire Detectors Ltd filed Critical Apollo Fire Detectors Ltd
Priority to AT83303841T priority Critical patent/ATE25781T1/de
Publication of EP0101172A1 publication Critical patent/EP0101172A1/en
Application granted granted Critical
Publication of EP0101172B1 publication Critical patent/EP0101172B1/en
Publication of EP0101172B2 publication Critical patent/EP0101172B2/en
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Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/02—Monitoring continuously signalling or alarm systems
    • G08B29/06—Monitoring of the line circuits, e.g. signalling of line faults

Definitions

  • the central control unit of a fire detection system monitoring extensive premises may need to be connected to a large number of fire detectors sited throughout the premises.
  • the central control unit of a fire detection system monitoring extensive premises may need to be connected to a large number of fire detectors sited throughout the premises.
  • precision is usually comprised by directly interconnecting closely associated detectors to form fewer, less localised fire zones and connecting each group of detectors to the control unit as shown schematically in figure 1.
  • the control unit 19 identifies in which zone a fire has been detected but not which detector 21 has responded.
  • the maximum number of detectors 21 grouped together to form a zone is normally restricted to about 25 detectors.
  • the interconnection of a larger number of detectors is not normally practiced, firstly because the greater area monitored by a greater number of detectors reduces to an unacceptable level the precision with which a fire can be located, and secondly because the occurrence of a circuit fault, such as a short circuit, in wiring interconnecting detectors can render all the detectors in that zone inoperative and place an unacceptably large area at risk pending repains, even if the presence of such a fault is indicated at the control unit 19.
  • control unit 20 is able to determine both the status and the precise location of every addressable detector 21 in a fire detection system of the type shown schematically in figure 2 without the need to zone detectors on separate circuits.
  • the elimination of a multiplicity of zone circuits and a simplification of installation wiring are apparent potential benefits of using addressable detectors.
  • the maximum number of addressable detectors connected on one circuit of this type is normally restricted to about 25 detectors because the occurrence of an open and short circuit fault in the wiring can render some or all of the detectors on the circuit inoperative and place an unacceptablly large area at risk pending rapairs. If detectors are interconnected on a wiring loop L, then a single open circuit fault will not render any of the detectors inoperative.
  • the improved reliability afforded by the use of ring circuit may in some circumstances permit a marginal increase in the number of interconnected addressable detectors but the vulnerability of the circuit to a short circuit fault remains a major constraining influence.
  • EP-A-O 042 501 discloses one solution to this problem.
  • a plurality of circuit elements, in thy form of fire detectors are connected in a loop circuit to a bi-directionally supply circuit.
  • the fire detectors are sequentially interrogated in order to send back information to a central station.
  • the interrogation process is interrupted on reaching a faulty fire detector.
  • the interrogation process then proceeds in the reverse direction until the faulty detector is reached once more whereupon the interrogation process again reverse its drection.
  • US-A-3652798 discloses a telecommunication system in which junction switches are provided in loop for detecting the absence of signals on a primary line, due to a fault, and for diverting the signals to a secondary line.
  • the junction switches all operate together to interrupt primary and secondary lines. They then need to be sequentially actuated, by a signal from the junction switch which first detected the absence of the signals so as to restore operation on a reconfigured loop which includes the primary and secondary lines but not the fault.
  • the invention provides an alternative solution as defined in claim 1.
  • FIG. 3 illustrates an embodiment of the invention in the form of a control unit 20 connected to a loop circuit L of detectors in which groups of one or more detectors 21 are separated by devices containing a novel circuit arrangement as disclosed herein and termed bi-directional short circuit isolators (1, 2, 3, 4).
  • Each isolator (1, 2, 3, 4) contains a circuit arrangement (see Figs. 4 and 5 and following description) which normally provides bi-directional low impedance circuit paths for both of the supply wiring circuits forming the loop circuit L such that detectors 21 may receive power and address signals from either end of the loop L and transmit data signals in either direction to the control unit 20.
  • the circuit arrangement also contains sensing means (TR2, D1, D7, of Fig.
  • the short circuit will be detected by sensing means in bi-directional isolators (1, 2, 3, 4) on both sides of the short circuit and the impedance of the isolators adjacent to the short circuit fault will switch to a high state thus isolating the short circuit fault from the detectors 21 and other isolators located between each high impedance isolator and the control unit 20. Only those detectors 21 located between the adjacent bi-directional isolators (e.g. 2 and 3) are rendered inoperative by a short circuit fault, since the detectors 21 will still receive current (via isolator 1) which passes through the lines which connect them on one side to unit 20 (i.e. as far as, but not beyond isolator 2), and (via isolator 4) which passes through the lines which connect them to the other side of unit 20 (i.e. as far as, but not beyond isolator 3).
  • bi-directional short circuit isolators could, with advantage, be connected alternately with detectors such that a short circuit fault of the loop wiring or of a detector renders only one detector inoperative. In practice this may not always be possible because of economic considerations and because isolators may have a low but finite impedence in the low impedence state which gives rise to a cumulative volt drop around the loop circuit if a large number of isolators are used. Embodiments of isolators based on semiconductor circuits can be expectd to provide a volt drop of less than 0.8 volts in the low impedance state.
  • ten isolators may produce up to a 7.2 volt drop from the first isolator to the 10th isolator if a short circuit occurs between the 10th and 11th isolator in a system fitted with 11 isolators for example.
  • a system of this type fitted with modern detectors having a wide operating voltage range can be expected to accommodate a 7.2 volt drop without any performance degradation.
  • the maximum number of detectors which may be connected between isolators will be largely determined by the maximum tolerable number of detectors than can be rendered inoperative in the event of a short circuit. By way of example this number may be approximately 25 if comparable performance with that of conventional fire detection systems using non addressable detectors is used as the criterion.
  • a loop system using say 11 bi-directional short circuit isolators may interconnect approximately 250 addressable detectors and be no more degraded by a short circuit fault than a conventional 10 zone system with 25 detectors per zone.
  • the loop system of addressable detectors also has advantages that an open circuit fault will not render any detectors inoperative and that the location of detectors can be identified with precision.
  • Figure 4 shows one form of a practical embodiment in component form of a bi-directional circuit isolator.
  • transistor TR2 When power is applied to terminals 31 and 32 transistor TR2 is driven into conduction by virtue of base drive derived from resistor R1 and bias resistor R5. Transistor TR2 in turn drives transistor TR1 into conduction via diode D4 steering diode D2, resistor R3 and bias resistor R2 thus effecting a low impedance path from terminal 31 to terminal 33 via TR1 and diode D3. Similarly and by virtue of the symmetry of the circuit it can be shown that a low impedance path can be effected between terminals 33 and 31 via transistor TR3 and diode D5 if power is applied to terminals 33 and 34. A low impedance always exists between terminals 34 and 32.
  • the transistor TR1 or TR2 associated with the input terminals receiving the higher supply voltage will be conductive and provide the low impedance path.
  • the terminals receiving the higher voltage are determined -by the proximity of the isolator to the control unit, the presence or absence of short or open circuit faults and possibly the voltage level of any superimposed data transmission signal.
  • Resistor R7 is an optional resistor normally of high value which may be necessary to improve the switch on characteristics of the isolator when power is first applied in circumstances where the detectors connected to the circuit have a capacitive input or require a higher quiescent current that can initially be sourced via resistors R1 and R6 in parallel with D7 or R6 and R1 in parallel with D1 as circumstances dictate.
  • FIG. 5 A further circuit arrangement incorporating short circuit isolators is shown in Figure 5.
  • the isolators are connected in a loop circuit with groups of detectors spurred off between isolators rather than being connected to the loop circuit directly.
  • FIG. 6 A further circuit arrangement is shown in Figure 6. This arrangement has the advantages of the loop circuit and the additional advantage that more than one open circuit fault in the wiring linking detectors does not render any detectors inoperative unless two or more open circuits occur on the same spur.
  • circuit arrangements formed by combining all or parts of circuit arrangements disclosed above and containing one or more isolators whether bi-directional or uni-directional are embodiments of the invention.
  • the short circuit isolatons disclosed here may constructed in various forms. They may with advantage be incorporated within control units and within detectors or they may be'constructed as separate units which are wired into circuit arrangements as required.
  • FIG. 7 A further embodiment of the invention having application with circuits using an alternating electrical supply is illustrated in schematic form in Figure 7.
  • a non-polarised bi-directional short circuit isolator23 (represented by the broken line) comprises two polarised bi-directional short circuit isolators 24a, 24b, interconnected as shown, and connected to a.c. supply lines 25 26.
  • Fig. 8 illustrates an improvement in the circuitry of Fig. 4 (similar reference numerals or letters identify similar components).
  • transistors TR1 and TR3 are VMOS field effect transistors.
  • VMOS devices have the advantage that their "on state" impedance is very low, typically 5 ohms to 0.3 ohms. This means that, in most applications, a smaller voltage drop will be developed across the isolator, thus permitting an increase in the number of isolators which may be introduced into a circuit.
  • VMOS devices conduct current bi-directionally in the "on state” it is possible to connect them in series. This has enabled diodes D5 and D3 to be eliminated thus further reducing the voltage drop across the device.
  • an LED indicator LED 1 which illuminates when the short circuit isolator switches to a high impedance state in response to the presence of a short circuit.
  • LED 1 is incorporated within a bridge rectifer circuit, including diodes D9-D12, which produces a rectified voltage in response to a short circuit on either side of the isolator.
  • LED 1 is caused to flash periodically by incorporating it in a oscillator circuit comprising a conventional programmable unijunction transistor oscillator and associated components TR4, R9-R13, C1. By causing LED 1 to flash, the current required to provide indication when a short circuit is detected is reduced.
  • two zener diodes D13, D14 are provided to protect the short circuit isolator from high voltage transients and accidental polarity reversal, and a 10K ohm resistor R14 is connected to the base of TR2 to give a degree of control over the threshold voltage of the short circuit sensing circuitry.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Alarm Systems (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
  • Electronic Switches (AREA)
  • Burglar Alarm Systems (AREA)
EP83303841A 1982-07-16 1983-07-01 Short circuit fault isolation means for electrical circuit arrangements Expired - Lifetime EP0101172B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83303841T ATE25781T1 (de) 1982-07-16 1983-07-01 Kurzschluss-fehler-isolierungsmittel fuer stromkreiseinrichtungen.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8220753 1982-07-16
GB8220753 1982-07-16

Publications (3)

Publication Number Publication Date
EP0101172A1 EP0101172A1 (en) 1984-02-22
EP0101172B1 EP0101172B1 (en) 1987-03-04
EP0101172B2 true EP0101172B2 (en) 1992-05-06

Family

ID=10531742

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83303841A Expired - Lifetime EP0101172B2 (en) 1982-07-16 1983-07-01 Short circuit fault isolation means for electrical circuit arrangements

Country Status (4)

Country Link
EP (1) EP0101172B2 (no)
AT (1) ATE25781T1 (no)
DE (1) DE3370089D1 (no)
NO (1) NO158479C (no)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0632517B2 (ja) * 1985-07-19 1994-04-27 ホーチキ株式会社 異常監視装置
JPS62117688U (no) * 1986-01-13 1987-07-25
US5400203A (en) * 1992-07-29 1995-03-21 Pittway Corporation, A Delaware Corporation Short circuit detector and isolator
JP3382370B2 (ja) * 1994-08-18 2003-03-04 能美防災株式会社 火災報知設備の伝送線路監視装置
GB9623277D0 (en) * 1996-11-08 1997-01-08 King K W Passive isolator
DE10048599C1 (de) 2000-09-30 2002-04-18 Bosch Gmbh Robert Vorrichtung zur elektrischen Energieversorgung von Meldern, Steuer- und Signalisierungseinrichtungen
GB0118442D0 (en) * 2001-07-28 2001-09-19 Computionics Ltd A fire alarm module
GB2484288A (en) 2010-10-04 2012-04-11 Thorn Security Isolator Circuit for detector
EP3822936B1 (en) * 2019-11-13 2023-09-13 Carrier Corporation Short-circuit isolator
EP3913594A1 (en) 2020-05-21 2021-11-24 Carrier Corporation Short circuit locating
EP4106125A1 (en) * 2021-06-18 2022-12-21 Carrier Fire & Security EMEA BV Short-circuit isolator

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH651688A5 (de) * 1980-06-23 1985-09-30 Cerberus Ag Verfahren zur uebertragung von messwerten in einer brandmeldeanlage und einrichtung zur durchfuehrung des verfahrens.

Also Published As

Publication number Publication date
DE3370089D1 (en) 1987-04-09
NO158479C (no) 1988-09-14
NO832563L (no) 1984-01-17
EP0101172A1 (en) 1984-02-22
EP0101172B1 (en) 1987-03-04
ATE25781T1 (de) 1987-03-15
NO158479B (no) 1988-06-06

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