Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B25/00—Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems
  • G08B25/01—Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems characterised by the transmission medium
  • G08B25/04—Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems characterised by the transmission medium using a single signalling line, e.g. in a closed loop
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B17/00—Fire alarms; Alarms responsive to explosion
  • G08B17/06—Electric actuation of the alarm, e.g. using a thermally-operated switch

Definitions

• This invention concerns a device for the detection of the alarm position of an alarm generated in a special cable defined as "linear heat detector " ' ("L.H.D. " ' from now on )
• the L.H.D. 's are cable used for fire alarm signalisation when exposed to temperatures in excess of the selected minimum alarm level produced in the environment or in a plant, as for an example, but not exclusively, in highway-railways-underground tunnels, belt conveyors, electrical cabinets and power lines cable trays, transformers, flammable storage tanks, cooling towers, in warehouses and in any case in all those installations where, caused by attrition, by chemical reactions or by short-circuit there could be the conditions for the development of a fire and in which it's useful to identify as soon as possible the exact location of the danger, above all in case of great plants or of long length runs.
• An L.H.D. is an electrical twisted pair of stainless steel conductors cable provided with a special thermoplastic sensitive insulation which melts at selected temperature levels. When exposed to temperature in excess of the selected minimum alarm level the specific sensitive insulation melts allowing the conductors to short-circuit. It's, therefore, an on-off digital device.
• the alarm condition is monitored through a fire control panel which monitors the status ( fire or fault) checking the current output from the control panel.
• the main problem in plants with linear heat detectors installed is that the fire control panels management system can identify the status of alarm of the "zone" in which the cable is installed, but can't identify precisely the location in that zone, i.e. the distance from a conventional reference distance, problem is particularly serious when , as in tunnels or in cable trays, the cable lengths are relevant.
• the solution according this invention is able to identify the distance of alarm in any digital cable, no matter which is the manufacturer, or in other terms no matter which are the electrical parameters of the digital cable electrical features.
• the device, object of this invention is capable to display the location of alarm in meters or feet or any other measuring unit, and the display can be local in alphanumeric display or remotely on a PC screen with a digital map or a drawing of the site indicating the exact location of the fire.
• the precision claimed is superior in the range of 1 % to 3%max for length of cable over 4.000mt, with environmental temperature variation ranging from +/-20°.
• the instrument is realized in portable or fixed version , the portable one for maintenance purposes , the fixed one to be installed in electrical cabinet or control rooms.
• the electronic unit features a microprocessor for measuring the voltage drop on L.H.D, comparing it with physical parameters stored in a memory as reference and displaying it locally or remotely via PC.
• the control unit is capable of discriminating short-circuit on L.H.D from a short-circuit on electrical junction cable or for its opening status ( as for example for interruption of its continuity ) There's the possibility to join the electronic board with other boards for the management of other types of fire detectors .
• Circuitry description of the device for cabinet version The electronic board, microprocessor based, is powered via a 24VDC charger through a connector .
• the power block generates a 15VDC - 10V- 12,5V supply reference voltages .
• Terminals are provided for L.H.D input, which is connected to a reference relay and in stand-by terminates on proper terminals ;
• Two steady current generators which supply a reference resistor and the L.H.D to be measured ;
• a suitable trimmer to zero the electrical junction cable resistance up to the beginning or the end of L.H.D. A trimmer for the circuit amplification control
• Circuitry description of the portable unit This version of the circuit capable of detecting the voltage drop on a L. H.D. cable is powered through 9Vdc battery and is provided with : voltmelric module capable of generating a reference voltage dependent from the L.H.D manufacturer ( its electrical parameters, R-L-C) proper terminals to connect the L.H.D cable; Control buttons for proper operation; Display.
• Fig. 1 is a diagram block of the electronic board showing the operating principle of the voltage drop
• Fig.2 shows the block diagram of inputs
• Fig.3 shows the block diagram function of the charger-comparator
• Fig.4 shows the block diagram of outputs
• Fig.5 shows the electronic board capability of discriminating fault conditions
• Fig.6,6a,6b show the portable version of the device.
• the device is constituted by an electronic board capable of measuring the voltage drop on L.H.D. cable digital type of any manufacturer and to compare it to reference parameters and displaying it with a precision in the range 1-3% max, in function of the environment temperature of the L.H.D. in alarm, as described in the following examples.
• Example 1 electronic board, fixed version
• the circuit is powered at 24 V dc through a proper connector (variable with the control unite).
• the circuit generates a 15 V dc voltage and 10 V dc-12.5 V dc reference voltages .
• the input line from the L.H.D. in the field passes through a relay and in stand-by terminates on terminals.
• two steady current generators power a reference resistor and the line to be measured.
• the relay When an alarm is generated, via terminal , or via manual pressure , the relay changes over an amplifier circuit .
• a trimmer zeroes the junction electrical cables resistence up to the beginning or the end of the L.H.D.
• a resistor regulates the amplification of the circuit.
• Example 2 (electronic port for the portable version)
• the electronic board is powered through a 9 V battery. Pressing the pushbutton, the voltmeter module is capable to produce a reference voltage proportional to the resistance calibration value, to set in function of the L.H.D. type ,which. has to be connected on provided terminals; two diodes are provided for a protection function.
• the device according invention provides means to reset the system, to store the data , to acknowledge the alarm until problem resolution, and to sequentially investigate many zones of L.H.D.
• the control unit is capable to control external devices for fire extinguishing. Operation
• the device operation is based on the current variation between a reference value and the alarm value.
• This variation r in turn depends from the distance of the alarm point (i.e. of the L.H.D. resistance).
• the circuitry sends continuously a signal into the cable and if the cable is whole the signal turns back unchanged. If on the contrary there is a short circuit the circuit measures the voltage drop and transduces it in a reference value which is properly displayed.

Landscapes

• Business, Economics & Management (AREA)
• Emergency Management (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Alarm Systems (AREA)
• Fire Alarms (AREA)
• General Induction Heating (AREA)
• Fire-Detection Mechanisms (AREA)
• Cable Accessories (AREA)
• Locating Faults (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2000
  • 2000-05-25 IT IT2000MI001153A patent/IT1317566B1/it active
• 2001
  • 2001-05-18 AU AU2001262667A patent/AU2001262667A1/en not_active Abandoned
  • 2001-05-18 DE DE60128220T patent/DE60128220D1/de not_active Expired - Lifetime
  • 2001-05-18 WO PCT/IT2001/000251 patent/WO2001091076A1/en not_active Ceased
  • 2001-05-18 AT AT01936809T patent/ATE361514T1/de not_active IP Right Cessation
  • 2001-05-18 EP EP01936809A patent/EP1290657B1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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