EP2437228B1 - Alarm, hazard warning assembly and method for detecting circuit faults - Google Patents

Description

Technical area

The invention relates to a danger detector, alarm system and method for detecting line faults such as short circuits, creeping short circuits, interruptions and creeping interruptions.

State of the art

In hazard detection systems, the communication of the various system devices takes place via both wired and wireless communication channels. In line-based security systems, hazard detectors and other peripheral system devices are connected via lines to a control center and to each other. The communication signals are routed via these lines. Frequently, the power supply of the detectors and the other peripheral devices is also provided by the control center. In the case of a communication and energy supply that takes place exclusively via these lines, there is the danger that the entire communication and the operation of the detectors and other peripheral devices will collapse in the event of a line fault such as an interruption and especially in the event of a short circuit. To avoid such a failure, it is known to lay the lines, starting from a central office, in a loop that ends again in the center. As a result, z. For example, in the event of an interruption in the line, the power supply and the communication take place via both sides of the loop, whereby the function and communication capability of all detectors and peripheral devices is maintained.

In the event of a short circuit, short-circuit disconnectors are known with which a short circuit can be isolated. Thus, as in the case of an interruption, the power supply and communication can take place via both sides of the loop. Short-circuit disconnectors can be arranged at regular intervals between the detectors or integrated into each detector. For short-circuit disconnectors that are controlled by the command station, the control panel must know the location of the short circuit on the line to isolate the short circuit.

When a short-circuit occurs in a detector loop, the supply voltage initially drops sharply, so that the detectors are no longer sufficient with Energy is supplied and then the Kurzschlusstrenner be opened in the loop. A detector loop damaged by a short-circuit must then be restarted by the control panel. This means that the open short-circuit disconnectors must be closed again in order. For this purpose, the control center first supplies the first detector or the first detector group with energy. As soon as the first detector or the detector group is ready for operation, the short-circuit switch in the detector or at the end of the group is closed in response to a command from the central unit. Now the next detector or detector group is supplied with voltage and the next short-circuit switch is closed. This takes place until the short circuit is reached. When the short-circuit is reached, the detector loop is de-energized again and the start-up procedure must start again. However, the control center now knows the detector or short-circuit disconnector behind which the short-circuit is located and, at the next startup, does not cause the short-circuit disconnector to close before the short-circuit. The first start of such a loop after the occurrence of a short shot is only for the purpose of experiencing the location of the short circuit and costs time. This time required for exploration could be avoided with automatic short-circuit disconnectors, which automatically re-open a connection switch or do not close it as soon as they automatically determine that there is a short circuit on the line section behind them.

Such a Kurzstrusstrenner is from the DE 695 14 445 T2 known. This recognizes too high a current in a line and disconnects it by opening a previously closed switch again. One from the DE 36 24 604 A1 Known short-circuit disconnector compares the input and / or output-side terminal voltages of the short-circuit disconnector or a detector with predetermined or adjustable voltage thresholds and opens when these thresholds below a possibly previously closed switch. Likewise in the EP 0 347 806 A1 a short-circuit disconnector is described in a detector, which opens a turn-on transistor again when a line voltage falls below a certain value for a predetermined test time.

The from the DE 695 14 445 T2 , of the EP 0 347 806 A1 and the DE 36 24 604 A1 However, known short-circuit disconnectors are constantly active and therefore require a lot of power. In addition, their comparison values are fixed and can not be automatically adapted to the installation position of the detectors within a loop, which means that creeping short circuits can only be recognized to a very limited extent.

document EP 1197936 discloses a hazard detection system with an inspection arrangement for detecting and locating faults such as short circuits or reverse polarity of conductors.

Object of the invention

The invention is therefore based on the object to provide a hazard detector, a hazard alarm system and a method for detecting line faults such as short circuits and interruptions, which bring about an improvement with respect to the disadvantages mentioned in the prior art.

Description of the invention

The object is achieved according to the preamble and the features of claims 1, and 5 and will be described in more detail below. Advantageous developments can be found in the subclaims.

The inventive method is used in a cable-bound hazard detection system, in the hazard alarms and other peripherals such. As alarm sirens, interface modules or actuators, which are connected via lines to a central office and each other, and in which line sections can be separated by short-circuit disconnector of the rest of the line. Short-circuit disconnectors can either be provided as separate devices, or integrated into the hazard detectors and other peripherals. For the sake of simplicity, the term detector is used below, which stands for both hazard alarms and other peripheral devices with an integrated short-circuit disconnector as well as for separate short-circuit disconnectors.

In the method according to the invention for detecting line faults in a hazard alarm system, a hazard alarm center connects in a first step a voltage source having a certain supply voltage with connecting lines. As a result, a supply voltage is applied to the, next to the central detector, via the connecting lines. Thereafter, existing energy stores are loaded in the detector and the detector is initialized. During initialization or thereafter, a first terminal voltage is measured in this detector. Terminal voltage is the voltage between two wires of the connecting cables. The measurement of the first terminal voltage takes place during the time in which the detector loads the voltage source only with its low quiescent current. After the value of the first terminal voltage has been stored, the voltage source is charged with a defined current, the z. B. 20 mA higher than the quiescent current of the detector. During the load of the voltage source with the increased defined current, a second terminal voltage is simultaneously measured. From the known current difference, the difference between the first and second Terminal voltage and the assumed maximum known starting current of one or more other detectors, a comparison voltage is determined. Subsequently, a connection switch is closed, whereby the voltage applied to the first detector is switched through to the next section of the connection lines, and thus a supply voltage is applied to a second / further detector. Immediately after closing the switch, a third terminal voltage is measured in the first detector. Subsequently, in the first detector the third terminal voltage is compared with the previously determined comparison voltage. If the third terminal voltage drops below the reference voltage, it is assumed that there is a short circuit or creeping short circuit and the previously closed switch is opened again. However, if the third terminal voltage is greater than or equal to the comparison voltage, then the switch remains closed and the steps described above are repeated with the newly energized detector.

As soon as the control panel tries to communicate with a detector to which the supply voltage has just been switched, it can detect the absence of a response that an error has occurred. In this case, a short circuit is detected when the previously started detector opens its connection switch again due to a too low third terminal voltage. This may be requested by the head office from this detector. Otherwise there will be an interruption or a faulty detector. If, in the latter case, a detector which could not be addressed from a first side of a detector loop responds to questions from the control center from a second side of the detector loop, there is an interruption in the line, otherwise a faulty detector.

In a preferred embodiment of the method according to the invention, the detectors send messages by means of a current modulation via the connecting lines. It can be z. B. a zero can be represented by the quiescent current of the detector, while a one by the significantly higher modulation current, the z. B. is 20 mA higher than the quiescent current, is shown. In this case, according to the invention, the higher modulation current is used as the load current for measuring the second terminal voltage. Therefore, according to the invention at least the measurement of the second terminal voltage during the transmission of a communication telegram by the detector takes place. The measurement of the first terminal voltage can also be done while sending a telegram.

When measuring the terminal voltages during a telegram, it may be particularly in hazard alarm systems with long detector lines, to which many detectors Inaccuracies occur at high baud rates at the end of the line because the load current is not applied long enough to cause a stable terminal voltage. Therefore, the first and / or the second terminal voltage are preferably measured at a point in the telegram in which several equivalent bits follow each other, which are represented by the high current.

However, in the case where the current modulation used, as in the case of the Manchester code, encodes different values due to rising or falling signal edges, the measurement of the first and / or second terminal voltage takes place within a transmitted telegram after a change from zero to one or from one zero.

The invention further relates to a short-circuit disconnector for carrying out the method described above. A short-circuit disconnector according to the invention comprises: a switch for connecting or disconnecting connecting lines, a device for generating a defined electrical current, a measuring device for measuring a first, second and third terminal voltage, a memory for storing a measured value of the first and / or second terminal voltage A memory for storing the value of a maximum inrush current of one or more devices connected to a connection line, a computing unit for determining a comparison voltage and a comparison unit for comparing the third terminal voltage with the comparison voltage.

The invention further relates to a detector for carrying out the method described above. Such a detector comprises a switch for connecting or disconnecting connecting lines, with which a supply voltage can be switched through to a second / further detector. A detector according to the invention further comprises a device for generating an electric current of defined height, a measuring device for measuring a first, second and third terminal voltage, a memory for storing a measured value of the first and / or second terminal voltage, a memory for storing the value of a maximum inrush current one or more detectors, a computing unit for determining a comparison voltage and a comparison unit for comparing the third terminal voltage with the comparison voltage.

The invention also relates to a hazard alarm system for carrying out the method according to the invention. Such a hazard detection system has at least one voltage source which supplies voltage to danger detector and / or other peripheral devices via connecting lines. In addition to the hazard alarm and / or other peripheral devices, collectively referred to simply as detectors, the hazard alarm system comprises at least one short-circuit disconnector, comprising: a switch for connecting or disconnecting connection lines, means for generating a defined electric current, measuring means for measuring a first one , second and third terminal voltage, a memory for storing a measured value of the first and / or second terminal voltage, a memory for storing the value of a maximum inrush current of one or more devices connected to a connecting line, a calculating unit for determining a comparison voltage, and a comparing unit for comparing the third terminal voltage with the reference voltage. In this case, such a short-circuit disconnector can also be integrated in a detector.

Finally, the invention relates to a hazard detector with an integrated short-circuit disconnector as previously described.

Brief description of the drawings

• FIG. 1 shows a hazard alarm system according to the invention with a control center, connecting lines and hazard detectors with short-circuit disconnectors.
• FIG. 2 shows a Kurzschlusstrenner invention.
• FIG. 3 shows another embodiment of a Kurzschlusstrenners invention.
• FIG. 4 shows a timing diagram with different current and voltage values that occur during the process according to the invention.

Description of the embodiments

The invention will be explained in more detail below with reference to the drawings.

FIG. 1 shows a hazard alarm system (1) according to the invention which z. B. may be a fire alarm system. The alarm system (1) consists of a central station (2) with a first terminal (5) and a second terminal (6) and a detector line (9), starting from the first terminal (5) several danger detectors (8) via a, in This example two-wire running, connecting line (7) connects to the center. In addition to the hazard detectors (8) connects the connecting line (7) and other peripheral devices such as sirens or interface modules with which z. B. devices that do not support the protocol of the detector line can be operated on the detector line, with the center. For simplicity, hazard detectors (8) and other peripheral devices are collectively called detectors (8). In the in FIG. 1 are shown in the detectors (8)

Short-circuit disconnector (11) integrated. However, the short-circuit disconnectors (11) can also monitor the connecting lines (7) as separate devices between the detectors (8). The short-circuit disconnectors (11), which, as in the embodiment shown, are integrated in the detectors (8), use devices already present in the detectors (8), such as a computing device (10) and a region of a memory (13).

In FIG. 2 some details of a short circuit breaker (1) are shown while in FIG. 4 a timing diagram is shown, with which the sequence of the method according to the invention is illustrated. A short-circuit disconnector (11) according to the invention is connected via terminals (3a, 3b, 4a, 4b) to the cores (3, 4) of the connecting line (7). Between the terminals 3a and 3b of the wire 3 is a controllable switch (12), with which a connection between the terminals 3a and 3b can be made and separated again. On both sides of the switch (12) are each a voltmeter (14) for measuring a voltage between the terminals 3a and 4a or 3b and 4b and a respective current sink (15) for generating a load current (I ₂ ) in the supply line ( 7). With the voltmeters (14), depending on which side of a detector (8) is connected to the center (2), the voltages between the terminals 3a and 4a or 3b and 4b are measured.

The sequence of a short circuit detection is now the example of the commissioning of a hazard alarm system (1) according to the invention on the basis of FIGS. 1 . 2 and 4 explained.

For this purpose, it is assumed that all detectors (8) incl. Short-circuit disconnector (11) are installed and all switches (12) in the short-circuit disconnectors (11) are open. If not all switches (12) should be open, it would be possible to allow them to close with a special command at a later time from the center (2). At the beginning of the startup, the control center (2) applies a supply voltage to the connection line (7) via the first terminal (5). Thus, this voltage is applied to the terminals 3a and 4a of the first detector (8), and it flows for a short time z. B. for 5 ms, a maximum inrush of z. B 60 mA. After the in the detector (8) existing, but not shown, energy storage are loaded, only a mean quiescent current (I ₁ ) flows from z. B. 100 μA. At the latest after the control panel (8) has sent a command to close its connection switch (12), the short-circuit disconnector (11) measures a first terminal voltage (U ₁ ) between the terminals at a time t ₁ with the voltmeter (14) 3a and 4a is applied to the detector (8) and stores the measured value in a memory (13) for later use. The first terminal voltage (U ₁ ) differs from the voltage; which is applied from the control center to the connecting line (7), only by the small amount that is on the connecting line (7) falls. At time t _2, the short-circuit disconnector (11) loads the voltage source in the first terminal (5) of the control center (2) by means of a current sink (15) with a load current (I ₂ ). The load current (I ₂ ) generates a higher voltage drop across the connection line (7) than the quiescent current (I ₁ ). As a result, at time t _2, the second terminal voltage (U ₂ ) is measured at the terminals ( _{3 a, 4 a} ), which is likewise stored in the memory (13) for later use. From the stored values for the first and second terminal voltage U ₁ , U ₂ ), the difference between the load current (I ₂ ) and quiescent current (I ₁ ) and the maximum inrush current I _max of subsequent detectors (8), is then in a computing device (10) determines a comparison value (U _min ) for the short-circuit detection. The difference between load current (I ₂ ) and quiescent current (I ₁ ) is known through the use of the current sink (15), and the comparison value U _min can z. B. be calculated from the following formula. $$U_{\min }<\frac{U_1-U_2}{I_2-I_1}\cdot I_{\mathrm{Max}}$$

Preferably, however, the comparison value U _min is reduced by an additional amount of security.

After determination of the comparison value U _min , the short-circuit disconnector (11) closes its switch (12) at time t _s and thereafter measures a third terminal voltage (U ₃ ) at time t ₃ . After closing the switch (12), a second / further detector (8) is connected to the center, whereupon the second / further detector (8) loads the voltage source in the first terminal (5) with its inrush current. As a result, the current I ₃ flows at time t ₃ and generates a new voltage drop via the connecting line (7) to the first detector (8). Finally, the short-circuit disconnector (11) compares the third terminal voltage (U ₃ ) with the comparison value (U _min ). If it is determined in this comparison that the third terminal voltage (U ₃ ) is greater than or equal to the comparison value (U _min ), it is initially assumed that there is no line fault and the switch (12) remains closed. Thus, the second / further detector (8) remains connected to the center and can communicate with this after a start time. The newly connected second / further detector (8) then takes on the further start of the detector line (9) the function of the previous first detector. However, if the control panel (2) detects at this stage that the second / further detector is not responding to their requests, the control panel (2) concludes that there is a line or detector error and sets the startup procedure at the second terminal (6). continued. Becomes the second / further detector finally reaches the center (2) via the second terminal (6) at a later time and can communicate with it, then there is an interruption in the connection line (7) between the first and the second / further detector ( 8) before, otherwise, it is assumed that the second / further detector (8) is defective.

However, if it is determined in the comparison that the third terminal voltage (U ₃ ) is smaller than the comparison value U _min , a short circuit or creeping short circuit is detected and the switch (12) in the short-circuit disconnector (11) is opened again. Also in this case, the center continues the startup process on the second terminal (6). However, the first detector (8) may notify the center, upon request, that there is a short circuit in the line section following it.

By measuring terminal voltages (U ₁ , U ₂ , U ₃ ), it is possible to dispense with a measuring resistor between the terminals _{3 a and 3} b or 4 a and 4 b, which is necessary for current measurement, and which measures the resistance of the connecting line (7) between the control center and other detectors (8). Thus, longer detector lines (9) with additional participants (8) are possible, as in a short-circuit detection by means of a current measurement.

The individual determination of the comparison value U _min for each individual detector (8) or short-circuit disconnector (11) enables improved detection of creeping short circuits.

Starting from the second terminal (6), the search for line faults is carried out at the start of the detector line (9) in the same manner as described for the starting from the first terminal (5).

In the FIG. 3 another embodiment of a short-circuit disconnector (11) is described. Unlike the in FIG. 2 shown short-circuit disconnector (11), the short-circuit disconnector (11) shown here, two connection switches (12), which are attached directly to the terminals 3a and 3b and are bridged by a respective diode (16). For this, this embodiment has only ever a voltmeter (14) and a current sink (15). When using this embodiment of the short-circuit disconnector (11), the voltage drop across the diodes must be taken into account when determining the comparison value. The diodes are used to supply voltage to the first or after the second or further detector (8), while the switches (12) in the respective detector (8) are still closed.

In a preferred embodiment of the invention, the communication transmitter (15) of a detector (8) or a separate short-circuit disconnector (11) serves as a current sink (15) for generating the load current (I ₂ ). In this case, the measurement of the first and second terminal voltage (U ₁ , U ₂ ) takes place at a time during which the detector (8) or a separate short-circuit disconnector (11) sends a telegram to the control center. In the in FIG. 4 As shown, the telegram starts at time t _M , where, as shown, the bit sequence 101010 is transmitted. In this case, the measurement of the first and the second terminal voltage (U ₁ , U ₂ ) is preferably carried out at the end of a bit sequence, each having the same values. For example, the first terminal voltage (U ₁ ) at the end of a sequence of three times 0 and the second terminal voltage (U ₂ ) at the end of a bit sequence with three times 1 measured.

However, if a Manchester code is used to send telegrams, the first terminal voltage (U ₁ ) is measured after a change from 1 to 0 and the second terminal voltage (U ₂ ) after a change from 0 to 1.

Claims (7)

1. Method for detecting line faults in a hazard detection system (1), in particular having a detector line which connects a plurality of detectors (8, 11) via a connecting line (7), the detectors (8, 11) comprising, in particular, a switch (12) for connecting or disconnecting the connecting lines (7), which switch can be used to connect through a supply voltage to a further detector, having the following method steps of:

   a. applying a supply voltage from a voltage source to a first detector (8, 11), the switch (12) of which is open,

   b. measuring a first terminal voltage (U₁) in the first detector (8, 11) during a time in which the detector loads the voltage source with its quiescent current (I₁),

   c. loading the voltage source with an increased defined current (I₂) by means of the detector (8, 11) and simultaneously measuring a second terminal voltage (U₂) in the first detector (8, 11),

   d. determining a comparison voltage (U_min) from the first and second terminal voltages (U₁, U₂), the current difference (I₂-I₁) and a maximum inrush current (I_max) which is assumed to be known,

   e. closing the switch (12) in the first detector (8, 11), as a result of which the voltage applied to the first detector (8, 11) is connected through to the next section of the connecting lines (7) and the supply voltage is therefore applied to a second/further detector, in particular,

   f. measuring a third terminal voltage (U₃) in the first detector (8, 11) after the switch (12) in the first detector (8, 11) has been closed,

   g. comparing the third terminal voltage (U₃) with the comparison voltage (U_min) determined in step d.,

   h. opening the previously (in step e) closed switch (12) if the third terminal voltage (U₃) falls below the comparison voltage, or repeating steps b to h with each further available detector (8, 11), the second/further detector then assuming the function of the previously first detector (8, 11).
2. Method according to Claim 1, characterized in that the detectors (8, 11) transmit messages by means of current modulation via the connecting lines (7) and the increased modulation current of the detector (8, 11) is used as the load current (I₂) for measuring the second terminal voltage (U₂) in step 1.c.
3. Method according to Claim 1 or 2, characterized in that the first and/or second terminal voltage (U₁, U₂) is/are each measured at a location with a sequence of two or more identical bits within a transmitted message.
4. Method according to Claim 1 or 2, characterized in that the first and/or second terminal voltage (U₁, U₂) is/are measured at a location with a sequence of two bits within a message, the values of which change.
5. Short-circuit isolator (11) for carrying out the method according to one or more of Claims 1 to 4, comprising a switch (12) for connecting or disconnecting connecting lines (7), a device for generating a defined electrical current (15), a measuring device (14) for measuring a first, a second and a third terminal voltage (U₁, U₂, U₃), a memory (13) for storing a measured value of the first and/or second terminal voltage (U₁, U₂), a memory (13) for storing the value of a maximum inrush current of one or more peripheral devices (8, 11) connected to a connecting line (7), a computing unit (10) for determining a comparison voltage (U_min), a comparison unit for comparing the third terminal voltage (U₃) with the comparison voltage.
6. Hazard detector (8), characterized in that it comprises a short-circuit isolator (11) according to Claim 5 which is integrated in the hazard detector (8).
7. Hazard detection system (1) for carrying out the method according to one or more of Claims 1 to 4, having at least one voltage source which supplies the hazard detectors (8) and/or other peripheral devices (8, 11) with voltage via connecting lines (7), the hazard detection system comprising at least one short-circuit isolator according to Claim 5 and/or at least one detector (8, 11) according to Claim 6.

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