An alarm loop (security, fire) is usually called an electrical circuit connecting detectors (security, fire), additional elements connected to a control panel (RCD). The loop diagram is shown in Figures 1,2.
Please note that here are block diagrams. Wiring diagrams for security detectors and wiring diagrams for fire detectors are considered separately.
I would like to explain why I offer two almost identical connection options. The relay output contacts of alarm detectors are characterized by two states - normally closed (I2), normally open (I1).
This is in the absence of supply voltage. Some people identify the normal state of the detector contacts as security fire alarm with the “norm (security)” mode, forgetting that in this case the alarm loop is energized, and, accordingly, the detector relays are also energized. Therefore, Fig. 1 shows the circuit when there is no supply voltage, Fig. 2 shows the circuit when the control panel is turned on.
The security loop and the fire loop have no fundamental differences, except that the security loop more often uses detectors that have “dry” contacts (relay). The fire loop uses such contacts in the presence of heat detectors. The fire alarm loop with smoke detectors is schematically represented in Figure 4 (For a two-wire line).
The control panel uses current monitoring of the alarm loop, which is usually of constant sign, i.e. The polarity of the voltage supplied to the alarm loop is unchanged. Current control of the loop means finding the amount of current flowing through the loop within certain limits (determined by the type of device, the value of the resistor Rok).
When the current changes in any direction, an alarm is generated. I note right away - for fire alarm detectors with "dry" contacts, the polarity of the loop connection does not matter.
All of the above is still more theoretical, if only because there are very few security detectors with normally closed contacts (I2 for Fig. 1,2). Therefore, in practice for burglar alarm The loop connection diagram shown in Figure 3 is used.
It is fair if applied security sensor, having a relay output and a separate power cable. (Astra 5, Astra S, Shorokh 2), well, of course, for reed switches. However, the security detector can also use the power supply method from the alarm loop. Then its connection to the security loop is made according to Fig. 4.
An alarm signal from such a sensor is generated due to a sharp increase in the current it consumes - therefore, the current value of the entire security (fire) alarm loop also increases.
The maximum number of such detectors for connection to a security alarm loop is limited - it is determined by the nominal value of the loop current of a particular fire and security alarm device.
Completing short review On this topic, I would like to note that both security and fire detectors can be addressable. In this case, their connection to the security (fire) alarm loop is made according to the scheme of Fig. 4.
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Fire alarm loop- this is the communication line between the fire control panel, fire detectors and other devices designed to work in this line. Physically, the loop can be made through wired communication lines, fiber-optic communication lines, over a radio channel, etc. Most often, loops perform two main functions: receiving (transmitting) information from fire detectors and supplying power to the detectors. Wired loops, depending on the number of wires, are divided into two-, three-, four-wire, etc. As a rule, communication between addressless control panels and addressless fire detectors is implemented using a two-wire loop, i.e., information is received (transmitted) from fire detectors and power is supplied to the detectors via the same two-wire line. In this case, the control panel continuously monitors the current flowing in the loop and, depending on the magnitude of this current, can issue notifications: “Normal”, “Attention”, “Fire”, “Open”, “Short circuit”. Addressable loops fire alarm with addressable fire detectors included in them, they allow registering and displaying on the addressable control panel not only the operation mode of the detector, but also its address. Data exchange between the addressable control panel and detectors (exchange protocol), as well as the power supply of the detectors can be performed different ways. In order to separate the information exchange lines and the power lines of detectors, three- and four-wire loops are often used, however, to reduce the cost of wired communication lines, many manufacturers of addressable systems transmit the supply voltage and exchange information between the device and the detectors via a two-wire loop. The exchange protocol (sequence, time characteristics, amplitude and information content of pulses) in addressable fire alarm systems is not standard. Most often, it is developed by manufacturers of address systems for specific equipment or series. The advantages of addressable loops are obvious, but there are certain difficulties in their development and use related to problems of electromagnetic compatibility. The presence of digital information exchange using pulse sequences leads to the fact that the introduction of pulse noise from external sources of electromagnetic radiation onto wired communication lines can lead to errors in the operation of the system. In this regard, it is advisable, and in some cases mandatory, to use shielded wire or wires made in the form of “twisted pair” as wire communication lines in address loops.
Plume ( security and fire alarm) - electrical circuit, connecting the output circuits of the detectors, including auxiliary elements and connecting wires and intended for transmitting notifications to the control panel, and in some cases for supplying power to the detectors.
A set of alarm loops, connecting lines for transmitting control notifications via communication channels or separate lines to the device, devices for connecting and branching cables and wires, underground sewers, pipes and fittings for laying cables and wires is included in the linear part of the alarm system.
Security alarm loops
Fire alarm loops
General requirements
Fire alarm loops, as a rule, are made of communication wires, if the technical documentation for fire alarm control devices does not provide for the use of special types of wires or cables. For fire alarm loops, it is possible to use only cables with copper conductors with a diameter of at least 0.5 mm. Automatic monitoring of the integrity of the cable along its entire length is required.
With parallel open installation, the distance from fire alarm loops with voltages up to 60 V to power and lighting cables must be at least 0.5 m. It is possible to lay loops at a distance of less than 0.5 m from power and lighting cables, provided they are shielded from electromagnetic interference .
In rooms where electromagnetic fields and interference have high level, fire alarm loops must be protected from interference.
At the end of the loop, it is recommended to provide a device that provides visual control of its on state, as well as a junction box for assessing the state of the fire alarm system, which must be installed at an accessible place and height. As such a device, a manual call point or loop control devices can be used.
Sign-constant loops
Scheme of a constant sign loop
The integrity of the constant-sign loop is controlled using a terminal device - a resistor installed at the end of the loop. The higher the value of the terminating resistor, the lower the current consumption in standby mode, respectively, the lower the capacity of the backup power source and the lower its cost. The state of the loop of the control panel is determined by its current consumption or, which is the same, by the voltage across the resistor through which the loop is powered. When smoke detectors are included in the loop, the loop current will increase by the amount of their total current in standby mode. Moreover, its value to detect a broken loop must be less than the current in the standby mode of an unloaded loop.
Alternating loops
Alternating loop diagram
The method of monitoring an alarm loop with the loop powered by alternating pulse voltage ensures an increase in the load capacity of the loop for powering current-consuming detectors. A series-connected resistor and diode are used as remote elements of alarm loops; in the forward voltage cycle it is switched on in the reverse direction and there are no losses on it. In the reverse cycle, due to its short duration, losses are also insignificant. The “Fire” signal is transmitted in the positive component of the signal, and the “Fault” signal is transmitted in the negative component. To continue operation when a “Fault” signal is issued due to the detector being removed from the base, a Schottky diode is installed in the base. Thus, the “Fault” signal due to a removed detector or a malfunction of a self-testing detector (for example, linear) does not block the “Fire” signal from manual call point.
The alternating loop allows the use of self-testing detectors in threshold loops. When a malfunction is detected, the detector automatically removes itself from the alarm loop, and this allows it to be used in conjunction with any fire alarm remote control, since control of detector removal is a mandatory requirement of the regulations fire safety for all PKP.
Loops with pulsating voltage
The control method of powering the alarm loop with pulsating voltage is based on the analysis of transient processes in the loop loaded with a capacitor.
Addressable loops
In addressable interrogation fire alarm systems, fire detectors are periodically interrogated, their performance is monitored and a faulty detector is identified by a control panel. The use of specialized processors with multi-bit analog-to-digital converters, complex signal processing algorithms and non-volatile memory in fire detectors of this type makes it possible to stabilize the level of sensitivity of the detectors and generate various signals when the lower limit of auto-compensation is reached when the optocoupler is dirty and the upper limit when the smoke chamber is dusty.
Addressable polling systems are quite simply protected from address loop breakage and short circuits. In interrogated addressable fire alarm systems, an arbitrary type of loop can be used: ring, branched, star, any combination of them and no terminal elements are required. In addressable interrogation systems, it is not necessary to break the addressable loop when removing the detector; its presence is confirmed by responses when querying the receiving and control device at least once every 5 - 10 seconds. If the receiving and control device does not receive a response from the detector during the next request, its address is indicated on the display with a corresponding message. Naturally, in this case there is no need to use the loop break function and when one detector is turned off, the functionality of all other detectors is maintained.
Good day everyone.
Today about addressable threshold loops of PPK. The word “addressable” means that each detector in the loop has its own unique address, this allows the control panel to localize the location of the fire with the accuracy of the detector. we were simply looking at threshold loops, where the triggering of the detector is localized to the loop: the detector in the loop is triggered - run along the entire loop (the Code of Rules allows one loop to be pulled through adjacent rooms up to ten in number), open the rooms, look where the sensor lights up if there is no smoke. In this case, everything is simpler - the control panel will report to the higher-level device the address of the triggered detector in the loop. This solution is intermediate between threshold and addressable analog loops (the next chapter is about them).
In reality, I know of only one device with such cables: the previously mentioned Bolide “Signal-10”. This is a relatively inexpensive control panel with ten threshold loops of a programmable type - smoke thermal, security, etc. Everything is strictly like Signal-20, which was discussed in. But there is an additional 14th type of loop - the same address-threshold one. By programming the loop type “14”, you can connect only special detectors to it: smoke detector DIP-34PA and heat detector S2000-IP-PA for a total of up to 10 pieces. With the help of some button manipulations, they can program the address from 1 to 10, and the device will catch alarms up to the detector. The detectors are powered by a loop; the connection diagram from the same Bolida website is below:
The connection diagrams are exactly the same. AND appearance detectors are the same (pictured at the beginning of the chapter). Please note: the terminating resistor in the address-threshold mode has a nominal value of 10 kOhm, and in the usual threshold mode - 4.7 kOhm (you can see the connection diagrams of threshold loops in the previous chapter).
Another feature of these detectors is that they give an "Accident" signal in case of a detector malfunction. Thus, in accordance with the Code of Rules, it is possible to seriously save on the number of detectors: in some cases it is allowed to install a smaller number of them than in the case of a threshold loop. This allows you to compensate for the higher cost of the detector with the greater functionality of the fire alarm system.
I looked at the previous picture for some reason - it looks too abstruse. Here is the connection diagram directly from the detector label:
So, I think, it’s clearer, only for some reason the tip sticks out at the beginning of the line, kindly it should be at the end: this will make it possible to distinguish a banal break from the theft of detectors.
Well, that's all for now: next there will be a chapter about the perfect type detectors - addressable analogue. And one more thing: while I was composing this post, I thought that I often refer to the Code of Rules, it will be necessary to collect some extracts from it with comments and roll it out as a separate chapter. I think many will be interested. Well, for now I’ll take my leave.
Ask questions in the comments, whoever needs it, subscribe - the form is at the bottom of the page.
I. Neplokhov, Ph.D., technical director for PS at ADT/Tyco
PART 1
Lack of classification of fire alarm loops and communication lines in systems fire automatics in domestic standards is a significant drawback that determines the low level of performance of fire alarm, warning and fire protection. The principles of constructing threshold, multi-threshold and addressable analog loops have already been repeatedly discussed in the industry press, however, increased regulatory requirements for ensuring the operability of loops and communication lines in fire conditions have led to the need to return to this topic once again.
It is obvious that only the use of fire-resistant FRLS and FRHF cables does not provide a significant increase in system performance; disconnecting one detector blocks the “FIRE” signal from all other detectors in this loop. What is the use of using an expensive cable with 3-hour fire resistance at a temperature of 750 ° C if the device connected to it burns out 5 minutes after the start of the fire and thereby ensures a break or short circuit in the communication line. Requirements for the performance of non-addressed and addressable fire alarm loops, Unfortunately, they have not undergone any changes in terms of ensuring full or at least partial operability in the event of a break or short circuit of loops and communication lines. True, the new version of GOST R 53325 will apparently introduce short-circuit insulators for ring and radial loops, but when the requirements for their mandatory use will be determined and in what form is still unknown.
On the other hand, the manuals of foreign non-addressable devices and addressable modules of non-addressable sub-loops define the possibility of creating and programming various styles and classes of loops and communication lines, but the methodology for selecting them taking into account our regulatory requirements is not given. The first part of the article mainly discusses the classification of loops according to NFPA72, and in the second part of the article an analysis will be carried out technical characteristics addressable modules of non-addressable sub-loops and addressable control modules when programming various styles and classes.
CLASSES AND CABLE STYLES ACCORDING TO NFPA72
Communication lines with actuators, with sirens, alarm loops with fire detectors, and so on can only be either class A or class B. Alarm loops and communication lines with actuators, which in the event of a single break or not simultaneously in the event of a single short circuit to the ground of any conductor retains the ability to generate an alarm signal from any fire detector of this loop or which ensure the operation of all devices connected to that communication line are defined as class A.
Tab. 1. Classes and styles of loop with detectors
|
Break of one conductor |
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|
Conductor short circuit to ground |
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|
Short circuit of loop conductors |
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P - Fire; N - Malfunction; N+P - Fire in the presence of a malfunction
Alarm loops and communication lines with actuators, which under these conditions ensure the transmission of an alarm signal only from fire detectors to the break point and do not ensure the operability of devices beyond the break point or a single ground fault of any conductor of the alarm loop or communication line, are defined as class B.
Moreover, if the conductor of the loop or communication line is broken, or if it is shorted to the ground, a fault signal should be generated within 200 seconds. No other classes of loops with other properties, for example, which do not ensure the operation of detectors not only after the break point, but also before it, are not classified, and their use in fire automation systems is not allowed.
Class B loops are subdivided by style into A, B, and C. They must all provide fault detection in the event of a single break in any conductor of the loop or a single short to ground. In case of a short circuit of the style A and B loops, a “Fire” signal is generated, and a “Fault” signal is generated for the style C loop. In style B and C loops, a fault like a single conductor short circuit to ground should not block the formation of the “Fire” signal (Table 1).
Class A trains are divided by style into D and Ea. They should provide fault detection in the event of a single break in any conductor of the loop or its single short to ground. In case of a short circuit of the style D loops, a “Fire” signal is generated, and a “Fault” signal is generated for the Ea style loop. In style D and Ea loops, a fault such as a single break in the loop conductor or a single short circuit of the conductor to ground should not block the formation of the “Fire” signal (Table 1).
Thus, taking into account the requirements of GOST R 53325 on loop failure control not only in case of breakage, but also in case of short circuit, when programming a loop style, you can only select style C for a class B loop and style Ea for class A. In style A, B loops and D, if the loop is short-circuited, a false alarm will be generated.
To understand the technical implementation when meeting the requirements for class A and B loops, consider what recommendations are given in NFPA72 Appendix C on how to test them.
CHECKING LINES OF DIFFERENT CLASSES AND STYLES
Functioning of two-wire class B loops (style A, B and C) with fire smoke detectors It is recommended to check as follows. Break the loop by removing the detector from the base or disconnecting the loop conductor. Activate the smoke detector, which is located between the control panel and the loop break, as recommended by the manufacturer of this type of detector. After this, install the removed detector into the base or restore the loop connection, or do both. The control panel must indicate a malfunction after a loop break and generate an alarm signal when the detector is activated, despite the presence of a loop break. It should be noted that class B can include both radial loops (Fig. 1a) and ring loops (Fig. 1b), while all detectors remaining connected to the alarm loop output must be able to detect a fire, and detectors located behind the break in the loop are in a disabled state. Class B ring loops are formed in non-addressable threshold systems when the terminal element of the loop is located in the receiving and control device. In this case, there is significantly more reliable information about the change in the state of the loop during operation by analyzing the change in voltage at the input and output of the loop compared to a traditional radial loop with a terminal element at the end of the loop.
Rice. 1. Class B cables (style A, B or C)
Rice. 2. Class A train (style D and E)
It is recommended to check the functioning of two-wire class A loops (style D and Ea) with fire detectors as follows. Break the conductor in the middle part of the loop by removing it from the broadcaster and disconnecting the conductor from the base contact. Activate the detectors on both sides of the loop break (Fig. 2). After this, reset the device to standby mode, restore the loop connection and install the detector. Then repeat the test when any loop conductor is shorted to ground in the place where the detector was disconnected. In both tests, an audible and visual fault indication must first be activated, followed by an alarm indication followed by restoration. Unlike the Class B ring loop, the Class A ring loop is converted into 2 radial loops when a break is detected, and all detectors continue to function despite the presence of a fault. This is checked during testing.
Communication lines with devices of any type used in fire automatics are classified in a similar way. For all types of devices included in the communication lines, it remains necessary to fulfill the requirement to ensure the operability of devices connected before the communication line break in class B, and maintaining the operability of all devices regardless of their location relative to the break in class A. But for each individual type of device, depending from fulfilling other requirements when various types device faults identified various styles, which are designated by various letters or numbers. For example, communication lines with class B sirens (Fig. 3), in addition to the obligatory provision of operability of sirens before the communication line is broken, must satisfy additional requirements defined for style W or style Y. And communication lines with class A sirens (Fig. 4), in addition to ensuring the operability of all sirens before and after a communication line break, must satisfy additional requirements specified for style X or style Z.
Rice. 3. Communication lines with class B sirens, styles W and Y
Rice. 4. Communication lines with class A sirens, styles X and Z
The principle of separation into classes B and A must also be followed when using communication lines with devices various types. For example, Figure 5 shows loops with addressable and addressable-analog devices of various types: detectors and sirens. A radial loop of class B ensures the operability of all devices until the loop breaks, and a ring loop of class A ensures the operability of all devices, both in standby mode and in fire mode, despite the presence of a malfunction. In the addressable system, if there is no response from devices beyond the break point when polling, the output circuits of the ring loop are switched to operate in the mode of two radial loops. The fault is automatically localized by the distribution of devices between two radial loops formed and it is determined between which addressable devices the loop break occurred.
It must be emphasized that devices with communication lines or loops that do not meet the requirements for Class A or B are not classified and cannot be used in fire automatic systems according to NFPA72. For example, if, when a radial loop breaks, the detectors that remain connected to the device are not able to generate a “FIRE” signal, perceived by the device against the background of a malfunction, then such a system does not meet the requirements for class B loops and cannot be operated, despite its operability when no malfunction. Likewise, if the ring cable breaks anywhere, it is not allowed for at least several devices to stop functioning in standby mode or in “Fire” mode.
Rice. 5. Loop with class B detectors and sirens
Rice. 6. Loop with class A detectors and sirens
REQUIREMENTS GOST R 53325-2009
In our regulatory framework, similar requirements for the classification of loops are completely absent, although, obviously, it is impossible to compensate for their low fault tolerance by installing three detectors instead of one. In GOST R 53325-2009, clause 7.2.1.1, there is a requirement that the control panels must ensure “preferential registration and transmission to external circuits of fire notifications in relation to other signals generated by the control panel.” Despite the fact that the same wording was already present in the NPB 75-98 of the last century, there are a lot of certified control panels on our market, in which a fire notification is not registered if there is a signal about a faulty loop, even if its end-of-line resistor and all alarms are turned off remain connected to the device and detect a fire, the “Fire” signal is blocked.
Ring addressable loops, despite their potential advantages over radial non-addressable ones, in our design cannot always be classified as class A. There is no method for checking the functioning of devices in the event of a malfunction in our regulatory documents, and checks to ensure operability in the event of a broken loop are not carried out. In addition, the loopback loop outputs can be combined on the board, and then a single loop break is not detected by the device. True, if the cable cross-section is chosen to be minimal, then in the event of a break the voltage drop can be significant and a large number of addressable devices stop functioning.
Sometimes installers, even on foreign addressable analog devices with separate loopback outputs, parallelize them in order to “eliminate” a malfunction that occurs due to a significant voltage drop on the loop with a small cable cross-section. But if the loop breaks, this error manifests itself in the form of a drop in the loop voltage below the permissible value and shutdown of a significant part of the devices.
For clarity, let’s consider an abstract example: a ring loop with a voltage of 20 V, approximately 1 km long, with a total current consumption of addressable devices of the order of 100 mA. The total cable resistance with a core cross section of 0.2 mm2 is about 200 Ohms. Assuming a uniform distribution of devices along the length of the loop, the current at each output of a parallel loop will be approximately equal to 50 mA, and taking into account the linear change along the loop, the average current in each half of the loop can be considered 25 mA. Accordingly, at a distance of 500 m at a resistance of 100 Ohms, the voltage will drop by approximately 2.5 V. That is, the loop is powered in parallel, and due to this, a relatively small voltage drop is obtained. And if you disconnect one of the loop inputs from the device, then the average loop current will be summed up and increase to approximately 50 mA. Accordingly, along the entire length of the loop with a resistance of 200 Ohms, the voltage drop will increase 4 times and amount to 10 V!
Rice. 7. Fail-safe loop
REQUIREMENTS OF Federal Law No. 123 AND GOST R 53316-2009
On the other hand, we have been living under the influence of Federal Law No. 123, where Article 82 unambiguously formulates the requirements for ensuring the preservation of operability in a fire of cable lines and electrical wiring, fire protection systems, means of ensuring the activities of fire departments, fire detection systems, warning and control of evacuation of people in case of fire, emergency lighting on evacuation routes , emergency ventilation and anti-water protection, automatic fire extinguishing, internal fire water supply, elevators for transporting fire departments in buildings and structures during the time necessary to perform their functions and evacuate people to a safe area.
To meet this requirement, low smoke FRLS flame retardant cable and even smokeless and halogen free FRHF with a fire resistance of more than 3 hours have begun to be widely used. However, it soon became clear that the fire resistance of such a cable is not ensured if there is no mechanical fastening when exposed to high temperature. Accordingly, a fire-resistant cable must have a fire-resistant fastening and it is no longer allowed, as before, to put it in a corrugated cable with fastening on polyethylene dowels, which instantly burn at a temperature of 750 ° C, which leads to the destruction of the fire-resistant cable.
GOST R 53316-2009 was issued, which defined test methods for cable lines that are subject to requirements for maintaining operability in fire conditions. This GOST defines a cable line: “a line intended for the transmission of electricity, its individual pulses or optical signals and consisting of one or more parallel cables with connecting, locking and end couplings (seals) and fasteners, laid in accordance with the requirements of technical documentation , in boxes, flexible pipes, on trays, rollers, cables, insulators, free hanging, as well as directly on the surface of walls and ceilings and in voids building structures or in some other way."
But the cable lines and electrical wiring of fire protection systems, means of supporting the activities of fire departments, fire detection systems, warning and management of evacuation of people in case of fire, emergency lighting on evacuation routes include automatic and manual call points, sound and light alarms, and so on, which they must also retain, if not operability, then the ability to “transmit electricity.” In essence, they are “connecting... couplings” and must also be tested according to GOST R 53316-2009 as part of a cable line.
How can the requirements of the Technical Regulations be considered fulfilled when using a fire-resistant cable, if in the room where the fire occurred, after a few minutes the burnt-out siren short-circuits or breaks the communication line and turns off all other sirens, without waiting for people to evacuate to a safe area? A burnt-out detector can block the formation of the “Fire” signal until the procedure for rechecking it is completed by resetting and waiting for confirmation from other detectors. One of possible solutions This problem is the use of ring loops and communication lines when constructively ensuring the absence of a short circuit of the device terminals in case of fire and when the short circuit insulators of the loop are turned on (Fig. 8). It is quite possible that there are more optimal solutions to this problem. Obviously, a reliable assessment of the correctness of the chosen solutions can be determined by analyzing the results of "field tests" of systems under fire conditions, which, unfortunately, we have in abundance.
PART 2
In the first part of the article, published in issue No. 5 of the Security Algorithm magazine for 2012, a foreign classification of fire alarm loops and communication lines in fire automation systems was considered. The second part of the article discusses the technical implementation of loops of different classes and styles. Given electrical parameters radial loops of class B, style C, ensuring the operability of detectors up to the point of a break in the loop; and ring loops of class A, styles D and E, ensuring the operability of detectors before and after a break. The use of a D-style cable makes it possible to distinguish between the operation of automatic and manual fire detectors.
In conclusion to the first part of the article, it was said that the lack of classification of loops in domestic standards is a significant drawback that determines the low level of performance of fire alarm, warning and fire protection systems. Indeed, to what style and class can the loops of domestic control and control devices be classified? Maybe everything is fine with us anyway? Not at all, regulatory requirements for Lately have changed more than once, many additional requirements have been introduced to improve the performance of fire automatic systems in fire conditions. The Technical Regulations on fire safety requirements Article 82. paragraph 2 states: “Cable lines and electrical wiring of fire protection systems, means of supporting the activities of fire departments, fire detection systems, warning and management of evacuation of people in case of fire, emergency lighting on evacuation routes, emergency ventilation and smoke protection, automatic fire extinguishing, internal fire-fighting water supply, elevators for transporting fire departments in buildings and structures must remain operational in fire conditions for the time necessary to perform their functions and evacuate people to a safe area.”
To fulfill this requirement, fire-resistant FRLS and FRHF cables began to be used in communication lines and fire alarm loops, but its break still puts the loop into the “Fault” mode, and “Fire” signals from fire detectors are blocked in almost all domestic fire equipment . There are no requirements to maintain the operability of communication lines and loops with detectors and alarms in fire conditions. Foreign experience in ensuring full (class A) and partial (class B) operability of fire alarm loops in the event of a break is also not used. The new version of GOST R 53325, as well as NPB 75-98, states that the control panel should provide only “preferential display and transmission to external circuits of fire notifications in relation to other signals generated by the control panel.” There is no clear requirement in our standards that it is inadmissible to block “Fire” signals by any other signals, and, accordingly, technical solutions are not used to ensure compliance with this requirement.
Not only do we not have non-addressable devices with ring loops of class A, but also radial loops do not fit into class B of style D. But almost all control panels are multi-threshold, which determines the low level of performance even when maintaining the integrity of the loop, not to mention the operation of fire detectors with broken loop.
Unacceptably high probability false positives smoke firefighters from broadcasters due to lack of protection against electromagnetic interference, regular Maintenance and for many other reasons, the result was that the “Fire” signal from the fire detector ceased to be considered as such. Paradoxical as it may seem, it has already become commonplace for many that now in domestic fire alarm systems any fire detector generates only the “Attention” signal, and the “Fire” signal is generated by the combined efforts of two fire detectors.
The use of this terminology led to the development of an appropriate algorithm for the operation of control panels. An approximate algorithm for the functioning of domestic devices is given in Table 1. The “Attention” signal from the first fire detector can be blocked by the “Fault” signal with an appropriate reaction to it. Although, in conditions of the development of an open fire, there is a high probability of a break or short circuit in the loop before the second fire detector is activated. Protection against false alarms cannot be achieved by reducing the level of fire safety. Why don’t security loops use similar methods of protection against false alarms? There are no “Attention” signals, no two-threshold loops with at least 3 security detectors in the room. Moreover, in the event of a break, a short circuit of the loop, and even just a change in the resistance of the loop, an “Alarm” signal is quite logically generated. Perhaps the likelihood of theft is much higher, but the lack of fire protection creates a real threat to the population, not to mention incomparable material losses.
Perhaps many readers who have become familiar with foreign requirements for the classification of fire loops and communication lines have the impression that this is only a theory. That it is technically difficult to ensure the determination of the formation of the “Fire” signal by a fire detector when the loop breaks. And that ring loops are used only in addressable systems, but certainly not in traditional non-addressed ones.
Consider the principles of building class B loops of styles B, C and class A of styles D, E using the example of a multifunctional module of non-address sub-loop DDM800 addressable analog fire system Zettler (Fig. 1). This module can be programmed to operate in various modes, including supporting two radial loops of class B, style C (short circuit of the loop is defined as a fault), or style B (short circuit generates a “Fire” signal) (Fig. 2), either one class A loop cable, style E (a short circuit of the loop is defined as a fault), or style D (a short circuit generates a “Fire” signal) (Fig. 3), with terminal elements in the form of resistors or zener diodes, when using detector bases with diodes , and operate in 4-20 mA protocol mode. Different durations for resetting detectors and a polling interruption mode without verification or with verification are programmed with different times for rechecking the confirmation of the “Fire” signal, depending on the type of detectors (Fig. 4). Depending on the operating mode, it can occupy from one to four addresses. Power supply for non-addressable sub-loops can be provided either from an addressable analog loop (Fig. 2) or from an additional power source with galvanic isolation (Fig. 3).
Tab. 1. Algorithm of fire plume operation
Rice. 1. Electronics of the DDM800 module
Rice. 2. Two Class B radial loops powered by an addressable analog loop
Rice. 3. Class A loopback cable with external power supply
Tab. 2. Operating modes of the non-addressable sub-loop
Tab. 3. Algorithm of operation of a non-addressed loop of class A and B
In addition, the DDM800 module operates as part of an addressable analog system and transmits to the panel not the “Fire” and “Fault” signals, but much more informative and convenient for analysis analog values associated with loop currents. These numerical values are broadcast with a polling period of 5 s and displayed on the panel display (Fig. 5-7).
What parameters should the loop have to ensure the possibility of receiving the “Fire” signal from fire detectors in the event of a break in the radial loop? First of all, it should be noted that in class A and class B loops, the use of series-connected broadcasters with normally closed contacts is not allowed. An indispensable condition for their operation is the absence of a cable break. If the loop breaks, all detectors before and after the break point are not able to change the voltage and current of the loop. In class A and B fire loops of any style, only fire detectors connected in parallel to the loop can be used.
For radial loops of class B, the parameters must be selected in such a way that, with sufficiently large technological reserves, it is possible to identify the standby mode of the detectors and the activation of the detector both with a working loop with an end-of-line resistor, and if the loop breaks anywhere. Table 2 shows the operating modes of the non-addressable loop. Maximum admissible current consumption of firefighter broadcasters in standby mode is 2.5 mA, which is significantly less than the loop break current threshold of 3.2 mA. Consequently, even if there is a break at the end of the loop, the current consumption of the detectors in standby mode will be less than the break current, and the fault will be identified. The minimum loop current in standby mode due to the terminal resistor is 4.2 mA, with maximum quantity for fire detectors it can increase to 6.7 mA. A wide range of loop currents in the “Fire” mode from approximately 10.5 mA to 24.5 mA ensures reliable generation of the “Fire” signal both in the case of a maximally loaded loop and in the event of a break. Even if only one of the broadcasters remains connected to the module as a result of a cable break, then if the detector current in “Fire” is more than 10.5 mA, the control panel fixes the “Fire” mode. On the other hand, as a rule, foreign and domestic detectors have zener diodes, which prevent the loop from going into short circuit mode even if several detectors go into fire at the same time. In this case, as a rule, no additional resistors are required to be connected to the detectors.
Rice. 4. Programming operating modes of the DDM800 module in the MZXConsys program
Unlike the algorithm of operation of domestic receiving and control devices, the logic of operation of foreign loops ensures unconditional priority of the “Fire” signal. Regardless of the previous state of the loop, as soon as its parameters fall into the range corresponding to the “Fire” mode, it is fixed by the addressable analog panel (Table 3).
To ensure the operability of all detectors in the event of a cable break, a class A loop structure without branches is used (Fig. 3). In standby mode, power is supplied only from the A terminals, and the loop end-of-line resistor is connected to the B terminals. This can be seen in the analog values associated with the loop current, which are transmitted to the control panel when polled. With a detector current in standby mode equal to 2.5 mA and a total loop current of 6.7 mA, the analog value at output A is 035. Output B is disabled, and its analog value is correspondingly equal to 001 (Fig. 5).
If a loop break occurs, the part of the loop connected to terminals B remains without power while the fault is identified. According to regulatory requirements, the time to detect a fault should not exceed about 100-200 s; in reality, this takes about 60 s. If a break occurs near terminals B, then the current at output A is reduced by the amount of current consumption of the terminal resistor and becomes equal to 2.5 mA, the analog value is reduced to 015, and the current at output B remains zero for 60 s, and its analog value remains equal to 001 (Fig. 6).
After detecting a break in the loop cable, output B is turned on and two radial loops are formed, respectively, the value of the analog value at output B becomes equal to 023, which corresponds to a current of 4.2 mA, which is consumed by a 4.7 kOhm terminal resistor connected to terminals B (Fig. 3).
Rice. 5. Loop loop readings in standby mode
Rice. 6. Class A loop in break detection mode
Rice. 7. A loop cable with a break has been converted into two radial cables
When using automatic and manual detectors in one loop, the type of activated detector can be determined. The “Fire” signal from a manual call point operates by interrupting the polling of the addressable analog loop, in the so-called Fast CallPoint mode. The response to activation of the automatic detector is programmed separately and can also be with interruption of the survey, or with verification by re-querying the status, or without verification. The control panel indicates the activation of manual and automatic call points at different addresses, indicating the type of detector. Accordingly, when using two radial loops of class B in Fast CallPoint mode, a total of four addresses are used, and when using a loopback loop of class A, two addresses are used. Moreover, a manual call point with normally open contacts is connected without an additional resistor and transmits the “Fire” signal by short-circuiting the loop, that is, loops of class A, style D, and class B, style B are implemented. The use of these modes at present, according to our standards, is problematic, since the serviceability of the loop must be monitored for open circuits and short circuits, but the interest in the experience of implementing the 2-threshold mode is obvious.
In addition to the fact that in the Fast CallPoint mode, to introduce the second threshold, the signal from manual call points is transmitted by short-circuiting the loop, the short-circuit current of the loop is doubled, to 50 mA. Accordingly, the operating current range of the loop is extended (Table 4). As a result, the loop current range from 0 to 50 mA is divided into 4 parts, corresponding to the loop break mode, standby mode, “Fire” mode from an automatic detector, and “Fire” mode from a manual call point. Naturally, the "Fire" modes are also formed in the presence of a break in the loop.
For comparison, in domestic devices the range of loop currents is half as large, from 0 mA to 20-25 mA, there are 5 modes for the smoke loop and 7 modes for the combined loop, and if the loop breaks, the only reliable signal remains “Fault”, and the signals "Fire" from detectors that have worked in the future are not accepted by the FACP.
Tab. 4. Class A loop thresholds, style D with detection of automatic and manual call points (Fast CallPoint mode)
Thus, the use of class A loop cables, style E, makes it possible to ensure the operability of all detectors in the event of a loop break, not only in addressable analogue systems, but also in non-addressable traditional systems. When laying a loop loop along different zones this can significantly improve the performance of the loops in fire conditions.
LITERATURE:
1. Not bad I. Classes and styles and trains. Ensuring performance. Part One // "Security Algorithm". -2012. - No. 5.
2. Not bad I. Loop control, protection against breakage and short circuit // “Safety Algorithm”. - 2005. - No. 5.
3. Not bad I. Addressless sub-loop in an addressable analogue system // “Security Algorithm”. - 2007. - No. 6.
4. Neplohov I. Gas fire extinguishing: requirements of British standards // Security Systems. - 2007 - No. 5.
5. Neplohov I. Classification of non-addressable loops, or Why there are no two-threshold devices abroad // “Security Algorithm”. - 2008. - No. 3.
6. Neplohov I. Analysis of the parameters of a two-threshold PPKP loop // “Security Algorithm”. - 2010. - No. 5.
7. Neplokhov I. Analysis of the loop parameters of a two-threshold control panel. Part 2 // "Security Algorithm". - 2010. - No. 6.
8. Neplokhov I. Analysis of the loop parameters of a two-threshold control panel. Part 3 // "Security Algorithm". - 2011. - No. 1.
9. Neplohov I. Problems of connecting heat detectors with indicators // “Fire Safety - 2011”. - "Grotek".
10. GOST R 53325-2012 Fire fighting equipment. Fire automatic equipment. Are common technical requirements. Test methods.
11. NFPA 72, National Fire Alarm Code.
PART 3
In the first and second parts of the article, published in Nos. 5, 6 of the Safety Algorithm magazine for 2012, the foreign classification of fire alarm loops and communication lines in fire automatic systems was considered. The third part of the article discusses the technical implementation of communication lines of different classes and styles. The parameters of class B radial communication lines according to the NFPA72 classification are given, ensuring the operability of sirens up to the point of a loop break, and class A ring communication lines, ensuring the operability of sirens before and after a communication line break.
FEDERAL LAW REQUIREMENTS
Federal Law No. 123-F3 of July 22, 2009 “Technical Regulations on Fire Safety Requirements” introduced requirements to ensure the operability of fire protection systems in case of fire. Article 51 “The purpose of creating fire protection systems”, paragraph 3 states: “Fire protection systems must be reliable and resistant to the effects of fire hazards for the time necessary to achieve fire safety goals.” Further in paragraph 4 it is said: “The composition and functional characteristics of fire protection systems for objects are established by regulatory documents on fire safety.” In addition, in article 84 “Fire safety requirements for systems for warning people about fire and managing the evacuation of people in buildings and structures”, paragraph 7 says: “Systems for warning people about fire and managing the evacuation of people must function for the time required to complete the evacuation of people from a building or structure.” Also in Article 84, paragraph 6. “The design and characteristics of smoke protection elements of buildings and structures, depending on the purposes of smoke protection, must ensure proper operation of supply and exhaust smoke ventilation systems during the time necessary to evacuate people to a safe place.” zone, or for the entire duration of the fire."
NORMATIVE BASE
Accordingly, requirements were introduced to improve performance fire protection systems in fire conditions into the regulatory framework. In the first edition of the Code of Practice SP 6.13130.2009 “Fire protection systems. Electrical equipment. Fire safety requirements" it was stated that "cable lines of fire protection systems must be made of fire-resistant cables with copper conductors that do not propagate combustion when laid in groups according to category A according to GOST R IEC 60332-3-22 with low smoke and gas emissions (ng-FRLS ) or halogen-free (ng-FRHF)”, and “cable lines of warning and evacuation control systems (SAEC) and fire alarm systems involved in ensuring the evacuation of people in case of fire must remain operational in fire conditions for the time required for complete evacuation people to a safe zone."
On February 25, 2013, a new Code of Practice SP 6.13130.2013 came into force, in which mandatory requirement there is no use of fire-resistant cable, it is only stated that “Electrical cable lines and electrical wiring of the SPZ must be made with cables and wires with copper conductors.”
In addition, Code of Practice SP 3.13130.2009 “Fire protection systems. Warning and management system for evacuation of people in case of fire. Fire Safety Requirements" contains a general technical requirement: "Cables, wires of the SOUE and methods of their installation must ensure the operability of connecting lines in fire conditions for the time necessary for the complete evacuation of people to a safe area."
Thus, the domestic regulatory framework considers ways to ensure the operability of communication lines when using fire-resistant cables and installation methods. Circuit solutions that improve the performance of communication lines are, for some reason, still not being considered. An expensive fire-resistant FRLS and FRHF cable is used, but there is no protection of the communication line from a simple break. The new version of GOST R 53325-2012 introduces requirements for short-circuit insulators (SCI) for addressable loops and communication lines, but the Codes of Practice do not define requirements for their mandatory use. Moreover, in most domestic addressable systems, the mandatory introduction of IKZ into addressable loops is a half-measure, since communication lines with the RS-485 protocol, through which modules with addressable loops are connected to the hub, still remain unprotected from breakage and short circuit. If a malfunction occurs in these communication lines, the entirety of one, several or all addressable loops with all detectors, modules, sirens and IKZ is switched off. The introduction of requirements to ensure the failure of no more than 32 devices, in the event of a break or short circuit of any communication lines, and not just loops, automatically leads to the use of loop communication lines.
Another significant drawback of our spontaneously emerging heuristic principles for constructing communication lines with control modules is the lack of control of the communication line with the power source and the presence of voltage at the module input. Usually only the control line to the relay module is controlled, which also determines the low performance of the system.
LINES OF COMMUNICATION WITH ANNOUNCERS ACCORDING TO NFPA72-2013
The 2002 version of NFPA72 defined communication lines with Class A, Style Z and Class B, Styles W, X, and Y sirens. In subsequent editions, only Classes A and B were retained for sirens without their division into styles. Class B lines ensure operability when one conductor is short-circuited to ground with the formation of fault signals (Fig. 1), but do not ensure the operability of sirens beyond the break point. Class A communication lines have a backup channel and ensure operability in the event of a single break or a single short circuit of one of the conductors to ground with the generation of fault signals (Fig. 2).
Moreover, class A communication lines made using physical conductors, for example, copper or optical fiber, must be laid separately: outgoing conductors and conductors returning to the control unit. Single path installation using 4-conductor cable is permitted, provided that the communication line is no more than 10 feet (3.0 m) long, only one device is connected, or several sirens are installed in the same room with an area of no more than 1000 ft2 (93 m2 ).
In addition, there is a requirement that loops or communication lines do not pass through the same room twice. Thus, when using short circuit insulators, high system performance is ensured as in normal conditions under mechanical damage plume, and in fire conditions.
ADDRESSABLE ANALOG MODULES
There is no mistake in the subtitle, as it might seem to some readers who are not familiar with the equipment of the world's leading manufacturers. In fact, to increase the level of monitoring of the state of communication lines in an analog addressable system, the modules transmit to the panel not the “Open” and “Short Circuit” fault codes, but analog values associated with the resistance of the communication line. Depending on the level of current consumption of the sirens in the “Fire” mode, various technical solutions can be used. In the simplest case, with relatively small load currents, for example up to 75 mA, the sirens are powered from an addressable analog loop, and controlled through transistor switches. The LPS800 siren control module has two pairs of outputs S+ S- and R+ R-. A class B radial communication line with an end-of-line resistor is connected to the S+ S- outputs (Fig. 3). The class A ring communication line is connected to the S+ S- and R+ R- outputs, and the end-of-line resistor is connected to the R+ R- terminals (Fig. 4). In this case, the sirens are powered from both outputs simultaneously and, despite the communication line being broken, they all remain operational.
In both cases, the analog-addressable panel monitors open and short-circuited communication lines using analog values of current and voltage, determined in standby mode by an end-of-line resistor. Figure 5 a, b, c shows the analog values on the display of the analogue addressable panel received from the LPS800 module with address A249, respectively, for standby mode, communication line break mode and communication line short circuit mode.
Sounders with high consumption currents of up to 2 A are powered from an external power source so as not to overload the addressable analog loop, and control is carried out using a polarized relay. Accordingly, the SNM800 siren control module, in addition to two pairs of outputs S+ S- and R+ R- for connecting sirens, additionally has two pairs of terminals I+ I- for connecting an external power source and connecting power to the next module (Fig. 6, 7). When using a class A ring communication line, the sirens are powered from both outputs and, despite the communication line being broken, they all remain operational (Fig. 7). In this case, the addressable analog panel monitors the voltage of the external power supply at the module input based on the readings of analog values transmitted by the SNM800 module, and generates the “Fault” and “Sounder Fault” signals when the supply voltage decreases.
a) standby mode; b) communication line break mode; c) mode of short circuit of the communication line
UNADDRESSED MODULES
To control sirens with high current consumption up to 15 A, additional non-addressable modules can be used - sound boosters (Fig. 8). 
The module contains 2 relays, dual terminals for connecting an external power source and for connecting a radial communication line with sirens. Inflows up to 10 A can be connected to codinary terminals; for higher currents, it is necessary to use a parallel connection of each conductor, as shown in Figure 9. The SB520 module is connected to the communication line of the LPS800 module or SNM800 module through the I/P terminals, and the end-of-line resistor is connected to the EOL terminals. The sound booster relay module provides monitoring of communication lines with sirens and monitoring external voltage input power. If a fault is detected, the SB520 module turns off the EOL resistor and thereby transmits a fault signal via the LPS800 or SNM800 address module to the control panel.
Thus, modern technical solutions with class A communication lines according to NFPA72 classification, ensuring the operability of all sirens when the communication line is broken, and relay modules with control of the communication line and voltage of the external power source can significantly increase the level of operability of fire protection systems in fire conditions. It should also be noted that in domestic standards there are no requirements for the classification of loops and communication lines, which leads to the widespread use of only radial communication lines, which are inoperative when broken. The lack of clear requirements in regulatory documents for monitoring communication lines allows the use of relay modules without monitoring the presence of supply voltage, which significantly reduces the level of control over the performance of fire protection systems.
To be continued...
LITERATURE
1. Not bad I. Classes and styles and trains. Ensuring performance. Part 1 // "Security Algorithm". - 2012. - No. 5.
2. Not bad I. Classes and styles and trains. Ensuring performance. Part Two // "Security Algorithm". - 2012. - No. 6.
3. NFPA 72-2013, National Fire Alarm Code.
4. No. 123-FZ Technical regulation on fire safety requirements.
5. Code of Practice SP 6.13130.2009 “Fire protection systems. Electrical equipment. Fire safety requirements.
6. GOST R IEC 60332-3-22-2005 Testing of electrical and optical cables under flame conditions. Part 3-22. Flame propagation along vertically located bundles of wires or cables. Category A.
7. Set of rules SP 6.13130.2013 “Fire protection systems. Electrical equipment. Fire safety requirements."
8. Code of Practice SP 3.13130.2009 “Fire protection systems. Warning and management system for evacuation of people in case of fire. Fire safety requirements."
9. GOSTR 53325-2012 Fire fighting equipment. Fire automatic equipment. General technical requirements. Test methods.
