【 Weak current College 】 electrical fire safety testing technology research and analysis---Power By 【 China power house network 】

Summary: the electric fire early warning technology application analysis, use the "doctrine of" related specification, effectively regulate the installation site and the related application standards, describes the electrical fire norms in China has reached a new level of technology.
Keywords: electrical leakage fire standards for fire alarm technology electrical installation considerations
As China's people's living standards, consumption continues to increase, but the electric fire is soaring, and thus also to the national economy and the people of life and property caused tremendous losses. According to "China Fire Statistics Yearbook statistics, 1993-2002 national-wide total electrical fire 203780, accounting for nearly 30% of the total number of fire, electrical fire caused personal injury figures are striking, only 2000 — 2002, causing 3215 casualties. Especially in the heavy and catastrophic fire, electrical fire greater proportion.
Japan in 1978, in its internal rules (JEAC8001 — 1978) No.190 explicitly request the building area of 150 square meters or more hotels, hotels, apartments, dormitories, family apartment, public houses, bathhouses, you must install automatically alarm fire alarm of leakage. This specification is Japan electrical fire control played an important role, the electric fire accounted for only 2% of the fires-3% (its per capita electricity consumption for the country's 8 times). IEC International Electrotechnical Commission 1200-53 1994-10 594.4 clear requires use of secondary or tertiary residual current protection device, protect against leakage caused by electrical fire and electric shock accident. In the 1990 's began in some electrical specification on ground fault prevention fire made. For example, the residual current protection equipment is installed and running (GB13955), the low-voltage distribution design code (GB50054), the residential design code (GB50096), the civil construction electrical design code (JGT/T16).
In 2005, for example, the top ten fire deaths up in two cases the Central Hospital of Jilin province liaoyuan fire, Shantou South Hotel fire, electrical fire, both as experts actively call as soon as possible to take effective technical preventive measures to curb rising momentum electrical fire, attracts public attention, we have drawn up or amended the relevant standards, the requirements in the building fire alarm system leakage. The tall buildings design fire protection standard "GB50045-95 (2005 Edition) partial amendments 9.5.1, mandatory national standard of the residual current operated protective devices installed and running on GB13955-2005 highlighted the residual current operated protective device to prevent ground fault caused electrical fire protection, the requirements in the building installation residual current operated fire monitoring system. Prevention of fire, electrical leakage fire alarm system of the National Institute of standards and norms have basic complete (there are other specifications are for approval), future site design, application leakage fire alarm system will more and more. Leakage current fire alarm system is a new type of alarm devices, according to the November 2005 issue of the "doctrine of" amendment provisions, and combined with leakage fire alarm system for product standards and install using the standard upgrade, currently, engineering design, installation, residual current fire alarm system, there is no uniform regulations, this new type of electric fire protection devices encounter new problems, and standardized.
First, the leakage current fire alarm system of function definition
(A) should have detected over current, leakage current, voltage, and other less-voltage signal, making accurate acousto-optic alarm, displays the failed status and actions to cut off the power.
(Ii) monitor the changes of the point of failure, the point of failure should be able to automatically record the current status.
(C) the storage of various kinds of failures and operational test signal, the signal storage time should not be less than 12 months.
(4) displays the system power state.
(5) should use the bus system, implementation of "remote control, telemetry, remote control, remote inquiry", communication distance 1.2km above, buses can take 1 mm2 copper conductors.
(6) the point of failure should have the site address coding capabilities
(VII) monitoring host should be used in industrial control machine or fire alarm system with a single monitoring host
2, leakage fire alarm system design
(A) specification of the leakage of fire alarm system of the relevant provisions
At present, the leakage current fire alarm system design was largely based on the high-level civil building design fire protection standard "GB50045-2005 partial amendments: 9.5.1 high-rise buildings in fire risk, personnel are crowded, and other places to set current fire alarm system. In addition, for approval of new building design fire protection standard of section 11.2.7: shops, theatres, cinemas, Sports Centre, personnel are crowded places to set current fire alarm system. New formulation and approval of the construction electrical fire prevention requirements and test methods "relevant provisions" should also explicitly requested in the power-set automatically cut off power supply or alarm for residual current operated protective devices ". Standard provisions for "leakage" of fire alarm system ", that should be a networking equipment as a whole, is a complete system, not a single previously scattered settings or leakage alarm can be traditional rccb. The doctrine of law by the description, also placed special emphasis on "these devices to adopt national fire electronic product quality supervision and inspection center of qualified products to ensure quality and safety", visible not use ordinary earth leakage switches can, many electrical designers often tend to have this error.
The word "should", standard terms Note: allows selection of slightly, when the conditions permit, should be done first. Visible, "Yi" principle is the first thing to consider is set, no exceptional circumstances whatsoever, without the consent of the competent authorities of the fire could not be set arbitrarily choose Cancel.
(Ii) specific leakage alarm design and installation location
Because of the tall buildings design fire protection standard of architecture design specifications, and not leakElectric fire alarm system products inspection standards, nor is the leakage current fire alarm system design, construction and acceptance, the provisions of the comparison, the current leakage fire alarm system design, installation, acceptance is not clearly labeled, inevitably affects the leakage of fire alarm systems engineering construction and running smoothly, affecting its leakage fire alarm system functions properly.
1. in accordance with the national standard of the residual current operated protective devices installed and running on GB13955-2005, the provisions on the classification of protection, installation of residual current fire monitoring device, the response to building fire region make reasonable distribution design, determine the appropriate scope of protection, intended for residual current operated values and actions, and should meet the rating protection characteristics, reduced failure caused by cutting off the power outage. Therefore, the design-time control of the distribution system should first of all relevant parameters have a clearer understanding of the relevant control distribution line of related drawings and construction electrical distribution investigate to determine power distribution equipment (distribution boxes, trays, Cabinet) of the location, the leakage alarm assignment to the appropriate distribution equipment, according to the actual situation, such as: setting current, normal exposure estimation, identification of current leakage alarm volume configuration. To avoid duplication, distribution is as follows: under construction electricity load and line specific circumstances, determined using two-or three-tier protection mode; General all levels switch all to install leakage detectors; third-level Office switch is installed according to the load conditions and construction purposes, actual fire risk, etc. To determine the leakage alarm installation location should take bus design, wiring, bus system for four cores, should form a separate system bus, bus to RS232 or RS485 serial port, and PC control system consisting of leakage, fire alarm system. Bus-transfer instrument and PC control system should be installed in the fire Centre or control room.
2. important load: including fire, security, emergency power supply, passage lighting circuits and power-off is not allowed, an important place, under GB13955 4.6 shall install leakage alarm-alarm with acquisition leakage current, overcurrent and other signal that exceeds the set value, only the issue of sound and light alarm signal, but do not cut off the power, at the same time, the acquisition of signals, by bus, to the control center, you can set manual power off mode, ensure that the electrical safety and guarantee the uninterrupted power supply. 3. the design must be careful to avoid classification protection, large-scale power outages in principle to prevent electrical fire, GB13955-2005 emphasizes the use of hierarchical protection, power supply side or branch lines of residual current protection devices should be the end of the residual current protection device operating characteristic should coordinate with the implementation of the rating with selective action to avoid massive power failure protection. In General, when the power-or branch-main loop, you should choose the low sensitivity of residual current protection, time delay. But in the end, out current I Δ n ≤ 30mA, rated action time 0.1s Tn ", mainly used for protection against personal electric shock, fire alarm system with electric leakage is a complementary relationship.
Total building floors into line Department can install one or several sets of leakage alarm, but according to the normal size, proper disclosure of the current and select parameters for leakage alarm. General total into the line of the residual current is 200 ~ 500mA.
4. the current installation of fire alarm system design based on leakage fire alarm system product selection and project distribution system characteristics, and generally have several design patterns: (1) the distribution box or control box internal form of installation design
Generally used for new projects in the floor is equipped with specialized floor distribution box or control box. Leakage alarm mounted directly in the distribution box or to the appropriate location within the control box. (2) the distribution box or control box (Cabinet) external forms of installation design
Leakage alarm creates a separate body, the total power through leakage alarm, power supply and then access distribution box or control box.
For new and old (retrofit) project, leakage alarm simply power first introduced leakage alarm switch device and then access distribution box or control box.
Specialized installation leakage controllers fire monitoring box located in the distribution box or control box. Revamping project of recommended torque-current transformer, you can try not to touch the original distribution box (Cabinet) of the internal wires and devices.
(3) distribution cabinet design of complete form of installation directly in the distribution box or control box Panel embedded leakage current controller, consider only the appropriate location within the Cabinet fixed current transformer (usually in the main air open top, or bottom), do not change the internal structure of distribution Cabinet, without increasing the separate enclosure leakage controller, that is, artistic, and does not occupy the space. Should be clearly stated requirements in the design, construction drawing triage, by distribution Cabinet complex plant consider reserved Panel embedded with leakage current controller's hole.
Third, the leakage of fire alarm system installed in the following (a) the leakage current fire alarm system construction of main unit based on the above leakage characteristics of fire alarm system, fire alarm system leakage current high independence, but distributing system are inseparable, into strong electric system construction comparison easy. On the other hand, the practice shows that those to the fire alarm system construction unit construction, easy pointing and coordination difficulties, combined with its strong to control cabinet with unfamiliar, the strong electricity conductor connection, installation location, and other relatively new, it is difficult to guarantee quality.
(Ii) residual current fire alarm system construction requirements of national standards of the residual current operated protective devices installed and running on GB13955 part 6 "residual current protection device installation" clearly pointed out: "residual current protection device setup should take full account of the power supply, power supply voltage, grounding and protection. Residual current protection device forms, rated voltage, rated current, short circuit breaking capacity and nominal residual current, breaking time should meet protection circuits and electrical equipment requires, on a different system grounding wiring should be the correct form. "
Fourth, the leakage current fire warning system put into use, you should note the following
(A) wiring should be leakage alarmDevices marked by the power-and outlet side, correct wiring shall be reversed.
(2) install the breaker should be required, in the direction of arc spraying out enough arcing distance.
(3) when you install, you must strictly distinguish between N and PE lines, four lines or 3P 4P four lines of N-line through the leakage current from the fire monitor system detectors mutual inductance. Through the leakage current of fire alarm system of the mutual induction detector N line, not as PE lines, not to repeat the grounding or received equipment exposed to near conductors. PE lines must not access the residual current protection device.
(4) the leakage current fire alarm system into the distribution system construction unit construction, both sides should fully communicate, coordinate relevant installation, dimensions, and electrical parameters. A new project using electrical leakage when the fire alarm system, power distribution cabinet (box) when ordering copies of the product should be made to the factory dimensions, hole, in order to calculate the location of the installation.
(5) the senior civil building design fire protection standard "GB50045-2005 requirements of section 9.1.1, leakage fire alarm system shall be in accordance with the provisions of the fire power. Therefore, regardless of the fire Centre sets the PC control system, in accordance with the provisions of the fire power, access the fire power.
(6) the leakage current of fire alarm system of the mutual induction detector in distribution cabinet (box) in the installation, we should pay special attention to construction safety, power, construction, and note the ELV separate alignment, with special attention to prevent wrong line or daxian, resulting in strong electric strings into the leakage of fire alarm system bus system four cores, burned the entire leak fire alarm system.
(VII) reconstruction project should normally be the leakage alarm/residual current probe placed in the bottom outlet molded case circuit breaker, inconvenience when installed, consider installing the breaker's line-side.
(8) construction unit should be equipped with mobile (handheld portable) residual current detector, and the first distribution system for residual current detection, timely elimination of residual current anomalies, and made detailed records. 5.7.3 under GB13955 standards and requirements, set 5.7.5 appropriate leakage current alarm threshold alarm set value is typically the value is greater than or equal to the line and device functioning leakage current value twice.
(9) bus system four cores in parallel mode, all leakage alarm, bus to the control centre, the bus-transfer apparatus into a RS232 serial port, connect to the receive host, the host should install leakage monitoring software, have a two-way communication capabilities for "remote control, telemetry, remote control, remote control. ”
(10) in accordance with the requirements of the standard 6.3.7 GB13955 after installation must have the following inspection items: pressing the leakage alarm of "post" button, the test of whether the test release action. This test should be conducted individually, use the test button to test three times consecutively, the correct action, fire Center PC control system should display the current status, address, and automatically record; with rated load current Division 5 times, reliable movement, should not have the phenomenon of false alarms; manual on the distribution box for remote power-off tests should be correct.
(11) in the fire control centre operations PC control system, should be on any point of the fault monitoring conducted operation control, when you press the "test" button, the PC control system should be able to automatically receive display fault status and address code and record the current status and query. (12) leakage alarm system uses a system of management: monthly in power on mode, you can temporarily allow power-off, press the test button to check the reliability of leakage alarm actions. Lightning or fire causes power outage so leakage alarm actions, should be checked. Leakage alarm actions, after examination did not find the cause of the accident, allows a trial transmission once, if the action again, should identify the reasons for finding fault, not continuous force transmission, no crossover, shorted use leakage alarm.
5. Summary
Leakage current fire alarm system since the doctrine of "published in November 2005, the current market system products is divided into two series, the first is to current leakage detectors, fire alarm controller and the Terminal console. Another is to current probes, leakage alarm modules, molded case circuit breaker set-one called "leakage fire alarm controller" and the Terminal Console System. Both have their advantages and disadvantages, first, its performance in a molded case circuit breaker products system, small footprint, easy for installation and feature comparison is complete, the product performance is good, wide application, you can replace the power supply into the line-end switch, circuit breaker. Second, to current leakage detectors, fire alarm controller and other components system, performance is feature simple, molded case switches can be selective, install, and easy to maintain, adapt occasions range.
Reference materials
The tall buildings design fire protection standard "GB50045
The JHA leakage fire alarm system of application design guide
The JHA leakage fire alarm system, user manual