Wu Chunhong Anke Rui Electric Co., Ltd. Shanghai Jiading
Abstract: This article briefly describes the composition principle of electrical fire monitoring system, and analyzes the design basis and related specifications of electrical fire monitoring system in application. Finally, through the example of the Ankerui residual current electrical fire monitoring system in Zoucheng Sports Center project, the realization of the function of the electrical fire monitoring system and its important significance are described.
Keywords :electrical fire; monitoring system; Acrel-6000/B; Zoucheng Sports Center
0 Foreword
Electrical fire generally refers to the thermal energy released due to the faulty release of electrical lines, electrical equipment and power distribution equipment, such as high temperature, arc, spark and non-failure release of energy; such as the hot surface of electric heating appliances, with combustion conditions Fires caused by igniting a body or other flammable materials also include lightning caused by lightning and static electricity. Electrical fires mainly include the following four aspects: electric leakage fire, short-circuit fire, overload fire, and excessive contact resistance fire.
The "China Fire Statistics Yearbook" of the Ministry of Public Security Fire Department shows that: In the 2010 fire accident, electrical fires took the first place, and the proportion of them was on the rise. The resulting losses were extremely heavy. In fact, electrical fires have become the main disaster-causing factors for fire safety, not only because of the large number of times, but also because of large losses, and they have remained high for many years.
The proportion of electrical fire accidents has increased year by year, which is worrying. For the severe electrical fire situation, early forecasting, early warning, and forecasting are the top priorities for firefighting, and eliminating the occurrence of electrical fires at the source has become the focus of attention. The task of preventing and effectively curbing electrical fires is imminent. Relevant state departments have successively formulated or revised relevant standards and specifications and required the installation of electrical fire monitoring and alarm systems in buildings.
1 Reference standard
In recent years, in order to increase the intensity of prevention and control of electrical fires, the state has successively formulated or revised a number of relevant standards and regulations to strengthen the prevention of electrical fires. There are:
1.1 is GB50045-95 (2005 edition) "High-rise Civil Building Design Fire Protection Code", which provisions in the provisions of 9.5.1: high-rise buildings in the fire risk, personnel intensive and other places should be set up a leakage fire alarm system.
1.2 is the GB50016-2006 “Code for the Fire Protection of Building Designsâ€. It is stipulated in Clause 11.2.7 that: The following places should be equipped with a residual current action electrical fire monitoring system. These venues include various types of theaters, halls, warehouses, residential quarters, hospitals, shops, schools, and so on.
1.3 The relevant provisions of the national standard “Building electrical fire prevention requirements and detection methods†also explicitly require that "the residual current protection device that automatically cuts off the power supply or alarm should be installed at the power supply inlet".
1.4 The product of the electrical fire monitoring system shall meet: GB14287.1-2005 "Electrical Fire Monitoring Equipment", GB14287.2-2005 "The Residual Current Electrical Fire Monitoring Detector", GB14287.3-2005 "Temperature-based Electrical Fire Monitoring" detector"
1.5 The installation and operation of electrical fire monitoring system should meet GB13955-2005 "Installation and Operation of Residual Current Operation Protection Device"
1.6 The power supply of the electrical fire monitoring system should meet the requirements of GB50052 "Design Specification for Power Supply and Distribution System"
1.7 The design of the electrical fire monitoring system should meet the requirements of the "Design Method for Electrical Fire Monitoring Systems" (Interim Provisions)
2 system components
According to the national standard GB14287-2005 "Electrical Fire Monitoring System" and related specifications "Design Method of Electrical Fire Monitoring System" (provisional regulations), the basic composition of the electrical fire monitoring system shall include: electrical fire monitoring equipment, residual current electrical fire Monitoring detectors and temperature-detection type electrical fire monitoring detectors are composed of the three most basic product categories.
2.1 The residual current type electric fire monitoring detector is again composed of a monitoring detector and a residual current transformer (two kinds of plug-in type and closed type); the temperature-type electric fire monitoring detector consists of a monitoring detector and a temperature sensor. composition.
2.2 The residual current type electrical fire monitoring system adopts a hierarchical distributed structure and consists of station management layer, network communication layer and field device layer. All electrical fire monitoring detectors are connected to the electrical fire monitoring host through a shielded twisted pair cable through a shielded twisted pair RS485 interface and a MODBUS communication protocol bus type connection.
2.2.1 The field device layer is mainly connected to various types of instruments and protection devices used for the collection and measurement of electrical parameters in the network, and it is also a necessary basic element for constructing the monitoring system. Not only shoulders the heavy responsibility of collecting data, but also is a terminal component that executes background control commands.
2.2.2 Communication control layer is mainly composed of communication server, interface conversion device and bus network. This layer is the bridge for data information exchange. Different interface conversion devices provide various interfaces such as RS232, RS422, RS485, SPABUS, and Ethernet, flexible networking methods, support for point-to-point communication, fieldbus networks, Ethernet, and other types. The configuration network. The communication server is mainly used to directly transmit various control commands of the host computer to the field instrument and meter, and is responsible for collecting, classifying, and storing the data information sent back by the field instrument, such as voltage/current and other electrical parameters and input switch status. , Modify the internal parameters of the instrument or various control relays to open / close operation commands; microprocessor protection device is mainly to ensure the normal operation of the host computer to avoid interference or damage caused by unstable signals in the network; interface conversion device It is due to differences in the communication interface between the field instrument or other series of devices and the host computer. It is necessary to perform the conversion before the data exchange.
2.2.3 Management The monitoring and control layer is for the management personnel of the monitoring network. This layer directly faces the users. This layer is also the uppermost part of the system, mainly by the electrical fire monitoring system software and necessary hardware equipment such as computers, printers, UPS and so on. The software part has a good human-computer interaction interface. It reads the various data information collected by the front-end machine through the data transmission protocol, and is automatically calculated and processed to reflect the operation status of the site by means of graphics, digital display, and sound. Accept the operation command of the management personnel, send and check the execution status of the operation in real time to ensure the normal operation of the power supply unit.
3 system features and working principle
The characteristics of the electrical fire monitoring system are that the residual current monitoring is an early warning system. Unlike traditional fire automatic alarm systems, early warning of electrical fire monitoring systems is to avoid losses, while traditional fire automatic alarm systems are used to reduce losses. Therefore, this means that no matter whether it is a new or reconstructed project, especially a unit that has already installed an automatic fire alarm system, it still needs to install the root cause of the electrical fire monitoring system.
The electrical fire monitoring system measures the two physical quantities of residual current and temperature.
Residual current measurement is based on Kirchhoff's current law: At the same time, the vector of the current flowing into and out of a node in the circuit is zero. Taking the TN-S system as an example, the A/B/C/N is passed through the residual current transformer at the same time. When the system is not leaking, the current vector flowing into and out of the residual current transformer is zero, and at this time, the residual current The secondary current induced by the transformer is also 0; when a leakage occurs on a relatively large ground, the current vector at the time of flowing into and out of the residual current transformer is no longer zero, and its magnitude is equal to the current flowing from the ground, ie the leakage current. The leakage signal is transmitted to the electrical fire detector through the secondary wiring of the residual current transformer, and is transmitted to the CPU after operation amplification, A/D conversion. After a series of algorithms, the amplitude of the change is analyzed, judged, and The alarm set value is compared. If the value exceeds the set value, an audible and visual alarm signal is sent and sent to the back-end electrical fire monitoring equipment.
The temperature measurement uses a temperature sensor, which is generally measured using a Pt100 sensor. This type of temperature sensor has a stable temperature measurement range and a large measuring range. It is suitable for on-site monitoring of cable temperature and ambient temperature. When the temperature changes, the resistance of Pt100 changes with the same proportion. The resistance signal is transmitted to the electrical fire detector. After a series of signal conversion and calculation, the final result is compared with the temperature alarm setting value. If the value exceeds the fixed value, An audible and visual alarm signal is sent and sent to the back-end electrical fire monitoring equipment.
4 System Design Considerations and Methods
4.1 The electrical fire monitoring system mainly monitors the residual current and temperature two types of objects, the basic points to pay attention to in the design
4.1.1 About Residual Current
Since the principle of residual current monitoring adopts Kirchhoff's current law, there is a certain requirement for the form of the applied low-voltage power distribution system. At present, low-voltage power distribution systems that can use residual current transformers are: TT systems, IT systems, TN-S systems, and cannot be used in TN-C systems. For users who will design and install an electrical fire monitoring system, whether it is a new project or an old one, it is first necessary to investigate and verify what the system grounding form of the user's low-voltage power distribution system is. Otherwise, design and install the point of the residual current transformer. Testing is simply not possible.
With regard to the AC220V single-phase power supply system, the residual current transformer can only cover two L/N power lines, but it is required that the neutral line N is not allowed to be grounded thereafter. For the AC380V three-phase power supply system, due to the use of three-phase three-wire system, three-phase four-wire system, three-phase five-wire system, etc., according to the specific circumstances of the residual current transformer will be at the same time jacketed A / B / C three-phase power line, Or cover the A/B/C/N line at the same time. Similarly, it is required that the neutral line N is not allowed to be grounded after that and the protection line PE must not pass through the transformer.
When the system is grounded in the form of a TN-C type industrial automation network, it must be converted to a TN-S type, TN-CS type, or a local TT type system before the residual current detection device can be installed.
4.1.2 About Temperature
The temperature measurement has nothing to do with the form of system grounding. It mainly considers the temperature of key parts in low-voltage power distribution equipment, including cables, and is generally applied in the secondary protection circuit. The temperature probe Pt100 can adopt the contact arrangement method. When the detected object is an insulator, the temperature sensor of the detector should be directly set on the surface of the object to be detected. When the detected object is a change in the internal temperature of the distribution cabinet, a non-contact arrangement can be used, close to the heat-generating components.
4.2 Point allocation in system design
According to the provisions of the national standard GB13955-2005 “Installation and Operation of Residual Current Operation Protection Device†4.4, concerning graded protection, when installing the residual current fire monitoring device, the steps of point allocation principle are:
4.2.1 Research and analysis Relevant drawings for AC380V/220V distribution lines controlled by low voltage, check and verify the distribution of construction electrical, and determine the location of distribution equipment (such as distribution cabinets, boxes, trays, cables and other important equipment). Each monitoring detector is assigned to the corresponding distribution equipment to determine the number of detectors and avoid resetting waste.
4.2.2 Determine graded protection. In order to reduce the scope of power outage caused by personal accidents and ground faults when cutting off the power supply, three-level (or two-level) residual current protection devices with different capacities are usually installed at different locations of the power supply line to form a hierarchical protection. According to the power load and the line conditions, it is generally divided into two or three levels of protection, which is suitable for the protection of the first and second levels in urban and rural areas.
Among them, the important lines should include security, fire protection, emergency power supply, channel lighting lines and important places that do not allow blackouts.
4.2.3 In the secondary protection, all switches shall be installed with a residual current fire monitoring detector, ie both at the power end of the line (first level protection) and at the beginning of the branch (second level also called end protection). Installation of residual current detectors, and access to electrical fire monitoring systems, only for fire monitoring and alarm.
4.2.4 In the tertiary protection, the residual current detector and action protection device shall be installed at the third level (ie end protection) switch, but the electrical fire monitoring system shall not be connected in order to prevent personal electric shock.
4.2.5 Temperature detection is based on the basic principle of heat generation in abnormal distribution equipment.
1) transformer low voltage side outlet terminal, transformer body temperature (wind temperature, oil temperature, water temperature) test point, load switch contacts.
2) Access points of the power distribution cabinets (boxes), contact points of automatic switches (circuit breakers, knife switches), concentrated current conductors, and cable connection points.
3) Master contact, knife switch contacts.
4) Compensation capacitor terminals and transfer switch contacts.
5) According to the total number of points installed, then select the appropriate wall, vertical or Qintai.
5 configuration of system parameters
5.1 alarm value setting range
According to the provisions of the national standard GB14287.2-2005, the alarm value of the residual current type electric fire monitoring detector is set in the range of 20~1000mA. According to this requirement, the residual current operating value at the total power supply line is generally set to 400~800mA, and the residual current operating value on the power branch line is set to 100~400mA. Generally, in the actual site, the residual current type electric fire monitoring and detection is set. The alarm value of the device shall not be less than 2 times the maximum value of the leakage current during normal operation of the protected electrical circuit and equipment, and shall not be greater than 1000 mA. Electrical fire detectors' alarm settings should take into account the normal leakage currents of the distribution system and electrical equipment.
5.2 About the cable temperature rise alarm setting reference, according to "power cable design specifications" on the cable temperature requirements
5.2.1 High temperatures above 60°C should be subjected to high temperatures, their duration and insulation type requirements. Heat-resistant PVC cables, cross-linked polyethylene or ethylene-propylene rubber insulation, etc. should be selected. High temperatures above 100°C should be used for minerals. Insulated cable. High-temperature places should not use ordinary PVC insulated cables.
5.2.2 The ambient temperature of the continuous allowable ampacity of the cable shall be determined according to the multi-year average of the meteorological temperature in the area of ​​use and shall comply with the regulations. When laying the cable trench in the house, the ambient temperature is the average of the highest daily temperature in the hottest month of the site plus 5°C.
5.2.3 Cable temperature rise is related to laying and heat dissipation conditions.
6 System Design Example
Zoucheng Sports Center is located in the northern part of Zoucheng District. The Zoucheng Gangshan Mountain covers an area of ​​480 mu and is one of the most important stadiums in Shandong. Zoucheng Sports Center is a sports plaza in the northern part of the stadium. There are 400-meter plastic runways and standardized football stadiums on the venue. The Roman side stands on the west side and the semi-circular continental corridors on both sides of the north and south. It can accommodate more than 20,000 people. Located in the south of Zoucheng Sports Center is Zoucheng Stadium, which is a 3-storey building with a total area of ​​more than 10,000 square meters. It has a total of 3,380 square meters of seats, which can be used for training and competitions in various sports events and undertake large-scale trade, performances, and rally events. Is a modern, high-grade, multi-purpose venues. The eastern part is a mass fitness area and entertainment area, while the western part is a sports training area and sightseeing area. The Zoucheng Sports Center is built on a hillside with an overall layout that is patchwork. The pavilion and the mountain are beautiful, with beautiful natural scenery, unique cultural landscapes, exquisite architectural construction, and spectacular central venues. It is an important sports activity center and iconic building in Zoucheng. In addition, a gymnasium for sports facilities is also built.
The electric fire monitoring system of the Zoucheng Sports Center consists of an electric fire monitoring device Acrel-6000/B, a leakage fire detector ARCM300-J1, and a leakage current transformer AKH-0.66L.
Acrel-6000 electrical fire monitoring system is an independent research and development by the company to receive the residual current electrical fire detectors and other field equipment signals, in order to achieve the protection of the electrical circuit alarm, monitoring, control, management of the computer running on the industrial level Hardware/software system. This system is applied to fire control centers in large shopping malls, living quarters, production bases, office buildings, shopping malls, hotels, etc., and remotely measure, remotely adjust, remotely control, and remotely locate the detectors scattered in the building to facilitate monitoring and management. The system uses a standard Modbus field bus to connect detectors with communication functions. When the detected parameters in the field protection circuit exceed the alarm setting value, it can send alarm signals, control signals, can indicate the alarm location and save the alarm. information.
There are 43 ARCM300-J1 residual current type fire detectors on the site of Lingang Bairun Times Square, installed at the entrance of the floor distribution box. On-site fire detectors are bus-connected to the Acrel-6000/B wall-mounted electrical fire monitoring system. This system has the advantages of convenient installation and transportation, high cost performance, and easy maintenance.
1. Power supply:
1 rated working voltage AC220V (-15% ~ +10%)
2 Standby power supply: When the main power supply is under voltage or power failure, maintain the monitoring equipment working time ≥ 4 hours
2. Work system:
24-hour work
3. Communication method:
RS485 bus communication, Modbus-RTU communication protocol, transmission distance 1km, can extend communication transmission distance through repeater
4. Monitoring capacity:
1 Monitoring equipment can monitor up to 200 monitoring units (detectors)
2 can be connected with ARCM series monitoring detector
5. Monitoring alarm items:
1 Residual current fault (leakage): Fault cell attributes (position, type)
2 Temperature alarm (over temperature): Fault cell attributes (part, type)
3 Current fault (overcurrent): Fault cell attributes (part, type)
Monitoring alarm response time: ≤30s
Monitoring alarm sound pressure level (A weighting): ≥70dB/1m
Monitoring alarm light display: red LED indicator, red light alarm signal should be maintained until manual reset
Monitoring alarm sound signal: Can be eliminated manually, when it is alarm signal input again, it can start again
6. Fault alarm items:
1 An open circuit or short circuit occurred in the communication cable between the monitoring equipment and the detector
2 Monitoring equipment main power supply undervoltage or power failure
3 An open circuit or short circuit occurred in the connection between the battery charger and the battery
Fault alarm response time: ≤100s
Monitoring alarm sound pressure level (A weighting): ≥70dB/1m
Monitoring alarm light display: yellow LED indicator, yellow light alarm signal should be maintained until troubleshooting
Fault alarm sound signal: can be eliminated manually, when the alarm signal input again, can start again
During faults, normal operation of non-failed circuits is not affected
7. Control output:
Alarm control output: 1 set of normally open passive contacts, capacity: AC250V 3A or DC30V 3A
8. Self-inspection project:
1 Indicator Check: Alarm, Fault, Operation, Main Power, Standby Power Indicator
2 display check
3 audio device inspection
Self-check time ≤60s
9. Event record:
1 Record content: record type, occurrence time, detector number, area, fault description, no less than 20,000 records can be stored
2 record query: according to the record of the date, type and other conditions
10. Operational rating:
1 daily shift: real-time status monitoring, event record query
2 monitoring operation level: real-time status monitoring, event record query, remote reset of the detector, device self-test
3 System management level: real-time status monitoring, event record query, remote reset of detector, device self-check, system parameter query of monitoring equipment, individual detection of each module of monitoring equipment, operator addition and deletion
11. Use environmental conditions:
1 Workplace: fire control room, manned power distribution (distribution room), on-call room walls
2 working environment temperature: 0 °C ~ 40 °C
3 working environment relative humidity: 5% to 95% RH
4 Altitude: ≤2500m
basic skills
1. Monitoring alarm function:
The monitoring equipment can receive the leakage and temperature information of multiple detectors. When the alarm sounds, an audible and visual alarm signal is emitted. At the same time, the red “alarm†indicator light on the equipment is on. The display indicates the alarm location and type of alarm, records the alarm time, and the sound and light alarm keeps Until the display resets the detector remotely. The audible alarm signal can also be manually cancelled using the display “Mute†button.
2. Fault alarm function
Communication failure alarm: When a communication failure occurs between the monitoring device and any connected detector, the corresponding detector in the monitoring screen displays a fault prompt, and the yellow “fault†indicator light on the device is on, and a fault alarm sound is emitted. .
Power failure alarm: When the main power supply or standby power supply fails, the monitoring device also emits an audible and visual alarm signal and displays the fault information. You can enter the corresponding interface to view the detailed information and cancel the alarm sound.
3. Self-test function
Check if all the status indicators, display screens and speakers in the device are normal.
4 alarm record storage query function
When leakage, over temperature alarm, or communication or power failure occurs, the alarm location, fault information, alarm time, and other information are stored in the database. When the alarm is removed and the fault is eliminated, it is also recorded. Historical data provides a variety of convenient and fast methods for searching.
5. Power function
When the main power supply has a power failure or undervoltage, the monitoring device can automatically switch to the standby power supply. When the main power supply resumes normal power supply, it automatically switches back to the main power supply, ensuring continuous and smooth operation of the monitoring device during the switchover process.
6. The detector control function
By monitoring the software operation, remote reset control can be performed on all detectors connected to the device.
7. Authority control function
In order to ensure the safe operation of the monitoring system, the monitoring device software operating authority is divided into three levels, and different levels of operators have different operating rights.
System network structure
1) Station control management
Station management The management personnel of the electrical fire monitoring system are the direct windows of human-computer interaction and the top part of the system. Mainly by the system software and necessary hardware devices, such as touch screen, UPS power supply and other components. The monitoring system software calculates, analyzes, and processes various types of data on the site, and responds to the on-site operations by means of graphics, digital display, sound, and indicator lights.
Monitoring host: used for data acquisition, processing and data forwarding. Provides data interfaces within or outside the system for system management, maintenance, and analysis.
UPS: Ensure the normal power supply of the computer monitoring system. When the power supply problem occurs in the entire system, ensure the normal operation of the station control and management equipment.
Background monitoring equipment is set in a layer of control center.
2) Network communication layer
Communication medium: The system mainly adopts shielded twisted pair, uses RS485 interface and MODBUS communication protocol to realize real-time communication between field device and host computer.
3) Field device layer
The field device layer is a data acquisition terminal, mainly ARCM300-J1 remaining electrical fire monitoring detector. The ARCM300 type residual current electrical fire monitoring detector is designed for TT and TN systems up to 0.4kV. It monitors and manages the fire hazard parameters such as residual current, wire temperature, overcurrent, and overvoltage in the distribution circuit. This prevents the occurrence of electrical fires and enables real-time monitoring of multiple power parameters, providing accurate data for energy management. Products using advanced microcontroller technology, high degree of integration, compact size, easy installation, intelligent, digital, network in one, is the building electrical fire prevention and control, insulation insulation system, such as the ideal choice. The product meets the standard requirements of GB 14287.2-2005 "Electrical fire monitoring system Part 2: Residual current electrical fire monitoring detector".
The distributed I/O controller connected to the fieldbus forms a data acquisition terminal and uploads the collected data to the data center. The measuring probes are responsible for the most basic data acquisition tasks. The data they monitor must be complete, accurate and transmitted to the monitoring host in real time. It is convenient for operating personnel to monitor the status of field equipment operation, fault alarms, etc. to effectively prevent the occurrence of fire accidents.
The system has been operating well since it was put into operation and has played an important role in preventing electrical fires. It has gained customers' recognition and trust in products and companies.
references
[1]. Ren Cheng, Zhou Zhongzhong. Principles and Application Guide for Digital Meters for Electric Power Measurement [M]. Beijing. China Electric Power Press, 2007. 4
[2].Zhou Zhong. Application of Electric Power Meters in Energy Metering of Large-scale Public Buildings [J]. Modern Building Electric 2010. 6
About the author: Wu Chunhong, female
Position: Current Position: Ankerui Electric Co., Ltd.
Contact number 18702111910
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