SummaryWith the continuous advancement and development of society, a variety of advanced electrical equipment has entered the public sphere, bringing convenience while rapidly increasing electrical safety hazards in various venues. Due to the use of large amounts of flammable materials like plastics, rubbers, insulating paints, and thinners in electrical equipment insulation, the operation of these devices can lead to overloading, short-circuiting, leakage, lighting, electric heating equipment, and switching actions, which can cause fuses to melt, poor contact, static electricity, and potentially result in high temperatures, high heat, and spark discharges. This can lead to fire and explosion accidents. Electrical fires are particularly dangerous, with rapid spread, prone to large-scale combustion, and during burning, they produce a large amount of smoke and toxic gases. These gases can cause poisoning and asphyxiation among workers, potentially leading to major tragic incidents with mass casualties. Therefore, the study of the causes of building electrical fires and the measures to prevent and control them has become extremely urgent. Taking the recent building electrical fires in our country as a case study, we analyze the electrical fire hazards in a Beijing supermarket and provide corresponding solutions.
KeywordsBuilding electrical fire; safety hazards; solutions
0 Introduction
The General Merchandise Store (GMS), also known as a lifestyle supermarket, is a combination of a standard food supermarket and a discount store, offering consumers a one-stop shopping experience to meet their basic living needs. Its popular and comprehensive range of products, along with flexible business practices, caters to modern consumer shopping habits. In recent years, the structures and functions of some large-scale lifestyle supermarkets have become more complex, with significant fire loads, high population density, and an increasing number of electrical equipment and installations within the buildings, which have raised higher requirements for electrical fire safety prevention.
1. Primary Causes of Electrical Fire Incidents
1.1 Electrical fire caused by overloading
The safe current-carrying capacity of conductors primarily depends on the conductor's core, that is, the material and cross-sectional area of the conductor. When the current in the conductor exceeds its safe load capacity, the conductor will heat up. The greater the excess load of the current, the more heat it generates. When the conductor's temperature exceeds 280°C, the rubber or plastic insulation layer of the conductor will catch fire. Additionally, if the "sleeve" of the wire is damaged, it can also cause a short circuit in the circuit, increasing the risk of fire. Moreover, if unsuitable fuses are used and circuit overloads are not detected in time, potential electrical fire hazards may arise. The main causes of electrical fires include: 1) excessive power of electrical equipment; 2) selecting a conductor cross-section that is too small; 3) adding too many loads to the circuit.
Overheating due to excessive contact resistance causes electrical fire
Improper wiring connections can lead to excessive contact resistance, which may cause overheating and potential fires. In circuit design, there are typically joints, usually connected by wires to each other, or wires to switches, fuses, and appliances. If these connections are incorrect, the current in the wires will be obstructed, resulting in significant heat generation. When the heat is high enough to melt the insulating material on the wire, it can ignite nearby flammable materials. Three reasons for electrical fires due to overheated contact resistance: 1) improper handling of copper-aluminum conductor connections; 2) the presence of impurities at the connection points, such as dirt, grease, and oxidation layers; 3) the contact points between wires or electrical equipment becoming loose due to thermal action or long-term vibration, or incorrect methods such as twisting or over-twisting more than two wires instead of using crimp connections.
March 1.3 Electrical fires caused by electrical lighting fixtures and lamps
Electrical lighting fixtures are widely used in daily life. However, improper use can lead to severe electrical fire accidents. The main causes of electrical fires caused by lighting fixtures include: 1. Faulty lighting fixtures can cause short circuits, overloads, and sparks that ignite surrounding flammable materials; 2. If the lighting tube breaks, the process can generate electrical sparks that ignite flammable substances nearby; 3. Lighting fixtures (including transformers and ballasts) installed directly on flammable decorative materials or structural components can easily ignite nearby flammable materials due to high temperatures of bulbs, tubes, sockets, etc., during operation.
1.4 Negligence due to Lack of Fire Safety Awareness
Many unit leaders, inspectors, and personnel from relevant departments exhibit a sense of complacency and neglect. They do not prioritize the popularization and learning of fire safety knowledge, fail to conduct regular safety inspections of electrical systems as required, and install fire protection facilities passively, such as not installing automatic alarms, automatic sprinklers, fire pumps, elevated fire water tanks, leaving fire doors not properly sealed, closing fire hydrant and sprinkler network valves, and even not having sufficient fire extinguishers. Some units also have obstructed fire escape routes, long-term accumulation of debris, and incomplete fire organization systems. Failing to promptly address issues raised during fire department inspections can lead to severe fire hazards.
Fire Safety Risk Analysis at a Beijing Supermarket
2.1 Overview of the Building
A lifestyle supermarket and shopping center in Beijing's Daxing District features a 4-story building above ground and a 1-story basement, with a total height of 18.00 meters. The total floor area is approximately 32,000 square meters. The first to third floors are shopping areas with similar structures, each with an area of about 8,000 square meters. The fourth floor is a restaurant, spanning approximately 4,000 square meters, and the basement houses a supermarket with an area of about 4,000 square meters.
The first floor building, in addition to retail shops, also includes property rooms, power rooms, employee offices, restrooms, and ground-level stores. Fire escape routes in all shops and rooms are clear, safety evacuation signs are prominently displayed, and fire exhaust facilities are reasonably designed.
The 2nd and 3rd floors, in addition to shops, also feature resting areas, restrooms, and storage rooms. The doors and windows are reasonably configured. A safe evacuation staircase is set in the central area. The windows in the evacuation staircase room are properly positioned for natural light and ventilation, and the fire exhaust facilities are reasonably arranged.
The 4th floor and basement level house a restaurant, supermarket, and storage rooms. A safety staircase is located in the central area, with no windows or doors on any of the floor's sides.
2.2 Fire Safety Hazard Analysis
2.2.1 Safety Awareness
The community supermarket was constructed too early, leading to a severe aging of both the shopping population and staff, and a lack of fire safety awareness among the management. There are also unsafe actions that could potentially lead to fire accidents, which are analyzed into two types of incidents. First, the causes of the incidents include the formation of fires, the management's ability and attitude towards fire safety, and the allocation of fire personnel during a fire. Second, the reasons for the expansion and spread of the incidents involve the understanding and mastery of fire rescue and self-rescue capabilities. The staff of the building have a shallow understanding and low concern for fire safety knowledge. The responsibilities of the lessee and property management for fire safety are unclear, and they tend to shirk their responsibilities when issues arise. Fire exits in the mall are often blocked by goods, and fire separation facilities are aging and components are missing, with no timely repairs. There is a "grey rhino" mentality, indicating a weak fire safety awareness, which makes electrical fires more likely to occur.
2.2.2 Risks Caused by Electrical Aging
The supermarket experienced issues with aging electrical equipment and wiring, as well as a complex array of electrical devices. Particularly, the EPS power supply showed signs of aging and leakage, rendering the main and backup power sources unreliable for switching. Both emergency lighting and evacuation signage could not be reliably activated in an emergency. Investigations revealed that the property department lacked an independent electrical maintenance and management department, failed to conduct regular safety inspections on electrical equipment, and did not promptly repair faults or address electrical hazards identified by relevant departments, posing a severe risk of electrical fires.
3 Electrical Fire Prevention Solutions
Through investigation and analysis, the supermarket is found to have issues such as weak safety awareness, inadequate fire equipment, unreasonable emergency exits, and a lack of a fire control department. Based on the on-site conditions, relevant suggestions are provided regarding the risk of electrical fires.
3.1 Characteristics of the Fire
(1) The commercial industry, compared to other sectors, has higher energy consumption in areas like decoration, air conditioning, etc., which is why fires are more frequent in the commercial sector.
(2) Seasonal. Due to the high energy consumption for air conditioning and longer lighting hours during winter and summer seasons, the impact is most pronounced during these two seasons.
(3) Human factors. Particularly, fires are often caused by violations of procedures or negligence, such as failing to promptly address discovered issues.
Fire Prevention Measures
3.2.1 Electrical Safety Precautions
Firstly, it is crucial to understand the pressure-bearing capacity of electrical meters and distribution lines, and avoid overloading them. Secondly, be cautious not to overload outlets; for high-power appliances, use separate power outlets. If multiple electrical devices share a single outlet, overheating of the distribution lines may occur when the current exceeds the rating, potentially leading to the insulation breakdown, melting, and even combustion of the plastic protective sleeve. Additionally, the fuse in the installed circuit breaker must be of the appropriate standard; never substitute with other metal wires, as this can easily damage appliances and cause fires. In the event of an electrical fire, ensure safety first, then cut off the power source before attempting to extinguish the fire to prevent electric shock injuries.
Fire Safety Awareness Education
Public security, fire supervision, and other departments should strengthen supervision and education of the property management of this residential supermarket in accordance with electricity safety regulations. The property management should actively learn and regularly inspect, maintain, and preserve electrical facilities within the building. If any damaged electrical equipment is found, it should be immediately suspended for use and replaced. Conduct daily checks on fire safety corridors to ensure that emergency exits are functioning properly and that escape staircases are clear. Meanwhile, supermarket employees should learn about and understand the dangers of hazardous activities in key fire-prone areas and locations, avoiding dangerous actions. Organize employees to familiarize themselves with which places are key locations, conducting unified and regular learning and drills. The employees in key locations should basically achieve the "three understandings and four abilities." Additionally, broadcast safety reminders to customers shopping in the supermarket.
3.2.3 Electrical Fire Safety Hazard Inspection
The convenience store should organize its fire safety management department to conduct unified management and inspections of electrical wiring and lighting equipment, identify and eliminate unsafe factors and fire hazards, and extinguish fire accidents in their nascent stages. Specific measures:
- Enhance maintenance management to minimize human factors in equipment risks. Conduct regular tests of wire insulation strength, and promptly replace any worn insulation layers if test results indicate damage.
- Strictly adhere to national or regional regulations for electrical equipment installation and maintenance related to electricity. Select the appropriate wiring and cables based on the environment. Also, consider the voltage requirements of different stores and ensure they match the rated working voltage of the cables. Additionally, take into account the potential for environmental and chemical corrosion to affect the wires.
- Maintain appropriate horizontal distances within the structure, compacting rods, pull angle rods, span distances, vertical distances, alternating distances, etc., in compliance with installation standards.
- Regularly inspect the load status of the lines, and promptly replace with larger cross-section conductors or lower the line load when overload is detected.
- Install appropriate safety devices.
- Apply a color-changing paint or install a temperature wax in areas prone to excessive contact resistance. This allows for early detection of overheating at contact points.
- Maintain the current parameters of the company's electrical engineering equipment within the national permitted range.
- Maintain electrical equipment cleanliness.
- Implement anti-static measures.
- Select the appropriate electrical equipment based on different environments, requirements, and functions.
Ankore 5 Electric Fire Monitoring System
(1) Overview
The Acre1-6000 Electrical Fire Monitoring System, developed by Ankoer Electrical Co., Ltd. in accordance with the current national standards, is a fully digital, independently operated system. It has passed the fire product test certification by the National Fire Product Quality Supervision and Inspection Center, and all have passed rigorous EMC electromagnetic compatibility tests. This ensures the safe and normal operation of the series in low-voltage power distribution systems. They are now in mass production and widely applied across the country. The system achieves early prevention and alarm of electrical fires through the collection and monitoring of signals such as residual current, overcurrent, overvoltage, temperature, and fault arcs. It can also disconnect power circuits with excessive residual current, temperature, and fault arcs when necessary. Additionally, it can meet user requirements for data exchange and sharing with the AcreIEMS corporate microgrid management cloud platform or fire automatic alarm systems.
Application Scenario
Applicable to intelligent buildings, high-rise apartments, hotels, restaurants, commercial buildings, industrial and mining enterprises, key fire protection units, as well as the fields of petrochemical, cultural education, healthcare, finance, and telecommunications.
(3) System Architecture
(4) System Features
Monitoring equipment can receive residual current and temperature information from multiple detectors. When an alarm is triggered, it emits both audio and visual alarm signals, with the red "ALARM" indicator light on the device illuminating. The display indicates the location and type of the alarm, records the alarm time, and the audio and visual alarm continues until the "RESET" button on the device or the "RESET" key on the touch screen is pressed remotely to reset the detector. The sound alarm signal can also be manually extinguished using the "Mute" key on the touch screen.
When the monitored loop alarms, the control output relay closes to control the protected circuit or other equipment. Once the alarm is cleared, the control output relay releases.
Communication Fault Alarm: When there is a communication failure between the monitoring equipment and any connected detector, or when the detector itself malfunctions, the corresponding detector on the monitoring screen will display a fault alert, and the yellow "FAULT" indicator light on the device will illuminate, along with an alarm sound. Power Supply Fault Alarm: In case of a failure in the main power supply or the backup power supply, the monitoring equipment will emit an audible and visual alarm signal, display fault information, and allow access to a corresponding interface for detailed information and to silence the alarm sound.
When residual current, over-temperature alarms, communication, or power failures occur, the alarm location, fault information, and alarm time are stored in the database. Similarly, records are kept when alarms are lifted and faults are resolved. Historical data offers various convenient and quick search methods.
Configuration Solutions
6 Closing Remarks
In recent years, numerous major electrical fires have caused significant economic and property losses to society, with some tragic accidents taking the lives of countless innocent people. By establishing and improving electrical fire prevention systems and safety management policies within the enterprise, widely developing preventive technologies against electrical fires, and enhancing public awareness and education on electrical fires, we aim to prevent accidents caused by ignorance and negligence.
References
- GB 50016-2014 (2018 Edition), Code for Fire Protection of Building Design [s]
- Ankorri's Microgrid Design and Application Manual, 2022.5 Edition
- GB51348-2019, Standard for Electrical Design of Civil Buildings [s]
- JGJ392-2016, Code for Electrical Design of Retail Building[s].
- GB50303-2015, Code for Acceptance of Construction Quality for Electrical Engineering Works[s].
- Zhou Jingdong, Wang Qingli, Analysis and Solution for Electrical Fire Safety Risks in a Beijing Supermarket.
