Executive SummaryThe news primarily introduces the main causes of electrical fires, the composition, and the significance of establishing several electrical fire monitoring systems. Referencing various regulations, it discusses the appropriate locations for the establishment of such systems. The implementation of this system can significantly reduce the occurrence of electrical fire accidents, holding great importance for ensuring people's lives and property safety.
KeywordsElectrical fires; Electrical fire monitoring systems; Fire alarm systems
Introduction
With China's modernization, while electricity has brought convenience to social production and people's lives, it has also introduced fire hazards to varying degrees. Today, China's electricity consumption is skyrocketing, with aging power cables or those reaching the end of their service life, along with irregular construction practices leading to decreased insulation performance of lines and installations. Coupled with the limitations of original design load capacity, the situation of electrical fires in China is particularly severe, posing a serious threat to people's lives and property safety. Statistics show that in 2007, electrical causes led to 46,247 fires, accounting for 28.3% of the total; in 2008, 40,000 fires were caused by electrical issues, making up 29.7% of the total; in 2009, 39,102 fires were attributed to electrical causes, accounting for 30.2% of the total; and in 2010, 41,237 fires were caused by electrical issues, representing 31.1% of the total. Looking at electrical fires in recent years, they account for about 30% of the total number of investigated fires, both in terms of frequency and loss. This indicates that electrical fires have become the main disaster source among various types of fires, and they are on the rise year by year.
Statistical Analysis of Severe and Extraordinary Electrical Fire Data
1.1 Distribution of Electrical Fire Locations
The distribution map of electrical fire incidents is shown in Figure 1. Analysis of Figure 1 reveals that the proportion of fires occurring in factories is the highest, followed by commercial buildings. The probability in residential, hotel, office buildings, and other locations is generally around 10%. Therefore, factories, commercial buildings, and residential areas should be prioritized as key targets for electrical fire prevention.
1.2 Area of electrical fire outbreak
Figure 2 illustrates the distribution map of the fire origin in electrical fires. Analysis of Figure 2 reveals that electrical fires *may occur in the following parts of the electrical system: electrical wiring, electrical appliances, electrical equipment, and other areas.
Electrical wiring is primarily composed of conductive materials for carrying current and insulating materials. Electrical equipment sets include energy conversion devices, electrical appliances for connecting and disconnecting circuits, electrical appliances for controlling and protecting circuits, grounding devices, and more.
It is apparent from the above analysis that aging electrical wiring and irregular construction are prone to cause electrical fires; electrical fires caused by electrical equipment follow closely. Transformers and transformer rooms, which are generally managed by designated personnel, account for only about 10% of electrical fire incidents. The key fire prevention focus in electrical fires is primarily on electrical wiring and electrical equipment, with a strong emphasis on preventing electrical wiring, while also reinforcing the safe operation and management of electrical equipment to prevent the majority of electrical fires.
The causes of the fire are primarily categorized into two types: sudden failure and gradual failure, as detailed in Figure 3.
An electrical fire caused by a sudden fault involved both short circuits and lightning strikes. Among the short circuits, 52% were phase-to-phase short circuits, accounting for 26%, and 26% were metallic grounding short circuits, which are the result of leakage. Sudden faults are mainly addressed by the distribution system's functions. The electrical fire monitoring system acts as a supplementary control measure to mitigate the potential for electrical fires caused by sudden faults. Electrical fires triggered by gradual faults include overheating, poor contact, overloading, electrical failures, and leakage. The electrical fire monitoring system should primarily focus on monitoring gradual faults, i.e., reducing the triggering factors for electrical fires and establishing early warning and control measures.
2. Cause Analysis of Electrical Fire
2.1 Relationship between residual current and the capacity and characteristics of distribution systems
1) There is no direct correlation between natural leakage residual current and the capacity of the distribution system.
2) Natural leakage residual current is directly related to the characteristics of the distribution system.
3) As time progresses, there is a tendency for the residual current from natural leakage of aging insulating materials to further increase.
4) In future changes, the residual current is closely related to the expansion of electrical equipment.
5) The state of residual current development is that of a ground fault.
Average distributed residual current is not a true fire hazard; it's the point heat accumulation effect residual current that poses the real fire risk.
2.2 Factors Influencing Long-Term Overload and Overheating of Electrical Lines and Equipment
Long-term overloading and overheating of electrical circuits and equipment can be influenced by the following factors:
The design flow capacity of the circuit is overestimated.
2) Principally, the long-term line calibration for overcurrent is limited by the thermal trip of the circuit breaker.
3) Overheating of the neutral line.
4) Overheating temperature rise of electrical equipment.
By analyzing the two main causes of electrical fires, the following conclusions can be drawn: To prevent electrical fires, the key issue is to understand the magnitude of residual current in the monitoring system, as well as the temperature rise of overheating electrical lines and equipment.
Electrical fire monitoring and control systems are solutions for monitoring residual current in electrical systems and overheating of lines and equipment. When the residual current suddenly increases or the temperature of related lines and equipment exceeds the limit, the system will alert that there may be issues with the electrical system and trigger an alarm. Management can then promptly send professional personnel to inspect and eliminate potential hazards in the areas indicated by the system, preventing electrical faults from causing electrical fires.
3. Electrical Fire Monitoring and Control Systems
The six major functional objectives of the system implementation include residual current, cable temperature rise, motor and large power-consuming equipment temperature rise, distribution box (cabinet) temperature rise, neutral line breakage, and trip control.
Below are several different types of systems: standalone electrical systems, multi-wire electrical systems, and busbar electrical systems. Their compositions and block diagrams are illustrated in Figures 4 to 6.
Ankorree Electrical Fire Monitoring System
4.1 Overview
The Acre1-6000 Electrical Fire Monitoring System has been certified by the central fire product testing and certification center and has passed rigorous EMC electromagnetic compatibility tests, ensuring the safe and normal operation of this series in low-voltage distribution systems. It is now in mass production and widely used across the country. The system collects and monitors signals such as residual current, overcurrent, overvoltage, temperature, and fault arcs to achieve early prevention and alarm of electrical fires. It can also disconnect over-standard distribution circuits detected for residual current, temperature, and fault arcs when necessary. Additionally, it can meet user needs for data exchange and sharing with the AcreIEMS enterprise microgrid management cloud platform or fire automatic alarm systems.
4.2 Application Scenarios
Ideal for intelligent buildings, high-rise apartments, hotels, restaurants, commercial complexes, industrial and mining enterprises, key fire protection units, as well as the oil and chemical, cultural and educational, health, financial, and telecommunications sectors.
4.3 System Structure
4.4 System Features
1) Our monitoring equipment can receive residual current and temperature information from multiple detectors. It emits both audio and visual alarm signals upon alert, with a red "ALERT" indicator light on the device illuminating, displaying the location and type of the alarm, recording the time of the alert. The audio-visual alarm persists until the "RESET" button on the device or the "RESET" key on the touchscreen remotely resets the detector. The audio alarm signal can also be manually silenced using the "Mute" key on the touchscreen.
2) When the monitored loop triggers an alarm, the control output relay closes to control the protected circuit or other equipment. Once the alarm is cleared, the control output relay releases.
3) Communication Fault Alarm: When there is a communication failure between the monitoring equipment and any connected detector, or when the detector itself fails, the corresponding detector on the monitoring screen displays a fault alert, and the yellow "Fault" indicator light on the device illuminates, 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 emits an audible and visual alarm signal and displays fault information. Detailed information can be viewed on the corresponding interface, and the alarm sound can be canceled.
4) In the event of residual current, over-temperature alarms, communication, or power supply failures, the alarm location, fault information, and alarm time are stored in the database. Similarly, records are made when the alarm is lifted and the fault is resolved. Historical data offers various convenient and quick search methods.
5. Closing Remarks
The distinction between electrical fire monitoring systems and fire automatic alarm control systems lies in their focus: the fire automatic alarm system emphasizes the alerting and handling of fires that have already occurred, while the electrical fire monitoring system focuses on early warning of potential hazards before an electrical fire happens. The former addresses a wide range of fire categories, whereas the latter is specifically for electrical systems. With the rising trend of electrical fires, effective countermeasures are crucial. As our country's modernization and the standard of living continue to advance rapidly, electricity consumption has surged, leading to a persistent high incidence of electrical fires with immeasurable losses. Considering the trend of fires in our country, installing electrical fire monitoring systems is urgent and necessary. If the latent hazards in low-voltage distribution systems, which have not yet caused fires, can be effectively predicted and monitored in advance for issues like abnormal changes in leakage and temperature, and the potential fires they might cause, it can significantly reduce the occurrence of fire accidents, ensuring the safety of people's lives and property.
Reference
GB50054-2011 Code for Design of Low-Voltage Distribution Systems [S]
JGJ16-2006 Code for Electrical Design of Civil Buildings [S]
[3] China Aviation Industry Planning and Design Institute. Industrial and Civil Power Distribution Design Manual [M]. 3rd Edition. Beijing: China Power Press, 2005.
[4] GB50303-2002 Code for Acceptance of Construction Quality for Electrical Engineering of Buildings [S]
GB50217-2007 Electric Power Engineering Cable Design Code [S].
Yu Ying, Gu Wei Guo. Application of Electrical Fire Monitoring Systems [S].
[7] Ankorri Emergency Lighting and Evacuation Guidance System/Fire Door Monitoring System/Fire Equipment Power Supply Monitoring System/Electrical Fire Monitoring System Selection Manual. 2022.05 Edition
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