Cable Fire Research Articles

Identification of the Ignition Point of High Voltage Cable Trenches Based on Ceiling Temperature Distribution

With the improvement of the development level of power systems, high voltage cable trenches are being widely used in power systems. The high voltage cable trench is characteristically strongly sealed, which makes it difficult to find a fire in the trench. In order to judge the development of an early cable fire, the relationship between the ceiling temperature distribution and the location of cable ignition points was studied. According to the idea of symmetry, this paper adopts the experimental method of symmetrical double ignition points, carries out several groups of longitudinally symmetrical cable fire combustion experiments with high voltage cable trenches as the carrier, and establishes an equation for calculating the fitness of the relationship between the ceiling temperature and the distance from the ignition point. The results show that the temperature measurement results of the 1:1 high voltage cable trench experimental platform are accurate; in the longitudinal direction, the ceiling temperature decreases from the ignition point to both sides, and the temperature change curve has obvious stage characteristics; within a range of 5 m from the expected ignition point, the average identification accuracy reaches 97.0%. In the early stage of a substation cable trench fire, the two-point temperature measurement and ignition point identification method of high voltage cable trenches based on ceiling temperature distribution proposed in this paper can effectively identify the location of the ignition point along the longitudinal direction of cable trench.

Study of Combustion Characteristics of Cables inside a Common Duct by Cone Calorimeter Test

The spacial characteristics of an underground common duct often lead to disasters resulting in great damage to life and property. In the case of a cable fire, additional damages such as failure of power and fire prevention equipment occur. Accordingly, to derive the risk factors of an underground common duct cable fire, a cone calorimeter test was performed in this study. The fire simulation factor was obtained by measuring temperature changes with time, while the heat release rate (which depends on the cable type) was determined by a combustion test of the subject. The test and measurements were conducted mainly for incombustible and general power and communication cables used in a common duct. According to the test, for a general power cable, the ignition time was measured to be 26 s with a maximum heat release rate of 187 kW/m<sup>2</sup> for 190 s. For a flame resisting power cable, the ignition time was measured to be 20 s with a maximum heat release rate of 179 kW/m<sup>2</sup> for 40 s. For a general communication cable, the ignition time was measured to be 20 s with a maximum heat release rate of 179 kW/m<sup>2</sup> for 40 s. For a flame resisting power cable, the ignition time was measured to be 40 s with a maximum heat release rate of 154 kW/m<sup>2</sup> for 100 s. The test results will be used as fire simulation factors in response to a fire originating from an underground common duct.

A combined real-time intelligent fire detection and forecasting approach through cameras based on computer vision method

Fire is one of the most common hazards in the process industry. Until today, most fire alarms have had very limited functionality. Normally, only a simple alarm is triggered without any specific information about the fire circumstances provided, not to mention fire forecasting. In this paper, a combined real-time intelligent fire detection and forecasting approach through cameras is discussed with extracting and predicting fire development characteristics. Three parameters (fire spread position, fire spread speed and flame width) are used to characterize the fire development. Two neural networks are established, i.e., the Region-Convolutional Neural Network (RCNN) for fire characteristic extraction through fire detection and the Residual Network (ResNet) for fire forecasting. By designing 12 sets of cable fire experiments with different fire developing conditions, the accuracies of fire parameters extraction and forecasting are evaluated. Results show that the mean relative error (MRE) of extraction by RCNN for the three parameters are around 4–13%, 6–20% and 11–37%, respectively. Meanwhile, the MRE of forecasting by ResNet for the three parameters are around 4–13%, 11–33% and 12–48%, respectively. It confirms that the proposed approach can provide a feasible solution for quantifying fire development and improve industrial fire safety, e.g., forecasting the fire development trends, assessing the severity of accidents, estimating the accident losses in real time and guiding the fire fighting and rescue tactics.

Numerical Simulation Research on Cable Fire of Urban Underground Comprehensive Pipe Gallery Using Suffocating Fire Extinguishing Method

The integrated pipe corridor cable is the lifeblood of urban power transmission and has a high fire hazard. Once a fire breaks out, the electricity supply of the entire city will be paralyzed. Aiming at the cable fire in the urban underground integrated pipe gallery and combining with the Pyrosim software, this paper adopts the method of fire suffocation, to study the changes of fire smoke in the pipe gallery. The results show that in the pipe gallery of the 200m fire compartment, the open flame can be completely extinguished in 264s under the simulated working condition of the fire source power of 1MW. At 300s after the cable fire, the temperature in the pipe gallery basically maintained a stable state of 40°C. After the fire broke out, the O2 concentration dropped rapidly and plunged to 16% within 195s and it was completely consumed in 515s. Studies have shown that the use of suffocation to extinguish fires produces less fire smoke in the pipe gallery, and the visibility can be well maintained above 30m.

Behaviour of electrical cables under fire conditions

Abstract A Fire Probabilistic Safety Assessment – called the Fire PSA – is being carried out by the French Institute of Radiological Protection and Nuclear Safety (IRSN) to be used in the framework of the safety assessment of operating 900 MWe PWRs. The aim of this study is to evaluate the core damage conditional probability which could result from a fire. A fire can induce unavailability of safety equipment, notably damaging electrical cables introducing a significant risk contributor. The purpose of this paper is to present the electrical cable fire tests carried out by IRSN to identify the failure modes and to determine the cable damage criteria. The impact of each kind of cable failure mode and the methodology used to estimate the conditional probability of a failure mode when cable damage occurred is also discussed.

Study of the Fire Behavior of Multilayer Cables in a Mine Tunnel

Fires caused by cables occur frequently in mines, which endanger the safety of workers. To explore the characteristics of a multilayer cable fire in a mine tunnel, multilayer cable fire simulations were carried out using the Fire Dynamics Simulator (FDS). The influence of cable tray spacing, ignition position, and tunnel ventilation speed on the characteristics of the fire were studied. The results showed that these factors change the amount of contact between the cable and air, the heat accumulation, and the heat transfer by the flame interaction between the cables. It was also noted that increasing the spacing or wind speed both made the peak of heat release rate (PHRR) initially increase and then decrease. The influence of wind speed on the cable burnout rate in the upstream and downstream sides of the fire source was not consistent, and the wind speed had a sensitive effect on the cable burn out rate in the upstream side of the fire source. The higher the ignition position was, the longer the arrival time of PHRR was and the slower the fire developed. There was a higher burn velocity close to the ceiling. The cable hooks obstructed the cable fire. This study provides a theoretical basis for cable fire prevention and control in mine tunnels.

Risk Assessment through Fire and Evacuation Simulation in the Main Control Room of a Domestic Thermal Power Plant

A fire in the main control room of a thermal power plant is a significant threat to the entire power plant by incapacitating the concept of performance design to secure the safety of the power plant. In this study, using the PyroSim and Pathfinder programs to evaluate fire and evacuation risk of the main control room, the appropriate time and fire shape for evacuating people calmly were confirmed when the available safe egress time and required safe egress time of the main control room were compared. In the case of a cable fire, the simulation results indicate the heat generation rate to be more serious than the actual experimental results showed. This is because heat generation was lower in the experiment as the polymer material constituting the cable fell to the floor during combustion and no loger burns. The fire dynamics simulator results indicate that the power plant facility is safe because even these points are not considered.

A Study on Strengthening Standards for Fire Prevention of Anti-freeze Electric Heating Cable

As per the fire statistics survey of 2019, 56.5% (152 cases) of the entire fire accidents (269 cases) caused by heating cables were due to electrical factors. Therefore, in the present work, the electrical factors responsible for heating cable fire have been analyzed, and fire prevention measures have been demonstrated through related reproduction experiments. According to heating cable fire statistics, the fire in anti-freezing appliances (heating cables), except for fires caused by electric cable arcing and other unknown factors, can be classified into four types based on installation configurations. These configurations have been classified and tested according to the Technical Regulations for Electrical and Telecommunications Products and Components (K 10013). The results of a comparative experiment on anti-freezing appliances (heating cable) revealed that the configuration “a type of water pipe with a heating cable wrapped around the water pipe and insulation on the outside” showed the highest temperature among the four installation arrangements. Additionally, the maximum difference between the test temperature (K 10013) and the actual temperature was 40 ℃.

Effects of Fire Compartmentation and Smoke Exhaust Measures on Smoke Spread Caused by Cable Fire in Utility Tunnel

Investigating the behavior of fire smoke in utility tunnel as well as smoke prevention and control measures are of vital significance for exhausting smoke from utility tunnel, realizing efficient firefighting and rescue, and guaranteeing the normal operation of cities. Taking utility tunnel as the research background, this paper builds a simulation calculation model for fire smoke prevention and control in the utility tunnel using PyroSim numerical simulation software and explores the rules of smoke spread under conditions such as building ceiling screen, changing fire compartmentation tightness, and adding smoke exhaust facilities. According to study results, before the tunnel was filled with smoke, ceiling screens lowered smoke spread rate, and smoke spread rate was inversely proportional to the ceiling screen height. When the fire door was opened, fire smoke spread to the adjacent fire compartment, and smoke spread rate was directly proportional to the fire door opening angle. Before the tunnel was filled up, mechanical smoke exhaust facilities significantly lowered the smoke spread rate by as much as 50%. When the entire tunnel was full of smoke, mechanical smoke exhaust facilities significantly reduced the smoke concentration in the utility tunnel; smoke layer temperature dropped by as much as 32°C, while visibility improved by as much as 66%. By studying smoke spread in utility tunnel, this paper aims to determine the optimal measures of preventing and controlling smoke spread in utility tunnel. This paper could also offer some reference for practical engineering applications in smoke prevention and control in utility tunnel.

Detection and Prediction of Internal-Caused Fire in Tunnel Cable by an Equivalent Transient Thermal Circuit Model

Internal-caused cable fires are one of the most common cable fires, and anomalous temperature increase of the cable core is one of the first signs. However, when a cable is operating with electricity, the temperature of the core conductor cannot be monitored directly; therefore, this characteristic cannot be used in detection and prediction of internal-caused fire in electric cable effectively. An analogous transient thermal circuit model is created, simplified, and optimized to properly compute the temperature of the cable core. Afterward, by using the cable internal-caused fire experimental platform and adjusting current carrying capacity of the tested cable, an experiment is conducted for stimulating the very early stage of three-core cable internal-caused fire. The maximum relative errors of the transient thermal circuit model and the trisection transient thermal circuit model are less than 10% when comparing the experimental data with the calculation results, and the average relative error of the calculated value of trisection transient thermal circuit model is 1.08% after layered optimization. The algorithm model can satisfy the requirement for early detection and prediction in the very early stage of cable internal-caused fire.

Detection of vapors from overheated PVC cables with modified sea urchin-like ZnO for fire warning

Detecting the emitted vapors from overheated polyvinyl chloride (PVC) cables has proven to be an effective way to monitor early electrical fires. In this work, the vapors generated from both conventional and phthalate-free PVC cables were first examined. 2-ethylhexanol (2-EH) was found to be ubiquitously present and can serve as a universal signature gas for the overheated cables. Sea urchin-like ZnO was then prepared via a template-free hydrothermal route for sensing 2-EH. A facile immersion-calcination method was adopted to further modify ZnO, and different CuO/ZnO and Cr2O3/ZnO composites were obtained. The surface modification led to significant improvement in the response of the ZnO sensors to 2-EH. Cable fire simulation tests were also conducted to evaluate the response of optimized gas sensors to overheated conventional and phthalate-free cables in comparison with a typical smoke detector.

BN-RA: A Hybrid Model for Risk Analysis of Overload-Induced Early Cable Fires

Cable overload is one of the most critical contributors to early cable fires. This study proposes a hybrid Bayesian network (BN)-based fire risk analysis model, to investigate the evolution of overload-induced early cable fire risks. In particular, the fire risk transmission paths caused by cable overload are reported, considering the critical factors that likely lead to fires. A BN with a specific structure was considered using the fire risk transmission paths. Later, given the risk index system, a hybrid fire risk assessment model caused by cable overload was developed based on the entropy weight method. Subsequently, the corresponding risk levels were evaluated based on the evolution of the fire risk, using numerical simulations. Finally, a case study was conducted to validate the proposed methods, and the results indicated that the proposed methods can effectively evaluate the state of the cable and explain the causes of fire risk, which can be used for early fire warnings.

Bench-scale experimental study on the fire behavior of electric cable arrays by considering different layouts

The effect of different cable layouts on the fire behavior of electric cable arrays was experimentally studied. The influence of external heat flux on cable fire characteristics was investigated. Several parameters for electrical cables such as the post-burning morphology, ignition time, heat release rate, peak heat release rate and total heat release were obtained. The results show that cable layouts could affect cable charring degrees according to the post-burning morphology. A linear relationship was found in the transformed form of time to ignition and radiant heat flux, and the critical radiant heat flux value for the single cable array appeared smaller than that for the other two layouts. The peak heat release rate for Cables A–D with the single array presents the increasing trend with an increase in radiant heat flux, while the two parallel and intersectional cable arrays present the different trends. Moreover, the total heat release values of Cables A–D in the different cable layouts were analyzed. This work provides the basic data and preliminary investigation to fire engineering of cable arrays with the different layouts.

Influence of Arc Size on the Ignition and Flame Propagation of Cable Fire

Cable fire caused by arc faults is one of the essential factors threatening the safe operation of a power system. The ignition and flame propagation of cable fire dependent on the characteristics of the arc discharge is lackingin in-depth understanding at present. In this work, with the constant electric power deposited into the arc discharge, the effects of arc size on the ignition and flame propagation of 110 kV XLPE cable fire are investigated for the first time. The arc size is changed by varying the gap distance of electrodes from 1.5 cm to 2.5 cm. It is interesting to find that the larger the arc size is, the faster the cable fire is ignited and propagates, and the larger the damaged area of the sheath of the cable is. Therein, when the gap distance increases from 1.3 cm to 3.1 cm, the equivalent impedance and the length of the arc discharge increase nearly seven times and three times, respectively. However, the gas temperature of the arc decreases slightly from 2280 K to 2100 K. In addition, a 3D model of the cable fire ignited by arc discharge is computed by Pyrosim software with fire dynamic simulation (FDS) module. Simulated results show that as the arc size increases, the cable fire is ignited faster, the flame propagates both vertically and horizontally increasing significantly, which is agreed well with the experimental results. This study deepens the understanding of the cable fire ignited by arc discharge and therefore it is useful for the evaluation and prevention of cable fire.

Fast elimination of cable fire smoke in underground tunnels using acoustic agglomeration technology

Reduction in light transmittance and visibility due to the obscuration of fine smoke particles has been regarded as the most critical threat to fire life safety. Therefore, it is essential for smoke control in underground spaces where electric cables are installed, especially for cable tunnels, underground utility tunnels, subway tunnels, etc. This paper presents a new method of fast elimination of cable fire smoke in underground tunnels using acoustic agglomeration technology. First, the smoke production characteristics of typical electric cables are studied. It is found that the light transmittance drops to 20% after burning for about 60 s. Comparing to vertical burning, more smoke is produced when the cables are burned horizontally. Then, the elimination effect of cable fire smoke is investigated experimentally. Typically, the light transmittance is rapidly increased from 10% to 60% in 11 s, and then reaching the threshold of safe escape in fire situation in only 60 s, at an optimal frequency of 1.5 kHz and an acoustic power of 12 W. In the acoustic agglomeration process, acoustic frequency significantly influences the time required for a light transmittance to reach a given value. The elimination effect is promoted with the acoustic power until the corresponding secondary acoustic effects become significant.

Experimental study on combustion parameters and temperature distribution of linear fire under different oxygen concentration in tunnel

Many cables are placed in the underground utility tunnel, which are with greater fire hazards. Once fire occurs in an enclosed tunnel, thermal radiation may ignite the adjacent cables, which will cause cable fire and further expanding of fire scale, and oxygen will be consumed over time. Thus, it's important to investigate cable fire under low oxygen concentration. In this paper, a fire experiment has carried out in a reduced-scale enclosed tunnel with different heights of linear fire near the side wall. The combustion parameters, as well as transverse temperature distribution and maximum ceiling temperature rise under different oxygen concentration are investigated. Based on oxygen consumption calorimetry, the combustion efficiency and heat release rate of each fire source can be obtained. And two formulas to predict transverse temperature distribution and temperature rise under ceiling are proposed based on dimensionless analysis. Results show that different combustion parameters changing under varies oxygen concentrations, two temperature peaks exist in the cross section and the highest temperature is directly above the fire source. Conclusions are given to provide references in fire protection work in utility tunnel.

Experiment and numerical simulation of cable trench fire detection

In this paper, the full-scale cable fire test is carried out in the fire compartment of cable trench in standard substation in order to explore the influence of fire detector sensitivity. The point-type temperature detector, point-type smoke detector, cable-type temperature detector, and suction-type smoke detector are used to test the fire alarm sequence. The temperature field, combustible gas concentration, and fire alarm sequence of fire detector with different sensitivity are simulated by FDS. The results show that: The numerical simulation results are in good agreement with the experimental results. The lower the alarm threshold, the shorter the response time of fire detector. The sensitivity of suction-type smoke detector has great influences on the detection results.

Influence of cable inclination angle and longitudinal ventilation on temperature distribution during cable fire in utility tunnel

Cable fire in utility tunnel commonly cause severe economic lost. This work experimentally investigates influence of cable inclination angle and longitudinal ventilation on temperature distribution during cable fire in utility tunnel. The position of the maximum ceiling temperature is located near the fire source. The position of the maximum ceiling temperature shifts with the increase of the wind speed. When the wind speed is less than 0.45 m/s, the maximum ceiling temperature increases with the increase of wind speed. When the wind speed is greater than 0.45 m/s, the conclusion is opposite. The dimensionless temperature rise and the longitudinal distance accord well with the attenuation law of power-exponential function. In the area between the cable bearer and the fan, larger wind speed corresponds to faster decay of the dimensionless temperature rise. In the area between the cable bearer and the outlet, the conclusion is opposite. The position of the maximum ceiling temperature is independent of the cable inclination angle. When the cable inclination angle is less than 15°, the maximum ceiling temperature increases with the increase of the cable inclination angle. When the cable inclination angle is greater than 15°, the conclusion is opposite.

Research on Aging and Burning Performance of AC 380V ZR-YJV Cable Insulation sheat

Carrying out research on the aging and burning performance of cable insulation sheath is an important means to prevent cable fires. The thermal aging test box, cone calorimeter and synchronous thermal analyzer were used to study the effect of thermal aging on the combustion performance of AC 380V ZR-YJV cable insulation sheath. The results show that in the early stage of thermal aging of the cable, the ignition time of the YJV cable insulation sheath material gradually increases; compared with unaged cables, the ignition time of cables being aged for 15 days has increased from 8 seconds to 57 seconds while the initial peak value of the heat release rate of the cable decreased from 123 kW/m2 to 22 kW/m2. A large amount of easily decomposable additives in the early stage of thermal volatilized from aging cable sheath may be responsible for the reduction trend of the ignition and fire occurrence of the cable insulation sheath. And for the condition of the aging time increasing, the ignition time decreases from 57s to 32s, and the heat release rate will increase from 22 kW/m2 to 85 kW/m2 in which the ignition and fire trend of the cable insulation sheath increase.

Extinguishment of cable fires at packaged transformer substations

Introduction. According to the statistical data, electrical fires account for the majority of all fire accidents. Hence, better fireproofing of fuel and energy facilities is a relevant issue. The article addresses electrical fire extinguishment using high-expansion foam. An extinguishment time analysis methodology, applicable to fire extinguishment using high-expansion foam, has been developed to validate these solutions. The purpose of this article is to calculate the dependence between the fire extinguishment time and the foam consumption rate. The research objectives are to 1) identify the principal values to be used in the calculations and the list of input data; 2) to identify the dependence between the extinguishment time and the foam consumption rate using packaged transformer substation 2BKTP (1,000 kVA) as an example. Calculation methodology. The calculation methodology is based on the material balance equation between the amount of foam, applied for firefighting purposes, and the amount of foam, destroyed as a result of its contact with the heated wire surface, which is the main fire load inside burning electrical facilities. Research results. The co-authors have calculated the fire suppression time using packaged transformer substation 2BKTP (1,000 kVA) as an example. Dependencies between fire extinguishment time, specific foam consumption rate, and foam application rate are identified. Conclusions. The co-authors have identified the main values, needed to simulate a fire extinguishing model. They have also shown optimal foam consumption and application rates and offered their assessment of the applicability of high-expansion foam to electrical fires.