Passive wireless temperature measurement cable fire monitoring early warning and fire extinguishing device and method

Abstract

The invention discloses a passive wireless temperature measurement cable fire monitoring early warning and fire extinguishing device and method, and belongs to the field of power cables. The method comprises the following specific steps: respectively acquiring temperature data and gas data of a cable according to a passive temperature sensor and a gas sensor; the fire occurrence rate is calculated according to the collected temperature data and gas data; comparing the calculated fire occurrence rate with a set threshold value, judging a fire when the fire occurrence rate is greater than the set threshold value, and outputting a judgment result; and according to the judgment result, early warning is performed through an early warning module, and a fire extinguishing device is triggered to extinguish fire, so that cable fire monitoring early warning and fire extinguishing based on passive wireless temperature measurement are realized. The system adopts passive wireless temperature measurement, is completely passive and does not have a battery, avoids hidden dangers of natural and chemical leakage of high temperature of the battery, sends early warning information to a power distribution main station through a wireless communication protocol, can monitor hidden dangers of cable faults of a cable trench in real time, and realizes self-starting high-sensitivity fire extinguishing by arranging a fire extinguishing device. And safe and stable operation of a power cable line is fully ensured.

Description

Technical Field

[0001] The invention belongs to the field of power cables, and in particular relates to a cable fire monitoring, early warning and fire extinguishing device with passive wireless temperature measurement. Background Art

[0002] As my country's economy continues to grow rapidly, the demand for electricity in daily life and enterprises is increasing. As one of the main ways to transmit electric energy, the reliability of power cables is of great significance. At present, under the influence of various factors such as cable design, production, installation and maintenance, and operating environment, power outages caused by cable damage are becoming more and more frequent, which is one of the important hidden dangers for the safe operation of the power grid.

[0003] The various faults that occur at the cable joints are not a sudden process, but because the temperature at the joints continues to rise, causing the insulation to gradually age and the leakage current to gradually increase. When it reaches a certain level, breakdown occurs again. It is a process from quantitative change to qualitative change. Therefore, by continuously monitoring the changes in the temperature of the cable joints, you can accurately understand its working conditions and carry out power outages and maintenance in a timely manner according to the situation. Although some cable wells are fully covered with dry powder fire extinguishing bombs, these fire extinguishing bombs cannot be remotely controlled and remotely monitored. When a fire occurs, the operation and maintenance personnel cannot know the location of the action and rush to the scene for repairs in time. In addition, the newly built domestic high-voltage cable lines are generally equipped with optical fiber temperature measurement systems throughout the line, but some old cable wells and cable trenches that have been in operation for many years are still lacking in temperature measurement methods, and the potential faults in these locations are greater. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a cable fire monitoring, early warning and fire extinguishing device and method with passive wireless temperature measurement. The passive wireless temperature measurement is completely passive and does not carry batteries, thus avoiding the hidden dangers of natural and chemical leakage of battery high temperature. Remote power supply and reading are achieved through wireless signals. After installation, it is basically maintenance-free and can operate stably and reliably for a long time with the same lifespan as the equipment being measured. Through the wireless communication protocol, sensor monitoring data, positioning alarm signals and other information are sent to the power distribution main station, so that users can monitor the operation of cable trenches and cable heads in real time and discover hidden faults in time, so that they can quickly go to the site for verification and investigation, so as to fully ensure the safe and stable operation of the power cable lines. By setting a fire extinguishing device, self-starting and highly sensitive fire extinguishing can be achieved.

[0005] The present invention adopts the following technical solution.

[0006] Embodiment 1 of the present invention provides a cable fire monitoring, early warning and fire extinguishing device with passive wireless temperature measurement, including a power supply module, a data acquisition module, a background relay module and a fire extinguishing module.

[0007] The power supply module is connected to the data acquisition module, the background relay module and the fire extinguishing module respectively, and is used to supply power to the data acquisition module, the background relay module and the fire extinguishing module;

[0008] The data acquisition module is connected to the background relay module. The data acquisition module includes a passive temperature acquisition module, a gas acquisition module and a data transmission module. The passive temperature acquisition module includes an electrostatic induction unit, a passive temperature measurement unit and a control unit. The electrostatic induction unit is connected to the passive temperature measurement unit to obtain electric field energy from the capacitance between the live cable and the earth to power the passive temperature measurement module. The data acquisition module is used to collect temperature data and gas data and send them to the background relay module.

[0009] The background relay module is connected to the early warning module, and is used to determine the occurrence of a fire when the fire incidence rate is greater than the set threshold according to the temperature data and gas data, and connect the early warning information to the early warning module;

[0010] The early warning module is used to issue a fire early warning after receiving the early warning information from the background relay module;

[0011] The background relay module is connected to the fire extinguishing module and is used to determine the occurrence of a fire when the fire incidence rate is greater than the set threshold calculated based on the temperature data and gas data, and send a fire signal to the fire extinguishing module;

[0012] The fire extinguishing module includes a relay and a fire extinguishing mechanism module, which is used to trigger the relay to close after receiving the fire signal sent by the background relay module, and then trigger the fire extinguishing mechanism module to extinguish the fire.

[0013] Preferably, the power supply module includes an online power supply unit, a lithium battery unit and a battery inverter unit. The electric energy of the online power supply unit is stored in the lithium battery. The electric energy of the lithium battery unit generates a DC voltage through the power inverter unit. The power supply module is respectively connected to the gas collection module and the data transmission module in the data acquisition module, and supplies power to the gas collection module and the data transmission module.

[0014] Preferably, the passive temperature acquisition module includes an electrostatic induction unit, a passive temperature measurement unit and a temperature processing unit. The passive temperature measurement unit is connected to the temperature processing unit and is used to transmit temperature data to the temperature processing unit for analog-to-digital conversion. The temperature processing unit has a built-in analog-to-digital converter to convert the temperature data from an analog signal to a digital signal.

[0015] Preferably, the passive temperature acquisition module is connected to the data transfer module, and is used to transfer the collected temperature data to the data transfer module via single bus communication;

[0016] The gas collection module is connected to the data transmission module and is used to transmit the collected gas data to the data transmission module through single bus communication.

[0017] Preferably, the data transmission module includes an MCU gas unit, an MCU temperature unit and a Lora unit. The MCU temperature unit obtains the temperature data collected by the temperature processing unit in the passive temperature acquisition module, and then transmits the temperature data to the Lora unit. The Lora unit sends the received temperature data to the background relay module.

[0018] The MCU gas unit obtains the gas data collected by the gas collection module, and then sends the gas data to the background relay module through the serial port mode.

[0019] Preferably, the early warning module includes a station terminal and a distribution main station, and the station terminal is connected to the distribution main station. The station terminal is used to receive the early warning information accessed by the background relay module through the serial port interface and the digital communication protocol, and then communicates through the dispatch channel using 4G mode, and sends the early warning information to the distribution main station using the digital communication protocol for fire warning.

[0020] Preferably, the fire extinguishing module includes a relay and a fire extinguishing mechanism module, the relay and the fire extinguishing mechanism module are connected, the fire extinguishing mechanism unit includes a waterproof lead, a thermal resistance wire, a power cord and a dry powder canister, and the fire extinguishing module is used to trigger the relay to close after receiving the fire signal sent by the background relay module, thereby triggering the power cord of the fire extinguishing mechanism unit to power the thermal resistance wire. The thermal resistance wire is heated to cause the waterproof lead to self-ignite, triggering the dry powder canister to spray dry powder.

[0021] The second aspect of the present invention provides a passive wireless temperature measurement cable fire monitoring, early warning and fire extinguishing method, which is used to operate on the passive wireless temperature measurement cable fire monitoring, early warning and fire extinguishing device, comprising:

[0022] The temperature data and gas data of the cable are collected respectively according to the passive temperature sensor and the gas sensor;

[0023] Calculate the fire occurrence rate based on the collected temperature data and gas data;

[0024] The calculated fire occurrence rate is compared with the set threshold value, and when it is greater than the set threshold value, a fire is determined and the determination result is output;

[0025] According to the judgment results, the early warning module will issue an early warning and trigger the fire extinguishing device to extinguish the fire, thus realizing cable fire monitoring, early warning and fire extinguishing by passive wireless temperature measurement.

[0026] Preferably, the gas data includes oxygen concentration data and carbon dioxide concentration data. A time t is set, and the change rate of the collected oxygen concentration data and carbon dioxide concentration data and temperature data within the time t is calculated. The change rate of the temperature data is expressed by the following formula:

[0027]

[0028] In the formula,

[0029] ΔT is the rate of change of temperature data within the set time t,

[0030] T i is the ith temperature data collected within the set time t,

[0031] N is the number of temperature data collected within the set time t,

[0032] It is the average value of all the temperature data collected within the set time t.

[0033] Preferably, the fire incidence rate is expressed as follows:

[0034]

[0035] In the formula,

[0036] P is the fire occurrence rate,

[0037] ΔT is the rate of change of temperature data within the set time t,

[0038] ΔCO2 is the rate of change of carbon dioxide concentration in gas data within the set time t.

[0039] ΔO2 is the rate of change of oxygen concentration data in gas data within the set time t,

[0040] λ1, λ2 and λ3 are the weights of ΔT, ΔCO2 and ΔO2 respectively.

[0041] The beneficial effects of the present invention are that, compared with the prior art, the passive wireless temperature measurement is completely passive, without batteries, thus avoiding the hidden dangers of natural and chemical leakage of batteries at high temperatures, realizing remote power supply and reading through wireless signals, being basically maintenance-free after installation, and being able to operate stably and reliably for a long time, with the same lifespan as the equipment being measured, and sending sensor monitoring data, positioning alarm signals and other information to the power distribution main station through the wireless communication protocol, so that users can monitor the operation of cable trenches and cable heads in real time, and discover hidden faults in time, so that they can quickly go to the site for verification and investigation, so as to fully ensure the safe and stable operation of the power cable lines, and realize self-starting and highly sensitive fire extinguishing by setting up a fire extinguishing device. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the cable fire monitoring, early warning and fire extinguishing device in the present invention;

[0043] Figure 2 It is a schematic diagram of the fire extinguishing mechanism in the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0045] Embodiment 1 of the present invention proposes a cable fire monitoring, early warning and fire extinguishing device with passive wireless temperature measurement, including a power supply module, a data acquisition module, a background relay module and a fire extinguishing module.

[0046] The power supply module is connected to the data acquisition module, the background relay module and the fire extinguishing module respectively, and is used to supply power to the data acquisition module, the background relay module and the fire extinguishing module;

[0047] The power supply module includes an online power supply unit, a lithium battery unit and a battery inverter unit. The electric energy of the online power supply unit is stored in the lithium battery. The electric energy of the lithium battery unit generates DC voltages of different sizes through the power inverter unit, which is used to power the data acquisition module, the background relay module and the fire extinguishing module.

[0048] The data acquisition module includes a passive temperature acquisition module, a gas acquisition module and a data transmission module. The power supply module is respectively connected to the gas acquisition module and the data transmission module in the data acquisition module, and supplies power to the gas acquisition module and the data transmission module.

[0049] The passive temperature acquisition module includes an electrostatic induction unit, a passive temperature measurement unit and a control unit. The electrostatic induction unit is connected to the passive temperature measurement unit and is used to obtain electric field energy from the capacitor between the live cable and the earth using the capacitance principle as the electric energy of the passive temperature measurement unit. The current obtained by the capacitor is about 0.8uA.

[0050] The passive temperature measurement unit uses the passive temperature sensor AM2301 for temperature measurement. The collected temperature is converted into a digital signal output after internal calibration. It has extremely high reliability and excellent long-term stability. The temperature resolution is 0.1°C. The passive temperature measurement unit is used to collect temperature data.

[0051] The passive temperature measurement unit is connected to the temperature processing unit and is used to transmit the temperature data to the temperature processing unit for analog-to-digital conversion. The temperature processing unit has a built-in analog-to-digital converter to convert the temperature data from an analog signal to a digital signal.

[0052] The passive temperature acquisition module is connected to the data transmission module and is used to transmit the collected temperature data to the data transmission module through single bus communication;

[0053] The gas collection module is connected to the data transmission module and is used to transmit the collected gas data to the data transmission module through single bus communication.

[0054] The data transmission module includes an MCU gas unit, an MCU temperature unit and a Lora unit. The MCU temperature unit obtains the temperature data collected by the temperature processing unit in the passive temperature acquisition module, and then transmits the temperature data to the Lora unit. The Lora unit sends the received temperature data to the background relay module.

[0055] The MCU gas unit obtains the gas data collected by the gas collection module, and then sends the gas data to the background relay module through the serial port mode.

[0056] The background relay module is connected to the early warning module, and is used to determine the occurrence of a fire when the fire incidence rate is greater than the set threshold according to the temperature data and gas data, and connect the early warning information to the early warning module;

[0057] The early warning module is used to issue a fire early warning after receiving the early warning information from the background relay module;

[0058] The early warning module includes a station terminal and a distribution main station. The station terminal is connected to the distribution main station. The station terminal is used to receive the early warning information accessed by the background relay module through the serial port interface and MODBUS protocol, and then communicates through the dispatching channel using 4G mode, and sends the early warning information to the distribution main station using the IEC104 protocol for fire warning.

[0059] The MODBUS protocol is briefly introduced as follows: The protocol uses a response connection (half-duplex) on a communication line. First, the signal of the host computer is addressed to a unique terminal device (slave), and then the response signal sent by the terminal device is transmitted to the host in the opposite direction. The protocol only allows data exchange between the host computer and the terminal device, but not between independent devices, which will not occupy the communication line when they are initialized, but only respond to the query signal reaching the machine.

[0060] The MODBUS transmission method is a series of independent data structures within a message frame and limited rules for transmitting data. When communicating on the MODBUS bus in RTU mode, each 8-bit byte in the message is divided into two 4-bit hexadecimal characters, and each message must be transmitted continuously. The following defines a transmission method compatible with the Modbus protocol-RTU method.

[0061] Table 1 MODBUS query and response frame format

[0062] address Function Starting address Number of registers Checksum 1 byte 1 byte 2 bytes 2 bytes 2 bytes

[0063]

[0064] Table 2 Monitoring function number and point table definition

[0065]

[0066]

[0067] According to the query and response frame format of MODBUS in Table 1 and the monitoring function number and point table definition in Table 2, the MODBUS communication function is realized. The RS232 and RS485 interfaces of the device can communicate with the DTU through the MODBUS protocol to realize the upload of real-time data, spectra and warning information.

[0068] The DTU and the main station communicate using 4G and transmit data using the IEC104 protocol. The main station obtains the real-time data and warning information of the cable head online monitoring equipment from the DTU, realizing data display and warning release.

[0069] The background relay module is connected to the fire extinguishing module. The background relay module uses the STM32L152 series single-chip microcomputer, which is used to calculate the fire occurrence rate based on the temperature data and gas data. When it is greater than the set threshold, it determines that a fire has occurred and sends a fire signal to the fire extinguishing module;

[0070] The fire extinguishing module includes a relay and a fire extinguishing mechanism module, such as Figure 2 As shown, the relay is connected to the fire extinguishing mechanism module, and the fire extinguishing mechanism unit includes a waterproof lead 1, a thermal resistance wire 2, a power line 3 and a dry powder tank 4. The fire extinguishing module is used to trigger the relay to close after receiving the fire signal sent by the background relay module, thereby triggering the power line 3 of the fire extinguishing mechanism unit to supply power to the thermal resistance wire 2. The thermal resistance wire 2 is heated to cause the waterproof lead 1 to self-ignite, triggering the dry powder tank 4 to spray dry powder.

[0071] Embodiment 2 of the present invention proposes a passive wireless temperature measurement cable fire monitoring, early warning and fire extinguishing method, which is used to operate on a passive wireless temperature measurement cable fire monitoring, early warning and fire extinguishing device described in Embodiment 1, including:

[0072] Step 1: Collect the temperature data and gas data of the cable respectively according to the passive temperature sensor and the gas sensor;

[0073] Step 2: Calculate the fire occurrence rate based on the collected temperature data and gas data;

[0074] Gas data includes oxygen concentration data and carbon dioxide concentration data. Set time t and calculate the change rate of the collected oxygen concentration data, carbon dioxide concentration data and temperature data within time t. The change rate of temperature data is expressed by the following formula:

[0075]

[0076] In the formula,

[0077] ΔT is the rate of change of temperature data within the set time t,

[0078] T i is the ith temperature data collected within the set time t,

[0079] N is the number of temperature data collected within the set time t,

[0080] It is the average value of all the temperature data collected within the set time t.

[0081] The fire incidence rate is expressed as follows:

[0082]

[0083] In the formula,

[0084] P is the fire occurrence rate,

[0085] ΔT is the rate of change of temperature data within the set time t,

[0086] ΔCO2 is the rate of change of carbon dioxide concentration in gas data within the set time t.

[0087] ΔO2 is the rate of change of oxygen concentration data in gas data within the set time t,

[0088] λ1, λ2 and λ3 are the weights of ΔT, ΔCO2 and ΔO2 respectively.

[0089] Step 3: Compare the calculated fire occurrence rate with the set threshold, determine that a fire occurs when it is greater than the set threshold, and output the determination result;

[0090] Step 4: According to the judgment result, the early warning module issues an early warning and triggers the fire extinguishing device to extinguish the fire, thus realizing cable fire monitoring, early warning and fire extinguishing by passive wireless temperature measurement.

[0091] The beneficial effects of the present invention are that, compared with the prior art, the passive wireless temperature measurement is completely passive, without batteries, thus avoiding the hidden dangers of natural and chemical leakage of batteries at high temperatures, realizing remote power supply and reading through wireless signals, being basically maintenance-free after installation, and being able to operate stably and reliably for a long time, with the same lifespan as the equipment being measured, and sending sensor monitoring data, positioning alarm signals and other information to the power distribution main station through the wireless communication protocol, so that users can monitor the operation of cable trenches and cable heads in real time, and discover hidden faults in time, so that they can quickly go to the site for verification and investigation, so as to fully ensure the safe and stable operation of the power cable lines, and realize self-starting and highly sensitive fire extinguishing by setting up a fire extinguishing device.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A cable fire monitoring, early warning and fire extinguishing device with passive wireless temperature measurement, comprising a power supply module, a data acquisition module, a background relay module, an early warning module and a fire extinguishing module, characterized in that: The power supply module is connected to the data acquisition module, the background relay module and the fire extinguishing module respectively, and is used to supply power to the data acquisition module, the background relay module and the fire extinguishing module; The data acquisition module is connected to the background relay module. The data acquisition module includes a passive temperature acquisition module, a gas acquisition module and a data transmission module. The passive temperature acquisition module includes an electrostatic induction unit, a passive temperature measurement unit and a control unit. The electrostatic induction unit is connected to the passive temperature measurement unit to obtain electric field energy from the capacitance between the live cable and the earth to power the passive temperature measurement module. The data acquisition module is used to collect temperature data and gas data and send them to the background relay module. The background relay module is connected to the early warning module, and is used to determine the occurrence of a fire when the fire incidence rate is greater than the set threshold according to the temperature data and gas data, and connect the early warning information to the early warning module; The early warning module is used to issue a fire early warning after receiving the early warning information from the background relay module; The background relay module is connected to the fire extinguishing module and is used to determine the occurrence of a fire when the fire incidence rate is greater than the set threshold calculated based on the temperature data and gas data, and send a fire signal to the fire extinguishing module; The fire extinguishing module includes a relay and a fire extinguishing mechanism module, which is used to trigger the relay to close after receiving the fire signal sent by the background relay module, and then trigger the fire extinguishing mechanism module to extinguish the fire.

2. According to the passive wireless temperature measurement cable fire monitoring, early warning and fire extinguishing device of claim 1, it is characterized by: The power supply module includes an online power supply unit, a lithium battery unit and a battery inverter unit. The electric energy of the online power supply unit is stored in the lithium battery. The electric energy of the lithium battery unit generates a DC voltage through the power inverter unit. The power supply module is respectively connected to the gas collection module and the data transmission module in the data acquisition module, and supplies power to the gas collection module and the data transmission module.

3. According to the passive wireless temperature measurement cable fire monitoring, early warning and fire extinguishing device of claim 1, it is characterized by: The passive temperature acquisition module includes an electrostatic induction unit, a passive temperature measurement unit and a temperature processing unit. The passive temperature measurement unit is connected to the temperature processing unit and is used to transmit temperature data to the temperature processing unit for analog-to-digital conversion. The temperature processing unit has a built-in analog-to-digital converter to convert temperature data from analog signals to digital signals.

4. The cable fire monitoring, early warning and fire extinguishing device with passive wireless temperature measurement according to claim 3 is characterized in that: The passive temperature acquisition module is connected to the data transmission module and is used to transmit the collected temperature data to the data transmission module through single bus communication; The gas collection module is connected to the data transmission module and is used to transmit the collected gas data to the data transmission module through single bus communication.

5. The cable fire monitoring, early warning and fire extinguishing device with passive wireless temperature measurement according to claim 4 is characterized in that: The data transmission module includes an MCU gas unit, an MCU temperature unit and a Lora unit. The MCU temperature unit obtains the temperature data collected by the temperature processing unit in the passive temperature acquisition module, and then transmits the temperature data to the Lora unit. The Lora unit sends the received temperature data to the background relay module. The MCU gas unit obtains the gas data collected by the gas collection module, and then sends the gas data to the background relay module through the serial port mode.

6. The cable fire monitoring, early warning and fire extinguishing device with passive wireless temperature measurement according to claim 1 is characterized in that: The early warning module includes a station terminal and a distribution main station. The station terminal is connected to the distribution main station. The station terminal is used to receive the early warning information accessed by the background relay module through the serial port interface and the digital communication protocol, and then communicates through the dispatching channel using 4G mode, and sends the early warning information to the distribution main station using the digital communication protocol for fire warning.

7. The cable fire monitoring, early warning and fire extinguishing device with passive wireless temperature measurement according to claim 1 is characterized by: The fire extinguishing module includes a relay and a fire extinguishing mechanism module. The relay and the fire extinguishing mechanism module are connected. The fire extinguishing mechanism unit includes a waterproof lead, a thermal resistance wire, a power cord and a dry powder canister. The fire extinguishing module is used to trigger the relay to close after receiving the fire signal sent by the background relay module, and then trigger the power cord of the fire extinguishing mechanism unit to power the thermal resistance wire. The thermal resistance wire is heated to cause the waterproof lead to self-ignite, triggering the dry powder canister to spray dry powder.

8. A passive wireless temperature measurement cable fire monitoring, early warning and fire extinguishing method, used to operate a passive wireless temperature measurement cable fire monitoring, early warning and fire extinguishing device as described in any one of claims 1 to 7, characterized in that: The temperature data and gas data of the cable are collected respectively according to the passive temperature sensor and the gas sensor; Calculate the fire occurrence rate based on the collected temperature data and gas data; The calculated fire occurrence rate is compared with the set threshold value, and when it is greater than the set threshold value, a fire is determined and the determination result is output; According to the judgment results, the early warning module will issue an early warning and trigger the fire extinguishing device to extinguish the fire, thus realizing cable fire monitoring, early warning and fire extinguishing by passive wireless temperature measurement.

9. The cable fire monitoring, early warning and fire extinguishing method based on passive wireless temperature measurement according to claim 8 is characterized in that: Gas data includes oxygen concentration data and carbon dioxide concentration data. Set time t and calculate the change rate of the collected oxygen concentration data, carbon dioxide concentration data and temperature data within time t. The change rate of temperature data is expressed by the following formula: In the formula, ΔT is the rate of change of temperature data within the set time t, T i is the ith temperature data collected within the set time t, N is the number of temperature data collected within the set time t, It is the average value of all the temperature data collected within the set time t.

10. A cable fire monitoring, early warning and fire extinguishing method using passive wireless temperature measurement according to claim 9, characterized in that: The fire incidence rate is expressed as follows: In the formula, P is the fire occurrence rate, ΔT is the rate of change of temperature data within the set time t, ΔCO2 is the rate of change of carbon dioxide concentration in gas data within the set time t. ΔO2 is the rate of change of oxygen concentration data in gas data within the set time t, λ1, λ2 and λ3 are the weights of ΔT, ΔCO2 and ΔO2 respectively.

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