阅读说明：本技术 一种基于温阻特性的感温电缆性能检测装置及方法 (Temperature-sensitive cable performance detection device and method based on temperature resistance characteristic ) 是由 谭风雷 张兆君 李义峰 朱超 曹勇 臧泽洲 赵宏飞 徐刚 吴兴泉 陈昊 于 2021-01-25 设计创作，主要内容包括：本发明公开了一种基于温阻特性的感温电缆性能检测装置及方法,该装置主要包括主控系统、温控系统和检测结构3个部分,主控单元控制温控系统将感温电缆周围温度加热至目标值,检测结构监测感温电缆周围温度和电缆阻值,通过不同温度下的电缆阻值,拟合温阻特性曲线,利用曲线偏差率、大偏差点数量和最大变化率定量判断感温电缆的性能。本发明可根据现场不同的电缆布置环境,设置不同的电缆加热方式,便捷的对现场感温电缆的性能进行评价,有效杜绝已损坏或低质量的感温电缆在现场使用。(The invention discloses a temperature-sensing cable performance detection device and method based on temperature-resistance characteristics, the device mainly comprises 3 parts of a main control system, a temperature control system and a detection structure, wherein the main control unit controls the temperature control system to heat the ambient temperature of a temperature-sensing cable to a target value, the detection structure monitors the ambient temperature of the temperature-sensing cable and the resistance value of the cable, a temperature-resistance characteristic curve is fitted through the resistance values of the cables at different temperatures, and the performance of the temperature-sensing cable is judged by utilizing the curve deviation rate, the number of large deviation points and the maximum change rate. The invention can set different cable heating modes according to different cable arrangement environments on site, conveniently evaluate the performance of the temperature sensing cable on site, and effectively prevent the damaged or low-quality temperature sensing cable from being used on site.)

1. The utility model provides a temperature sensing cable performance detection device based on temperature hinders characteristic which characterized in that includes: the system comprises a main control system, a temperature control system and a detection structure;

the main control system is used for controlling the temperature control system to heat the ambient temperature of the temperature sensing cable to a target value, fitting a temperature resistance characteristic curve based on the ambient temperature of the temperature sensing cable and the resistance value of the cable, and evaluating the performance of the temperature sensing cable;

the temperature control system is used for heating the temperature sensing cable;

the detection structure is used for monitoring the ambient temperature of the temperature sensing cable and the resistance value of the cable;

the temperature control system is wrapped outside the temperature sensing cable;

the detection structure is arranged on the stable control system;

the temperature control system and the detection structure are communicated with the master control system in a wireless mode.

2. The temperature-sensing cable performance detection device based on the temperature-resistance characteristic of claim 1, wherein the master control system comprises a master control unit, a communication module, a voltage and current monitoring module, a temperature-resistance curve fitting module, an AD acquisition module and a photoelectric coupling module;

the communication module is used for communication between the main control system and the temperature control system and between the main control system and the detection structure;

the voltage and current monitoring module is used for sampling the voltage and the current of the temperature sensing cable resistance measuring loop;

the AD acquisition module is used for converting the ambient temperature of the temperature sensing cable into an electric signal which can be acquired by the main control unit;

the temperature resistance curve fitting module is used for fitting a temperature resistance characteristic curve according to the resistance and the temperature of the temperature sensing cable;

the main control unit is used for controlling the temperature control system to heat the temperature sensing cable, calculating the resistance of the temperature sensing cable according to the voltage and current electric signals, and judging the performance of the temperature sensing cable according to the temperature resistance characteristic curve;

the photoelectric coupling module is used for isolating input and output signals.

3. The temperature-sensitive cable performance detecting device based on temperature-resistance characteristics according to claim 1,

for the field non-detachable temperature sensing cable structure, the temperature control system adopts a cylindrical silica gel heating sheet;

for the detachable temperature sensing cable structure, the temperature control system adopts an accommodating type constant temperature bag.

4. The temperature-sensitive cable performance detecting device based on temperature-resistance characteristics according to claim 1,

the detection structure comprises a temperature sensor and a voltage and current sensor;

the temperature sensor is used for measuring the ambient temperature of the temperature sensing cable;

the voltage and current sensor is used for measuring the voltage and current of the temperature sensing cable resistance measuring loop.

5. A temperature-sensitive cable performance detection method based on temperature resistance characteristics is characterized by comprising the following steps:

controlling a temperature control system to heat the temperature sensing cable to a target temperature according to the step length in sequence;

monitoring the ambient temperature and the resistance value of the temperature sensing cable at different target temperatures through the detection structure;

fitting a temperature resistance characteristic standard curve and a measurement curve of the temperature sensing cable according to the resistance values of the temperature sensing cable at different target temperatures;

and evaluating the performance of the temperature sensing cable based on a temperature resistance characteristic standard curve and a measurement curve of the temperature sensing cable.

6. The method for detecting the performance of the temperature-sensitive cable based on the temperature-resistance characteristic according to claim 5, wherein the fitting of the temperature-sensitive cable resistance characteristic standard curve and the temperature-sensitive cable resistance characteristic measurement curve according to the temperature-sensitive cable resistances at different target temperatures comprises:

the temperature resistance characteristic curve of the temperature sensing cable between the ith measurement point and the (i + 1) th measurement point is expressed as follows:

wherein, fx (t)_iA temperature-sensitive cable temperature-resistance characteristic measurement curve from the ith measurement point to the (i + 1) th measurement point is shown, one target temperature corresponds to one measurement point, R_iMeasuring resistance, R, for the temperature sensing cable of the ith measuring point_i+1Measuring resistance value of the temperature sensing cable at the (i + 1) th measuring point, wherein T represents a target temperature value corresponding to the measuring point, and T_GFor temperature separation of adjacent measurement points, N_GThe total number of measurement points in the whole temperature range;

sequentially calculating to obtain temperature-resistance characteristic measurement curves of the temperature-sensing cables from all measurement points to adjacent measurement points, and obtaining the temperature-resistance characteristic measurement curve of the temperature-sensing cables in the whole temperature range;

similarly, the temperature resistance characteristic standard curve of the temperature sensing cable in the whole temperature range is obtained by calculating according to the standard resistance values of the temperature sensing cable at different target temperatures.

7. The method for detecting the performance of the temperature-sensitive cable based on the temperature-resistance characteristic as claimed in claim 6, wherein the temperature range is selected from 20 ℃ to 120 ℃;

the total number of measurement points in the whole temperature range is calculated as:

8. the method for detecting the performance of the temperature-sensitive cable based on the temperature-resistance characteristic of claim 5, wherein the evaluating the performance of the temperature-sensitive cable based on the temperature-resistance characteristic standard curve and the measurement curve comprises:

calculating the deviation rate and curve deviation score of the temperature-sensitive cable temperature-resistance curve, calculating the number of large deviation points of the temperature-sensitive cable temperature-resistance curve and calculating the maximum change rate of the temperature-sensitive cable temperature-resistance curve;

and establishing a temperature sensing cable evaluation system based on the temperature resistance characteristic curve deviation rate, the curve deviation score, the large deviation point number and the maximum change rate of the temperature sensing cable, and dividing the temperature sensing cable into three grades I, II and III according to the performance.

9. The method for detecting the performance of the temperature-sensitive cable based on the temperature-resistance characteristic according to claim 8, wherein the calculating the temperature-sensitive cable temperature-resistance curve deviation rate and the curve deviation score includes:

the curve deviation ratio is calculated as follows:

wherein e is_zRepresenting the deviation ratio of the curve, R_MtThe actual resistance value of the temperature sensing cable is obtained by a standard resistance measuring instrument when the target temperature is t_TtThe resistance value R of the temperature sensing cable is measured when the target temperature is t_CtC represents the standard resistance value of the temperature sensing cable when the target temperature is t, and c represents the temperature change quantity;

the curve deviation score is calculated as follows:

P＝∑P_t

wherein P represents the total curve deviation score of the temperature sensing cable, P_tRepresents a curve deviation score when the target temperature of the temperature sensing cable is t, c_1t、c_2tE is a deviation score coefficient when the temperature of the temperature sensing cable is t_tThe resistance deviation ratio at temperature t is shown.

10. The method for detecting the performance of the temperature-sensitive cable based on the temperature-resistance characteristic according to claim 9, wherein the calculating the number of large deviation points of the temperature-resistance curve of the temperature-sensitive cable comprises:

when e is_tGreater than E_maxThe corresponding measuring point is a large deviation point, and the number N, E of the large deviation points is calculated_maxIndicating a resistance deviation ratio preset threshold.

11. The method for detecting the performance of the temperature-sensitive cable based on the temperature-resistance characteristic according to claim 9, wherein the calculating the maximum change rate of the temperature-resistance curve of the temperature-sensitive cable comprises:

M_max＝max||R_T(t+1)-R_Tt|-|R_C(t+1)-R_Ct||

wherein M is_maxAnd the maximum change rate of the temperature resistance characteristic standard curve and the measurement curve of the temperature sensing cable is represented.

12. The method as claimed in claim 11, wherein the step of establishing a temperature-sensing cable evaluation system based on the deviation rate, the large deviation point number and the maximum change rate of the temperature-sensing cable temperature-resistance characteristic curve to classify the temperature-sensing cable into three grades i, ii and iii according to performance comprises:

the performance of the temperature sensing cable is an evaluation standard of I grade: rate of curve deviation e_zLess than 5 or P > 80, and a maximum rate of change M_maxIs less than 1, and

no large deviation point;

the evaluation standard of the temperature sensing cable performance of level II is that the temperature sensing cable meets any condition as follows:

condition 1: rate of curve deviation e_zLess than 5 or P > 80, and a maximum rate of change M_maxGreater than 1, but no large deviation point exists;

condition 2: rate of curve deviation e_zMore than 5 or 60-80, and the maximum rate of change M_maxLess than 1, and the number N of large deviation points is less than or equal to 10;

the performance of the temperature sensing cable is the evaluation standard of grade III: rate of curve deviation e_zGreater than 5 or P < 60, and maximum rate of change M_maxGreater than 1 and the number of large deviation points N is greater than 10.

Technical Field

The invention relates to a temperature-sensitive cable performance detection device and method based on temperature resistance characteristics, and belongs to the technical field of transformer state detection.

Background

The temperature sensing cable applied to the electrical equipment in the transformer substation has the problem of mistakenly sending an alarm signal due to the lack of quantitative detection equipment suitable for the site.

Disclosure of Invention

The invention aims to provide a temperature-resistance characteristic-based temperature-sensitive cable performance detection device and method.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides a temperature-sensitive cable performance detection device based on temperature resistance characteristics, which comprises: the system comprises a main control system, a temperature control system and a detection structure;

the main control system is used for controlling the temperature control system to heat the ambient temperature of the temperature sensing cable to a target value, fitting a temperature resistance characteristic curve based on the ambient temperature of the temperature sensing cable and the resistance value of the cable, and evaluating the performance of the temperature sensing cable;

the temperature control system is used for heating the temperature sensing cable;

the detection structure is used for monitoring the ambient temperature of the temperature sensing cable and the resistance value of the cable;

the temperature control system is wrapped outside the temperature sensing cable;

the detection structure is arranged on the stable control system;

the temperature control system and the detection structure are communicated with the master control system in a wireless mode.

Furthermore, the master control system comprises a master control unit, a communication module, a voltage and current monitoring module, a temperature resistance curve fitting module, an AD acquisition module and a photoelectric coupling module;

the communication module is used for communication between the main control system and the temperature control system and between the main control system and the detection structure;

the voltage and current monitoring module is used for sampling the voltage and the current of the temperature sensing cable resistance measuring loop;

the AD acquisition module is used for converting the ambient temperature of the temperature sensing cable into an electric signal which can be acquired by the main control unit;

the temperature resistance curve fitting module is used for fitting a temperature resistance characteristic curve according to the resistance and the temperature of the temperature sensing cable;

the main control unit is used for controlling the temperature control system to heat the temperature sensing cable, calculating the resistance of the temperature sensing cable according to the voltage and current electric signals, and judging the performance of the temperature sensing cable according to the temperature resistance characteristic curve;

the photoelectric coupling module is used for isolating input and output signals.

Further, in the above-mentioned case,

for the field non-detachable temperature sensing cable structure, the temperature control system adopts a cylindrical silica gel heating sheet;

for the detachable temperature sensing cable structure, the temperature control system adopts an accommodating type constant temperature bag.

Further, in the above-mentioned case,

the detection structure comprises a temperature sensor and a voltage and current sensor;

the temperature sensor is used for measuring the ambient temperature of the temperature sensing cable;

the voltage and current sensor is used for measuring the voltage and current of the temperature sensing cable resistance measuring loop.

The invention also provides a temperature-sensitive cable performance detection method based on the temperature resistance characteristic, which comprises the following steps:

controlling a temperature control system to heat the temperature sensing cable to a target temperature according to the step length in sequence;

monitoring the ambient temperature and the resistance value of the temperature sensing cable at different target temperatures through the detection structure;

fitting a temperature resistance characteristic standard curve and a measurement curve of the temperature sensing cable according to the resistance values of the temperature sensing cable at different target temperatures;

and evaluating the performance of the temperature sensing cable based on a temperature resistance characteristic standard curve and a measurement curve of the temperature sensing cable.

Further, the fitting of the temperature-resistance characteristic standard curve and the measurement curve of the temperature-sensitive cable according to the resistance values of the temperature-sensitive cable at different target temperatures includes:

the temperature resistance characteristic curve of the temperature sensing cable between the ith measurement point and the (i + 1) th measurement point is expressed as follows:

wherein, fx (t)_iA temperature-sensitive cable temperature-resistance characteristic measurement curve from the ith measurement point to the (i + 1) th measurement point is shown, one target temperature corresponds to one measurement point, R_iMeasuring resistance, R, for the temperature sensing cable of the ith measuring point_i+1Measuring resistance value of the temperature sensing cable at the (i + 1) th measuring point, wherein T represents a target temperature value corresponding to the measuring point, and T_GFor temperature separation of adjacent measurement points, N_GThe total number of measurement points in the whole temperature range;

sequentially calculating to obtain temperature-resistance characteristic measurement curves of the temperature-sensing cables from all measurement points to adjacent measurement points, and obtaining the temperature-resistance characteristic measurement curve of the temperature-sensing cables in the whole temperature range;

similarly, the temperature resistance characteristic standard curve of the temperature sensing cable in the whole temperature range is obtained by calculating according to the standard resistance values of the temperature sensing cable at different target temperatures.

Further, the temperature range is selected from 20 ℃ to 120 ℃;

the total number of measurement points in the whole temperature range is calculated as:

further, the evaluating the performance of the temperature sensing cable based on the temperature resistance characteristic standard curve and the measurement curve comprises:

calculating the deviation rate and curve deviation score of the temperature-sensitive cable temperature-resistance curve, calculating the number of large deviation points of the temperature-sensitive cable temperature-resistance curve and calculating the maximum change rate of the temperature-sensitive cable temperature-resistance curve;

and establishing a temperature sensing cable evaluation system based on the temperature resistance characteristic curve deviation rate, the curve deviation score, the large deviation point number and the maximum change rate of the temperature sensing cable, and dividing the temperature sensing cable into three grades I, II and III according to the performance.

Further, the calculating the deviation rate of the temperature-resistance curve of the temperature-sensitive cable and the curve deviation score includes:

the curve deviation ratio is calculated as follows:

wherein e is_zRepresenting the deviation ratio of the curve, R_MtThe actual resistance value of the temperature sensing cable is obtained by a standard resistance measuring instrument when the target temperature is t_TtThe resistance value R of the temperature sensing cable is measured when the target temperature is t_CtC represents the standard resistance value of the temperature sensing cable when the target temperature is t, and c represents the temperature change quantity;

the curve deviation score is calculated as follows:

P＝∑P_t

wherein P represents the total curve deviation score of the temperature sensing cable, P_tRepresents a curve deviation score when the target temperature of the temperature sensing cable is t, c_1t、c_2tTemperature indicationCoefficient of deviation score for cable temperature t, e_tThe resistance deviation ratio at temperature t is shown.

Further, the calculating the number of large deviation points of the temperature resistance curve of the temperature sensing cable includes:

when e is_tGreater than E_maxThe corresponding measuring point is a large deviation point, and the number N, E of the large deviation points is calculated_maxIndicating a resistance deviation ratio preset threshold.

Further, the calculating the maximum rate of change of the temperature resistance curve of the temperature sensing cable includes:

M_max＝max||R_T(t+1)-R_Tt|-|R_C(t+1)-R_Ct||

wherein M is_maxAnd the maximum change rate of the temperature resistance characteristic standard curve and the measurement curve of the temperature sensing cable is represented.

Further, the temperature sensing cable evaluation system is established based on the deviation rate of the temperature resistance characteristic curve of the temperature sensing cable, the number of large deviation points and the maximum change rate, and the temperature sensing cable is divided into three grades I, II and III according to the performance, including:

the performance of the temperature sensing cable is an evaluation standard of I grade: rate of curve deviation e_zLess than 5 or P > 80, and a maximum rate of change M_maxLess than 1 and no large deviation point;

the evaluation standard of the temperature sensing cable performance of level II is that the temperature sensing cable meets any condition as follows:

condition 1: rate of curve deviation e_zLess than 5 or P > 80, and a maximum rate of change M_maxGreater than 1, but no large deviation point exists;

condition 2: rate of curve deviation e_zMore than 5 or 60-80, and the maximum rate of change M_maxLess than 1, and the number N of large deviation points is less than or equal to 10;

the performance of the temperature sensing cable is the evaluation standard of grade III: rate of curve deviation e_zGreater than 5 or P < 60, and maximum rate of change M_maxGreater than 1 and the number of large deviation points N is greater than 10.

The invention has the beneficial effects that:

the invention provides a temperature-sensitive cable performance detection device and method based on temperature-resistance characteristics. Has the following advantages: 1. the device can be applied to the quantitative detection of the temperature resistance characteristic of the temperature sensing cable. 2. The device can judge the performance level of the temperature sensing cable, can effectively prevent the damaged or low-quality temperature sensing cable from being used on site, and improves the reliability of a fire-fighting system of a transformer substation.

Drawings

Fig. 1 is a structural view of a temperature-sensitive cable detection device according to the present invention.

FIG. 2 is a flow chart of the detection of the temperature-sensitive cable according to the present invention.

Detailed Description

The invention is further described below. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.

The invention provides a temperature-sensitive cable performance detection device based on temperature resistance characteristics, which comprises 3 parts of a main control system, a temperature control system and a detection structure, as shown in figure 1.

The master control system is communicated with the temperature control system in a wireless mode.

The main control system is used for controlling the temperature control system, heating the ambient temperature of the temperature sensing cable to a target value, fitting a temperature resistance characteristic curve based on the ambient temperature of the temperature sensing cable and the resistance value of the cable, and evaluating the performance of the temperature sensing cable.

The temperature control system is used for heating the temperature sensing cable.

The detection structure is used for monitoring the ambient temperature of the temperature sensing cable and the resistance value of the cable.

Specifically, the main control system mainly comprises 6 parts of a main control unit, a communication module, a voltage and current monitoring module, a temperature resistance curve fitting module, an AD acquisition module and a photoelectric coupling module.

The communication module is used for communication between the main control system and the temperature control system and between the main control system and the detection structure.

The voltage and current monitoring module is used for sampling the voltage and the current of the temperature sensing cable resistance measuring loop;

the AD acquisition module is used for converting the temperature of the cylindrical silica gel heating sheet or the accommodating type constant temperature bag into an electric signal which can be acquired by the main control unit;

the temperature resistance curve fitting module is used for fitting a temperature resistance characteristic curve according to the resistance and the temperature of the temperature sensing cable;

the main control unit is used for calculating the resistance of the temperature sensing cable according to the voltage and current electric signals and judging the performance of the temperature sensing cable according to a temperature resistance characteristic curve;

the photoelectric coupling module is used for isolating input and output signals and realizing accurate control of temperature.

Specifically, for a field non-detachable structure, the temperature control system adopts a cylindrical silica gel heating sheet; to the structure that can conveniently dismantle, temperature control system adopts and holds the type constant temperature bag, can once only put into temperature sensing cable is whole, realizes temperature sensing cable constant temperature heating.

Specifically, detect the structural installation on temperature control system, detect the structure and adopt temperature sensor and voltage, current sensor, carry out temperature monitoring through temperature sensor, carry out resistance monitoring through voltage and current sensor.

The invention also provides a temperature-sensitive cable performance detection method based on temperature resistance characteristics, as shown in fig. 2, comprising:

heating the temperature sensing cable to a target value;

the ambient temperature and the resistance value of the temperature sensing cable are monitored in real time through the detection structure;

fitting a temperature resistance characteristic measurement curve of the temperature sensing cable according to the resistance values of the temperature sensing cable at different temperatures, and displaying the temperature resistance characteristic measurement curve on a screen of the detection device;

and evaluating the performance of the temperature sensing cable based on a temperature resistance characteristic standard curve and a measurement curve of the temperature sensing cable.

Specifically, the temperature-resistance characteristic measurement curve fitting method of the temperature-sensing cable comprises the following steps:

setting the temperature interval of the measuring point of the temperature sensing cable performance detection device as T_GThen the total number of measurement points N_GCan represent that:

in the embodiment of the invention, each target value corresponds to one measuring point, and the measuring range is 20-120 ℃.

Let the temperature sensing cable of the ith measuring point measure the resistance value as R_iThe resistance value of the temperature sensing cable of the (i + 1) th measuring point is R_i+1Then, the temperature-resistance characteristic curve of the temperature-sensing cable between the ith measurement point and the (i + 1) th measurement point can be represented as follows:

in the formula, fx (t)_iAnd (3) a temperature-resistance characteristic measurement curve of the temperature-sensing cable between the ith measurement point and the (i + 1) th measurement point is represented, and t represents a target temperature value corresponding to the measurement point.

And sequentially calculating to obtain temperature resistance characteristic curves of the temperature sensing cables from all the measuring points to adjacent measuring points, and obtaining the temperature resistance characteristic measuring curve of the temperature sensing cables in the whole temperature range.

Similarly, a temperature resistance characteristic standard curve of the temperature sensing cable can be obtained according to the standard resistance value of the temperature sensing cable at different temperatures.

Specifically, the method for evaluating the performance of the temperature sensing cable by adopting the temperature resistance characteristic standard curve and the measurement curve of the temperature sensing cable comprises the following steps:

step 1: calculating the deviation rate of the temperature resistance curve of the temperature sensing cable and the curve deviation score,

according to the temperature resistance characteristic standard curve and the temperature resistance characteristic measurement curve of the temperature sensing cable, firstly, the deviation ratio of the two temperature resistance characteristic curves is calculated as follows:

in the formula, e_zRepresenting the deviation ratio of the curve, R_MtThe actual resistance value of the temperature sensing cable is obtained by a standard resistance measuring instrument when the target temperature is t_TtThe resistance value of the temperature sensing cable is measured when the target temperature is t, and R is obtained by measurement of the device_CtThe standard resistance value of the temperature sensing cable at the target temperature t is obtained from the factory test result of a temperature sensing cable manufacturer, and c represents the temperature change quantity.

Calculating the deviation ratio of the standard resistance value and the measured resistance value of the temperature sensing cable at a certain temperature, wherein the expression is as follows:

in the formula, e_tThe resistance deviation ratio at temperature t is shown.

Defining the temperature of the temperature sensing cable as t time deviation score, and the calculation formula is as follows:

in the formula, c_1t、c_2tA deviation score coefficient P representing the temperature of the temperature sensing cable as t_tThe performance deviation score when the temperature of the temperature sensing cable is t is shown. c. C_1tAnd c_2tIs set artificially, c_1tCan be selected from 15% to 30%, c_2tThe value can be 30-45%.

Calculating performance deviation scores of t at 10 times of 20 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃ and the like respectively to obtain deviation total scores of the temperature sensing cables:

P＝∑P_t (6)

in the formula, P represents a total curve deviation score of the temperature-sensitive cable.

Step 2: and calculating the number of large deviation points of the temperature resistance curve of the temperature sensing cable.

Definition when e_tGreater than E_maxFor large deviation points, the number of large deviation points N is calculated.

Wherein E is_maxIndicating a resistance deviation ratio preset threshold.

And step 3: and calculating the maximum change rate of the temperature resistance curve of the temperature sensing cable.

According to the temperature resistance characteristic standard curve and the measurement curve of the temperature sensing cable, the maximum change value of the temperature resistance characteristic curve with 1 ℃ as the minimum unit is calculated, and the calculation method is as follows:

M_max＝max||R_T(t+1)-R_Tt|-|R_C(t+1)-R_Ct|| (7)

in the formula, M_maxAnd the maximum change rate of the temperature resistance characteristic standard curve and the measurement curve of the temperature sensing cable is represented.

And 4, step 4: and establishing an evaluation system of the temperature sensing cable.

The method adopts a temperature sensing cable evaluation system which takes the deviation rate of a temperature resistance characteristic curve of the temperature sensing cable as a basis and takes the large deviation point quantity and the maximum change rate as auxiliary criteria, and divides the temperature sensing cable into three grades I, II and III according to the performance, wherein the specific evaluation mode is as follows:

1. the performance of the temperature sensing cable is an evaluation standard of I grade: rate of curve deviation e_zLess than 5 or a deviation score greater than 80, maximum rate of change M_maxLess than 1, no large deviation point.

2. The evaluation standard of the temperature sensing cable performance of level II is that the temperature sensing cable meets any condition as follows:

condition 1: rate of curve deviation e_zLess than 5 or a deviation score greater than 80, maximum rate of change M_maxGreater than 1, but no large deviation point exists.

Condition 2: rate of curve deviation e_zGreater than 5 or a deviation score less than 80 but greater than or equal to 60, maximum rate of change M_maxLess than 1, and the number of large deviation points N is less than or equal to 10.

3. The performance of the temperature sensing cable is the evaluation standard of grade III: rate of curve deviation e_zGreater than 5 or deviation score less than 60, maximum rate of change M_maxGreater than 1, the number of large deviation points N is greater than 10.

According to the evaluation standard of the temperature sensing cable, the performance is defined as follows:

the I-grade temperature sensing cable has good performance and is suggested to be continuously applied.

The II-grade temperature sensing cable is qualified in performance, can be used or replaced, and can be continuously used if needed, and corresponding parameters of the temperature sensing cable terminal box are required to be adjusted according to field conditions, so that the over-temperature state can be sensitively monitored.

The III-grade temperature sensing cable is unqualified in performance and needs to be replaced in time so as to avoid the situation of false alarm or fire alarm rejection.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.