JP2613132B2 - Monitoring method of conductor temperature of laid power cable joint - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conductor temperature monitoring method for a laid power cable joint for monitoring a conductor temperature of a power cable joint and performing maintenance of a cable line.

(Problems to be Solved by the Prior Art and the Invention) The joint portion of the power cable has a heat capacity larger than that of the cable main body because an insulating member or the like is wound around the conductor thicker than the cable main body. And there is a characteristic that heat is not dissipated satisfactorily. Therefore, at the joint portion of the cable, the temperature tends to be relatively high, and the heat accelerates the deterioration and damage of the insulator, causing transient heat generation of the joint conductor. This temperature increase further promotes the deterioration of the joint performance. May be.

In order to solve the above problem, when monitoring the conductor temperature of all the cable lines, it is particularly necessary to accurately grasp the conductor temperature of the joint.

However, for the method of monitoring the conductor temperature in the cable portion, for example, a method as disclosed in Japanese Patent Application Laid-Open No. 60-223521 can be used. There has been a demand for the development of means that can be easily measured without being studied in detail.

(Object of the Invention) The present invention can easily measure a temperature at a joint portion of a cable route based on measured temperatures at seven measurement points and accurately measure the measured value. It is an object of the present invention to provide a method of monitoring the conductor temperature of an installed power cable joint.

(Means and Actions for Solving the Problems) In order to achieve the above-mentioned object, in the conductor temperature monitoring method for a laid power cable joint according to the present invention, the method for measuring the surface temperature of a power cable and a cable joint is performed. Seven temperature sensors are arranged along the power cable and the cable joint. Then, from each sensor, a plurality of thermocouples are connected in parallel usage,
The average surface temperature in the circumferential direction is measured by a single sensor, and the temperature sensor is sequentially switched to obtain a measured value, so that the average surface temperature is measured and the conductor current of the power cable joint is measured. Measured by a transformer,
The conductor temperature of the current cable joint at the corresponding location is estimated based on the measured temperature value and the conductor current at the corresponding location.

In the present invention, a distributed optical fiber temperature measuring device is used, and instead of the thermocouple, an optical fiber is wound around the surface of the power cable and the power cable joint a plurality of times to obtain a circle at the relevant location. While measuring the surface temperature average value in the circumferential direction, the conductor current of the power cable joint is measured by a current transformer, and the conductor temperature of the power cable joint at the corresponding location is determined based on the temperature measurement value and the conductor current at the corresponding location. Can be estimated.

Therefore, in the temperature monitoring method of the present invention, the surface average temperature of a plurality of locations (seven locations) is measured on the cable and the cable joint, and the conductor current is used as a temperature measurement parameter. It can be easily and highly reliable.

(Example) The present invention will be described in detail based on an illustrated example.

FIG. 1 is an apparatus configuration diagram using a thermocouple as a temperature sensing element for performing a method according to the present invention. Seven temperature sensors 3a to 3g are arranged along a power cable 1 and a power cable joint 2. Have been placed. The temperature sensors 3a to 3g are connected in parallel with thermocouples, and the sensors are attached to the cable 1 and the joint 2 on the respective circumferential surfaces at the corresponding seven locations. Each one temperature sensor can measure the average value of the surface temperature in the circumferential direction at a corresponding portion of one cable or joint.

In the present invention, each of the temperature sensors 3a to 3g is connected in parallel to the multipoint temperature monitoring device 4, and one of the temperature sensors is responded to a data transfer request from the multipoint temperature monitoring device 4. A measurement signal is transmitted to the multipoint temperature monitoring device 4.

Further, the output of the multipoint temperature monitoring device 4 is connected to a computer 5 for calculation processing. On the other hand, the current transformer 6 is attached to one or a plurality of locations in the power cable joint section to be measured, and is connected to the computer 5 via the current measuring device 7.

In the measuring device of the present invention configured as described above,
When measuring the temperature, the multipoint temperature monitoring device 4 sequentially outputs the identification code to each of the sensors, and the temperature sensors 3a to 3g.
, And sequentially outputs the received information to the computer 5. Further, the current measuring device 7 detects the strength of a magnetic field generated by the current flowing through the conductor of the power cable joint by the current transformer 6, and sequentially outputs a current value corresponding to the detected value to the computer 5.
The computer 5 estimates the conductor temperature of the corresponding power cable joint 2 based on the taken temperature value and current value.

FIG. 2 shows another method according to the present invention, and is a configuration diagram of an apparatus using an optical fiber as a temperature sensing element. In the example shown in FIG. 2, the optical fiber 10 is arranged on the surface along the power cable 1 and the power cable joint 2, and seven measurement points are set as shown in FIG. An optical fiber is wound around the surface of the cable or the joint a plurality of times around the measurement point to provide measurement points 10a to 10g. Then, the average value of the surface temperature in the circumferential direction at the seven measurement devices 10a to 10g can be measured using the optical fiber 10.

Furthermore, the end of the optical fiber 10 is connected to a distributed optical fiber thermometer 11, and the pulsed light incident on the optical fiber 10 from the distributed optical fiber thermometer 11 is used to generate Raman rearward light generated in the optical fiber. From the intensity of the scattered light, temperatures at multiple points along the optical fiber are measured at once. The output of the distributed optical fiber temperature measuring device 11 is connected to a computer 12 for calculation processing. On the other hand, a current transformer 13 is attached at one or a plurality of locations to a power cable joint section to be measured, and the current transformer 13 is connected to the computer 12 via a current measuring device 14.

In the device configured as described above, the distributed optical fiber temperature measuring device 11 collectively measures the temperature at multiple points along the optical fiber 10 and outputs the result to the computer 12. Further, a magnetic field generated by a current flowing through the conductor of the power cable joint is detected by a current transformer 13, and a current measuring device 14 sequentially calculates a current value corresponding to the detected value obtained by the current transformer 13 into a computer. Output to 12. Then, the computer 12 estimates the conductor temperature of the power cable joint 10 from the taken temperature value and current value.

Next, a description will be given of a method of calculating the conductor temperature on the cable 1 and the cable joint portion 2 configured as described above, using the sensors arranged respectively, based on the information obtained respectively. In the example shown in FIG. 3, (a) shows a cross section of the joint part of the cable, and (b) shows the temperature of each component at each part corresponding to (a).

In the example shown in FIG. 3B, the thermal resistance of the insulator 21 in the cable 1 or the joint 2 is R _{11 to} R ₇₁ , the thermal resistance of the anticorrosion layer 22 is R _{13 to} R ₇₃ , the dissipation heat resistance R ₁₂ · R ₂₂ · R ₆₂
・ R ₇₂ , the thermal resistance of insulation compound 27 of joint 2 is R ₃₂・ R
₄₂・ R ₅₂

Also, the heat capacity of the conductor 20 is C _{11 to} C ₇₁ , the heat capacity of the insulator 21 is C _{15 to} C ₇₅ , the heat capacity of the copper tape 26 and the gap layer is C _{12 to} C ₇₂ , the anticorrosion layer 22 and the sheath 23, or the joint copper. The heat capacity of the pipe 28 is C _{13 to} C ₇₃ , and the heat capacity of the insulating compound 27 of the joint 2 is C ₃₄ · C
₄₄ and C ₅₄ .

Further, the thermal resistance in the axial direction of the conductor 20 is r ₁ to r ₆ , and the thermal resistance in the axial direction of the sheath / copper tube / copper tape is r ₇ to r ₁₆
And

With respect to each portion the temperature, T ₁ through T ₇ are conductors, T ₂₅ through T ₃₁ are insulators, T ₁₅ through T ₂₁ is a sheath or copper tube, T _Z1 through T _Z7 surface, T
_{22 to} T ₂₄ is the temperature of the insulating monpound, and regarding the loss that generates heat flow, W _{1 to} W ₇ are conductor loss, W _{22 to} W ₃₁ are dielectric loss, and W _{15 to} W ₂₁ are sheath loss. The equivalent thermal circuit of the power cable joint and its extension cable is as shown in FIG. 3 (b).

As shown in the equation (1), a 31-dimensional simultaneous differential equation is obtained from the equivalent thermal circuit of FIG.

Here, the elements of the matrix H in the equation (1) are as shown in Table 1, where G is the reciprocal (1 / R) of the thermal resistance R in the radial direction.
Where g is the reciprocal (1 / r) of the thermal resistance r in the axial direction,
The blank part represents 0.

Further, the heat flow W ₁ to _W-7 produced by the conductor loss, the heat flow W ₁₅ to _W-21 produced by the heat flow W ₂₂ to _W-31, the sheath loss generated by the derivative loss, the current flowing through the conductors of all power cable joints I Can be expressed using Further, since the heat capacity C, the radial heat resistance R, and the axial heat resistance r are obtained in advance, the 31-dimensional simultaneous equation of the equation (1), the conductor current I, and the surface temperatures T _{Z1 to} T _{Z7 of the} cable and the joint are obtained.
, The conductor temperatures T _{1 to} T _{7 of} the joint are obtained.

In the calculation process, by increasing the number of temperature sensors and current transformers, it is possible to simultaneously monitor the conductor temperatures of other joints and cables.

Also, if the joint structure can be considered as left and right symmetric, take a temperature sensor on only one side of the joint. In addition, since it suffices to monitor the temperature, it is also possible to perform the measurement with four temperature sensor attachment points provided for seven joints for one joint as in the above embodiment.

(Effect of the Invention) As described above, the conductor temperature monitoring method for a laid power cable joint according to the present invention measures the surface average temperature at a plurality of locations (seven locations) on the cable and the cable joint, and measures the conductor current. Because it is used for the parameters of the above, it is easy to monitor the conductor temperature of the joint,
The reliability of the estimated value can be increased.

Further, in the multipoint temperature monitoring device of the present invention, since the parallel use method of the electric thermocouple is adopted, the number of sensors can be reduced.

Furthermore, in the temperature monitoring method of the present invention, since an optical fiber sensor is used, the average temperature in the circumferential direction of the cable surface can be obtained, similarly to the multipoint temperature monitoring device.
The measurements are not affected by the magnetic field.

[Brief description of the drawings]

The drawings show an embodiment of the method for monitoring the conductor temperature of a laid power cable joint according to the present invention. FIG. 1 is a configuration diagram using a thermocouple as a temperature sensing element for performing the method of the present invention. FIG. 3A is a configuration diagram using an optical fiber for performing the method of the present invention as a temperature-sensitive element, FIG. 3A is a cross-sectional view of a cable joint, and FIG. Circuit. Reference numerals in the drawing 1 ... power cable, 2 ... power cable joint,
3 ... Temperature sensor, 4 ... Multipoint temperature monitoring device, 5.12 ...
... Computer, 6/13 ... Current transformer, 7/14 ... Current measuring instrument, 8 ... Optical fiber, 10 ... Optical fiber, 11 ...
... optical fiber temperature measuring device.

Claims (1)

(57) [Claims] 1. For a power cable joint part, three sensors along said joint part, two sensors on both sides of said joint part to measure the cable surface temperature at the joint end, In order to measure the cable surface temperature in the longitudinal extension direction of both sides, one sensor is arranged for each, a total of seven measurement points are set by the sensors,
At each of the seven measurement points, the average surface temperature in the circumferential direction is measured by a temperature sensor, and the conductor current of the power cable joint is measured by a current transformer. A conductor temperature monitoring method for a laid power cable joint, comprising estimating a conductor temperature of the cable joint at a corresponding location based on a current.