JP2002271929A - Conductor temperature estimation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductor temperature estimation method which can highly precisely and easily estimate a conductor temperature at an arbitrary time or a peak value of a conductor temperature when a load current having a daily load pattern is applied to an installed power cable line. SOLUTION: There is provide a conductor temperature estimation method, wherein a temperature of an inner wall of a conduit of a power cable line is measured, a daily load current pattern row of the hourly change of an applied current is measured, heat generation quantity of a cable are calculated in units of an hour for a day (last 24 hours) according to the applied current and a conductor resistance, the heat generation quantity of the cable are resolved into respective frequency components Ck, conductor temperature rise components Tr(t) of the respective frequency components Ck are obtained from products of the respective frequency components Ck and equivalent impedances, corresponding to the respective frequency components Ck, of an RC multistage circuit comprising a thermal resistance R and a heat capacity C of the cable line, and temperatures Tw(t) measured on the line in units of an hour are added to the conductor temperature rise components Tr(t) to obtain conductor temperatures Tc(t) in units of prescribed hours of a day.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating a conductor temperature of a power cable, and more particularly to a method for estimating a conductor temperature of a power cable line such as an underground conduit buried underground or a power cable laid on the ground. It is.

[0002]

2. Description of the Related Art As a method of estimating a conductor temperature of a power cable line, a JCS method for calculating a conductor temperature in a steady state and under a short-time overload has conventionally been used. The JCS method is generally used widely in line design as a conductor temperature calculation method. The conductor temperature in a steady state is calculated based on a constant load current, and the conductor temperature in a short-time overload is calculated. Are calculated on the assumption that the load current changes stepwise.

For this reason, it is extremely important to measure the conductor temperature in the steady state of the power cable and the change in the conductor temperature during a short-time overload, and various methods for detecting the temperature have been proposed. For example, an optical thermometer for measuring the surface temperature of a power cable and a cable conductor temperature measuring device for an optical heat flow sensor for detecting a heat flow are disclosed in Japanese Utility Model Laid-Open Publication No. 64-46.
No. 731 discloses a cable conductor temperature measuring device using a first optical fiber and a second optical fiber.
No. 46732. In addition, Japanese Unexamined Patent Publication No.
Japanese Patent No. 2574187 describes a method of estimating the internal temperature of a power cable from actual measured values of the outermost layer surface temperature of the cable and the amount of heat dissipated on the surface. A conductor temperature monitoring method of arranging temperature sensors and measuring the temperature is described. JP 2
Japanese Patent Application Publication No. 000-88666 proposes a method of calculating a conductor temperature of a power cable based on a temperature in a pipe measured by an optical fiber distributed temperature sensor inserted in the pipe and a soil temperature in the ground. ing.

[0004]

However, according to the conventional method of measuring the conductor temperature of the power cable, it is relatively easy to detect the conductor temperature in the steady state of the power cable or when the power cable is overloaded for a short time. As described above, it is not easy to easily determine the conductor temperature or the peak value of the conductor temperature at a predetermined time in the case where the load current of the line repeatedly changes. For this reason, from the viewpoint of power cable line maintenance, there has been a strong demand for a method of detecting the conductor temperature or the peak value of the conductor temperature when the load current of the line changes every moment.

Accordingly, an object of the present invention is to accurately and simply estimate a conductor temperature or a peak value of a conductor temperature at an arbitrary time when a load current having a daily load pattern repeatedly flows in a laid power cable line. It is an object of the present invention to provide a conductor temperature estimating method which can be performed.

[0006]

In order to achieve the above object, the present invention provides a method for estimating the conductor temperature of a power cable line buried underground or laid on the ground, the method comprising: In parallel with the measurement, the time-varying current flowing through the power cable line is
Measuring the power cable line as a daily load current pattern sequence at a predetermined time interval of one day, and the power cable based on the cable conduction current and the conductor resistance value of the power cable in the daily load current pattern sequence. Calculating a calorific value of the cable at predetermined time intervals of the track, a step of temporarily dividing the temporal change of the calorific value of the cable into discrete Fourier expansions to separate each frequency component (Ck), The product of each frequency component (Ck) of the quantity and the equivalent impedance for each frequency component (Ck) of the RC multistage circuit by replacing the power cable line with an RC multistage circuit composed of a thermal resistance (R) and a heat capacity (C). From the conductor temperature rise [Tr] in each of the frequency components (Ck) of the power cable line.
(T)], and each of the frequency components (C
k) is added to the measured conductor temperature rise [Tr (t)] of the power cable line at predetermined time intervals of the day [Tw (t)]. Calculating a change [Tc (t)] in the conductor temperature at predetermined time intervals.

[0007] The present invention has also been made to achieve the above object.
The daily load current pattern in the power cable line.
Measuring the power cable line
The time-varying energization of the road at predetermined time intervals in one day
Measuring the current and placing a cloth in the conduit of the power cable line;
Predetermined time of day by installed optical fiber for temperature measurement
Characterized by including measurement of the pipe inner wall temperature of the notch,
The power cable line at a predetermined time interval of the day.
Calculating the calorific value of the power cable,
The power supply of the cable at predetermined time intervals of the day on the track
Current and the conductor resistance at the allowable temperature of the power cable conductor
Based on the predetermined of the day of the power cable line
Calculating the cable heating value at time intervals.
Wherein each of the frequencies of the power cable line is
Conductor temperature rise in several components (Ck) [Tr (t)]
The step to determine is the thermal resistance of the cable insulation
(R₁), Thermal resistance (R_Two),cable
Surface dissipation heat resistance (R_Three) And a cable
Heat capacity of conductor and insulator of cable (C₁), Cable anticorrosion layer
Thermal resistance (C _Two), Heat capacity of air in the pipeline (C_Three From)
Heat capacity (C) and RC three-stage consisting of cable conductors
Equivalent impedance for each frequency component (Ck) of the circuit
And the frequency component (Ck) of the heat generation amount of the cable.
From the product, the respective frequency components (C
k) to determine conductor temperature rise [Tr (t)]
Provide a conductor temperature estimation method characterized by including steps
I do.

[0008]

FIG. 1 shows a power cable laid in a pipeline in a conductor temperature estimating method according to an embodiment of the present invention. Inside the conduit 1, a single power cable 2 and a temperature measuring optical fiber 3 are laid. The power cable 2 includes a conductor 4, an insulator 5, and an anticorrosion layer 6, and an air layer 7 exists between the pipeline 1 and the power cable 2. Hereinafter, it is assumed that the heat source of the power cable 2 laid in the conduit 1 of the embodiment is only the conductor 4, and the optical fiber for temperature measurement 3 measures the inner wall temperature of the conduit 1. The procedure for calculating the temperature will be described.

FIG. 2 shows a daily load pattern of a current flowing through the power cable in the conductor temperature estimating method according to the embodiment of the present invention. In FIG. 2, the curve of the daily load current pattern 8 of the energizing current is drawn with a predetermined time step of one day as one hour. In the embodiment, first, the daily load current pattern 8 of the conduction current (A) with a predetermined time interval of 1 hour and the conductor resistance value (Ω / m) at the allowable temperature of the cable conductor of 90 ° C. are used. The cable calorific value (W / m) at predetermined time intervals is obtained by Expression 1.

[0010]

(Equation 1)

FIG. 3 shows a change over time of the heat generation amount of the power cable in the conductor temperature estimation method according to the embodiment of the present invention. In FIG. 3, the curve of the cable heating value 9 is drawn by the time change of the cable heating value (W / m) obtained from the daily load current pattern 8 in FIG. Next, with respect to the time change W (n) of the cable heating value 9 (W / m), a discrete Fourier expansion is once performed by Expression 2 to decompose the cable heating value into frequency components 10 (Ck). .

[0012]

(Equation 2) It is.

FIG. 4 shows an RC multistage equivalent circuit of a power cable in the conductor temperature estimation method according to the embodiment of the present invention. The RC multi-stage equivalent circuit of FIG. 4 is a case of an RC three-stage circuit in which the power cable (FIG. 1) is replaced by a circuit composed of a thermal resistance (R) and a thermal capacity (C). ₁ ) and 12 are the thermal resistance (R ₂ ) of the anticorrosion layer of the cable, 13 is the thermal resistance (R ₃ ) dissipated on the cable surface,
4 is the heat capacity (C ₁ ) of the cable conductor and the insulator, 15 is the heat resistance (C ₂ ) of the cable anticorrosion layer, 16 is the heat capacity of the air in the conduit (C ₃ ), and 17 is the cable conductor.

According to the RC three-stage circuit shown in FIG. 4, each frequency ω = kωo, k = 0 to
The equivalent impedance Z (ω) for (N−1) can be calculated in the same manner as in the case of an electric circuit, and the calculation is as shown in Expression 3.

[0015]

(Equation 3)

Further, each frequency component (C
When the time change of the conductor temperature rise Tr (t) with respect to k) is added, the calculation is as shown in Expression 4.

[0017]

(Equation 4) It is.

FIG. 5 shows a change in the conductor temperature of the power cable in the conductor temperature estimation method according to the embodiment of the present invention. In the curve of the change over 24 hours in FIG. 5, the conductor temperature rise 18 [Tr (t)] from the pipe inner wall and the pipe inner wall temperature 19 [3] measured by the temperature measuring optical fiber (3 in FIG. 1). Tw (t)], a change in conductor temperature of 20 [Tc (t)] is obtained. these,
Conductor temperature rise Tr (t) and pipe inner wall temperature Tw (t)
And the conductor temperature change Tc (t) is as shown in Equation 5.

[0019]

(Equation 5)

According to FIG. 5, the change in the conductor temperature with respect to the daily load current pattern of the supplied current (FIG. 2) is 20 [Tc].
(T)] shows that the conductor temperature at 10 am is about 51 ° C., the peak value of the conductor temperature is 62 ° C. at 18:00 pm, and At 22:30, the conductor temperature was (52.9
(° C. + 49.4 ° C.) / 2 = about 51 ° C.

According to the conductor temperature estimating method according to the embodiment of the present invention, the inner wall temperature of the power cable line on a date and time basis, the time-varying current flowing through the power cable line (daily load current pattern), 1 It can be seen that data necessary for maintenance and inspection of the power cable line, such as the heat generation of the cable, the power cable conductor temperature, and the power cable conductor temperature rise at predetermined time intervals of the day, are grasped.

In the conductor temperature estimating method according to the embodiment of the present invention, when the calculation is performed including the influence of the soil portion outside the power cable pipeline (FIG. 1), the cable portion is connected to the RC two-stage circuit, and the soil portion is connected to the soil portion. Using an equivalent impedance using an RC three-stage circuit as an RC one-stage circuit, or using a four RC four-stage circuit as an RC three-stage circuit for a cable portion and an RC one-stage circuit for a soil portion, a predetermined value for one day The daily change of the conductor temperature at the time interval of can be calculated in the same manner.

In the embodiment of the present invention, when the predetermined time interval does not coincide with the predetermined time interval of the day (predetermined 24 hours), the conductor is interpolated from a predetermined value before and after the predetermined time interval. The temperature can be determined. Also,
The conductor temperature peak value of the daily load current pattern at the time of energization is obtained as a conductor temperature peak value at the time of energization of the daily load current pattern, which is the maximum value of the conductor temperature obtained from the 24 hour change of the conductor temperature with respect to the daily load current pattern. be able to.

[0024]

According to the conductor temperature estimating method according to the embodiment of the present invention, in a laid power cable line in which a load current having a daily load current pattern flows, the cable conductor temperature and the conductor temperature at a predetermined time of day are measured. The effect is obtained that the maximum conductor temperature at which the peak value is reached can be estimated very accurately and easily. In addition, by accurately detecting and estimating the conductor temperature or the peak value of the conductor temperature of the laid power cable in 24 hours,
There is an advantage that inspection and maintenance of the power cable line on a date and time basis can be easily realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a power cable laid in a conduit in a conductor temperature estimation method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a daily load pattern of a current flowing through a power cable in a conductor temperature estimation method according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a time change of a heat generation amount of a power cable in the conductor temperature estimation method according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an RC multistage equivalent circuit of a power cable in the conductor temperature estimation method according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a change in the conductor temperature of the power cable in the conductor temperature estimation method according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pipeline 2 Power cable 3 Optical fiber for temperature measurement 4 Conductor 5 Insulator 6 Corrosion protection layer 7 Air layer 8 Daily load current pattern 9 Cable calorific value (W / m) 11 Thermal resistance of cable insulator (R ₁ ) 12 Cable Thermal resistance of anticorrosion layer (R ₂ ) 13 Heat dissipation of cable surface (R ₃ ) 14 Heat capacity of conductor and insulator of cable (C ₁ ) 15 Thermal resistance of cable anticorrosion layer (C ₂ ) 16 Air of air in pipeline Heat capacity (C ₃ ) 17 Cable conductor 18 Increase in conductor temperature from the inner wall of the conduit [Tr (t)] 19 Inner wall temperature of the conduit [Tw (t)] 20 Change in conductor temperature [Tc (t)]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02G 1/00 H02G 1/00 A 9/00 9/00 D

Claims (4)

[Claims] 1. A method for estimating a conductor temperature of a power cable line buried underground or laid on the ground, the method comprising: measuring a temperature of an inner wall of a pipe of the power cable line; Measuring the energizing current to be performed as a daily load current pattern sequence at predetermined time intervals in the power cable line, based on the cable energizing current and the conductor resistance value of the power cable in the daily load current pattern sequence. Calculating the calorific value of the power cable line at predetermined time intervals in one day; and temporally decomposing the temporal change in the calorific value of the cable into discrete frequency Fourier transforms into frequency components (Ck). And each frequency component (Ck) of the cable heating value, and the power cable line is composed of a thermal resistance (R) and a thermal capacity (C). Each frequency component (Ck) of the power cable line is obtained from the product of the RC multistage circuit and the equivalent impedance for each frequency component (Ck) of the RC multistage circuit.
Determining the conductor temperature rise [Tr (t)] at the time of the measurement; and calculating the conductor temperature rise [Tr (t)] at each of the frequency components (Ck) by a predetermined value of the measured one day of the power cable line. Pipe wall temperature at time intervals [Tw (t)]
And calculating a change [Tc (t)] in the conductor temperature at predetermined time intervals of one day. 2. The step of measuring as the series of daily load current patterns in the power cable line includes measuring the time-varying energizing current of the power cable line at predetermined time intervals of one day, and measuring the power cable. The conductor temperature estimating method according to claim 1, further comprising: measuring a temperature of the inner wall of the conduit at predetermined time intervals of one day by a temperature measuring optical fiber laid in the conduit of the line. 3. The step of calculating a calorific value of the cable of the power cable line at predetermined time intervals of the day includes the step of: calculating a power supply current of the cable at predetermined time intervals of the day of the power cable line; The conductor according to claim 1, further comprising: calculating the calorific value of the cable at predetermined time intervals of the day on the power cable line based on a conductor resistance value at an allowable temperature of the cable conductor. Temperature estimation method. 4. The frequency components of the power cable line
The conductor temperature rise [Tr (t)] in (Ck) is obtained.
Is the thermal resistance of the cable insulator (R₁ ), K
The thermal resistance (R_Two ), Cable surface heat dissipation resistance
(R_Three ) And the conductor of the cable.
Heat capacity of edge (C₁), Thermal resistance of cable corrosion protection layer
(C _Two), Heat capacity of air in the pipeline (C_Three) Consisting of heat volume
Quantity (C) and each of the RC three-stage circuits consisting of cable conductors
The equivalent impedance for the frequency component (Ck)
From the product of the cable heating value and each frequency component (Ck),
For each frequency component (Ck) of the power cable line,
The step of obtaining the conductor temperature rise [Tr (t)]
The conductor temperature estimating method according to claim 1, further comprising:
Law.