JPH08242534A - Electric line temperature monitoring method - Google Patents

Abstract

(57) [Abstract] [Purpose] To monitor the wire temperature itself, especially for the stranded wire structure, using the measured temperature on the wire surface. [Composition] Calculated by calculating the estimated value of the internal temperature of the wire based on the amount of heat generated inside the wire of the monitoring line from the detected value of the energizing current, and from the detected value of the meteorological conditions the surface temperature of the wire based on the amount of heat generated on the surface of the wire of the monitoring line The temperature difference between the inside of the wire and the wire surface of the monitoring line is calculated from the difference between the two estimated values, and the temperature difference is added to the measured value of the wire surface temperature of the monitoring line to determine the Monitor temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature monitoring method for an electric line, which is suitable for detecting abnormal overheating of an electric line having a twisted wire structure such as an overhead transmission line.

[0002]

2. Description of the Related Art Conventionally, the temperature (electric wire temperature) of various electric lines such as an overhead transmission line having a stranded wire structure is indirectly detected by the current flowing therethrough.

That is, in the case of the overhead power transmission line, which is an example of this type of power line, in order to protect the electric wire from abnormal overheating due to an increase in the power transmission current, a current transformer for electric power (CT) installed in the power transmission line is provided. The energization current is detected by the secondary output of (1). Then, when the energized current reaches a predetermined threshold value, the current relay is activated, and power transmission is stopped by an open trip of the circuit breaker or the like.

[0004]

In the case of the conventional method for monitoring the temperature of the electric line, only the current flowing through the electric line is detected, and the temperature of the electric line cannot be actually detected.
There is a problem that the realistic thermal operation state cannot be monitored.

Further, the predetermined threshold value serving as a reference value for stopping power transmission is a preset constant value, and its magnitude is assumed to be the maximum temperature at which the air temperature is predicted in order to ensure protection. The temperature is set in consideration of a considerable design margin.

In this case, since the predicted maximum temperature is generally about 40 ° C., the temperature during the time when the power demand by the electric heater or the like increases in winter is 5 ° C., which is sufficiently lower than the predicted maximum temperature. For example, depending on the thermal operating conditions of the electric line, power can be transmitted safely without abnormal overheating until the amount of current flowing increases by an amount corresponding to the temperature difference (40-5 =) 35 ° C. Power transmission stops.

The electric line is, for example, a hard copper stranded wire HDC.
C100mm ² or steel core aluminum stranded wire ACSR 160mm ²
In the above overhead power transmission line, the amount of transmission current corresponding to the temperature difference of 35 ° C. reaches 20% of the maximum amount of current that can be transmitted, but there is also a problem that the transmission efficiency is significantly reduced. The maximum amount of current that can be transmitted varies not only with the temperature but also with various weather conditions such as solar radiation and wind and rain.

The present invention focuses on the fact that the amount of heat generated inside the wire due to energization becomes larger than the amount of heat generated on the surface of the wire due to weather conditions, at least when abnormal overheating due to overcurrent occurs. The purpose of the present invention is to measure the temperature of the wire surface and monitor the wire temperature itself in a stranded wire structure where a temperature difference occurs between the wire surface and the wire surface.

[0009]

In order to achieve the above object, in the temperature monitoring method of the electric line of the present invention, first, the temperature of the electric line is monitored with high accuracy in consideration of actual weather conditions. When performing, the estimated value of the wire internal temperature based on the amount of heat generated inside the wire of the monitoring line is calculated from the detected value of the current flowing through the monitoring line, and the detected value of weather conditions around the monitoring line such as insolation intensity and temperature. From the calculated value of the wire surface temperature based on the amount of heat generated on the wire surface of the monitoring line, the temperature difference between the inside of the wire and the wire surface of the monitoring line is calculated from the difference between the two estimated values, and the wire surface of the wire is monitored. The temperature difference is added to the measured temperature value to monitor the temperature of the monitoring line.

Next, when the temperature of the electric line is monitored by a simpler method, the estimated value of the wire surface temperature of the electric line is calculated instead of being calculated from the detected value of the weather conditions around the electric line. , Set to a predetermined value.

[0011]

In the method of monitoring the temperature of the electric line of the present invention constructed as described above, the temperature inside the electric wire is estimated by calculation from the current flowing through the monitoring line. In addition, the temperature of the wire surface of the monitoring line is estimated by calculation from the measurement result of the meteorological conditions.

Then, the temperature difference between the temperature inside the wire and the temperature on the wire surface is added to the measured temperature on the wire surface, and by this addition, the temperature rise based on the energizing current is corrected to the measured temperature on the wire surface according to the meteorological conditions. It is applied and added.

At this time, if the monitoring line is an electric line having a stranded wire structure, when a temperature difference occurs between the inside of the wire and the surface of the wire due to the difference in the amount of heat generated, and abnormal overheating due to overcurrent occurs, The amount of heat generated inside the electric wire becomes larger than the amount of heat generated on the surface of the electric wire, and the electric wire temperature is obtained from the temperature obtained by adding the temperature difference to the actually measured temperature of the electric wire surface.

Since the temperature of the electric wire is corrected by the meteorological condition, the temperature itself of the monitoring line at the time of occurrence of the abnormal overheating is monitored with high accuracy in consideration of the actual meteorological condition.

Next, when the temperature of the electric wire surface of the monitoring line is set to a predetermined value, the actual measurement and estimation calculation of the temperature of the electric wire surface can be omitted, and the temperature of the electric line can be monitored more easily.

[0016]

EXAMPLES Examples will be described with reference to FIGS. 1 to 7. Figure 2 shows the substation equipment. In the figure, 1
a and 1b are two two-system feed substations (feed A substation,
Feeding B substation) 2 is a secondary substation on the load side of the substations 1a and 1b, which receives electric power of two systems transmitted from the substations 1a and 1b, respectively, and through the plurality of transformers 3. Power is distributed to each load side system.

Reference numeral 4 is a plurality of circuit breakers at the substations 1a and 1b.
Is a switchgear at each place of the substation 2, and 6 is a current transformer for an instrument at each place of the substation 2.

Reference numeral 7 is a meteorological observation device provided with various sensors for detecting meteorological conditions such as temperature and solar radiation, and 8 is a supervisory control device, which is a required current transformer 6 for measuring instruments as transmission current information in the substation 2. The detection information of the energization current, the required detection information of the energization current of the instrument current transformer 6 and the detection information of the meteorological observation device 7 as the load current information are supplied to the respective signal input units 9.

Each signal input unit 9 is provided with a serial circuit of an insulating amplifier 10 and a noise-removing low-pass filter 11 for each input channel.

Reference numeral 12 is a multiplexer for selecting the output of each signal input section 9, 13 is an A / D converter for digitizing the output of the multiplexer 12, 14 is a microcomputer to which the output of the A / D converter 13 is given, 15 Is an operation / setting panel connected to the computer 14 and has various operation keys such as a numeric keypad.

Reference numeral 16 denotes a load control contact output unit connected to the computer 14, which opens and trips the switchgear 5 of a required system when the monitoring line is abnormally overheated to stop the power transmission of the system. Reference numerals 17 and 18 denote a status display unit and a recording printer connected to the computer 14.

Reference numeral 19 is a processing device for monitoring results of a computer configuration connected to the computer 14 via the GPIB 20, and performs monitoring of the computer 14, storage of various data for control, processing, and the like. An infrared radiation temperature measuring device such as a telephoto thermometer (not shown) is also connected to the computer 14 via the multiplexer 12, the A / D converter 13 and the like.

Then, for example, when the bus of the overhead power transmission line configuration of the substation 2 is used as a monitoring line, the surface temperature of this line is actually measured by the infrared radiation temperature measuring device in a non-contact manner, and the data of the measured value is obtained. Multiplexer 12, A / D
It is transmitted to the computer 14 via the converter 13.

The multiplexer 12, A / also collects the detection data of the energizing current of the monitored line based on the current detection of the current transformer 6 for each instrument and each observation data of the meteorological condition such as the temperature and the solar radiation intensity of the meteorological observation device 7. It is transmitted to the computer 14 via the D converter 13.

Further, the computer 14 constantly monitors the temperature of the electric wire of the monitoring line based on each data, and performs control such as opening of the required switchgear 5 when abnormal overheating of the overcurrent of the line occurs. Next, the processing of the computer 14 will be described. First, the principle of detecting the wire temperature will be described.

When the monitoring line is an electric line having a stranded wire structure such as an overhead power transmission line, according to experiments, its thermal conductivity λ [W / cm
・ ° C] is 1/1000 to 1/5 of solid conductor path of the same material
The thermal ohm (thermal specific resistance) Rh [° C./W] is 500 to 1000 times that of the solid conductor path.

Therefore, this type of stranded wire structure electric line is
Amount of heat generated per unit length inside the wire due to energization Qi [W
/ Cm] and the amount of heat generated per unit length Qs [W / cm] on the surface of the wire due to radiant heat from solar radiation etc., the heat flow q [W] is inside the wire via the thermal resistivity Rh. Flows from the wire surface to the surface or vice versa.

This heat flow causes a difference in temperature θ [° C.] between the inside of the electric wire and the surface of the electric wire, and this temperature difference causes the amount of generated heat Qi, Q.
proportional to the difference of s.

If the difference between the temperatures θ based on the generated heat quantities Qi and Qs is "heat potential" corresponding to the electric potential of the electric circuit, the heat flow q and the thermal specific resistance Rh correspond to the electric current and resistance of the electric circuit, There is a relation of θ = q · Rh, and these various amounts θ,
The calorific value calculation can be performed by treating q and Rh in the same manner as the quantities of the electric circuit.

Further, the heat generation amounts Qi and Qs are logically obtained by the calculation of the following equation (1). However, the generated heat quantity Qs is obtained by ignoring the influence of other weather conditions such as wind and rain on the radiant heat quantity.

[Equation 1] Qi = I ² · Rdc · 10 ⁻⁵ · {1 + α (T _max −2
0)} Qs = η · Ws · D Note that each parameter I, Rdc, ... In the formula represents the following values. I is the conduction current [A], Rdc is the electrical resistance [Ω / km] at 20 ° C, α is the temperature coefficient of resistance [° C ^-1 ], T
_max is the maximum ambient temperature (maximum temperature) (40) [° C], η is the surface radiation coefficient ratio (0.9), Ws is the solar radiation intensity [W / cm
² ], D is the outer diameter of the electric wire [cm]. For example, in the case of the aluminum alloy stranded wire ACSR 80 mm ² , the heat generation amounts Qi, Qs based on the calculation of the formula 1 show the characteristics shown in FIGS.

As is apparent from both of these figures, the amount of heat Qi generated by energizing the nominal permissible current (reference energizing current) is approximately 0.3 [W / cm], and the daytime solar radiation intensity is, for example, 1 [ kW / m ² ] (= 0.1 [W / cm ² ]), the amount Qs of heat generated by radiant heat is almost 0.1 [W / cm]
Is.

Therefore, the generated heat quantities Qi and Qs are 0.2
A difference (Qi> Qs) of about [W / cm] occurs, and the temperature inside the wire becomes higher than the surface temperature due to this difference. In addition,
When the generated heat quantity Qs becomes small due to the influence of other weather conditions such as wind and rain, the temperature difference between the inside of the wire and the surface of the wire further increases.

Further, the above-mentioned aluminum alloy stranded wire ACSR8
In the case of 0 mm ² , ignoring the influence of weather conditions such as wind and rain,
The characteristic of the internally generated heat quantity difference Qd with respect to the surface radiation heat quantity for each generated heat quantity Qs is as shown in FIG.

The characteristic curves a, b, c, d,
e and f are generated heat Qs [kW / m ² ] of 0, 0.2,
The values are at 0.4, 0.6, 0.8 and 1.0.

That is, in the case of a so-called solid conductor path, since the thermal conductivity λ is large and the temperature difference between the inside of the conductor and the conductor surface is small, the temperature (conductor temperature) is “(temperature) + (surface rise due to radiant heat). Temperature) + (internal temperature rise due to energization) ".

On the other hand, in the case of an electric line having a twisted wire structure such as an overhead transmission line, the thermal conductivity λ is small as described above,
Since the temperature difference between the inside of the wire and the surface of the wire becomes large, when monitoring the higher temperature as the wire temperature,
If the electric wire temperature is "heat quantity Qi generated by energization> radiant heat quantity (heat quantity Qs)", it is calculated from "(wire surface temperature) + (temperature difference corresponding to the difference between heat quantity Qi and Qs generated)" If the heat quantity Qi <radiant heat quantity (generated heat quantity Qs), then it is obtained from “(air temperature) + (wire surface temperature rise due to radiant heat)”, and it varies depending on the magnitude relationship between the generated heat quantities Qi and Qs.

Then, as described above, the generated heat amounts Qi, Q
Since s usually has a relation of Qi> Qs, the wire temperature of the monitoring line of this kind of twisted wire structure is “(wire surface temperature) +
(Temperature difference corresponding to difference between heat generation amounts Qi and Qs) ”.

In the case of this type of stranded wire structure, this is because there is a difference (temperature difference) between the temperature inside the wire and the temperature on the wire surface due to the heat balance between the energizing current and the weather conditions (weather environment). Therefore, even if the temperature of the electric wire surface is measured by non-contact measurement using an infrared radiation temperature measuring device or the like, the actual electric wire temperature cannot be detected only from this actual measured value, and the amount of heat generated Qi cannot be detected in order to detect the electric wire temperature. , Qs needs to be found.

Since the thermal specific resistance Rh of the electric wire is known and the energizing current and the weather conditions can be detected by various sensors, the heat generation amount Qi, Qs is estimated by calculation,
If the temperature difference between the inside of the wire and the surface of the wire corresponding to the difference is obtained and this temperature difference is added to the actual measurement value, the wire temperature can be actually detected and monitored.

Next, a method of estimating the amount of heat generated and the temperature inside the wire and on the surface of the wire will be described. Generally, unit time dt
The amount of heat generated in the object (generated heat amount) is the sum of the amount of heat that raises the object temperature by the unit temperature dθ and the amount of heat that is released to the outside, and the time change of the temperature of the object is Heat quantity (heat quantity) Q [KW], heat capacity C [KW seconds / ° C] of object and heat dissipation coefficient H [KW / ° C]
Is the parameter, the temperature is θ [° C], and the elapsed time is t
If it is [second], it is expressed by the following heat transfer equation.

[Equation 2] Qdt = Cdθ + Hθdt Then, the heat dissipation coefficient H corresponds to the thermal specific resistance Rh, and the heat transfer equation of Equation 2 can be solved as follows.

First, at the time of heating by the generated heat quantity Q, the heat transfer equation of the equation 2 is expressed by the following equation 3 based on the equivalent circuit at the time of heating in FIG.

[Equation 3] C (dθ / dt) + Hθ = Q The general solution θ of the equation of Equation 3 is θ = θ _c + θ _t (θ _c is a steady term and θ _t is a transient term). The steady term θ _c is obtained from the heat transfer equation when dθ = dθ _c = 0, and corresponds to the rising saturation temperature of the following equation (4).

[Equation 4] θ _c = Q / H Further, the transient term θ t is based on the equivalent circuit at the time of heat dissipation in FIG.
It can be obtained from the following heat transfer equation when Q = 0.

[Equation 5] C (dθ _t / dt) + Hθ _t = 0 Then, the following equation 6 is obtained from this equation 5.

[Equation 6] ∫dθ _t / θ _t = − (H / C) · ∫dt Further, based on this equation 6, the following equation 7 is obtained. Note that α in the formula is a constant.

[Equation 7] Log θ _t =-(H / C) t + α In this equation 7, e is the power of α, and C / H = T
Then, the following equation 8 is obtained as the equation of the transient term Q _t .

[0049] [Equation _{8] θ t = A · e} -t / T and the number 4 on the basis of the two equations having 8, represented by the number 9 expression of general solutions theta Hatsugi number 2 in formula.

[Equation 9] θ = Q / H + A · e ^{−t / T Further} , the initial condition of the heat transfer equation of Equation 2 is found as θ = 0 when t = 0 in Equation 9 and the following is obtained. The expression of Expression 10 becomes the expression of the initial condition.

[Equation 10] A = -Q / H Then, if Q / H = θ _max , the general solution θ is expressed by the following equation 11.

[0052] [Expression _{11] θ = θ max · (} 1-e -t / T) As is apparent from the equation the number 11, its raised saturation temperature material temperature theta of θ _{ma x} (= Q / H ), Time constant T (= C
/ H) is a constant and changes exponentially with respect to time t.

The temperature of the electric wire having the stranded wire structure also changes with a constant time constant according to the exponential function characteristic of the equation (11) due to the change in the amount of heat. This time constant is not so long, it is theoretically about 5 to 30 minutes, and it is necessary to grasp this characteristic when constantly monitoring the temperature of the electric line.

By the way, in a power transmission line such as an overhead power transmission line, the wire temperature can be estimated by obtaining from the following "logical formula calculation" or "approximate formula calculation".

First, according to the literature such as the handbook of electric power transmission line manufacturers, the temperature of the electric power transmission line is obtained by the heat transfer equation (differential equation) of the equation 2, and the generated heat quantity Q, the heat capacity C and the heat are the parameters in the equation. The radiation coefficient H is determined by the following equation 12 for each type and size of electric wire.

[Equation 12] Amount of heat generated per unit length Q [W / cm]: Q = I ² · R _ac (θ + T) · 10 ⁻⁵ + η · W _s · D Heat capacity C per unit length [J / ℃ · cm]: C = G · c · a · 10 -2 (1 + τ) heat dissipation coefficient per unit length H [W / ℃ · cm] : H = π · D · (h w + η · h r ) In the equation, each parameter I, θ, ... Shows the following values.

I is the energizing current [A], θ is the wire temperature [° C], T is the ambient temperature [° C], and R _ac (θ + T) is (θ +
AC electric resistance [Ω / km] at T) ° C, which is a calculated value based on the wire specifications and empirical constants.

Η is the wire surface emissivity, W _s is the solar radiation intensity [W
/ Cm ² ], D is the outer diameter of the wire [cm], G is the density of the wire [g /
cm ³ ], c is the specific heat of the wire [J / cm · ° C], A is the cross-sectional area of the wire [mm ² ], τ is the twisting ratio of the wire, h _w is the convection heat dissipation coefficient per unit area [J / ℃ ・ cm ² ], h _r is the radiant heat dissipation coefficient [J / ℃ ・ cm ² ] per unit area, and the coefficient h
Both _w and h _r can be obtained from the calculated values based on wind speed, θ, T, D and empirical constants.

Then, I ² · R _ac (θ + T) · 1 in the formula
The term 0 ^-5 is the amount of heat generated Qi based on the energizing current, and
Section of the W _s · D is the amount of heat generated Qs based on the solar radiation. Further, G · c · A · 10 ⁻² (1 + τ) in the equation is a fixed value for each wire type and its size, and π · D · (h _w + η ·
h _r ) is a value that changes depending on the wind speed.

Then, in the case of "logical expression operation", each value θ, C, H of the expression of Expression 12 including the variable element at that time is
As it is, the electric wire temperature is obtained by predictive calculation by substituting it into the heat transfer equation of Formula 2 and solving the high-order differential equation.

In the case of the "approximate equation calculation", the parameters of the equation (12) are fixed by setting the energizing current to be the continuous allowable current of the wire and the constant (θ + T) to be the maximum allowable temperature of the wire. It is treated as a value, this condition is substituted into the solution of the heat transfer equation of Equation 2, and the electric wire temperature is calculated by a simple exponential temperature calculation. In this case, the calculation is easier than the "logical calculation". is there.

In this temperature monitoring, the temperature rise of the electric line based on the energizing current and the temperature rise of the electric line based on the meteorological condition may be separately estimated.
Considering the changes in i and Qs as temperature changes,
The heat quantity Qi generated inside the wire, the estimated temperature θi [° C] and the heat quantity generated Qs at the wire surface, the estimated temperature θs [° C] are individually calculated from the temperature calculation of the exponential function based on the "approximate equation calculation".

That is, the amount Q of heat generated inside the electric wire at each time
i (= Qi _n), the estimated temperature θi (= θi _n) is determined from two equations having the following 13.

[0064] [Expression _{13] Qi n = Qi MAX ·} (I n / I MAX) Ki -Qi n-1 θi n = Qi n · Rh · [1-exp {- (t n -t n-1)
/ Ti}] + θi _n-1

The parameters t _n , t _n-1 , and
... are the following values. t _n, at t _n-1 is n, at n-1 calculation time (one previous time n) [min], Qi _n, Qi _n-1
At the time of n, wire internally generated heat o'clock n-1 [W], θi n,
.theta.i _n-1 at the time n, n-1 at an internal temperature [° C.], I _n is n
It is the energizing current [A] at the time.

Further, I _MAX is a reference current value (nominal allowable current value) [A], Qi _MAX is a saturation value [W] of internally generated heat of the wire when I _MAX is energized, and Ki is a saturation value of internally generated heat according to current ratio. A correction index, Rh is a thermal specific resistance [° C / W], and Ti is an internal temperature change time constant [min].

Then, these parameters I _MAX , Qi
_MAX , Ki, Rh, and Ti are characteristic setting values for each type of electric wire, and are set by grasping the characteristic determined by the internally generated heat amount Qi.

Further, the generated heat quantity Qs (= Qs _n ) and the generated heat quantity Qi at each time, which are corrected for the influence of the wind and rain, etc., based on the observed values of the meteorological conditions such as the temperature, the solar radiation intensity, the wind speed, and the rain-sensitive level are set to zero. Estimated temperature θs (= θs
_n ) is also obtained from the following formula 14 similar to the formula 13.

[Equation 14] Qs _n = [Qs _MAX · (Sn / S _MAX ) ^Ks −Qs
_n−1 ] · f ₁ (Wn, Rn, θ _A ) θs _n = Qs _n · Rh · [1-exp {− (t _n −t
_n−1 ) / Ts}] + θs _n−1 Among the parameters in the equation, the same parameters as those in the equation (13) have the same values, and different parameters have the following respective values.

Qs_n , Qs_n-1 Is an electric wire at n o'clock and n-1 o'clock
Surface heat generation [W], θi, θi_{n- 1}Is n hour, n-1 hour
Surface temperature [℃], Sn is the solar radiation intensity at n hours, S_MAX Is based
Quasi-solar radiation intensity, Qs_MAX Is the wire surface generation at the standard solar radiation intensity
Calorie [W], Ks is a finger for correcting the calorific value of surface heat generated by the insolation ratio
Number, Ts_n Is the surface temperature change time constant at n, Ts is a reference table
Surface temperature change time constant, f₁ Is a correction function for wind and rain, temperature, etc.
Formula, Wn is wind speed at n hours, Rn is rain level at n hours, θ_A 
Is the temperature. Also, the time constant Ts_n Considers the effects of wind and rain
Considering this, the value is calculated from the following formula (15).

[Equation 15] Ts _n = Ts · f ₂ (Wn, Rn, θa) Note that f ₂ is a correction function based on wind, rain, temperature, and the like. Then, regarding the estimated temperature of the “logical formula calculation” and the estimated temperature of the “approximate formula calculation”, the “logical formula calculation” was simulated and compared using, for example, a fourth-order Runge-Kutta method at 1 minute intervals. As a result, there was no great difference between the two estimated temperatures, and sufficient accuracy was obtained with the simple calculation of "approximate formula calculation".

Next, a specific processing operation of the computer 14 will be described. The computer 14 operates as shown in FIG. 1 in order to detect and monitor the wire temperature at the set sampling / control time interval Δt (= t _n -t _n-1 ).

That is, when the start is notified from the operation / setting panel 15, the parameters I _MAX and Qi _MAX of the equations (13) to (15) preset by the "initial setting" in step [i] are first set. , Ki, Ti, S _MAX , Qs
Excluding _MAX , Ks, Ts, Rh, f ₁ , f ₂ , Δt and initial judgment exclusion time N, energizing current In, solar radiation intensity Sn, wind speed Wn, rain-sensitive level Rn, temperature θ _A , non-contact of wire surface The contents of each parameter obtained by actual measurement or calculation of the measured temperature (measured temperature) θ _B etc. are reset to zero.

Next, the interval Δt is counted by the “time count” of the step [ii], and after the lapse of Δt, the conduction current In is calculated by the “data sampling” of the step [iii].
Sampled data, various observation data of meteorological conditions and data of measured temperature θ _{B on} the wire surface are sampled and captured.

In order to accurately estimate the temperature of the electric wire surface in consideration of the influence of various weather conditions, in this embodiment, as the observation data of the weather conditions, the solar radiation intensity Sn and the wind speed W are used.
n, the rain level Rn, and the temperature θ _A data are sampled.

[0076] Then, in step [iv] By "heat generation amount, the calculation of the surface temperature change time constant", number 13, number 14, the heat generation amount Qi at that time from the number 15 formula (= Qi _n), Q
s (= Qs _n ) and the surface temperature change time constant Ts _n are calculated.

At this time, the heat generation amount Qs _n and the time constant Ts _{n on the} surface of the electric wire are corrected by the predetermined correction functions f ₁ and f ₂ based on other weather conditions such as wind and rain, temperature, etc. Required with high accuracy.

Further, according to the "calculation of the estimated temperature inside the wire and the surface of the wire" in step [v], the wire internal temperature is calculated from the equations (13) and (14) based on the generated heat quantities Qi, Qs obtained in step [iv]. The estimated value of the wire surface temperature, that is, the estimated temperatures θi _n and θs _n are calculated and obtained.

Next, it is judged whether or not the generated heat quantities Qi and Qs are Qi> Qs by the judgment in step [vi], and Qi> Q.
When s is normal, this step [vi] is passed in the affirmative (YES), and the process proceeds to step [vii], "estimation of electric wire temperature".

Then, the calculation of the following equation 16 is executed by the "calculation of electric wire temperature" in this step [vi], and the temperature difference θ between the estimated temperatures θi _n and θs _n is calculated as the measured value of the electric wire surface temperature.
i _n −θs _n is added to obtain and detect the wire temperature θn of the monitoring line.

[0081] [Expression _{16] θn = θ B + (} θi n -θs n) + (δ) Note, [delta] is high the temperature inside the electric wire from the arithmetic value, early abnormal overheating due to energization of the electric wire temperature for high eyes It is an adjustment constant that is added when the eye is detected, and is set to a desired size as necessary based on preset settings and added.

When Qi ≦ Qs, step [vi] is passed negatively (NO) and the process proceeds to step [viii]. At this time, since the wire surface temperature is extremely high, θn = the equation calculation of θ _B + (δ '), without adding the temperature difference θi _n -θs _n, detects the measured value of the wire surface temperature of the electric wire temperature .theta.n. Note that δ '
Is an adjustment constant similar to the constant δ in the equation (16).

By the way, at a constant initial time from the start notification, each calculation result becomes inaccurate due to lack of data at n-1 hour and the like. Therefore, the judgment of step [ix] after step [vii] or [viii] is executed, and the electric wire temperature θn is invalid until Δt · N has elapsed from the start notification, and after Δt · N has elapsed, the electric wire temperature θn is invalidated. The temperature θn is validated and used for monitoring abnormal overheating.

Then, the process proceeds from step [ix] to step [x], and the occurrence of abnormal overheat due to the energization of the monitoring line is constantly monitored from the wire temperature by the wire temperature θn, and based on the monitoring result, the load control contact output unit 16 and the like, and outputs the monitoring control command to the status display unit 17, the recording printer 18, the processing device 19 and the like, and outputs the maintenance information of the monitoring result.

In this case, since the occurrence of abnormal overheating of the monitoring line is monitored from the wire temperature itself, the realistic thermal operation state is accurately monitored, and the occurrence of abnormal overheating is accurately detected.

Then, the temperature of the wire surface is measured, and the wire temperature is obtained using this measured temperature θ _B.
Since the estimated temperature [theta] s _n of the required wire surface in the calculation of the temperature difference θi _n -θs _n is determined in consideration of the various weather conditions surrounding the occurrence of abnormal overheating can be detected considering its temperature, etc. As a result, it becomes possible to continue power transmission until the amount of current to be transmitted reaches the maximum amount of current that can be transmitted in accordance with weather conditions such as temperature, and the power transmission efficiency is greatly improved.

Further, by adding the adjustment constants δ and δ ′, it is possible to freely set the margin from the viewpoint of safety etc. to a desired size. Further, the heat generation amount Qi _n, Qs _n
Since the estimated temperatures θi _n and θs _n are obtained from the “approximate equation calculation”, there is also an advantage that the temperature can be monitored quickly by a relatively easy calculation.

The observation contents of the meteorological conditions are not limited to the examples, and the heat generation amount Qs _n and the estimated temperature θs _n based on the observation contents of a larger number of items than the examples.
On the contrary, the heat generation amount Qs _n and the estimated temperature θs _n may be calculated based on the observation contents of less items than the embodiment, and for example, the calculation of the correction function expressions f ₁ and f ₂ may be omitted. Good.

Next, in order to simplify the arithmetic processing and the equipment, the estimated temperature θs _n is preliminarily calculated without omitting the meteorological observation device 7 shown in FIG. The wire temperature θn may be obtained by setting an appropriate predetermined value including zero and fixing the estimated temperature θs _n .

Also in this case, the occurrence of abnormal overheating of the electric line is monitored from the temperature of the electric wire itself, so that the same effect as in the above embodiment can be obtained. The computer 14
The calculation process of is not limited to the embodiment,
For example, the steps [vi] and [viii] in FIG. 1 may be omitted and monitoring may be performed.

[0091]

Since the present invention is configured as described above, it has the following effects. The temperature difference between the temperature inside the wire and the temperature on the wire surface, which is estimated by calculation, is added to the measured temperature on the wire surface. It is applied and added.

If the monitoring line is an electric line having a stranded wire structure, a temperature difference occurs between the inside of the wire and the surface of the wire due to the difference in the amount of heat generated, and when abnormal overheating due to overcurrent occurs, the inside of the wire is The amount of heat generated exceeds the amount of heat generated on the surface of the wire, and the temperature of the wire is obtained from the temperature obtained by adding the temperature difference to the measured temperature of the surface of the wire. The temperature itself of the electric line of the structure can be monitored.

Moreover, since the electric wire temperature is obtained by correcting the weather condition, the temperature of the monitoring line can be monitored with higher accuracy in consideration of the actual weather condition. It becomes possible to transmit the maximum amount of current that can be transmitted in accordance with the meteorological conditions, and it is possible to significantly improve the power transmission efficiency.

When the temperature of the electric wire surface of the monitoring line is set to a predetermined value, the actual measurement and estimation calculation of the temperature of the electric wire surface can be omitted, and the temperature of the electric line can be easily monitored.

[Brief description of drawings]

FIG. 1 is a flowchart for explaining a process according to an embodiment of the present invention.

FIG. 2 is a block diagram of substation equipment provided with a monitoring control device that performs the processing of FIG.

FIG. 3 is a characteristic diagram of an example of an amount of heat generated inside an electric wire based on an energized current.

FIG. 4 is a characteristic diagram of an example of the amount of heat generated on the surface of an electric wire based on the intensity of solar radiation.

FIG. 5 is a characteristic diagram of an example of the amount of heat generated inside an electric wire for each solar radiation intensity.

FIG. 6 is a first equivalent circuit diagram for explaining the calculation principle of FIG. 1.

FIG. 7 is a second equivalent circuit diagram for explaining the calculation principle of FIG. 1.

[Explanation of symbols]

 1a, 1b, 2 Substation 7 Meteorological observation device 8 Monitoring and control device 9 Signal input section 12 Multiplexer 13 A / D converter 14 Microcomputer

Claims (2)

[Claims] 1. An estimated value of the wire internal temperature based on the amount of heat generated inside the wire of the monitored line is calculated from the detected value of the current flowing through the monitored electric line (hereinafter referred to as the monitored line), and the solar radiation intensity and the temperature are calculated. The estimated value of the wire surface temperature based on the amount of heat generated on the wire surface of the monitored line is calculated from the detected value of the weather conditions around the monitored line such as, and the inside of the wire of the monitored line is calculated from the difference between the two estimated values. And a surface temperature of the electric wire, and the temperature difference of the electric wire surface of the monitoring line is added to the measured value of the surface temperature of the electric wire to monitor the temperature of the electric line. 2. The temperature monitoring method for an electric line according to claim 1, wherein the estimated value of the wire surface temperature of the monitoring line is set to a predetermined value instead of being calculated from the detected value of the weather condition around the monitoring line. A method for monitoring the temperature of an electric line characterized by setting.