JPH08242533A - Method for monitoring temperature of electric line - Google Patents

Abstract

PURPOSE: To monitor the temperature of an electric line to be monitored by detecting the temperature itself from the detected results of conduction current without measuring the temperature of the electric line by finding the temperature of the electric line by adding a temperature difference to the set surface temperature value of the electric line responding to the air temperature. CONSTITUTION: After initialization (i), a interval Δt is counted (ii) and the data about conduction current In and air temperature QA are fetched through sampling after the interval Δt has elapsed (iii). Then, the quantities of generated heat Qi, and Qs are found (iv) and estimated values Qin and Qsn of the internal temperature and surface temperature of an electric line to be monitored are found by calculation (v). Thereafter, the temperature Qn of the electric line is found by adding the difference Qin-Qsn between the estimated temperatures Qin and Qsn to the set surface temperature value of the electric line (vi). In addition, the abnormal overheating of the electric line is monitored by making the temperature Qn of the electric line ineffective until Δt.N has elapsed after the start is informed and making the temperature Qn effective after the Δt.N has elapsed (vii). Moreover, a monitoring control command, maintenance information, etc., are outputted based on the monitored results (viii).

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 electric wire due to energization is larger than the amount of heat generated on the surface of the electric wire due to weather conditions. In particular, the thermal conductivity is small and a temperature difference occurs between the inside of the electric wire and the surface of the electric wire. The purpose of the present invention is to detect and monitor the wire temperature itself from the detection result of the energized current in the stranded wire electric line without actually measuring the temperature of the wire.

[0009]

In order to achieve the above-mentioned 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 weather conditions. , Calculate the estimated value of the wire internal temperature based on the amount of heat generated inside the wire of the monitoring line from the detected value of the current flowing through the monitoring line, and monitor from the detected values of the weather conditions around the monitoring line such as temperature and solar radiation intensity. Calculated by calculating the estimated value of the wire surface temperature based on the amount of heat generated on the wire surface of the line, and using the difference between the estimated value of the wire internal temperature and the estimated value of the wire surface temperature, the temperature difference between the inside and the wire surface of the monitored line Then, the temperature difference is added to the set value of the wire surface temperature of the monitoring line according to the air temperature to obtain 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 estimated from the energizing current and the temperature on the wire surface estimated from the meteorological condition is added to the set value of the wire surface temperature according to the air temperature,
By this addition, the temperature rise on the surface of the electric wire due to the current flowing is corrected and added according to the meteorological conditions.

At this time, if the monitoring line is an electric line having a stranded wire structure, a temperature difference occurs between the inside of the electric wire and the surface of the electric wire, and if abnormal overheating due to overcurrent occurs, the inside of the electric wire Is larger than the amount of heat generated on the surface of the electric wire, and the electric wire temperature can be obtained from the temperature obtained by adding the temperature difference to the set value of the electric wire surface temperature without actual measurement.

Since the wire temperature is estimated by correcting the weather condition, the temperature of the monitoring line when the abnormal overheat occurs is monitored with high accuracy in consideration of the actual weather condition.

Next, in the case of setting the wire surface temperature of the monitoring line to a predetermined value to estimate the temperature difference,
The calculation is simplified and the temperature of the electric line is easily monitored.

[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 temperature detection sensor or a weather observation device provided with this sensor and various detection sensors for weather conditions such as solar radiation, and 8 is a supervisory control device, which is required as transmission current information in the substation 2. The detection information of the energization current of the instrument current transformer 6, the detection information of the required energization current of the instrument current transformer 6 as the respective load current information, and the detection information of the meteorological observation device 7 are supplied to each signal input unit 9. To be done.

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.

For example, when the bus of the overhead power transmission line configuration of the substation 2 is used as the monitoring line, the detection data of the current flowing through the monitoring line based on the current detection of the current transformer 6 for each instrument and the meteorological condition of the meteorological observation device 7 are obtained. Observation data of multiplexer 1
2, transmitted to the computer 14 via the A / 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 detection by calculating 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 an experiment, 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, the electric line of this type of stranded wire structure is
Amount of heat generated per unit length inside the wire due to energization Qi [W
/ Cm] and the amount of heat generated Qs [W / cm] per unit length of the wire surface due to radiant heat etc., the heat flow q [W]
Flows from the inside of the wire to the surface of the wire or vice versa via the thermal resistivity Rh.

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 amounts Qi and Qs is defined as “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, and θ = q There is a relation of Rh, and calorific value calculation can be performed by treating these quantities θ, 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 electric current [A], Rdc is the electric resistance [Ω / km] at 20 ° C., α is the temperature coefficient of resistance [° C. ^-1 ],
T _max is the maximum ambient temperature (highest temperature) (40) [° C], η
Is the surface radiation coefficient ratio (0.9), Ws is the solar radiation intensity [W / cm
² ] and D are the outer diameter of the wire [cm].

And, for example, the stranded wire ACSR of aluminum alloy
In the case of 80 mm ^2, the amount of heat generated Q based on the calculation of the formula 1
i and Qs show the characteristics of FIG. 3 and FIG. 4, and as is apparent from both these figures, the heat generation amount Qi generated by energizing the nominal permissible current (reference energizing current) is approximately 0.3 [W / cm]. , And the intensity of solar radiation in the daytime is, for example, 1 [KW / m ² ] (= 0.
1 [W / cm ² ]) High heat generation Q due to radiant heat
s is approximately 0.1 [W / cm].

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 amount of heat generated Qs decreases due to the effects of 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, the heat generation Q
The characteristics of the internally generated heat quantity difference Qd with respect to the surface radiant heat for each s are as shown in FIG. The characteristic curves a, b, and
c, d, e, f have a heat generation amount Qs [KW / m ² ] of 0,
The values are at 0.2, 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 obtained from "(wire surface temperature) + (temperature difference corresponding to the difference between heat quantity Qi, Qs generated)" If the heat quantity Qi <radiant heat quantity (generated heat quantity Qs), then it can be obtained from “(temperature) + (wire surface temperature rise due to radiant heat)”, and it depends on the magnitude relationship between the generated heat quantities Qi and Qs.

Then, as described above, the generated heat quantities 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) ”.

This is because in the case of this type of stranded wire structure electric line, there is a difference (temperature difference) between the temperature inside the electric wire and the temperature on the electric wire surface due to the heat balance between the energizing current and the meteorological condition (meteorological 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.

By the way, since the thermal specific resistance Rh of the electric wire is known and the energizing current and the meteorological conditions can be detected by various sensors, the heat generation amount Qi, Qs is estimated by calculation,
The temperature difference between the inside of the electric wire and the surface of the electric wire, which corresponds to the difference, can be obtained.

If the wire surface temperature is set to a set value (fixed value) according to the ambient temperature, and the temperature difference is added to this set value, the wire surface temperature is measured by an expensive infrared radiation temperature measuring instrument such as a telephoto thermometer. It is possible to detect and monitor the wire temperature of the monitoring line by a simple method without performing non-contact measurement using the above.

Next, a method for 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 the equation 2 can be solved as follows. First,
At the time of overheating by the generated heat amount Q, the heat transfer equation of the equation 1 is expressed by the following equation 3 based on the equivalent circuit at the time of overheating of 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). Shown. Then, the stationary 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 the 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, e is the power of α, and C / H = T
Then, the following equation 8 can be obtained as the equation of the transient term θ _t .

[Equation 8] θ _t = A · e ^{−t / T} Then, based on the two equations 4 and 8, the general solution θ of the equation 2 is represented by the following equation 9.

[Equation 9] θ = Q / H + ^{Ae −t} _{/ T} 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 equation 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.

[0050] [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.

Further, the temperature of the electric wire having the stranded wire structure also follows and changes with a constant time constant according to the exponential characteristic of the formula (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 being obtained from the following "logical formula calculation" or "approximate formula calculation". First, according to the literature such as the electric wire handbook of the power transmission line manufacturer, the temperature of the power transmission line is obtained by the heat transfer equation (differential equation) of the equation 2, and the heat generation amount Q, the heat capacity C and the heat dissipation coefficient H which are the parameters in the equation. Is the following number 12 for each wire type and size
It is determined by each arithmetic expression of.

[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 per unit length C [J / ° C.cm]: C = G ・ c ・ A ・ 10 ^-2 (1 + τ) per unit length heat dissipation coefficient H [W / ℃ · cm] : H = π · D · (h w + η · h r) Note that shows the parameters I in the formula, theta, ... the values of Hatsugi.

I is the electric 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.

And I ^{2 in} the formula ・ R _ac (θ + T) ・ 1
The term 0 ^-5 is the amount of heat generated Qi based on the energizing current, and
The term Ws · D is the amount of heat Qs generated by 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", the respective values θ, C, H of the expression of Expression 12 including the variable element at that time are
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 fixing the energizing current to be the continuous allowable current of the wire and (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, it is sufficient to separately estimate 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, so that the generated heat quantity Q
Considering the changes in i and Qs as temperature changes,
The heat quantity Qi generated in the electric wire and the estimated temperature θi [° C.] are calculated from the exponential temperature calculation based on the “approximate 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.

[0061] [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 Each parameter t _n , t _n-1 , ... In the equation is the following value.

[0062] t _n, t _n-1 at the time n, at n-1 (once before at the time of n) computation time [min] of, Qi _n, Qi _n-1 at the time n, n
Wire internally generated heat o'clock _{-1 [W], θi n,} θi n-1 at the time n, n-1 times of the wire internal temperature [℃], I _n is the current current [A] at the time n.

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]. The 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.

Regarding the estimated temperature of the "logical formula calculation" and the estimated temperature of the "approximate formula calculation", the "logical formula calculation" was simulated by using, for example, a fourth-order Runge-Kutta method at 1-minute intervals. As a result of comparison, there was no great difference between the two estimated temperatures, and sufficient accuracy was obtained by the simple calculation of "approximation formula".

On the other hand, when the occurrence of abnormal overheating due to energization is monitored with high safety, the estimated temperature θs [° C] of the wire surface is
It is not necessary to actually measure, but it is possible to set the generated heat quantity Qs according to the temperature condition, estimate it to be relatively smaller than the generated heat quantity Qi inside the electric wire, and multiply the estimated value by the thermal specific resistance Rh. .

Therefore, the heat generation amount Qs of the electric wire surface at each time
(= Qs _n ) and the estimated temperature θs (= θs _n ) are calculated from the following two equations 14 when the weather condition is the temperature θ _A [° C.] only.

[0067] [Equation _{14] Qs n = Qs R ·} f (θ A) θs n = Qs n · Rh Incidentally, Qs _R is cable surface heat generation amount reference value in the equation, f is is a correction function according to the temperature theta _A .

When abnormal overheating due to energization occurs,
Since the generated heat amount Qi is sufficiently larger than the generated heat amount Qs,
The temperature difference between the estimated temperatures θi and θs obtained from the equations 13 and 14 is almost the same as the actual temperature difference.

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) and (14) set in advance are firstly set by the "initial setting" in step [i]. , Ki, Ti, Qs _R , R
Except for h, f, Δt and initial judgment exclusion time N, the contents of each parameter obtained by actual measurement or calculation of the energization current I _n , the temperature θa, etc. are reset to zero.

Next, the interval Δt is counted by the “time count” of step [ii], and after the lapse of Δt, the energizing current I _{n is} calculated by “data sampling” of step [iii].
The sampled data and the temperature θ _A observation data are sampled and captured.

[0072] By "calculation of heat generation amount" in step [iv], the number 13, generated heat Qi (= Qi _n) at that time from the number 14 equation to determine the Qs (= Qs _n).

At this time, the amount of heat Qs _n generated on the surface of the electric wire changes according to the temperature θ _A, and can be accurately obtained without actual measurement. Further, by the "calculation of the estimated temperature inside the wire and the surface of the wire" in step [v], the wire internal temperature and the wire surface temperature are calculated from the equations (13) and (14) based on the heat generation amounts Qi and Qs obtained in step [iv]. The estimated value of, that is, the estimated temperatures θi _n and θs _n are calculated.

Next, the calculation of the following equation 16 is executed by the "calculation of electric wire temperature" in step [vi] to obtain the temperature θ _A
Or temperature θ value obtained by adding the adjustment value δ in _A, i.e. the estimated temperature .theta.i _n the set value of the wire surface temperature, temperature difference .theta.i of [theta] s _n
n− θs _n is added to obtain and detect the wire temperature θn of the monitoring line.

[0075] [Expression _{16] θn = θ A + (} 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 (margin constant) that is added when it is detected by the eye, and is set to an appropriate value in consideration of the surface temperature drop due to radiative cooling at night.

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, in step [vii], the electric wire temperature θ
n is invalidated, and after the lapse of Δt · N, the wire temperature θn is validated and used for monitoring abnormal overheating.

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

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

[0079] Then, the obtained is estimated without the temperature of the wire surface is measured, the temperature difference θi _n -θs
_Since the estimated temperature θs _n of the wire surface required for the calculation of _n is calculated in consideration of the temperature, the occurrence of abnormal overheating can be detected in consideration of the temperature, and as a result, the amount of transmission current is It becomes possible to maintain power transmission until the maximum amount of current that can be transmitted according to weather conditions is reached, and power transmission efficiency is greatly improved.

Further, when the adjustment constant δ is added, there is an advantage that the margin from the viewpoint of safety can be freely set to a desired size.

[0081] In addition, the amount of heat generated Qi _n "approximate expression calculation"
Since it is calculated from the above, there is also an advantage that the temperature can be quickly monitored by a relatively easy calculation.

By the way, in the above-mentioned embodiment, the electric wire surface temperature is estimated by considering only the temperature as the meteorological condition, but it may be estimated by taking into consideration the solar radiation intensity, the wind and rain, etc. in addition to the temperature. Although the parameter of the correction function equation of increases,
The temperature difference &thgr; i- &thgr; s is obtained with higher accuracy, and the wire temperature detection accuracy is improved.

In the above embodiment, the set value of the wire surface temperature according to the air temperature is described as the air temperature θ _A or the air temperature θ _A plus the adjustment constant δ. A value that takes into account the temperature decrease and the like may be used as the set value of the wire surface temperature.

Next, when achieve further simplification of the calculation process, without operation of the equation 14 expression is set to an appropriate predetermined value, including a pre-zero estimated temperature [theta] s _n, the estimated temperature [theta] s _n Alternatively, the wire temperature θn may be obtained by fixing.

Also in this case, the occurrence of abnormal overheating of the electric line is monitored from the electric wire temperature itself, so that the same effect as described above can be obtained. The calculation process of the computer 14 is not limited to the embodiment.

[0086]

Since the present invention is configured as described above, it has the following effects. The temperature difference between the temperature inside the wire estimated from the energizing current and the temperature on the wire surface estimated from the meteorological conditions is added to the set value of the wire surface temperature according to the air temperature. The temperature rise based on is corrected and added according to the weather conditions.

If the monitoring line is an electric line having a stranded wire structure, a temperature is generated inside the wire and on the surface of the wire due to the difference in the amount of heat generated, and when abnormal overheating due to overcurrent occurs,
The amount of heat generated inside the wire becomes larger than the amount of heat generated on the surface of the wire, and the wire temperature can be obtained from the temperature obtained by adding the temperature difference to the set value of the wire surface temperature. It is possible to monitor the temperature itself (electric wire temperature) of an electric line having a stranded wire structure such as a transmission line.

Moreover, since the electric wire temperature is obtained by correcting the weather condition, it is possible to monitor the temperature of the monitoring line 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 wire surface of the monitoring line is set to a predetermined value, the calculation of the temperature of the wire surface can be omitted,
The temperature of the electric line can be more 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 temperature and insolation intensity are calculated. The calculated 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 estimated value of the wire internal temperature and the wire surface temperature The temperature difference between the inside of the wire of the monitoring line and the surface of the wire is obtained from the difference with the estimated value, and the temperature of the monitoring line is calculated by adding the temperature difference to the set value corresponding to the temperature of the wire surface temperature of the monitoring line. A method for monitoring the temperature of an electric line, characterized by: 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.