JP2002238147A - Temperature calculation type overload protective relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a temperature calculation type overload protective relay 3, which can eliminate unnecessary cut-offs of a load, even if the load has much fluctuations such as flicker load, and which enables stable operation. SOLUTION: Currents, flowing through monitor lines 1L and 2L, are detected and weather conditions (the temperature, wind velocity, and sunshine) around the monitor lines 1L and 2L are detected. The wire temperatures of the monitor lines 1L and 2L are estimated, according to the detected current values and weather conditions and are compared with a set value to decide the overload conditions of the monitor lines 1L and 2L. With such a constitution, since the overload conditions are decided according to the wire temperature estimated taking the weather conditions into account, the frequency of unnecessary cut-offs of a load is reduced, and hence more stable power supply can be realized, in comparison with a case using a conventional overload protective relay which decides overload states, according to a current value only and controls the conditions according to the total time of overload periods, and hence more stable power supply can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature calculation type overload protection relay capable of responding to abnormal heating of a line such as an overhead transmission line.

[0002]

2. Description of the Related Art Overload protection relays are determined by the type of wire.
The upper limit of the allowable current is set, and the load current
This is a device that cuts off the load when it detects that the load has been exceeded.
This action prevents the temperature of the wire from rising and melts the wire.
Disconnection can be prevented. By the way, the behavior of the load current
Or the type of load.
In a flicker load, a large load current flows intermittently.
For this reason, overload protection relays are generally used as shown in FIG.
In addition, within a certain time T, the load current becomes equal to the set value I. ₀ Exceeded
Time T₁ , T_Two , T_Three Sum of (T₁ + T_Two + T_Three ) Is
Operates based on exceeding the Ima setting value
(K51 relay).

[0003]

The overload protection relay is
Load current is controlled by the amount of time that exceeds the set value I ₀ as described above. In other words, the load current is equal to the set value I ₀
Is not subject to management. When the rate at which the load current exceeds the set value I ₀ is referred to as “overload rate (%)”, in the overload protection relay, whether the overload rate is large or small,
The load current is operated on the basis of the total time exceeds the set value I _0, there is possible to perform load shedding than necessary.

For example, FIGS. 2 (a) and 2 (b) show graphs of the transition of the overload ratio and the wire temperature with time. As shown in the figure, even if the total time of overload is the same, the overload ratio is 160% in the case of FIG. 2A and the overload ratio is 120% in the case of FIG. It is. Due to the difference in the overload rate, the temperature rise rate of the electric wire differs. In the case of FIG. 2A, the wire is cut off when the temperature of the wire reaches the dangerous temperature (100 ° C.), but in the case of FIG. 2B, the wire is cut off when the temperature of the wire does not reach the dangerous temperature.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a temperature calculation type overload protection relay which operates stably without useless interruption even with a load having a large fluctuation such as a flicker load. .

[0006]

Means for Solving the Problems (1) A temperature operation type overload protection relay according to the present invention comprises a current detection means for detecting a current flowing through a monitoring line, and a weather condition detection for detecting a weather condition around the monitoring line. Means, a predictive calculating means for predicting and calculating the electric wire temperature of the monitoring line based on the current value detected by the current detecting means and the weather condition detected by the weather condition detecting means, Determining means for judging an overload condition of the monitoring line by comparing the electric wire temperature with the set value (claim 1).

[0007] According to the above configuration, it is determined whether or not an overload is present based on only the current value, and compared with a conventional overload protection relay that manages the total overload time, the prediction operation means is used. Since the electric wire temperature based on the weather condition can be predicted and the judgment based on the predicted value can be performed, the number of unnecessary load cutoff cases is reduced, and more stable power supply can be performed. (2) Hereinafter, the prediction method of the wire temperature by the prediction calculation means
An example in which the weather condition is selected from among temperature, solar radiation intensity, and wind speed will be described (claim 2). This prediction method is described in the patent application (Japanese Patent Application No. Hei 7-67090, Japanese Patent Application Laid-Open No. Hei 8-2425) based on the earlier application of the same applicant as the present applicant.
No. 33) and the drawings.

In this prediction method, a predicted value of the temperature inside the electric wire based on the amount of heat generated inside the electric wire of the monitored line is calculated and calculated from the detected current value of the monitored line, and each weather condition such as temperature, solar radiation intensity, wind speed, etc. From the detected values of the above, a predicted value of the wire surface temperature based on the amount of heat generated on the wire surface of the monitoring line is calculated and obtained.
Further, a temperature difference between the inside of the wire and the wire surface is determined from a difference between the predicted value of the wire inside temperature and the predicted value of the wire surface temperature, and the temperature difference is added to a set value of the wire surface temperature of the monitoring line according to the temperature. To obtain the temperature of the monitoring line.

The predicted temperature θi in consideration of the wind speed of the temperature inside the electric wire based on the amount of heat generated inside the electric wire of the monitoring line, which is predicted from the above-mentioned current, is obtained by the following equation. θin = θin-1 + (Δθin -θin-1) {1- exp (-Δt / Tin)} (1) Δθin = Δθimax (In / Imax) k f (Rt) fi1 (Wn) (2) Tin = {Ti / F (Rt)｝ fi2 (Wn) (3) The meanings of the symbols in the expression are as follows.

Tn, tn-1: n-th (current) and n-1-th (previous) calculation time [minutes] Δt: time interval of calculation (sampling / control) (for example, 30 seconds; Δt = tn−tn− 1) θin, θin-1: predicted temperatures (temperature predicted values) at times tn and tn-1 [° C] In: detected current values of monitoring lines at time tn [A] Imax: nominal allowable current values [A] Δθimax: Saturation temperature rise value at Imax [° C.] Ti: Temperature change time constant due to change in conduction current k: Internally generated calorific value saturation value correction index due to current ratio (takes a value around 2) Rt: Resistance value due to temperature rise Coefficient of change Wn: wind speed [m / s] f (Rt): temperature correction function formula fi1 (Wn), fi2 (Wn): wind speed correction function formula based on 20 ° C. where f (Rt), fi1 (Wn) and fi2 (Wn) are respectively f (Rt) = 1 + 1 / ｛Rt / (θn-1 − 0) +1} is expressed by (4) fi1 (Wn) = {α1 / (Wn + β1)} + γ1 (5) fi2 (Wn) = {α2 / (Wn + β2)} + γ2 (6). α1, α2, β1, β2, γ1, and γ2 are constants, differ depending on the type of electric wire, and are numerical values obtained by experiments and the like.

On the other hand, the predicted temperature θa in consideration of the wind speed due to the air temperature is obtained as follows. θan = θan−1 + (An−θan−1) [1−exp ｛−Δt / (Tafa (Wn)}] (7) The meanings of the symbols in the equation are as follows: θan, θan−1: Predicted temperature [° C] based on air temperature at time tn, tn-1 An: Measured temperature at time tn [° C] Imax: Nominal allowable current value [A] Ta: Temperature change time constant due to temperature change fa (Wn) Here, fa (Wn) is represented by fa (Wn) = {α3 / (Wn + β3)} + γ3 (8), where α3, β3, and γ3 are constants, and It depends on the type, and is a numerical value obtained by experiments and the like.

Finally, the predicted temperature θs taking into account the wind speed based on the solar radiation intensity is obtained as follows. θsn = θsn−1 + {SnΔθsfs1 (Wn) −θsn−1} × [1−exp} −Δt / (Tsfs2 (Wn)}] (9) The meanings of the symbols in the equation are as follows. θsn, θsn-1: Predicted temperature [° C] based on insolation intensity at times tn, tn-1, respectively Sn: Measured insolation intensity at time tn [kW / m ² ] Δθs: Temperature rise coefficient due to insolation Ts: Temperature due to insolation Change time constant fs1 (Wn), fs2 (Wn): wind speed correction function expression where fs1 (Wn) and fs2 (Wn) are respectively fs1 (Wn) = {α4 / (Wn + β4)} + γ4 (10) fs2 (Wn) = {α5 / (Wn + β5)} + γ5 (11) where α4, α5, β4, β5, γ4, and γ5 are constants, which vary depending on the type of electric wire, and are obtained by experiments and the like. Is a numerical value.

The electric wire temperature θ at the time point n of the monitoring line finally obtained by the predicting operation means is calculated from the predicted temperature θin at the time point n calculated from the current, the predicted temperature θan at the time point n calculated from the air temperature, and the solar radiation. The calculated predicted temperature θ at the time point n
sn is added. θn = θin + θan + θsn + α (12) Here, α is the temperature (margin) calculated from the safety coefficient. In this way, it is possible to make a correction based on weather conditions for the temperature rise based on the energizing current.

When the wire temperature θ is calculated, the overload condition of the monitoring line can be determined by comparing the wire temperature θ with a set value. (3) The temperature calculation type overload protection relay according to claim 1 or 2 is provided with "weather condition detecting means for detecting weather conditions around the monitoring line", but instead of this,
A "meteorological condition storage means for storing statistical weather conditions around the monitoring track" may be provided (claim 3).

The past statistical weather conditions include, for example, the season,
It may be stored for each month and time zone. in this case,
Based on the past statistical weather conditions, the temperature of the electric wire on the monitoring line is estimated and calculated, so some errors will inevitably occur depending on the weather on that day, but nonetheless, the weather condition data will not be considered at all. Monitoring accuracy can be improved as compared with the conventional technology.

(4) The temperature calculation type overload protection according to claim 2, wherein the weather condition stored by the weather condition storage means may be selected from among temperature, solar radiation intensity, and wind speed. This is the same as a relay (claim 4). (5) In the above configuration, if the monitoring line is a flicker load transmission line (Claim 5), a large load current flows intermittently, so the temperature calculation type overload of the present invention responding to abnormal heating of the line. A protection relay can be suitably used.

[0017]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 3 is a diagram showing an outline of a connection state when the temperature calculation type overload protection relay of the present invention is installed in a substation. In the figure,
1L and 2L indicate parallel two-circuit transmission lines. The substation 2 receives the power of these two systems and sends it to one or more load-side power distribution systems (only one is shown in the drawing).

[0018] The transmission line 1L, the 2L, current transformer CT _1, CT ₂ for detecting a current is provided, the current transformer CT _1, C
Data of the detected current of T ₂ are are inputted to the temperature calculating overload protection relay 3. Also, detection data of various weather condition sensors are input to the temperature calculation type overload protection relay 3. In this embodiment, three sensors of a temperature sensor, a wind speed sensor, and a solar radiation sensor are illustrated as weather condition sensors.

One of the load-side power distribution systems is connected to a flicker load, and a cut-off output for operating a switch CB of the power distribution system is output from a temperature calculation type overload protection relay 3. FIG. 4 is a block diagram showing an internal circuit configuration of the temperature calculation type overload protection relay 3. The current transformer CT
_The current data detected by ₁ and CT _{2 and the} detection data of the temperature sensor, the wind speed sensor, and the solar radiation sensor are supplied to the signal input unit 4, respectively. The signal input unit 4 includes an insulating amplifier and a low-pass filter for removing noise. The output of the signal input unit 4 is converted into a serial signal through a multiplexer 5 and further converted into a digital signal through an A / D converter 6.

The output of the A / D converter 6 is given to a CPU 7. Reference numeral 8 denotes an operation / setting panel connected to the CPU 7 and has various keys such as numeric keys. 9 is CP
A load control contact output unit connected to U7,
The switch CB is opened and tripped at the time of abnormal heating of L and 2L, and power transmission to the load side distribution system is stopped. This trip may be performed via a timer element as is commonly used.

10 is a status display unit connected to the CPU 7,
Reference numeral 11 denotes a recording printer. Reference numeral 13 denotes a monitoring result processing device connected to the CPU 7 via the transmission control device 12, and monitors and controls the CPU 7, and stores and processes various data. The CPU 7 performs an electric wire temperature calculation process. First, the initial values θi0, θa0, θs0 of the predicted temperature θin at the time n calculated from the current, the predicted temperature θan at the time n calculated from the temperature, and the predicted temperature θsn at the time n calculated from the solar radiation,
Each is set to a predetermined value.

Then, n is incremented by one,
The following operation is performed. Since the initial values θi0, θa0, and θs0 tend to be irregular, the initial predicted temperature θ
May not be obtained. Therefore, it is previously refused that it is desirable to invalidate some of the initial samplings as the predicted temperature θ for determining the overload condition of the monitoring line. The CPU 7 obtains a correction function value by applying the wind speed data, temperature data, and the like at the time point n to the above-described equations (4), (5), and (6). Further, by applying these correction function values and the current data In to the above equation (1), a predicted temperature θin at the time point n calculated from the current is obtained.

Next, the wind speed data at the time point n is described in (8) above.
A correction function value is obtained by applying the equation, and the correction function value and the temperature data An are applied to the equation (7) to obtain a predicted temperature θan at the time point n calculated from the temperature. Next, the wind speed data at the time point n is applied to the above-mentioned equations (10) and (11) to obtain a correction function value, and the correction function value and the solar irradiance data Sn are applied to the above-mentioned equation (9) to obtain the correction value. The predicted temperature θsn at the time point n is obtained.

Further, the predicted temperature θin, the predicted temperature θan at the time n calculated from the air temperature, and the predicted temperature θsn at the time n calculated from the solar radiation are summed up, and the predicted temperature θn of the monitoring line is calculated based on the equation (12). Ask for. At this time, as shown in Expression (12), since the margin α is taken into consideration, the safety margin can be set to a desired size. By comparing the predicted temperature θn thus obtained with the set value, the overload condition of the monitoring line can be determined.

If it is determined that the condition is an overload condition, the CPU 7
Open-trips the switch CB through the load control contact output unit 9 to stop power transmission from the substation 2 to the load-side distribution system. At the same time, the monitoring result is output to the status display unit 10, the recording printer 11, and the monitoring result processing device 13. By performing the above processing, the occurrence of abnormal heating of the transmission lines 1L and 2L, which are monitoring lines, can be accurately predicted in consideration of weather conditions. As a result,
Transmission can be maintained until the transmission current reaches the maximum amount of power that can be safely transmitted, and the transmission efficiency is greatly increased.

The embodiment of the present invention is not limited to the above. In the above embodiment, the temperature, wind speed,
Weather condition data such as solar radiation was directly obtained from sensors. However, it is also possible to store these weather condition data in a fixed value in advance based on past statistical information. For example, if past temperature data, solar radiation data, and wind speed data are calculated and classified for each season, month, and time zone, data corresponding to the same location, the same season, month, and time zone can be used. Of course, some errors are unavoidable depending on the weather of the day, but even so, the accuracy can be significantly improved as compared with the conventional technology that does not consider the weather condition data at all.

Although various classification methods are conceivable, for example, temperature data and solar radiation data can be expected to fluctuate, so that they are classified relatively in detail by season and time zone, and wind speed data is determined according to the weather of the day. Since they are so different, they cannot be clearly defined and a fixed value may be used. Also, statistical data and actual measurement data can be used in combination. For example, when only a temperature sensor is provided, actual temperature data may be used as temperature data, and past statistical data may be used as solar radiation data and wind speed data.

[0028]

As described above, according to the temperature calculation type overload protection relay according to the first aspect of the present invention, the temperature inside the electric wire predicted from the current flowing through the monitoring line and the electric wire predicted from the weather condition. The temperature difference from the surface temperature is added, and by this addition, the accurate temperature of the electric wire under the weather condition can be predicted with high accuracy without directly measuring. Therefore, it is possible to transmit the maximum amount of current that can be transmitted according to actual weather conditions, and it is possible to significantly improve the power transmission efficiency.

In particular, when the statistical weather conditions around the monitoring line are stored and used as described in claim 3, there is no need to install a weather condition detecting means, and the temperature of the electric line is reduced. Monitoring can be performed more easily. When the monitoring line is a flicker load transmission line, a large load current flows intermittently.
The present invention that can accurately predict abnormal heating of a line can be suitably used.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle that a relay operates based on the total time during which a load current exceeds a set value in a flicker load in which a large load current flows intermittently.

FIGS. 2A and 2B are graphs showing the transition of the overload rate and the wire temperature with time, wherein FIG. 2A shows the case where the overload rate is high, and FIG.

FIG. 3 is a diagram showing an outline of a connection state when the temperature calculation type overload protection relay of the present invention is installed in a substation.

FIG. 4 is a block diagram showing an internal circuit configuration of a temperature calculation type overload protection relay.

[Explanation of symbols]

1L, 2L parallel two-circuit transmission line CT _1, CT ₂ current transformer CB switch 2 substation 3 temperature calculating overload protection relay 4 signal input section 5 the multiplexer 6 A / D converter 7 CPU 8 setting and operation panel 9 Load control contact output unit 10 Status display unit 11 Recording printer 12 Transmission control unit 13 Monitoring result processing unit

Claims (5)

[Claims] 1. A relay device for detecting an overload condition of a monitoring line, a current detecting unit for detecting a current flowing through the monitoring line, a weather condition detecting unit for detecting a weather condition around the monitoring line, A prediction operation means for predicting and calculating the electric wire temperature of the monitoring line based on the current value detected by the current detection means and the weather condition detected by the weather condition detection means; and an electric wire temperature obtained by the prediction operation means. A temperature calculation type overload protection relay, comprising: determination means for determining an overload condition of a monitoring line by comparing the set value with a set value. 2. A temperature calculation type overload protection relay according to claim 1, wherein the weather condition detected by said weather condition detecting means is selected from among temperature, solar radiation intensity, and wind speed. 3. A relay device for detecting an overload condition of a monitoring line, a current detecting means for detecting a current flowing through the monitoring line, and a weather condition storing means for storing a statistical weather condition around the monitoring line. And a prediction calculation means for performing a prediction calculation of the electric wire temperature of the monitoring line based on the current value detected by the current detection means and the weather condition stored by the weather condition storage means; A temperature calculation type overload protection relay, comprising: determination means for determining an overload condition of the monitoring line by comparing the wire temperature with a set value. 4. The overload protection relay according to claim 3, wherein the weather condition stored by said weather condition storage means is selected from the group consisting of air temperature, solar radiation intensity, and wind speed. 5. The overload protection relay according to claim 1, wherein said monitoring line is a transmission line having a flicker load.