JP3290797B2 - Overcurrent relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overcurrent relay used for overload protection.

[0002]

2. Description of the Related Art There is an overload protection relay for protecting an overload of a power line or a power device. In addition, as a typical power system protection, transmission line overload protection relay,
There is a transformer overload protection relay. For example, as shown in FIG. 20, this type of overload relay has a plurality of overload characteristics having different set values with respect to an overload characteristic curve (hereinafter referred to as an overload curve) of a power line or a power device to be protected. It was common to apply and protect the current relay step by step. In this case, a protection method has been adopted in which the load is cut off by combining each overcurrent relay with a time limit timer having a different settling time so that the operation state does not reach the dangerous state of the overload curve.

[0003] However, there is a possibility that the overload in the vicinity of the operating value limit of the overcurrent relay cannot be cut off, and it is necessary to set the overcurrent relay in a region sufficiently safer than the overload curve in consideration of the load fluctuation. Therefore, there is a case where it is necessary to shut down the overload in a short time even if the overload has enough time, and the overload operation within the allowable range, that is, the range that does not reach the danger area, is sufficiently performed. There was a problem that it could not be performed.

[0004] In order to solve such problems, the overload relay at the time of overtime is intended to improve the service of power supply by performing load interruption at the time of overload by a method according to overload characteristics. Has been proposed in JP-A-62-178115.

[0005] According to this proposal, there is shown means for realizing appropriate relay characteristics by accurately simulating the thermal behavior of a power line to be protected or a power device in the relay. Specifically, the temperature rise is determined from the value of the load current taken into the relay by a predetermined temperature rise formula, and when this reaches a predetermined temperature, for example, an allowable limit temperature of a protection target, a load shedding output is generated. is there.

Generally, since the overload curve is obtained by assuming that a constant overload current is continuously supplied in the temperature rise equation, the thermal behavior can be accurately determined in the relay. The constant current characteristic of the above-mentioned proposed relay in consideration of the simulation described above assumes the form shown in FIG. 21 and matches the overload curve. That is, even in a system in which operation in a region that does not reach the danger region can be sufficiently performed and the load frequently fluctuates, overload operation that always maximizes the capacity of the protection target can be performed.

Here, what is important in the above-mentioned proposal is to accurately simulate the thermal behavior. Generally, the temperature rise of transmission lines or transformers is (1)
Is given by the differential equation

(Equation 1) Here, theta: Temperature rise I: load current f: I, except for the function and the theta variable, the load current I is intended to represent a normalized with continuous allowable current I _N overload factor (hereinafter the same) .

As for the means for calculating this in the relay, the calculation of equation (2) may be performed as described in the above-mentioned proposal.

[Equation 2] θ _m = θ _m-1 + Δt · f (I, θ _m-1 ) (2) where, θ _m : temperature at the present time θ _m-1 : temperature before Δt time Δt : Calculation cycle. Such an operation can be realized by a protection relay (hereinafter, referred to as a digital relay) in which a microcomputer is applied to the protection and control device for the power system.

[0009]

If the temperature rise equation is to be realized accurately in the relay, the problem is how to set the temperature rise equation in the relay. Said (1)
If the formula is a simple formula with few coefficients and constants that multiply each variable, it can be realized by setting these coefficients and constants.However, if there are many coefficients and constants, the setting work becomes complicated and human error occurs. There is a problem that it is easy. or,
When testing a relay having a large number of integer constants, there is a problem that the test verification work becomes complicated.

The coefficients and constants generally used in the temperature rise equation have physical meanings such as the conductors of transmission lines and oil and windings in transformers, and these values are determined by setting the protective relay. There is a high possibility that you will not be able to know when performing business,
For the setting operation of the protection relay using the current and the voltage as input, there is a problem that since the value is not directly linked to the response of the protection relay, the setting operation is complicated and human error is likely to occur. The problem described above will be described with a specific example. Equation (3) is the temperature rise equation of the power transmission line shown on page 37 of the Electric Cooperative Research Vol. 23, No. 2, “Aluminum Distribution Lines”.

[0011]

(Equation 3)

V: Wind speed (m / s) T: Ambient temperature, summer (May to October) 40 ° C, winter (11 to 4)
Month) 25 ° C. R: AC resistance of conductor at operating temperature (Ω / cm) R = R _DC · K ₁ · K ₂ ｛1 + α (T + θ−20)｝ R _DC : DC resistance at 20 ° C. (Ω / km) K _1: skin effect coefficient K _2: iron loss coefficient alpha: resistance temperature coefficient eta: the ratio of the radiation coefficient of the wire and black body W _s: insolation

The physical meaning is shown in FIG. When calculating the temperature rise by the equation (3), in order to simulate an accurate temperature rise, the coefficients, constants C, D,
_{h r, h w, V,} T, R DC, K 1, K 2, α, η, W s
Then, the operation of equation (4) may be performed in the relay.

(Equation 4) _{However, D, h r, h w} , be handled transmission lines inherent physical constants such as R _DC, coefficients as setting value may aforementioned problems.

As a solution to this problem, there is a method of simplifying the expression (3). That is, it is conceivable to adopt the form shown in equation (5).

(Equation 5) Therefore, A ₁ , A ₂ , and A ₃ may be set as set values, and the set constants are reduced and simplified.

However, when such simplification is performed, there is a problem that the temperature rise cannot be accurately simulated. FIG. 23 shows an overload curve when the above simplification is performed and characteristics of the relay when a constant current is continuously input. As shown in FIG. 23, the two characteristics are separated as time passes. This is because A ₁ , A ₂ , and A ₃ are simplified as coefficients and constants that do not depend on the current, and it cannot be considered that the temperature rise is accurately simulated.

In addition, even in the case of such a simplification, in order to treat the above-mentioned set value as a settling service, a value which is not directly connected to the response of the protective relay is set as a work of setting a protection relay which inputs current and voltage. , Settling work becomes complicated,
There is a problem that human error is likely to occur.

In addition, since the thermal behavior over a long period of time is simulated, it takes a long time to test, it is difficult to recognize a setting error / failure of the overcurrent relay itself, and it is necessary to input different setting values depending on the season. There is a problem that there is a problem that the setting work becomes complicated, and furthermore, it is necessary to perform load shedding at an appropriate time within a range not exceeding the allowable limit temperature of the transmission line.

The present invention has been made in view of the above circumstances, and provides an overcurrent relay that accurately simulates the thermal behavior of a protection target in overload protection of a power line or a power device. It is an object of the present invention to provide an overcurrent relay capable of giving a given set value in a relationship between current and time which can be read from an overload curve.

[0019]

An overcurrent relay according to a first aspect of the present invention relates to a function h (I, t) of a current I and a time t simulating a current-time-temperature rise characteristic of a protected object. , At least one current value I _i , time t _i (i
Is an integer) as a variable of the function h (I, t), and a function determining means for determining the function h (I, t); and a function h (I, t) obtained by the function determining means. coefficient·
It comprises temperature rise calculating means for calculating the temperature rise of the protected object using a constant, and output determining means for generating an output by detecting that the temperature obtained by the temperature rise calculating means is equal to or higher than a predetermined value. .

An overcurrent relay according to a second aspect of the present invention comprises:
3. The function determining means according to claim 1, wherein the function h (I, t)
The equation is used to calculate the transmission line temperature rise by stabilizing the value (I, t) on the transmission line overload curve as a variable of the function h (I, t).

An overcurrent relay according to a third aspect of the present invention comprises:
Regarding a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of an object to be protected, at least one or more current values I _i and a time t _i (i is an integer) are functions h
By setting as a variable of (I, t), the function h (I,
function determining means for determining t), a temperature rise calculating means for performing a temperature rise calculation based on a given function, and a predetermined value using a temperature obtained from the temperature rise calculation means and a function h (I, t). A prediction operation means for obtaining the temperature after the time and an output determination means for generating an output when the predicted operation value exceeds the allowable limit temperature of the transmission line or a predetermined value.

An overcurrent relay according to claim 4 of the present invention is:
Regarding a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of an object to be protected, at least one or more current values I _i and a time t _i (i is an integer) are functions h
By setting as a variable of (I, t), the function h (I,
function determination means for determining t), temperature rise calculation means for performing a temperature rise calculation based on a given function, and prediction calculation means for determining a temperature after a predetermined time using the temperature obtained from the temperature rise calculation means When the value of the predicted time T _p which gives the prediction operation unit, the current I or the estimated time control means for providing a current function value the temperature value theta _m a variable, the predicted calculated value transmission lines permissible limit temperature or a predetermined Output judging means for generating an output when the value is exceeded.

An overcurrent relay according to claim 5 of the present invention is:
Regarding a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of an object to be protected, at least one or more current values I _i and a time t _i (i is an integer) are functions h
By setting as a variable of (I, t), the function h (I,
function determination means for determining t), temperature rise calculation means for performing a temperature rise calculation based on a given function, and temperature for obtaining a difference between the transmission line allowable limit temperature and the current temperature obtained by the temperature rise calculation means. It comprises a difference output means and an output determination means for generating an output when the difference exceeds a predetermined value.

An overcurrent relay according to claim 6 of the present invention is:
Regarding a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of an object to be protected, at least one or more current values I _i and a time t _i (i is an integer) are functions h
By setting as a variable of (I, t), the function h (I,
function determining means for determining t), temperature rising calculating means for performing a temperature rising calculation based on a given function, and the function h
Error calculating and displaying means for calculating the difference between the value on the overload curve obtained from (I, t) and the set value, and the temperature obtained by the temperature rise calculating means exceeding the allowable limit temperature of the transmission line or a predetermined value. And output determination means for generating an output.

An overcurrent relay according to claim 7 of the present invention is:
Regarding a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of an object to be protected, at least one or more current values I _i and a time t _i (i is an integer) are functions h
By setting as a variable of (I, t), the function h (I,
function determining means for determining t), temperature rising calculating means for performing a temperature rising calculation based on a given function, and the function h
A characteristic display means for displaying on a display panel a time limit characteristic of current versus time of the overcurrent relay obtained from (I, t); and a temperature obtained by the temperature increasing means exceeding a transmission line allowable limit temperature or a predetermined value. And output determination means for generating an output.

An overcurrent relay according to claim 8 of the present invention comprises:
Regarding a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of an object to be protected, at least one or more current values I _i and a time t _i (i is an integer) are functions h
By setting as a variable of (I, t), the function h (I,
function determination means for determining t), temperature rise calculation means for performing a temperature rise calculation based on a given function, and a function h corresponding to a plurality of overload curves f _{1 to} f _n (n is a positive integer). _{1
(I, t) ~h n (} I, t) determined and stored, and functions selection means for outputting to the temperature rise arithmetic means functions corresponding either at the time or an external control a predetermined time, the temperature rise arithmetic And output judging means for generating an output when the temperature obtained by the means exceeds the transmission line allowable limit temperature or a predetermined value.

An overcurrent relay according to claim 9 of the present invention is:
Regarding a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of an object to be protected, at least one or more current values I _i and a time t _i (i is an integer) are functions h
By setting as a variable of (I, t), the function h (I,
function determining means for determining t), temperature rise calculating means for performing a temperature rise calculation based on a given function, time shortening means for performing a time reduction simulation of the temperature rise calculation, and the temperature rise calculation means. And output judging means for generating an output when the temperature exceeds the transmission line allowable limit temperature or a predetermined value.

According to a tenth aspect of the present invention, there is provided an overcurrent relay, wherein at least one or more of a function h (I, t) of a current I and a time t simulating a current-time-temperature rise characteristic of a protected object. By setting the current value I _i and the time t _i (i is an integer) as variables of the function h (I, t), the function h
Function determining means for determining (I, t), temperature rising calculating means for performing a temperature rising calculation based on a given function, and determining a temperature after a predetermined time using the temperature obtained from the temperature rising calculating means. It is composed of a predicting operation means, a temperature display means for displaying a result of the temperature operation, and an output judging means for generating an output when the predicted operation value exceeds a transmission line allowable limit temperature or a predetermined value.

[0029]

According to the overcurrent relay according to the first aspect of the present invention, the current value I _i and the time t _i (i is an integer) are set as variables of a function h (I, t) that simulates a temperature rise characteristic. , H (I, t). As a result, a function, a coefficient, and a constant for performing the temperature rise calculation are obtained, and the temperature calculation is performed.

An overcurrent relay according to a second aspect of the present invention comprises:
Using a transmission line transient temperature rise calculation formula as a function h (I, t), the value (I, t) on the overload curve is converted into a function h (I, t).
The transmission line temperature rise is calculated, and the output is output when the calculated temperature exceeds a predetermined value.

An overcurrent relay according to a third aspect of the present invention comprises:
Using the temperature and function h calculated so far (I, t), performs temperature rise prediction operation after the predetermined T _p time prediction calculation temperature output by equal to or larger than a predetermined value.

An overcurrent relay according to claim 4 of the present invention is:
The value of the predicted time T _p, a function value with at least one variable of the current I or the current temperature value, thereby performs temperature rise prediction calculation, the prediction calculation temperature output by equal to or larger than a predetermined value .

An overcurrent relay according to claim 5 of the present invention is:
The difference between the allowable limit temperature and the current temperature obtained by the temperature rise calculation means is calculated, and the difference is output when the difference exceeds a predetermined value.

An overcurrent relay according to claim 6 of the present invention is:
By setting the current value I _i and the time t _i (i is an integer) as variables of a function h (I, t) that simulates a temperature rise characteristic,
Determine the function h (I, t). The determined function h (I,
t), an error between the obtained overload curve and the set value is calculated and displayed.

An overcurrent relay according to claim 7 of the present invention is:
By setting the current value I _i and the time t _i (i is an integer) as variables of a function h (I, t) that simulates a temperature rise characteristic,
Determine the function h (I, t). The determined function h (I,
t) and the resulting overload curve is displayed on the relay.

The overcurrent relay according to claim 8 of the present invention comprises:
A function h ₁ (I, t)... H _n (I, t) corresponding to a plurality of overload curves f ₁ ... F _n (n is a positive integer) is determined and stored, and when a predetermined time has elapsed or when external control is performed. Sometimes, it is determined whether to calculate the temperature rise by any of the above functions. Temperature calculation is performed using coefficients and constants obtained from the function selected by the judgment, and an output is made when the calculated temperature becomes equal to or higher than a predetermined value.

An overcurrent relay according to claim 9 of the present invention is:
In the overload protection relay according to the first aspect, a time shortening temperature simulation is performed by selecting a test mode, and an output is output in a shorter time than in actual operation.

An overcurrent relay according to a tenth aspect of the present invention, in the overload protection relay according to the first aspect, displays a temperature obtained by a temperature calculation.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an overcurrent relay according to claim 1 of the present invention will be described below. FIG. 1 shows the configuration of this embodiment. In FIG. 1, reference numeral 10 denotes an overcurrent relay which receives a current I flowing through the protection target 1 and generates an output for protecting the protection target by a temperature rise operation.
11, a temperature rise calculating means 12, an output determining means 13, and a function determining means 14.

As an operation, first, the current I from the protection target is obtained by the data obtaining means 11, and after the digital conversion, the effective value is calculated. This means is realized by a general method of a digital relay, that is, acquisition of digital data by an analog / digital converter and conversion from an instantaneous value to an effective value by rectification addition, binary addition, and the like. A temperature rise calculation is performed by the temperature rise calculation means 12 using the current data obtained here, and the temperature to be protected is obtained. The output determining means 13 outputs an output when the temperature obtained by the temperature rise calculating means 12 exceeds the allowable limit temperature. Temperature rise calculation means 1
2. Various coefficients and constants for the temperature rise calculation used in the output determination means 13 are calculated by the function determination means 14 from the set values given to the overcurrent relay. This means is a feature of the present invention.

The function determining means 14 and the set value will be described below. The temperature rise calculating means 12 performs the calculation by the temperature rise formula shown by the equation (1). For this purpose, the function f (I, θ) is used.
Need to ask. Specifically, a coefficient and a constant of the function f (I, θ) may be given. Here, when Expression (1) is integrated with respect to time t, Expression (6) is obtained.

(Equation 6) Equation (7) is obtained by rearranging equation (6) assuming that a constant current I is input during time t.

(7) θ = h (I, t) (7) The above equation (7) is a function indicating the temperature rise with respect to the current.

In the present invention, using the equation (7), the coefficient of the equation (1)
A constant is obtained. Specifically, the function f in the equation (1) is used.
(I, theta) coefficients _{a 0, a 1, a 2} , ..., a n, a constant _{k 0, k 1, k 2} , ..., When k _m, these coefficients, the constant (7) Can be obtained by solving a maximum of (m + n + 1) simultaneous equations satisfying the following equation (8).

(8) θ _L = h (I ₁ , t ₁ ), θ _L = h (I ₂ , t ₂ )... Θ _L = h (I _U , t _U ) where U ≦ m + n + 1 (8) Here, I _i and t _i (1 ≦ i ≦ U) are current and time at a predetermined temperature θ _L.

These values of I _i and t _i are generally known as values on an overload curve to an operator of equipment such as a transformer or a transmission line, which is an object of the overcurrent relay of the present invention. The setting of the overcurrent relay described with reference to FIG. 20 is also performed based on this overload curve. In other words, the overload curve for a given temperature (allowable limit temperature) theta _L, (I,
12 is a plot of a plurality of combinations of t). That is, the function determining means 14 inputs a pair of h (I, t) I _i and t _{i having} the same function value θ _L as a settling value,
By solving the simultaneous equations expressed by the equation (8), the above-mentioned coefficients and constants are obtained.

FIG. 2 shows a procedure for obtaining coefficients and constants using the equation (8). In equation (8), the coefficients, constants, and θ _L are unknowns, and h (I, t) is generally a nonlinear function. Therefore, the unknowns are obtained by a numerical analysis method such as the Newton method. Therefore, the initial value of each unknown is set in S1, and the set value of (I, t) is read in S2. Next, in step S3, each is substituted into equation (8), and in step S4, whether equation (8) is satisfied or not, the convergence is determined. If converged, the process is terminated. If not, the variable is updated in step S5. Then, the above-described processing is repeated from S3.

According to this embodiment, as described above,
Each coefficient and constant are obtained. By using this in equation (2), an accurate temperature rise simulation can be performed. Further, since these coefficients and constants are obtained from the overload curve used in the setting of the conventional multistage overcurrent relay, an overcurrent relay having good reliability, operability, and accuracy can be provided.

An embodiment of the overcurrent relay according to claim 2 of the present invention will be described below. FIG. 3 shows the configuration of the present embodiment. In this case, the overcurrent relay generates an output for protecting an overload of the transmission line by a temperature rise calculation by using a current flowing through the transmission line as an input. In FIG. 3, 3-1 is a transmission line to be protected, 3-2 is a current transformer for taking current flowing in the transmission line into a relay, and 10 is an overcurrent relay.

Since the configuration inside the overcurrent relay is the same as that shown in claim 1, the description is omitted. The feature of the present embodiment is that the configuration and operation principle shown in claim 1 are applied to transmission line overload protection, and the operation will be described below. First, the transient temperature rise equation of the transmission line is given by the above equation (3). When performing overload protection on a transmission line, the above equation is simulated in an overcurrent relay, and an output is output when the temperature exceeds the transmission line allowable limit temperature, but as described in claim 1, It is difficult to set the above various coefficients and constants as set values, which may cause human error.

The present embodiment solves this problem, and is characterized in that the setting can be performed by using an overload curve of a transmission line used for setting a conventional multistage transmission line overload protection relay. . Specifically, the combination of (I ₁ , t) at five points on the transmission line overload curve as shown in FIG.
t ₁ ), (I ₂ , t ₂ ), (I ₃ , t ₃ ), (I ₄ , t
₄ ), (I ₅ , t ₅ ) are given as set values. Here, the relationship between the transmission line overload curve and the above-mentioned transmission line transient temperature rise equation (Equation (3)) will be described. (3) By integrating the equation with time t, the following equation is obtained. The following equation corresponds to the above equation (7) θ = h (I, t).

(Equation 9)

However, in the equation (9), when the initial state t = 0, θ
= Θ ₀ . here,

[Equation 10]

Θ _x is the final temperature rise when the current I is supplied, τ is the time constant of the temperature change, and r = RK ₁ K ₂ . h _w, h _r is strictly's function of θ, but has been a constant since it depends on the degree of θ is small. Note that _θo is an initial temperature, which is obtained by the following equation by setting the load current I _{init in} advance.

[Equation 11]

By summarizing the above, the coefficients and constants necessary for calculating equation (3) are obtained from equations (9), (10) and (11). Here, the unknowns are as follows.

(Equation 12)

Since the overload curve shows the relationship between the overload current and the energizing time when the temperature reaches the allowable limit temperature θ _L , the values of (I, t) at the five points on the overload curve are represented by ( By substituting into equation (9) and solving the simultaneous equations equivalent to equation (8),
The unknowns a _{1 to} a ₅ in the expressions (17) to (17) can be obtained. FIG. 5 shows the procedure for the determination. The procedure for the details is the same as that in FIG. 2 and the description is omitted. The following calculation is performed by the temperature rise calculation means 12 based on the coefficients and constants obtained as described above.

[0053]

(Equation 13)

When the temperature obtained by the above calculation exceeds the transmission line allowable limit temperature θ _L , it is determined that the transmission line is in an overload state and an output is issued. As described above, according to the present embodiment, by simulating the five points on the transmission line overload curve, it is possible to accurately realize the temperature rise simulation, without having to know various constants of the transmission line itself. And accurate transmission line overload protection can be realized.

An embodiment of the overcurrent relay according to claim 3 of the present invention will be described below. FIG. 6 shows the configuration of the present embodiment. In this case, the overcurrent relay performs overload protection of the transmission line. In the figure, a function determining means 14 for determining a function for performing a temperature rise calculation using a set value as an input, and a temperature rise calculation means 12 for performing a temperature rise calculation based on a given function are the same as those in claim 2 and will be described. Omitted.

The feature of the present embodiment is that a temperature rise prediction operation after a predetermined time is performed by using the temperature obtained by the temperature rise operation means 12 and the function h (I, t), and the predicted operation value is transmitted to the transmission line. by exceeding the allowable limit temperature or a predetermined value, it is the provision of the prediction computation unit 15 to issue an output theta _TP. Accordingly, it is possible to appropriately perform load shedding before reaching the dangerous area where the transmission line is blown.

The temperature rise prediction calculation value θ _TP is calculated as h (I,
t) gives:

[Equation 14] Here, theta _m: current of the transmission line temperature theta _x: ultimate temperature theta _TP at present the current I: a transmission line temperature after T _p time. Incidentally, the prediction time T _p are given to the prediction operation unit 15 as a setting value.

The output judging means 13 outputs an output when the predicted temperature rise obtained by the predicting operation means exceeds the permissible limit temperature of the transmission line. FIG. 7 shows time-current characteristics of the overcurrent relay according to the present embodiment. This characteristic is a characteristic when a constant overload current is supplied. In the figure is the overload curve of the transmission line, which indicates that out output of the over current relay is in front than this T _p time. As described above, according to the present embodiment, since the output of the overcurrent relay is output before the allowable limit temperature of the transmission line is reached, a sufficient margin is provided as compared with the method of performing load shedding after the allowable limit temperature is reached. Thus, the overload can be eliminated.

An embodiment of the overcurrent relay according to claim 4 of the present invention will be described below. FIG. 8 shows the configuration of the present embodiment. In this case, the overcurrent relay performs overload protection of the transmission line. In the figure, function determining means for determining a function to perform the temperature rise operation as input set point 14, the temperature rise arithmetic means 12 for performing temperature increase calculated on the basis of a given function, temperature after set predetermined time T _p Prediction calculation means for predicting rise
The description of 15 is the same as that of the third aspect, and the description is omitted. The feature of this embodiment is that a prediction time control means 16 for controlling the prediction time Tp used in the prediction calculation means 15 is provided.

The predicted time control means 16 determines the value of the predicted time Tp given to the prediction calculation means 15 by the current I or the current temperature value θ.
_This is a means to give _m as a function value as a variable. As an example, a case where the prediction time control is performed by the following equation will be described.

T _p = K ₁ I + K ₂ (19) where T _p : predicted time I: energizing current K ₁ : coefficient K ₂ : constant

The above equation uses the current I as a variable to calculate the predicted time T
_{Since p} is calculated, the estimated time T depends on the overload situation.
You can control _p . In general, when the overload current is small, T _p may be short because the urgency of load shedding is small, and when the overload current is large, T _p may be lengthened to allow for more safety. It may be necessary to perform an overload cutoff earlier. According to this embodiment, since the changing in accordance with the prediction time T _p to the current I in the above equation, it is possible to load shedding in accordance with the conditions of overload. FIG. 9 shows the overload curve in this case and the characteristics of the overcurrent relay at a constant current. Here, the coefficient K ₁ and the constant K in the above equation
₂ can be given as a settling, and the effect is the same.

As another embodiment of the present invention, there is a case where the current temperature θ _m is a variable of T _p as shown by the following equation.

Equation 16] _{T p = K 1 θ m +} K 2 ............... (20) In this case also it is possible to load shedding in accordance with the conditions of the same overload the previous embodiment. That is, without possible overload blocking shorter T _p if low temperatures, acceptable can be performed operation to near the limit of the transmission lines. Further, when the temperature is high, T _p is prolonged because of high urgency, it is possible to perform relatively early load shedding. Here, the coefficient K ₁ and the constant K ₂ in the above equation can be given as settling, and the effect is the same. As described above, when performing load shedding in accordance with the situation of the accordance if overload present invention, i.e., it is possible to correct the transmission line overload protection since it can control the estimated time T _p.

An embodiment of the overcurrent relay according to claim 5 of the present invention will be described below. FIG. 10 shows the configuration of the present embodiment. In this case, the overcurrent relay performs overload protection of the transmission line. In the figure, a function determining means 14 for determining a function for performing a temperature rise calculation using a set value as an input, and a temperature rise calculation means 12 for performing a temperature rise calculation based on a given function are the same as those in claim 2 and will be described. Is omitted. The feature of the present embodiment is that the difference between the transmission line allowable limit temperature θ _L and the current temperature θ _m obtained by the temperature rise calculating means 12 is obtained, and the difference exceeds a predetermined value K (the difference is reduced). The difference is that a temperature difference output means 17 for outputting the output of the overcurrent relay is provided.

The above means can be realized by the following equation.

Equation 17] _{θ d = θ L -θ m ..................} (21) where a predetermined value (temperature difference) K is given as a set value or a fixed value. According to the above equation, the output from the overcurrent relay can be obtained before the transmission line reaches the allowable limit temperature, and the overload can be eliminated with a sufficient margin compared to the method of performing load shedding after the allowable limit temperature is reached. Can be performed.

An embodiment of the overcurrent relay according to claim 6 of the present invention will be described below. FIG. 11 shows a configuration of the present invention. In this case, an overcurrent relay for protecting a transmission line from overload is shown. In the figure, a function determining means 14 for determining a function for performing a temperature rise calculation using a set value as an input, and a temperature rise calculation means 12 for performing a temperature rise calculation based on a given function are the same as those in claim 2. Also, as the function h (I, t), a transmission line transient temperature rise calculation formula is used, and the value (I, t) on the transmission line overload curve is settled as a variable of the function h (I, t). The coefficients and constants of the function h (I, t) are obtained, but since this point has already been described, detailed description will be omitted. This embodiment is characterized in that an error between the function h (I, t) obtained by the function determining means and the set value, that is, the overload curve of the target transmission line is calculated and displayed. This is the point that the display means 18 is provided.

As shown in FIG. 12, the error calculating means is determined from h (I, t) obtained by the function determining means (I, I, t).
t) and the set values (I ₁ , t ₁ )... (I ₅ , t ₅ ) are sequentially compared to calculate an error. The obtained error ε ₁ ,
ε ₂ , ε ₃ , ε ₄ , ε ₅ are displayed on the display panel of the overcurrent relay in the form shown in FIG. According to the present embodiment, the difference between the function h (I, t) and the actual target overload curve becomes clear to the driver, and human errors such as erroneous selection of the set value can be prevented.

An embodiment of the overcurrent relay according to claim 7 of the present invention will be described below. FIG. 13 shows a configuration of the present invention. In this case, an overcurrent relay for protecting a transmission line from overload is shown. In the figure, a function determining means 14 for determining a function for performing a temperature rise calculation using a set value as an input, and a temperature rise calculation means 12 for performing a temperature rise calculation based on a given function are the same as those in claim 2.

As the function h (I, t), the equation for calculating the transient temperature rise of the transmission line is used, and the value (I,
t) is settled as a variable of the function h (I, t), and the coefficients and constants of the function h (I, t) are obtained. This point has already been described. Omitted. The feature of the present embodiment is that a characteristic display means 19 is provided for displaying on the display panel of the overcurrent relay the time limit characteristic of the current versus time of the overcurrent relay obtained from the function h (I, t). The procedure for displaying the time limit characteristic of the current versus time of the overcurrent relay from the function determining means 14 will be described below.

First, predetermined overload rates I ₁ , I ₂ ,.
_{For q} (q is a positive integer), θ _L finds t ₁ , t ₂ ,..., t _q that satisfies h (I, t). Next, the obtained (I
₁ , t ₁ ) (I ₂ , t ₂ )... (I _q , t _q ) are sequentially transferred to the display panel. The display panel displays the time limit characteristic by interpolating the transferred data. FIG. 14 shows a display example of the current-time reversal time characteristic of the overcurrent relay thus obtained.

According to the present invention, the operator visually confirms the time limit characteristic of the current versus time of the overcurrent relay obtained by settling, that is, the approximate curve to the overload curve of the transmission line to be simulated. As a result, it is easy to verify how accurately approximation can be performed and whether setting has been performed correctly, and an overcurrent relay having high reliability and operability can be provided. It should be noted that the same effect can be obtained when the display data or the coefficients and constants of h (I, t) are transferred to an external personal computer and the approximate curve is drawn as a display medium.

An embodiment of the overcurrent relay according to claim 8 of the present invention will be described below. FIG. 15 shows a configuration of the present invention. In this case, an overcurrent relay for protecting a transmission line from overload is shown. In the figure, a function determining means 14 for determining a function for performing a temperature rise calculation using a set value as an input, and a temperature rise calculation means 12 for performing a temperature rise calculation based on a given function are the same as those in claim 2. Also, as the function h (I, t), a transmission line transient temperature rise calculation formula is used, and the value (I, t) on the transmission line overload curve is settled as a variable of the function h (I, t). The coefficients and constants of the function h (I, t) are obtained, but since this point has already been described, detailed description will be omitted.

This embodiment is characterized in that a function h ₁ corresponding to a plurality of transmission line overload curves f ₁ ,..., F _n (n is a positive integer)
(I, t)... H _n (I, t) are determined and stored, and a function selecting means for determining whether to calculate the transmission line temperature rise by any of the above functions when a predetermined time has elapsed or during external control.
20 is provided. The operation of the present embodiment will be described below.

[0073] operator, as shown in FIG. 16, a plurality of transmission lines overload curve f _1, ..., a point on the overload curve, each corresponding to _{f n (I 11, t 11} ) ... (I 1u, t _1u ), (I ₂₁ , t ₂₁ )
.. (I _2u , t _2u ), (I _n1 , t _n1 )... (I _nu , t _nu ) are settled, and the function h ₁ (I, t)
... H _n (I, t) are determined. The determined coefficients and constants of each function are passed to the function selection means 20 and stored. The function selecting means 20 receives the time from the clock held in the overcurrent relay, and at a predetermined time, a specific function h ₁ (I, t) (i is 1
To n) and passes it to the temperature calculation means 12. In the case of transmission line overload protection, since the outside air temperature and the amount of solar radiation around the transmission line change every season, it is necessary for the operator to perform a setting operation based on the overload curve corresponding to each season.

According to the present invention, a function corresponding to the overload curve for each season can be provided in the overcurrent relay by the above-described operation, and the internal clock function automatically sets the function in units such as spring, summer, autumn, and winter. Function selection and temperature calculation can be switched, and the setting work can be significantly labor-saving. In the above embodiment, the control is performed by the internal clock function. However, a function can be selected by external control via a communication device or the like.
The effect in that case is also equivalent to the above embodiment.

An embodiment of the overcurrent relay according to claim 9 of the present invention will be described below. FIG. 17 shows the configuration of this embodiment. Figure
Reference numeral 17 denotes an overcurrent relay which has a time limit characteristic used for overload protection and includes temperature calculating means for simulating a current / time vs. temperature rise characteristic of a protected power line or a power device. The means and operation are the same as those in the first aspect, and thus detailed description is omitted. The feature of this embodiment is that a time shortening means 21 for simulating the time reduction of the temperature calculation is provided.

The test of the overcurrent relay proposed in this embodiment is generally performed by applying a constant current and measuring the time until an output is output. This will be performed for at least some points on the overload curve. Therefore, it takes several minutes to several tens of minutes per point in the case of transmission line protection and several tens of minutes to several hours in the case of transformer protection. This is determined by the inherent time constant of the protected power line or power device. As described above, the characteristic test of the overcurrent relay according to the present embodiment requires a long period of time, which is problematic in terms of economy, efficiency, and the like.

Therefore, claim 9 solves this problem and proposes an overcurrent relay having time reducing means for easily performing a characteristic test. The operation of the time reducing means will be described below. As shown in the figure, a switch for setting the overcurrent relay to the test mode at the time of the test is provided, and this state is introduced to the time reducing means 21. In the time shortening means, Δt in the above-mentioned temperature rise calculation equation (2) is multiplied by k times (k
Is a positive real number) and is given to the temperature calculating means, so that a time-reduction simulation can be performed.

[Equation 18] θ _m = θ _m−1 + (kΔt) · f (I, θ _m−1 ) (22)

That is, in the actual operation, even when the output is performed after the time T, the test can be performed in the time T / k by setting the test mode. The hardware constituting the overcurrent relay and the software other than the portion of Δt are not different from the actual operation state, and have an effect that highly accurate test verification can be performed in a short time. As another embodiment, there is a means for controlling the temperature calculating means from the time reducing means so that the time cycle of the temperature calculation is set to k times when the test mode is set. The effect in this case can be said to be equivalent to the above embodiment.

An embodiment of the overcurrent relay according to claim 10 of the present invention will be described below. FIG. 18 shows the configuration of the present invention. Figure
Reference numeral 18 denotes an overcurrent relay having a time limit characteristic used for overload protection and having a temperature calculation means for protecting a current / time vs. temperature rise characteristic of a protected power line or a power device. Since the means and operation are the same as those in the first aspect, a detailed description is omitted.

A feature of the present invention is that a temperature display means 22 for displaying the result of the temperature calculation is provided. The current temperature obtained by the above equation (2) and the predicted temperature obtained by the equation (18) are led from the temperature calculating means to the temperature display means, and are displayed in real time on the display panel of the overcurrent relay. As a result, the driver can easily know how much margin the transmission line has with respect to the allowable limit temperature, and can judge the setting error or the failure of the overcurrent relay itself, etc. A high overcurrent relay can be provided. As another embodiment, a case where the current temperature, the predicted temperature, and the like are output to the outside of the overcurrent relay using communication means and the state of temperature change is displayed on a personal computer or the like in a form as shown in FIG. ,
The effect is equivalent.

[0081]

As described above, according to the present invention, the settling operation is facilitated, and the load can be properly and accurately cut off. According to the second aspect, by setting the value on the transmission line overload curve, it is possible to simulate the transmission line temperature with high accuracy, and to provide an overcurrent relay with high reliability and operability. Further, according to the third aspect, it is possible to appropriately perform load shedding within a range not exceeding the allowable limit temperature, and it is possible to provide a highly reliable overcurrent relay. Claims 4 and 5
According to this, it is possible to appropriately perform load shedding in accordance with the load condition, and it is possible to provide a highly reliable overcurrent relay. According to the sixth, seventh, and tenth aspects, it is easy to recognize the setting error and the failure of the overcurrent relay itself, and it is possible to provide an overcurrent relay having high reliability and operability. According to the eighth aspect, it is necessary to input a different set value depending on the season, and the problem that the setting work becomes complicated is solved, and an overcurrent relay with high operability can be provided. Further, according to the ninth aspect, it is possible to provide an overcurrent relay having a short test time and high economic efficiency.

[Brief description of the drawings]

FIG. 1 is a structural example diagram of an overcurrent relay according to claim 1 of the present invention.

FIG. 2 is a flowchart illustrating a process of determining a coefficient and a constant in a function determining unit.

FIG. 3 is a structural example diagram of an overcurrent relay according to claim 2 of the present invention.

FIG. 4 is a diagram showing a combination of settling using an overload curve of a transmission line.

FIG. 5 is a flowchart for obtaining coefficients and constants required for calculating a temperature rise equation.

FIG. 6 is a structural example diagram of an overcurrent relay according to claim 3 of the present invention.

FIG. 7 is a time-current characteristic diagram of the overcurrent relay for explaining FIG. 6;

FIG. 8 is a structural example diagram of an overcurrent relay according to claim 4 of the present invention.

FIG. 9 is a characteristic diagram of an overload relay at an overload curve and a constant current.

FIG. 10 is a configuration example diagram of an overcurrent relay according to claim 5 of the present invention.

FIG. 11 is a configuration example diagram of an overcurrent relay according to claim 6 of the present invention.

FIG. 12 is a display example of a setting error of a display panel of an overcurrent relay.

FIG. 13 is a configuration example diagram of an overcurrent relay according to claim 7 of the present invention.

FIG. 14 is a display example diagram of a time limit characteristic of current versus time of an overcurrent relay.

FIG. 15 is a configuration example diagram of an overcurrent relay according to claim 8 of the present invention.

FIG. 16 is a diagram showing a plurality of transmission line overload curves.

FIG. 17 is a configuration example diagram of an overcurrent relay according to claim 9 of the present invention.

FIG. 18 is a configuration example diagram of an overcurrent relay according to claim 10 of the present invention.

FIG. 19 is a diagram showing a predicted temperature and a display example.

FIG. 20 is a diagram showing a representative overload characteristic curve.

FIG. 21 is a diagram showing an overload curve based on constant current characteristics.

FIG. 22 is a diagram physically showing a heat generation mechanism of the transmission line.

FIG. 23 is a characteristic diagram of an overload curve when simplification is performed and a relay when a constant current is continuously input.

[Explanation of symbols]

 1 Protection target 10, 10-1 to 10-8 Overcurrent relay 11 Current data acquisition means 12 Temperature rise calculation means 13 Output judgment means 14 Function determination means 15 Prediction calculation means 16 Prediction time control means 17 Temperature difference output means 18 Error calculation Display means 19 Characteristics display means 20 Function selection means 21 Time reduction means 22 Temperature display means

──────────────────────────────────────────────────続 き Continued on the front page (72) Katsuhiko Sekiguchi 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Fuchu Plant, Toshiba Corporation (72) Inventor Yoji Watanabe 1-1-1, Shibaura, Minato-ku, Tokyo Stock Company (56) References JP-A-4-317511 (JP, A) JP-A-62-178116 (JP, A) JP-A-56-1728 (JP, A) JP-A-62-178115 (JP) JP-A-6-14448 (JP, A) JP-A-6-22438 (JP, A) JP-A-58-172927 (JP, A) JP-B 5-72168 (JP, B2) (58) Field surveyed (Int.Cl. ⁷ , DB name) H02H 3/08-3/253

Claims (10)

(57) [Claims] In an overcurrent relay used for overload protection, at least one or more of a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of a protected object. Current value I _i , time t _i (i is an integer)
Is determined as a variable of the function h (I, t) to determine the function h (I, t), and the coefficient / constant of the function h (I, t) obtained by the function determining means. Temperature rise calculating means for calculating the temperature rise of the object to be protected, and output determining means for generating an output by detecting that the temperature obtained by the temperature rise calculating means is equal to or higher than a predetermined value. Overcurrent relay characterized by the following. 2. The function determining means uses a transmission line transient temperature rise calculation formula as a function h (I, t), and converts a value (I, t) on a transmission line overload curve into a variable of the function h (I, t). The overcurrent relay according to claim 1, wherein the transmission line temperature rise is calculated by setting as follows. 3. An overcurrent relay for performing overload protection, wherein at least one or more currents are included in a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of a protected object. By setting the value I _i and the time t _i (i is an integer) as variables of the function h (I, t), the function h
Function determining means for determining (I, t); temperature rising calculating means for performing a temperature rising calculation based on a given function; and a temperature obtained by the temperature rising calculating means and a function h (I, t).
Prediction calculation means for determining the temperature after a predetermined time using
An output determining means for generating an output when the predicted operation value exceeds a transmission line allowable limit temperature or a predetermined value. 4. An overcurrent relay for performing overload protection, wherein at least one or more currents are provided for a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of a protected object. By setting the value I _i and the time t _i (i is an integer) as variables of the function h (I, t), the function h
Function determining means for determining (I, t), temperature rising calculating means for performing a temperature rising calculation based on a given function, and obtaining a temperature after a predetermined time using the temperature obtained from the temperature rising calculating means. and prediction calculation means, the value of the predicted time T _p which gives the prediction operation unit, the current I or the current temperature value θ
overcurrent characterized by comprising predicted time control means for giving a function value with _m as a variable, and output determination means for generating an output when the predicted calculated value exceeds a transmission line allowable limit temperature or a predetermined value. relay. 5. An overcurrent relay for performing overload protection, wherein at least one or more currents are included in a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of a protected object. By setting the value I _i and the time t _i (i is an integer) as variables of the function h (I, t), the function h
Function determining means for determining (I, t), temperature rising calculating means for performing a temperature rising calculation based on a given function, and a difference between a transmission line allowable limit temperature and a current temperature obtained by the temperature rising calculating means. And an output determining means for generating an output when the difference exceeds a predetermined value. 6. An overcurrent relay for performing overload protection, wherein at least one or more currents are included in a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of a protected object. By setting the value I _i and the time t _i (i is an integer) as variables of the function h (I, t), the function h
Function determining means for determining (I, t), temperature rising calculating means for performing a temperature rising calculation based on a given function, and setting and setting values on an overload curve obtained from the function h (I, t) Error calculating and displaying means for calculating a difference from the value, and output determining means for generating an output when the temperature obtained by the temperature rise calculating means exceeds a transmission line allowable limit temperature or a predetermined value. Over current relay. 7. An overcurrent relay for performing overload protection, wherein at least one or more currents are included in a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of a protected object. By setting the value I _i and the time t _i (i is an integer) as variables of the function h (I, t), the function h
Function determining means for determining (I, t); temperature rising calculating means for performing a temperature rising calculation based on a given function; and a current vs. time of an overcurrent relay obtained from the function h (I, t). Characteristic display means for displaying the time limit characteristic on a display panel, and output determination means for generating an output when the temperature obtained by the temperature increasing means exceeds a permissible limit temperature of a transmission line or a predetermined value. And overcurrent relay. 8. An overcurrent relay for performing overload protection, wherein at least one or more currents are provided for a function h (I, t) of a current I and a time t simulating a current-time-temperature rise characteristic of a protected object. By setting the value I _i and the time t _i (i is an integer) as variables of the function h (I, t), the function h
Function determining means for determining (I, t), temperature rising calculating means for performing temperature rising calculation based on a given function, and corresponding to a plurality of overload curves f _{1 to} f _n (n is a positive integer) Functions h ₁ (I, t) to h _n (I, t) are determined and stored,
Function selection means for outputting a corresponding function to the temperature rise calculating means when a predetermined time has elapsed or during external control, and when the temperature obtained by the temperature rise calculation means has exceeded a transmission line allowable limit temperature or a predetermined value. An overcurrent relay comprising output determination means for generating an output. 9. An overcurrent relay for performing overload protection, wherein at least one or more currents are included in a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of a protected object. By setting the value I _i and the time t _i (i is an integer) as variables of the function h (I, t), the function h
Function determining means for determining (I, t), temperature rising calculating means for performing a temperature rising calculation based on a given function, time reducing means for performing a time reduction simulation of the temperature rising calculation,
An overcurrent relay comprising: an output determination unit that generates an output when the temperature obtained by the temperature rise calculation unit exceeds a transmission line allowable limit temperature or a predetermined value. 10. An overcurrent relay for performing overload protection, wherein at least one or more currents with respect to a function h (I, t) of a current I and a time t simulating a current / time-temperature rise characteristic of an object to be protected. By setting the value I _i and the time t _i (i is an integer) as variables of the function h (I, t), the function h
Function determining means for determining (I, t), temperature rising calculating means for performing a temperature rising calculation based on a given function, and determining a temperature after a predetermined time using the temperature obtained from the temperature rising calculating means. Prediction calculation means, temperature display means for displaying a result of the temperature calculation, and output determination means for generating an output when the predicted calculation value exceeds a transmission line allowable limit temperature or a predetermined value. Over current relay.