JPS61285023A - Overcurrent relay - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an overcurrent relay having inverse timing characteristics used for overload protection.

[Technical background of the invention]

In recent years, various proposals have been made to protect motors and transformers from overload using electronic circuits. For example, JP-A-56-
The electronic overload protection proposed in No. 1728 is
In order to accurately simulate the thermal behavior of the equipment to be protected, this method interrupts one main circuit when the current i of the equipment exceeds a permissible value determined by the equipment.

As the inventor explains using Figure 3 of the above-mentioned publication, when a relatively large overcurrent continues for a short time and then changes to near the rated current, the conventional method This comparison shows that it is an effective method.

[Problems with background technology]

According to the above proposal, since the integral calculation starts after i>in, the magnitude of the steady special current that would have heated the equipment before overloading is not added to the integral calculation result. I can say that it has not been done.

In other words, although equipment generally has the characteristic of being able to tolerate large short-term overloads as the load during steady state is smaller, in the proposed method, even if the operating state before overload is no-load, the rated Regardless of the load, the protection operation is performed in the same zero operation time, and this is a serious problem in overload protection.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned problems.The present invention has been made to solve the above-mentioned problems. Another object of the present invention is to provide an overcurrent relay that prevents equipment from being turned on again depending on the degree of overload of the equipment, and that improves maintenance and testability of built-in elements.

[Summary of the invention]

The present invention provides an overcurrent relay with a characteristic that takes into account the current value at a steady load before an overload condition occurs, and for this purpose, a value KI2 proportional to the input current is introduced, From this value and the internally held previous value Sn-1, '(K'(KI2-Sn-4)+Sn
-1, (where ' is a positive constant) t- is calculated, the result of these additions is Sn, and by comparing this Sn with the operation judgment level held internally in advance, the trip is determined. It is designed to determine whether or not to send a signal.

[Embodiments of the invention]

Example 1 An example will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of an overcurrent relay according to the present invention.

In FIG. 1, l is a first means of introducing an electric current into the electric power system by a known means, and calculating an electric quantity K' (KI2) proportional to the square of the electric current by a known means such as a multiplier;
introduces 2 to the electrical quantity obtained by means of Ml, and the second
3 is a second means for calculating the addition result Sn obtained by the second means by the signal processing means shown in the figure, which will be described later. A third means for sending a trip signal is shown.

FIG. 2(a) shows an example of the configuration of the means for g2 in the embodiment of FIG.
Analog/digital (ψ) that converts into digital quantity
The converter 5 reads the electric quantity KII converted into a digital quantity, and uses this value and the internally held numerical value 51-1.
2(b) according to the processing procedure shown in the flowchart of FIG. 2(b) and calculates the addition result Snt-.

Next, the flowchart shown in FIG. 2 will be explained.

First, Step 1 is an initialization procedure, specifically, it includes all the procedures that give the initial value of the addition result SnK.

Steps and steps 8 are procedures for saving the addition result Sntl''Sn-1. Steps and steps 8 are procedures for reading the electrical quantity K' (KI2) converted into a digital quantity by the converter.

Step 9 uses the data of K'(KI2 and S.-1) to calculate '(K'(KI2 -81-1) + s,,
, (x/ is a positive constant) and set the result as Sn. Step 10 shows a procedure for making the addition result Sn the output of the second means.

FIG. 3(1) shows an example of the configuration of the third means in the embodiment of FIG. 11 reads the input amount Sn, and combines this value with the internally held numerical value L? The microcontroller is comprised of a microcomputer, etc., and determines whether or not to send a tripping signal according to the processing procedure of the flowchart shown in FIG. 3(b)K.

In the flowchart of FIG. 3(b), step 12
is the procedure to read the input amount Sn. Stella 7'13 is a procedure for determining the magnitude relationship between the read input amount S3 and the expected value LT. Steps 14 and 14 are procedures for blocking the tripping signal. Step 15 is a procedure for sending a trip signal.

Next, the operation of the second means will be explained. It has already been mentioned that the addition result Sn of the second means is calculated by the following equation.

Sn==ni'(K'(KI2-Sn-1) +Sn-1
・rl) When this is transformed, the following equation (2) is obtained.

Sn Sn-1"K'(K'(KI2-Sn-1)
``'(2) The left side of equation (2) represents the increase/decrease in the addition result Sn during the time (Δt) in which the processing completes one cycle in the flowchart.

Here, if this time Δtt is an extremely short time, then (2
) can be approximated by the following equation.

Su=ni'(K'(KI2-8) ・
...(3)t Using this approximation formula, when the input current I changes, Sn
Explain how it changes.

(1) When the input current I changes like a step function. Figure 4 (,) shows the case where the input current changes from zero like a step function. In this case, the function value S is s -KIz (1-e
−”' ) −(4).

That is, it can be said that the function value S has a constant time constant on both sides of KI2.

The time when this function value S becomes the scheduled value LT is K'(KI2
(1-e-”t)≧Lt t-By solving, I
It is expressed as Lt t≧-H, log (1-stone 2).

Therefore, the larger the input current, the shorter the time it takes for the function value S to reach the expected value.

FIG. 4(b) shows a case where the input current changes from k' in a step function manner, and the function value S in this case is S = (K' (KI
2 -K(1')"(1-e-")+K(I')"
...It is expressed as (5). The function value S in this case is
Planned value L? The above time is similarly expressed as t≧−j71og(1−伶千舒)I′. As shown in the figure, under the conditions of I>I', K(x')'(tT(['), therefore, when there is a prior current I',
When there is no preliminary current (as shown in Figure 4 (, ))
The time required for the function value S to reach the expected value LT is shorter than that shown in FIG.

(2) If the input current I is intermittently overcurrent, the 4th
Figure (c) shows a case where the input current is intermittently overcurrent, and the function value S in this case changes exponentially as shown. This is clear from the fact in FIG. 4(&)#(b) that "the function value S follows the input amount K' (KI2 by a -order function"), and detailed explanation will be omitted.

As is clear from the figure, when the input current (2) intermittently becomes an overcurrent, the function value S follows the input (with a constant time constant).

Therefore, in this case, the time required for the function value to reach the expected value LT is shorter than in the case shown in FIG. 4(-).

As described above, the relationship between the input current factor and the function value S generally also holds true for the relationship between the input current factor and the addition result Sn.

Next, the operation of the third means will be explained. The third means compares the addition result Sn obtained by the second means with the predetermined value Lt', and when Sn≧L〒, sends out a tripping signal, and when Sn<LT, blocks the tripping signal. It is.

Here, the value of the planned value L↑ is generally selected such that LT, > KI: with respect to the rated current X of the protected equipment.Next, the effects of this embodiment will be explained.

(1) When the input current l changes as shown in FIG. 4(a) K, in this case the output Sn of the second means
increases with time like S shown in the figure. After 15 o'clock t = -K1 o g (1-Kr), Sn becomes larger than L7, so a tripping signal is sent from the third means, and the interrupter (not shown) is tripped. , carry out equipment overload protection.

(2) When the input current I changes as shown in FIG. A disconnection signal is sent, tripping an interrupter (not shown) and implementing overload protection for the equipment.

FIG. 5 shows an example of the operating time characteristics of this overcurrent relay, where LT ""K(1,15XIn)", (In!
! equipment rated current), 17R' -700 seconds, (time constant)
This shows the characteristics when selected.

As is clear from the drawings, the relay of the present invention has operating time characteristics such that when the steady load current I' of the protected equipment is small, the operating time is slow, and when the steady load current I' is large, the operating time is fast. Therefore, it is possible to provide more accurate overload protection than conventionally proposed methods.

(3) Even when the input current changes as shown in FIG. 4(e), the output Sn of the second means increases and decreases with time as shown in the figure, so for example, a short-term overload Even if a long-term overload continues to occur after a short-term overload has occurred, the history of short-term overloads will be
Therefore, the operating time of the relay becomes faster depending on the value of Sn, which is the sum of the times at which a long-term overload occurs, and highly accurate overload protection becomes possible. It can be said that there is no concern that failures such as delays in overload protection due to overlooking short-term overloads will occur as in conventional proposals.

As explained above, this embodiment has the feature that the operating characteristics change in the same manner as the equipment characteristics depending on the magnitude of the steady-state load, so it has a higher performance than the conventionally proposed ones. The present invention realizes an overcurrent relay that enables accurate overload protection.

Embodiment 2 FIG. 6 is a block diagram of another embodiment of the overcurrent relay according to the present invention.

In FIG. 6, the parts having the same functions as those in FIG. Reference numeral 16 denotes a second means which introduces the electric quantity Klj obtained by the first means and calculates the addition result by the signal processing means shown in FIG. 7 and which will be described later. The second means includes means for setting the addition result Sn to a predetermined value when an external command signal is received from an external device or a control switch (not shown).

FIG. 7(,) is an example of the configuration of the second means in the embodiment of FIG. 6, and the reference numeral 4 corresponds to FIG. 2(a). 1
7 is a microcontroller that reads the electric quantity KII converted into a digital quantity, and calculates the addition result Sn by adding this value and the internally held numerical value Sn-1 according to the processing procedure in the flowchart described later. Composed of Ashi, Micro Combi, and Yuu. Furthermore, it has a function of forcibly setting the addition result S to a specific value based on external command conditions.

Fig. 7) is a 70-chart for explaining the process, and ST2) '6, 7, 8, 9, and 10 are the same as those in Fig. 2). Steps 18 and 18 are procedures for determining the presence or absence of an external command, and if there is no external command, the process proceeds to steps 7, 8, 9, and 10, and is similar to that shown in FIG. If it is determined in step 18 that there is an external command, the process moves to step 19, where the addition result is forcibly set to SnMA.

Here, the following values can be considered as the value of A.

■　A-0 ■　A proverb ■ A-Lτ+α (α is positive or negative) Specific explanations of these will be given later.

Next, the effect will be explained. First, if there is no external command, it is obvious that the embodiment is the same as the embodiment shown in FIG. 1 already explained, and the explanation fIA"ft will be omitted. Therefore, the operation when there is an external command will be described below.

■ In the case of A-0 In this case, as is clear from the flowchart, the output 8 of the second means has steps for initialization s, m o as well as f6, so in the third means , Sn≧
The condition L↑ is not satisfied, and no tripping signal is sent from the relay.

(2) Case of A- In this case, the output 81 of the second means becomes SnsIIK as is clear from the 70- chart. This is the constant rated current for the relay! , t - is equal to the value of the addition result C when the current is flowing. Therefore, generally 8>Lr
The condition is not satisfied, and no trip signal is sent.

(2) In the case of A−L+α In this case, the output S1 of the second means becomes +α, as is clear from chart 7a. And α〉
In the case of 0, the value of the addition result Sn is set to the operation judgment level Lt.
This means setting it to a slightly larger value.

Therefore, the condition of Sn>L〒 is established, and a tripping signal is sent out by the third means.

In the case of α×O, it means that the value of the addition result Sn is set to a value slightly smaller than the operation determination level LT.

Therefore, Sn≧L? The condition is not satisfied, and the trip signal is not sent from the relay.

Next, before explaining the effects of this embodiment, the background technology will be explained. That is, as in the present invention, the internal state of the relay (specifically, the value of Sn) is determined by the past input condition (specifically, the input current I).
(history) and has a long time constant, there is a problem that it takes a long time to test the relay.

Here, the operating time of the relay is measured using the operating time from zero input (called cold characteristic) as shown in Figure 4(a).
And, the operation time from the presence of input as shown in Fig. 4(b) (
However, in any case, in order to accurately measure the operating time, the internal state of the relay must be steady, that is, the value of the addition result Sn must be almost constant. It is necessary that it remains constant. For this reason, it is generally necessary to maintain this for a longer time than the internal time constant, with zero input in the former case, and with input (steady value) in the latter case, and then measure the operating time. be. However, as shown in the example of FIG. 5, the internal time constant is usually as large as several hundred seconds, and it is not efficient to require such a long time for -1 tests.

Therefore, the present embodiment is intended to improve such unreasonableness, and since the internal state of the relay can be instantaneously set by an external command, it does not require a long period of time for - times of testing as described above.

For example, to measure the operating time from zero input, the trap is
It is sufficient to give an external command as -0 and then measure the operating time by applying a predetermined current ■.Also, in order to measure the operating time from the input amount, set the external command as A-. After that, it is sufficient to energize the specified electrician and measure the operating time. Also, A! By giving an external command as LT+α(α〉0) and checking the operation of the relay at this time, the operating side can be inspected as A m LT+α(α〈
By giving an external command as 0) and confirming that the relay is not operating at this time, it is possible to inspect the non-operating side, which also improves the maintainability of the relay compared to conventional methods.
By measuring the return value, operating value and return value tests can be performed in a very short time.

As explained above, this embodiment is an overcurrent relay for overload protection, which has the features of the embodiment shown in Fig. 1, as well as superior functions that improve maintenance and testing work compared to the conventional one. can be realized.

Embodiment 3 FIG. 8 is a block diagram of another embodiment of the overcurrent relay according to the present invention. Reference numerals 1 and 2 have the same functions as in FIG. 1, and the explanation thereof will be omitted.

20 is a third means, which introduces the addition result Sn obtained by the second means 2, connects to the protected machine, and performs a display for waiting for the interrupter to be turned on.

FIG. 9 (Otori) is an example of the configuration of the third means in the embodiment of FIG.
It is constituted by a microcontroller, a microcomputer, etc., which determines whether or not to send a trip signal and an indication signal from Lr (Lt)Lt) according to the processing procedure of the flowchart shown below. Incidentally, 22 is a display device for making a display to wait for the interrupter to be turned on.

FIG. 9(b) is a flowchart illustrating the process. Steps 12, 12 are the same as those in FIG. 3, so the explanation will be omitted. Steps 7'' and 23 and 24 respectively indicate procedure 1 for determining the magnitude relationship between the read input quantity and the operation judgment level LTpLl.Here, steps 25 and 25 output a tripping signal in the case of Sn-L? This shows a procedure for sending out a trip signal and lighting up the display 22. Steps 26 and 26 show a procedure for lighting only the display 22 without sending a trip signal when Sn≧L! .And Step 27 is Sn(L
This shows a procedure for not sending out both a tripping signal and a display signal in the case of x. Note that the difference between this embodiment and the embodiment shown in FIG. The difference is that there is a display to wait for the interrupter to be turned on. That is, in the relationship between the input current of the relay and the tripping signal, there is no difference between this embodiment and the already explained embodiment of FIG. 1. Therefore, the explanation of the effects of this embodiment will be limited to the display, which is the characteristic part.

First, let's talk about the need to wait for the interrupter to be turned on.
This will be explained using the example shown in Figure 0.

Figure 10 shows a power outage in the system connected to equipment that is in rated operation for some reason, and as a result, the equipment is disconnected from the system by an undervoltage detection protection device (not shown), and then the power is restored and the equipment is disconnected from the system. Sn≧L? The condition is met, and as a result, a decoupling signal is sent, and the interrupter (C
B) is the bird.

This indicates that the device has been disconnected from the grid.

Note that during rated operation, the addition result Sn is relatively at the operation judgment level L? Therefore, if the power is turned on again after being stopped for a short time, the resulting starting current will often exceed the overload protection level of the equipment.

This can result in failure in attempts to rejoin equipment that has been separated from the grid due to a transformer load, causing unnecessary disturbance to the grid and prolonging the outage of equipment. I don't like it.

In the past, to prevent this problem, it was necessary to wait for a while before turning on the circuit breaker again and wait for the equipment to sufficiently recover from the overload condition, but on the other hand, it is preferable to stop the equipment for a short period of time. Naturally, the demands are strong.

This embodiment is intended to solve the above-mentioned problems.
By clearly informing operators whether or not equipment can be re-injected, the probability of re-introduction failure is greatly reduced.

The operation of this embodiment will be explained using the example shown in FIG.

Figure 11 shows a situation in which a power outage occurred for some reason in the system connected to equipment that was in rated operation, and as a result, the equipment was temporarily suspended from the system by an undervoltage detection device (not shown), and then the power outage was restored. 't-representing.

As is clear from the figure, the addition result Sn gradually decreases from a substantially constant value during rated operation during power outage.

However, when the power is restored, the display becomes Sn)L, and therefore the display 22 remains lit. Then, as time passes further, the addition result Sn further gradually decreases until Sn<LI, and the display 22 turns off. Therefore, the operator turns on the equipment again, and at this time a starting current is generated in the same way as described above, but the addition result Sn is at the operation judgment level LT.
Since it is sufficiently smaller than Lr, Sn will not exceed Lr, and therefore the equipment will not be shut off again when it is turned on again.

In short, the interrupter (CB) in FIGS. 10 and 11
) Comparing the magnitude of the value of Sn at the time of reinsertion, the former is S
n2RL〒, the latter is Sn''Lt (Lr>Ll), and it can be said that the latter has more margin for the overload limit of the equipment. Generally speaking, the latter (this example) is not possible for the AL appliance to respond to an overcurrent (this takes into account inrush current, etc.), make an exception again, and send out the entire signal. It is possible to prevent almost all failures.

As described above, in addition to the features of the embodiment shown in FIG. 1, this embodiment can realize a T.6 electric appliance for overload protection that can prevent failure in re-attachment of equipment.

Embodiment 4 FIG. 12 is a circuit diagram showing the application of another embodiment of the present invention, in which 28 is a bus bar, 29 is an interrupter (CBλ30 is a current transformer (CT), and 31 is a circuit diagram of the embodiment according to the present invention). Overcurrent relay 32 indicates equipment to be protected against overload.

Here, the interrupter 29 is controlled by a trip signal and a closing signal sent from the overcurrent relay 31. That is, the tripping signal opens the interrupter, and the closing signal invalidates the closing command of a device that issues a closing command (not shown), thereby keeping the interrupter open.

The configuration of the overcurrent relay 31 is as shown in FIG. A tripping signal and a closing prevention signal are transmitted by the third means shown in FIG.

Note that since the first means and the second means have already been described, the third means, which is a characteristic part of this embodiment, will be explained.

FIG. 13 (,) reads the input amount Sn, and calculates this value and the operation determination levels LT and L that are stored internally in advance.

(However, Lr) Lc) is a microcontroller that determines whether or not to send a tripping signal and a closing prevention signal according to the processing procedure shown in the flowchart shown in FIG. be done.

Steps 23 and 34 of the flowchart shown in FIG. 13(b) show procedures for determining the magnitude relationship between the read input amount Sn and the operation determination level LT p IJC. Step 35 shows a procedure for sending out a tripping signal and sending out a closing prevention signal when Sn≧L〒. Also, ST, G36 is Lt > Sn > Lc
This shows the procedure for sending only the closing signal without sending the tripping signal in the case of . Furthermore, in step 37, Sn<
The procedure for not sending both the tripping signal and the closing prevention signal in the case of Lc is shown.

The difference between this embodiment and the embodiment shown in FIG. 8 already explained is in the configuration of the third means. In contrast, in the present embodiment, a closing prevention signal is directly sent to the circuit breaker.

Therefore, the explanation of the effects of this embodiment will be limited to this characteristic part, the input prevention signal.

The need to wait for the interrupter to be turned on has already been explained, and in the embodiment shown in FIG. This embodiment provides a method for improving the problem when the interrupter is automatically turned on.

The response of this embodiment can be easily understood by replacing the operation determination level Lf with Lc and the lighting of the display with the sending of the input prevention signal in the response of the embodiment shown in FIG.

That is, to explain this example in the same manner as in Figure @11, which has already explained this example, a power outage occurs for some reason in the system connected to equipment that is in rated operation, and as a result, an undervoltage detection device (not shown) causes the equipment to malfunction. This shows the power outage being interrupted from the power grid and then being restored. At this time, the addition result S
Yu gradually decreases from a nearly constant value during rated operation during a power outage.

However, when the power is restored, Sn>Lc, and therefore the input prevention signal continues to be sent.
The input circuit is disconnected from the interface and the interrupter is never activated. Next, as time passes, the addition result Sn
gradually decreases, and eventually Sn<Lc, and the closing signal is restored, and the closing circuit is released.

As a result, if there is a breaker closing command, the breaker will be automatically closed. As mentioned above, when the interrupter is turned on, the addition result Sn increases due to the starting current, but Sn≧L.

is not reached and therefore no trip signal is sent out.

In short, in this embodiment, instead of issuing a warning to the operator in the embodiment shown in FIG. It can be said that this is the same as the embodiment shown in FIG.

Embodiment 5 FIG. 14 is a circuit diagram showing the entire application of another embodiment of the present invention, and the symbols 28, 29, 30 and 32 have the same functions as those already explained in FIG. The explanation will be omitted. 38 is an overcurrent relay of this embodiment according to the present invention, 3
9 is a temperature sensor that measures the ambient temperature of the protected device, the ambient temperature of the contents stored in the protected device, or the ambient temperature of the protected part of the protected device, and uses the measurement result as a temperature signal θ to connect the overcurrent relay. 38. In addition, the configuration of the overcurrent relay 38 is such that the air flow K' (KI2lk is obtained by the first means described above, and the addition result Sn is obtained by the second means described previously, and further, as shown in FIG. 15 (1). The third means also uses the temperature signal θ obtained from the temperature sensor 39 to send out a trip signal.

Here, since the configurations of the first means and the second means have already been described, the third means, which is a characteristic part of this embodiment, will be explained.

FIG. 15 (,) is an example of the configuration of the third means of the relay in FIG. From the motion determination level LT,k (>O), Fig. 15 (
In accordance with the processing procedure shown in the flowchart shown in b), it is determined whether or not to send a tripping signal.The microcontroller is comprised of a microcomputer, etc.

In the flowchart shown in FIG. 15(b), steps 41 and 42 show the procedure for reading the temperature signal θ, and steps 42 and 42 show the procedure for reading the temperature signal θ and the operation judgment level LT. The procedure for determining the size relationship is shown.

The other stages, 7'12, 14 and 15, are placed in the third position first.
Since it is the same as that explained in the figure, the explanation will be omitted.

The difference between this embodiment and the embodiment shown in FIG. The point is that the reference amount for this is controlled by the temperature signal θ.

That is, in the third means, using the addition result Sn obtained in the second means, the temperature signal θ, and the operation judgment level L, the trip is performed when S > (L↑− to θ). Send a signal.

S! When l<(L!- θ), no tripping signal is sent.

It is something. Here k) is selected as 0, and the operation judgment level L
When 〒 is the amount of continuous operating current at the ambient temperature θ1 of the protected equipment, it is generally selected so as to satisfy (L〒-to θ,)>KII'. The value of (L〒- to θ) mentioned above increases as the ambient temperature decreases, so the lower the ambient temperature,
It can be said that if the value of the addition result Sn is large, a tripping signal (from the relay) will be sent. Therefore, it can be seen that the overcurrent relay of this embodiment operates with a larger input current I as the ambient temperature is lower, and the operating time becomes slower for the same overcurrent.

For example, the operating time of a relay when the input current I changes as shown in FIG. Figure 16 shows the operating time characteristics of this overcurrent relay.
Here, at an ambient temperature of θ - 30°C, the device continuously allows a current of 1.15 times the rated current In, and also allows an overload of 0.8 inches for every 1°C drop in the ambient temperature θ. Ly-(1+0.008x30)xKx(1,15xI
,))"k-=0.008xKx(1,15xIn)"
This shows the characteristics when 1/ic' -700 seconds (time constant) is selected.

Generally, single-power equipment can be subjected to a larger load as the ambient temperature decreases.

For example, overload operation guidelines for power transformers (Noboru Ooka).

“Transformer” by Sadao Maeyo, Tokyo Denki University Press series, 196
8) provides the following explanation. In other words, ``Every time the maximum daily temperature of the cooling air drops by 1℃ below 30℃, the overload can be applied by 0.8% of the rated output.This is independent of the cooling method; for example, if the maximum ambient temperature is 10℃ For °C, 0.8X(30-10)-16%
Can be overloaded. However, even if the temperature of the cooling air or cooling water is 0°C or lower, it is not possible to overload it more than when it is at 0°C. By the way, conventional overload protection overcurrent relays rely solely on the magnitude of the device's current to detect overloads, regardless of the ambient temperature. Even if the equipment has increased margin against overload, it is possible that the equipment may stop operating under certain current conditions, or conversely, the ambient temperature may rise and the equipment may have less margin against overload. Even when the current is gone, protection is delayed because only the current conditions are looked at, and there are concerns that this could lead to malfunctions that could damage the equipment. However, in this embodiment, since the ambient temperature θ is used as a condition for determining operation, the occurrence of such problems can be significantly reduced compared to the prior art.

Embodiment 6 FIG. 17 shows another embodiment of a modified overcurrent relay according to the present invention. The only difference in this embodiment is that the way the input current is taken in is modified and the calculation position of the 2-day power value is changed.

That is, as the configuration is shown in FIG.
3 is an input circuit that introduces the amount of current from the power system by a known means and sends out a V lamp with an amount of electricity proportional to the amount of current, and 44 is an analog that converts the amount of electricity obtained from the input circuit 43 into a digital amount. - A digital (VD) conversion circuit 45 reads the electrical quantity iI converted into a digital quantity, and uses this value and the internally held numerical value Sn-1 to process the flowchart shown in FIG. 17(b). This is a microcontroller that performs arithmetic processing according to procedures and determines whether or not to send out a trip signal.

In the flowchart of FIG. 17(b), step.

7'6, 7, 9, 13, 14, and 15 have the same functions as those shown in FIG. 2(b) and FIG. 3(b), so the explanation will be omitted. In addition, the procedure for reading the electric quantity V lamp converted into a digital quantity from the converter 44 will be described. Further, Step 47 shows a procedure for calculating this square value KI2 using the above-mentioned drunkenness data.

Therefore, the operation of this embodiment is as follows.

First, the input circuit 43 converts the amount of current from the introduced power system into an amount of electricity. Next, this quantity of electricity 4 is converted into a digital quantity by a converter 44 and introduced into a microcontroller 45, where a square value KIIi is obtained.

Furthermore, this data K' (from KI2 and Sn-1, K'
(K'(KI2-sn, ) +Sn-t t-operation, and the result is the full addition result Sn. Then, this Sn
When Sn is equal to or higher than the operation determination level L〒, a tripping signal is sent out, and conversely, when Sn is less than LtK, no tripping signal is sent out. Thereafter, it is replaced with data SntSn-1, and the same operation is repeated.

This is because the embodiment shown in FIG.
2, then ψ conversion, and the process is performed using the value K' (KI2, whereas in this embodiment, the current amount Ii is converted to the electrical amount 4I, and then ψ conversion is performed, and the value 4I
Th is further squared and processed as KIj. Therefore, there is no essential difference between this embodiment and the embodiment of FIG. is the same as in Figure 1. That is, the present invention does not have the feature of the structure in converting the electric quantity KI2, but instead converts the electric quantity J2 into Y as in the embodiment of FIG.
After converting I, the square value K' is obtained by digital calculation.
(Of course, it is also possible to adopt a configuration that obtains KI2.

In each of the above embodiments, single-phase current was used to simplify the explanation, but instead of this, two-phase or three-phase current was introduced,
A symmetrical current synthesized from these may be used, and
As the amount of current, not only an effective value but also an average value or a maximum value may be used.

〔Effect of the invention〕

As explained above, according to the present invention, the operating characteristics are changed according to the magnitude of the steady-state load, and the possibility of re-starting is determined according to the degree of overload. It is possible to provide an overcurrent relay that provides good overload protection and is easy to maintain and test.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the overcurrent relay according to the present invention, FIG. 1) is an example of the configuration of the third means, FIG. 3(b) is a flowchart explaining the operation, and FIG. 4(,) is the operating time when the input current changes from zero to step function. A diagram explaining
Figure 4(c) is a diagram explaining the operating time when the input current changes from a predetermined value as a Stellar f function, and Figure 4(c) is a diagram explaining the entire operating time when the input current changes intermittently. , FIG. 5 shows the operating time characteristics of the overcurrent relay according to the present invention, FIG. 6 is a configuration diagram of another embodiment, FIG. Fig. 7(a) is a flowchart explaining the entire operation of the embodiment of Fig. 6, Fig. 8 is a block diagram of still another embodiment, and Fig. 9(,) is a configuration example of the third means of Fig. 8. 9(b) is a flowchart showing the operation of the embodiment of FIG. 8, FIG. 10 is a diagram fully explaining the necessity of waiting for the interrupter to be inserted, and FIG. 11 is a detailed diagram of the present invention. FIG. 12 is a circuit diagram showing the application of another embodiment of the present invention, and FIG. (b) is a flowchart explaining the entire operation of the overcurrent relay in Fig. 12;
Figure 15 is a circuit diagram showing the application of another embodiment of the present invention.
Figure 15 (b) is a flow chart explaining the entire operation of the overcurrent relay shown in Figure 14, and Figure 16 is a diagram showing the configuration of the third means of the overcurrent relay in Figure 14. The operating time characteristics of the overcurrent relay shown in Fig. 17(a)
is a block diagram of still another embodiment, and FIG. 17(b) is a flowchart explaining the operation of the embodiment of FIG. 17(a). 1...First means, 2...Second means, 3
．． 20...Third means, 4.44...A/l) converter, 5.11, 17, 21, 33.40, 45...
・Microcontroller, 22...Display device,
28...Bus bar, 29...Interrupter, 30
...Current transformer, 32...Protected equipment, 31.3
8... Overcurrent relay, 39... Temperature sensor. Patent Applicant Toshiba Corporation (and 1 other person) Agent Patent Attorney Nori Ishii Ojima Figure 1 (α) Figure 2 (α) (b) Oni Figure 3 (b) (C) Seiji Figure 4 (Conditions) Input Current (11 Yu current 1-= number) 5th ward Oni 6 figure (α) List 9 figure 10 '-1'' 8 figure 11 (α) (b) Party 13 figure input current (rated current T1 ＠＠ り 16 fig. (α) (b') 范 17 fig.

Claims (6)

[Claims] (1) In an overcurrent relay having an inverse time limit characteristic used for overload protection, a first means for calculating a value KI^2 proportional to the square of the current, and a value calculated by the first means are used. a second means for adding and calculating the addition result S_n; and a third means for producing an output when the calculated value of the second means exceeds a predetermined value; The addition is a value K' (KI^2-S_n_-_1), which is proportional to the difference between the calculated value KI^2 of the first means and the calculated value S_n_-_1 of the second means before the present time, (however, K, K
' is a positive constant) and a previously calculated value S_n_-_1. (2) The overcurrent relay according to claim 1, wherein the predetermined value is a constant value. (3) The overcurrent relay according to claim 1, wherein the predetermined value decreases as the ambient temperature of the protected portion or the object stored therein increases. (4) In an overcurrent relay having an inverse time limit characteristic used for overload protection, a first means for calculating a value KI^2 proportional to the square of the current, and a value calculated by the first means are used. a second means for adding and calculating the addition result S_n; and a third means for producing an output when the calculated value of the second means exceeds a predetermined value; The addition is a value K' (KI^2-S_n_-_1), which is proportional to the difference between the calculated value KI^2 of the first means and the calculated value S_n_-_1 of the second means before the present time, (however, K, K
' is a positive constant) and the calculated value S_n_-_1 before the current time, and the second means is added with means for forcibly setting the calculated value to a specific value by an external command. An overcurrent relay characterized by: (5) In an overcurrent relay having an inverse time limit characteristic used for overload protection, a first means for calculating a value KI^2 proportional to the square of the current, and a value calculated by the first means are used. a second means for adding and calculating the addition result S_n; and first and second means corresponding to each of the predetermined values when the calculated value of the second means exceeds the first and second predetermined values. a third means for generating an output, a fourth means for tripping the circuit breaker by the first output, and a fifth means for preventing closing of the circuit breaker by the second output. , the first predetermined value is set to be larger than the second predetermined value, and the addition of the second means is based on the calculated value KI^2 of the first means and the calculated value of the second means before the present time. S_n
The value K'(KI^2-S_n_
-_1) (where K and K' are positive constants) and a previously calculated value S_n_-_1. (6) In an overcurrent relay having an inverse time limit characteristic used for overload protection, a first means for calculating a value KI^2 proportional to the square of the current, and a value calculated by the first means are used. a second means for calculating the addition result S_n; and when the calculated value of the second means exceeds the first and second predetermined values, the first and second outputs correspond to the respective predetermined values. a fourth means for tripping the circuit breaker by the first output; and a fifth means for displaying an indication to wait for closing of the circuit breaker by the second output. , the first predetermined value is set to be larger than the second predetermined value, and the addition of the second means is based on the calculated value KI^2 of the first means and the calculated value of the second means before the present time. S_
The value K'(KI^2-S_n
_-_1) (where K and K' are positive constants) and a previously calculated value S_n_-_1.