JPS6032212A - Circuit breaker - 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 a circuit breaker that detects fault currents in electrical circuits and allows optimal protection.

[Prior art]

Generally, a circuit breaker equipped with a microcomputer is configured such that the ability to shut off a fault current in an electric circuit is obtained by executing a predetermined program stored in ROM K6 in the microcomputer. There is. The above-mentioned time-interrupting property is normally designed to provide an inverse time-limiting property as shown in FIG. 1 in order to protect the electric circuit and the load. In general, the interruption property shown in FIG. 1 is set in consideration of the heat resistance of the distribution line, the blowout characteristics of the upper fuse, and the like. Conventional equipment of this type M,
separable contacts, current sensor means for detecting fault current;
The device is configured to include means for sampling the detection signal at a predetermined sampling rate, means for determining the level of the detection signal, and means for performing a time-limiting operation based on the inverse time-limiting characteristic as shown in FIG. 1 corresponding to the level. was. In order to cope with the above-mentioned case, it is possible to take into account the heat dissipation characteristics of the electric circuit and load and store the heat dissipation characteristics in the above-mentioned program. Generally, it is known that the heat dissipation characteristics of power distribution lines and loads have such characteristics that the temperature is attenuated. Therefore, based on this attenuation characteristic, a device that can respond to fluctuations in fault current, etc. can be realized within a microcomputer.

However, when performing processing in consideration of the heat dissipation characteristics as described above in a program, the following problem occurs. That is, when calculating on a program, a complicated and enormous program is required to obtain heat dissipation characteristics with high accuracy. Therefore, the processing time becomes very long, making it difficult to achieve optimal protection. On the other hand, the above calculation results are RO
If the program is stored as a data table in M, the program itself can be shortened, but in order to obtain accurate heat dissipation characteristics, the amount of data becomes enormous and a large-capacity ROM is required. Particularly when using a one-chip microcomputer, the capacity of the ROM is extremely limited and cannot store sufficient data, making it difficult to obtain optimal characteristics.

There is also an even more serious problem. That is, when the power supply temporarily trips or disturbances such as surges and noises enter, the electronic computer is reset. When the microcomputer is restarted after such an unexpected reset operation, all processing is restarted from the beginning in conventional devices, and the data stored up to that point is also erased.・This is a major problem regarding the basic function as a circuit breaker. Furthermore, this problem has a particularly serious effect when the secondary output of the current sensor means is used as a power source for a microcomputer. That is, in the case where no fault current or normal current flows, the above-mentioned restart process is executed each time for intermittent current because the operating power supply for the microcomputer is exhausted. Therefore, it has the disadvantage that thermal protection (that is, the operation of cutting off the current according to the amount of heat generated by the excessive current) cannot be performed at all.

The present invention has been made to solve the problems in conventional devices as described above. In other words, when the fault current returns to a normal state by generating an exponential attenuation characteristic based on the heat dissipation characteristics using the discharge characteristics of the capacitor, the alternating current of the capacitor is reduced at a rate of the duration of the fault current to a predetermined time period. Change the voltage. By doing this,
We aim to provide a small and inexpensive device of this type that can shorten the time required to perform calculations based on heat dissipation characteristics and provide ideal heat dissipation characteristics without the need for storage means for huge data tables. It is something to do.

Another object of the present invention is to provide a microcombustion breaker that uses the residual voltage of the capacitor as an initial value when a fault current flows again.

The present invention will be clarified by describing embodiments of the present invention in detail below using the drawings.

FIG. 2 is a block diagram showing an overcurrent detection device as an embodiment of the present invention. In FIG. 2, 201 is a power supply side terminal to be connected to the power supply.

The power supply side terminal 201t is connected to a load side terminal 203 via a breaking contact 202. The power supply side terminal 201
A current detector 20 for detecting current is provided in the electric path 10 between the load-side terminal 203 and the load-side terminal 203 . A rectifier circuit 30 for obtaining the absolute value of the secondary output is connected to the secondary side of the current transformer 20. A burden circuit 40 is connected to the output side of the rectifier port w530. The burden circuit 40 converts the output current of the current transformer 20 into a voltage signal, and also serves as a level adjustment circuit for obtaining an output signal within a predetermined level range. The output side of the load circuit 40 is connected to a waveform conversion circuit 90. The waveform conversion circuit 90 is for obtaining the effective value of the output signal induced in the burden circuit 40. Waveform conversion port Wr90
The output terminal is the input terminal 10 of @l of the A//D conversion circuit 100 that converts the analog output signal into a digital signal.
Connected to 1. The output of the vD conversion circuit 100 is input to a microcomputer 110. The microcomputer 110 has an output port 117.
a and 117b are provided. This output boat】1
An output device 80 is connected to 7a. This output device 80 includes, for example, a cylisk as an actuating device, a release engraving magnetic tripping device for opening the opening contact 202, and the like. That is, the output device 80 is provided 50 so as to be mechanically interlocked with the breaking contact. A resistor 61 (for public use) is arranged in parallel with this capacitor 50. A diode 70 is connected between the output port 117b of the microcomputer 110 and the other end of the MO capacitor 50 in the forward direction toward the capacitor 50 (for backflow prevention). A charging resistor 62 is connected to the anode side of the diode 70.

The configuration of the microcomputer 110 will be outlined based on the block diagram of FIG. In FIG. 3, the microcomputer 110 has a data bus 112 of a CPU 111.
and the ROM 114° RAM via the address bus 113.
1is and I10 ports 116. Iq boat 116 output points 17a, 117b t
As stated in riMfT, the output device 80. It is connected to the anode of diode 70. Parts of the data bus 112 and address bus 113 are connected to the A/D conversion circuit 100. - The ROM 114 contains a program for executing predetermined signal processing, and the CPU 111 executes the program in synchronization with a predetermined clock signal. The RAM 115 still functions as seven registers necessary for signal processing.

The signal processing process in the above-mentioned microcomputer 110 is shown in the main flowchart of FIG.

This flowchart includes at least a level determining means 1001 for determining the level of an input signal as a basic function.
and a time limit generating means 1002 for executing a predetermined time limit operation based on the level determined value. In addition, this flowchart is designed to operate the circuit breaker according to the above-mentioned discharge characteristics and heat storage characteristics, so if overcurrent continues and the current value fluctuates, Means 1003 for generating accurate heat storage characteristics
It is included.

The operation of the apparatus of the present invention configured as described above will be explained below.

When a fault current flows through the electric line 10, the current transformer 20 detects the fault current at its own current transformation ratio and induces an output current on the secondary side. This output current is converted into direct current by the prefectural current circuit 30. This DC-converted output current of the rectifier circuit 30 is supplied to the burden circuit 40. The output signal of burden circuit 40 is converted by waveform conversion circuit 90 into a signal corresponding to its effective value. The effective value output of the waveform conversion circuit 90 is input to an A/Df conversion circuit 100. The OA/D conversion circuit 100 is controlled by a microcomputer 110 and converts the input signal into a digital signal in a time-sharing manner. These digital signals are connected to the data bus 112 of the microcomputer 110.
supplied to The microcomputer 110 executes level determination of these digital input signals according to a predetermined program. Further, based on the result of this level determination, a predetermined time-limited operation is performed and an output signal is generated from the output capo 117a. The time-limited operation in this case is performed, for example, along the characteristic curve shown in FIG. Microcomputer 11
The output device 80 is driven by the output signal emitted from the output port 117a.

When the output device ft 80 operates, a break-off contact 202 mechanically interlocked with the output device ft 80 opens, and the current in the electric circuit is cut off.

Next, a case in which the current in the electric circuit returns to a normal state below the rated value within a predetermined time period will be described based on FIGS. 4 and 5. FIG. 4 is a characteristic diagram showing the state of change in the current flowing through the electric path and the operating characteristics of the circuit breaker of the present invention. Further, FIG. 5 is a waveform diagram showing how the capacitor 50 is charged and discharged. As shown in FIGS. 4 and 5, when the fault current (1) returns to the normal current (2) before a predetermined operating time (i.e., time limit) elapses, the microcomputer 110 controls the output port according to a predetermined program. 11
7b outputs a square wave voltage output (one shot pulse) as shown in FIG. 5(a). This square represents the actual duration T of the fault current with respect to the operating time T1 determined by the magnitude of the fault current ■1. The ratio *”rr.

has a pulse width having a predetermined relationship with . With such a square wave voltage output, the charging resistor 62 and the voltage are connected to each other.

Capacitor 50 is charged through diode 70.

As shown in FIG. 5(b), the capacitor 50 is discharged at a predetermined time constant through a discharging resistor 61 until a fault current is detected by a person after the capacitor 50 has finished charging once. Next, when the fault current flows again, the microcomputer 11
0 determines the level of the input signal from the A/Df conversion circuit 100, and executes the program again to perform the predetermined time j (ilJ operation). At this time, the microcomputer 110 The voltage level is read through the A/Df conversion circuit 100, and the read voltage level is processed as an initial value for generating a new time limit.

As shown in FIG. 5(b), the voltage waveform of the capacitor 50 during the above-described charging operation is a curve having a constant time constant. This nonlinear characteristic can be easily linearized by correcting it by changing the charging voltage in an inverse exponential manner, or by correcting data in the microcomputer 110 when the voltage of the capacitor 50 is read. Also, by charging the capacitor 50 with a constant current, the fifth
It is also possible to obtain a linear charging characteristic as shown in Figure tc+K. In this case, even if the voltage output of the capacitor 50 is used as it is, sufficient practical circuit interoperability can be obtained.

The signal processing process in the above-mentioned microcomputer 110 will be explained in detail along the main flowchart of FIG.

The microcomputer 110 is activated and ready for operation 18
Once completed, the program starts, initializes the system (ie, sets the I10 port, sets flags, resets, etc.), and enters the main processing flow for overcurrent detection. Next, a control operation (A/D conversion process) of the A/D conversion circuit 100 is executed. By this control operation, the signal of the effective value of the current of the electric path outputted from the waveform conversion circuit 90 is selected in a time division manner, converted into a digital signal t7t4, and written into the RAM 115 in the microcomputer 110. Next, regarding the input signal data written into the RAM 115K as described above, an operation is performed to determine whether or not the value is an overcurrent value. As a result, if there is no overcurrent, the 6th
The process exits the heat storage routine shown in the figure and returns to the above-mentioned A conversion process. Next, if there is an overcurrent, the tip or R
A predetermined number of bits is added every predetermined unit time using AM115. The predetermined focus number is selected to realize a time-limited operation along the characteristic curve shown in FIG. Next, an operation is performed to determine whether the number of added pits has reached a value corresponding to a predetermined time limit as described above. If the number of bits added as a result does not reach the predetermined time limit, the process deviates from the main 70- in FIG. 6 and returns to the A/D conversion process described above. Next, when the above-mentioned added focus number reaches a value corresponding to a predetermined time period, an output signal is generated via the output capacitor 117a to drive the output device 80.

Next, a case will be described in which the overcurrent returns to a current within a normal range. As mentioned above, when the heat storage flag H is set and the time-limited timing operation has progressed to a certain extent, A
//If the maximum value of the D-converted data falls below a predetermined level, the routine deviates from the overcurrent determination routine and
Heat storage flag H indicating the state at the stage immediately before the relevant stage
is set. As a result, if the heat flag H is not set, the process returns to the A/Df conversion process. Next, if the heat storage flag H is set, a square wave voltage output is generated with a pulse width corresponding to the number of bits in the count register that has been added up to that point (i.e., the number of bits corresponding to the time measured). ,
Charge the capacitor 50. Next, reset the count register, and also reset the heat storage flag XH,
Returning again to the A/D conversion process.

The program is configured and the process is executed as described above, but the microcomputer 110 always reads the voltage of the capacitor 50 and starts the counting register during the A/D conversion process.

Even if a fault current flows intermittently, or even if the microcomputer 110 is reset and restarted for some reason, the capacitor 50 retains a residual voltage corresponding to the thermal energy that had been accumulated in the electrical circuit. has been done. Therefore, the device of the present invention can realize an operation that conforms to the heat dissipation characteristics of the electric circuit.

〔Effect of the invention〕

According to the present invention, by appropriately selecting the discharge time constant of the above-mentioned capacitor 5 (in the above-mentioned example, appropriately selecting the value of the discharge resistor 61), the heat dissipation characteristics of the power distribution line and load can be improved. A damping characteristic (actuation characteristic) extremely close to . Furthermore, the program can be simplified, the capacity of the storage means can be reduced, and the calculation processing time can be shortened. Furthermore, from the standpoint of providing protection against intermittent fault current according to the heat resistance of the distribution lines and loads, it is possible to realize a highly accurate and ideal circuit breaker. Therefore, the circuit is not cut off unnecessarily frequently, and unnecessary wear and tear caused by opening and closing the gate is prevented.

Furthermore, even if the detection operation is temporarily stopped and then restarted due to disturbances such as a drop in power supply voltage or surge/noise, the heat storage data up to that point is retained, so appropriate protection can be provided.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing general characteristics of a circuit breaker, Fig. 2 is a block diagram showing an embodiment of the circuit breaker of the present invention, and Fig. 3 is a microcomputer in the circuit breaker of Fig. 2. FIG. 4 is a characteristic diagram showing the state of change in current flowing through the electrical circuit and the operating characteristics of the circuit breaker of the present invention. FIG. 5 is a block diagram of the circuit breaker of the present invention. A waveform diagram showing the state of charging and discharging of 50,
FIG. 6 is a flow chart of the basic operation of the microcomputer in the circuit breaker of the present invention. DESCRIPTION OF SYMBOLS 10... Electric circuit, 20... Current transformer, 30... Rectifier circuit, 40... Burden circuit, 50... Capacitor, 61
．． 62...Resistor, 70...Diode, 80...
Output device, 90...Waveform f detection device, 100...A/
D conversion circuit, 11O... microcomputer, 20
1... Power supply side terminal, 202... Open 'NIF contact, 2
03...Load side terminal agent Patent attorney Masuo Oiwa Figure 3 Figure 4-1 - Sung by Anne & I (A) Figure 5 Figure 6 Procedural amendment (voluntary) 1981 °1016EI T , IP Office Commissioner's Palace 3, Representative Hitoshi Katayama of the person making the amendment Department 4, Agent 5, Target of amendment ``Claims column of the specification'' and ``Detailed description of the invention column of the specification ” 6. Contents of the amendment (1) The scope of claims in the specification will be amended as shown in the attached sheet. (2) On page 5, line 12 of the specification, "trip" is corrected to "power outage". (3) On page 6, line 18, "AC voltage" is corrected to "charging voltage." (4) Correct "bit" on page 14, line 18 to "thermal storage bit". (5) "...is obtained" on page 16, line 19.
Add the following sentence after . ``Here, in the embodiment of the present invention, the charging and discharging characteristics of a capacitor are directly used, but basically, a circuit configuration (such as a Miller integrating circuit) having so-called charging and discharging characteristics can be used without directly using a capacitor. It is clear that the same effect can be achieved even if the contact is retractable.'' Claims (1) A retractable contact, a releasable device that opens the contact, an actuator that releases the releasable device, and a predetermined A circuit breaker equipped with a control device F that operates the actuating device in response to a fault current, the control device comprising:
current sensor means for detecting a fault current flowing in the electrical circuit;
Level determining means for determining the level of the secondary output of the current sensor means; time limit generating means for performing a predetermined time-limiting operation corresponding to the level determined by the level determining means; responsive to the time-limiting operation of the time limit generating means; When the fault current returns to the normal current during the time-limited operation of the output means and the time limit generation means, a charge corresponding to the thermal energy generated by the current is charged while the fault current continues, and then a predetermined amount is charged while the normal current continues. The charging/discharging circuit means is provided with a charging/discharging circuit means for discharging at a time constant of A circuit breaker characterized in that the circuit breaker is configured to be read into the microcomputer as an initial value for calculating the generation time limit of the time limit generation means. (2) The charging/discharging circuit means includes a capacitor, a charging means for generating a one-shot pulse having a pulse width controlled by the microcomputer, and a C
The circuit breaker according to claim 1, wherein the circuit breaker includes a discharge means in the form of an R time constant circuit. (3) The charging/discharging circuit 1R is configured to include a capacitor and charging means that generates a constant current by being driven by a one-shot pulse having a pulse width controlled by the microcomputer. The circuit breaker according to any one of range (1) or (2). (4) the current sensor means includes a current transformer;
The level determining means, the time limit generating means, the output means, and the charging/discharging circuit (2) are constructed so that power for their operation is supplied from the secondary side of the current transformer. ), (2) or (3).

Claims (1)

[Scope of Claims] Il+ A releasable contact, a releasable device that opens the contact, an actuating device that releases the releasable device, and a control device that actuates the actuating device in response to a predetermined fault current. A circuit breaker comprising:
current sensor means for detecting fault current flowing in the electrical circuit;
Level discrimination means for discriminating the level of the secondary output of the current sensor means, time limit generation means for performing a predetermined time limit operation corresponding to the level determined by the level discrimination means, and an output responsive to the time limit operation of the time limit generation means. means, and when the fault current returns to normal current during the time-limited operation of the time limit generation means, the fault current is charged with an electric charge corresponding to the thermal energy generated by the current while the fault current continues, and then a predetermined amount of electricity is charged during the continuation of the normal current. It is provided with a charging/discharging circuit that discharges with a time constant, and at least the level determining means and the time limit generating means are one
It consists of an Italo converter, and when a fault current occurs again, the residual voltage of the charging/discharging circuit is read into the g+I microcomputer as an initial value for calculating the generation time of the time limit generating means. A circuit breaker characterized by: (2) The charging/discharging means includes a capacitor, charging means for generating a one-shot pulse having a pulse width controlled by the microcomputer, and discharging means in the form of a CR time constant circuit using a resistor. 112. The circuit breaker according to claim 111. (3) Claims in which the charging/discharging circuit includes a capacitor and charging means that generates a constant current by being driven by a funshot pulse having a pulse width controlled by the microcomputer. +1st
) or the circuit breaker according to any one of Item 121. (4) the current sensor means includes a current transformer;
Claim H: The level determining means, the time limit generating means, the output means, and the charging/discharging enclosure 118 are constructed so that power for their operation is supplied from the secondary side of the current transformer. , i21 or the circuit breaker according to any one of item (3).