JP3777750B2 - Commutation type DC circuit breaker - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a commutation type DC circuit breaker that forcibly generates a current zero point by superimposing a commutation current that changes sinusoidally on a DC current that flows through a circuit breaker during a circuit breaking operation, and that interrupts the current at the zero point.
[0002]
[Prior art]
FIG. 5 is a circuit diagram of a conventional commutation type DC circuit breaker. In this figure, a commutation type DC circuit breaker 210 is provided between a DC power supply 100 and a load 300, and detects the current value when the load current suddenly increases due to a ground fault or the like on the load 300 side. The load current is cut off. The circuit breaker in the AC system uses the zero point at which the polarity of the current is reversed to cut off the current. However, in the case of DC current, since there is no zero point, the commutation circuit 3 is provided to cut off the DC current. The principle of the commutation type DC circuit breaker is to forcibly make a zero point and cut off.
[0003]
In order to provide a current zero point, a commutation circuit 3 is provided in parallel to the vacuum circuit breaker 1. The commutation circuit 3 is composed of a series circuit of a commutation capacitor 31, a commutation reactor 32, and a commutation switch 33, and the commutation capacitor 31 is previously charged to a predetermined voltage by a charging circuit 34. The control circuit 40 outputs a closing command signal S ₂ to the commutation switch 33 after a predetermined time after outputting the blocking command signal S ₃ to the vacuum circuit breaker 1.
[0004]
The control circuit 40 is a circuit on the load 300 side when the load current i _L is measured by the DC current transformer 5 in addition to the interruption command signal S ₁ from the outside, and the current i _L exceeds a predetermined value. An accident cutoff command signal S ₀ is generated when it is determined that an accident such as a ground fault has occurred, and the cutoff command for the vacuum circuit breaker 1 is activated when any of the aforementioned external cutoff command signals S ₁ becomes High. The signal S ₃ and the input command signal S ₂ for the commutation switch 33 are output.
[0005]
Note that the control circuit 40 also issues a closing command signal to the vacuum circuit breaker 1 that is in the shut-off state, but the closing command signal at this time is not shown.
The commutation circuit 3 generates a commutation current i _C based on the signal S _2, and the waveform of the commutation current i _C is a sinusoidal oscillation waveform determined by the capacitance of the commutation capacitor 31 and the reactance of the commutation reactor 32. Become. The first first wave is the load current i _L
The commutation capacitor 31 is charged by the charging circuit 34 so as to have a current of the opposite polarity.
[0006]
Since peak value shutoff commutation current current i _C is set larger than the value of the load current i _L when issued, the vacuum interrupter within at least half-wave from the commutation current i _C starts to flow 1 A zero point at which the sign of the current i _S is reversed is generated.
6 is a basic arrangement view of a vacuum circuit breaker of FIG. In this figure, the vacuum circuit breaker 1 of the commutation type DC circuit breaker 210 includes a vacuum valve 11 having a fixed main contact 11A and a movable main contact 11B, and a required contact force between the movable main contact 11B and the fixed main contact 11A. An insulating connecting bar 123 that transmits the applied force of the pressing wipe spring 124 to the movable main contact 11B via the opening / closing drive rod 122 and a spring seat 125 that serves as a scaffold for the pressing wipe spring 124 are integrally provided at the front end portion to be cut off. The connection bar 126 that transmits the spring force of the spring 131 to the opening / closing drive rod 122 via the insulating connection bar 123 having the rotating shaft 1231 and the tip of the connection spring 126 are normally engaged to keep the blocking spring 131 in the open drive standby state. And a rotating shaft 127 that transmits the force of the cutoff spring 131 to the movable main contact 11B by driving the connecting bar 126 downward with the force of the cutoff spring 131 when the engaging portion is released. And an engagement portion that engages with an engagement portion at the tip of the engagement lever 127, and is pulled out by a tripping coil 133 for driving opening by the cutoff spring 131 of the movable main contact 11B. a latch lever 132 having a rotary shaft 1321 being driven the engagement of the tip is tripped, the manual shut-off switch 134 for viewing cutoff operation characteristics by only opening spring 131, is output from the control circuit 40 of FIG. 5 comprises as main components a thyristor Th to the input cutoff command signal S ₃ to the gate for the opening drive by the opening spring 131 that.
[0007]
[Problems to be solved by the invention]
In the vacuum circuit breaker 1 having such a configuration, when there is a problem in the operation mechanism for operating the opening / closing of the main contact, after the vacuum circuit breaker 1 is turned on, the turned-on state cannot be maintained and the circuit is opened immediately. In this case, since no commutation current is supplied, no current zero point is generated, so that current interruption is impossible.
[0008]
Since the electric current flows as an arc that short-circuits between the main contacts of the vacuum circuit breaker 1, if this arc continues, there is a risk that the vacuum circuit breaker 1 is broken and further a ground fault occurs. For example, in FIG. 6 , since one or both of the engaging portions of the latch lever 132 and the engaging lever 127 are worn out and sufficient engagement is not achieved, the engaging portion after the closing operation is performed. In such a case that the engagement lever 127 performs a shut-off operation in which the engagement lever 127 rotates clockwise.
[0009]
Since the probability of such a failure of input is very small and it is a kind of wear failure, it is thought that no special measures need to be taken because it can be detected in advance during periodic inspections. Countermeasures for this problem have been considered to improve reliability.
The object of the present invention is to solve such a problem, and in the unlikely event that the closing operation fails and the main contact of the circuit breaker is reopened, the current can be interrupted and the accident does not develop. The object is to provide a commutation type DC circuit breaker.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, according to the present invention, a commutation circuit is provided in parallel with the circuit breaker, and a current zero point is generated by superimposing the commutation current generated by the commutation circuit on the load current during the breaking operation. In the commutation type DC circuit breaker designed to cut off the current at the zero point, it is detected that the closing operation has failed and the main contact of the circuit breaker has been opened after the closing operation, and the commutation current is applied to the load current. A commutation type DC circuit breaker capable of interrupting current by superimposing to generate a current zero point, and when the load current that flows after being applied exceeds a predetermined value and continues for a predetermined time Even if the current is superimposed, that is, even if the load current flows, if it disappears for some reason within a predetermined time, it is possible to further save energy if the commutation current is not superimposed.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on examples. Figure 1 is a circuit diagram of a commutation type DC blocking device showing an embodiment of the present invention, the same components as Fig omitted redundant description with the same reference numerals. The difference from FIG. 5 in FIG. 1 is that the signal S ₄ of the auxiliary a contact 41 that synchronizes ON / OFF with the main contact of the vacuum circuit breaker 1 is inputted to the control circuit 4. Many auxiliary a-contacts of the main contact are prepared because they are used for various purposes. Therefore, one of them may be used as the auxiliary a contact 41.
[0013]
The control circuit 4 detects that the output signal S ₄ after the closing operation the auxiliary a contact 41 is turned OFF from ON, the main contacts of the vacuum circuit breaker 1 is accidentally opening after turning, so turned knowing that failed, function of outputting a closing command signal S ₂ is added to subsequent commutation switch 33 after a predetermined time has elapsed.
FIG. 2 is a graph showing a current waveform and a time chart when the commutation type DC circuit breaker 200 of FIG. In this figure, the horizontal axis is time, the uppermost stage is the breaking current i _S flowing through the vacuum circuit breaker 1, the lower stage is the ON / OFF of the main contact of the vacuum circuit breaker 1, and the lower stage is the main contact. A time chart showing the high and low of the output signal S ₄ of the auxiliary contact a 41 is shown, and the bottom stage is a time chart of the input command signal S ₂ to the commutation switch 33. In these figures, it is assumed that the vacuum circuit breaker 1 performs a closing operation at time t ₁ and its main contact is turned on. Therefore, after this, the load current i _L flows, but since there is no commutation current i _C at this time, the load current i _L is simultaneously the cut-off current i _S shown in the figure. The main contacts and turned OFF by opening become a point in time t ₂ is not locked after engagement became ON. The signal S ₄ is turned on at time t ₁ together with the main contact, and is turned off at time t ₂ . The signal S ₄ by the control circuit 4 is detected to have turned OFF, and outputs a closing command signal S ₂ of the time t ₃ when a little delayed from the time t ₂ to a commutation switch 33. As a result, a commutation current having a sinusoidal waveform is superimposed on the breaking current i _S , and a current zero point is generated at time t ₄ as shown in the figure. Since the main contact is open at this point, the arc that has been short-circuited between the main contacts at this current zero point disappears and the current is interrupted, leading to subsequent breakdown of the vacuum circuit breaker 1 and a ground fault. To prevent. Represent the current when the waveform of the current i _S indicated by the dashed line after time point t ₄ was not been if current interruption at time t _4.
[0018]
FIG. 3 shows a logic circuit provided in the control circuit 4 for generating the input command signal S ₂ to the commutation switch 33. In this figure, 422 is a monostable multivibrator (abbreviated Monosute), 44 3 delay elements, 45 4, 452, 453 is inverted elements, 463, 46 4, 462 is an AND element. Further, the signal S ₄ as the input signal, the signal S ₁ and the signal S ₂ as the output signal are as described above, and the signal S ₀ is based on the output signal of the DC current transformer 5 in the control device 4. This is an accident detection signal that is High when there is an abnormality such as a ground fault, and Low otherwise. In the figure, the number indicates the signal at that position.
Note that the logic circuit for generating the signal S ₂ when the shut-off command is issued when the signals S ₀ and S ₁ are High is not shown in this figure.
[0018]
As shown in this figure, in adding load current existence signal S ₅ as the input signal is characterized. In other words, if the load current is zero or the current is so weak that the vacuum circuit breaker 1 can be cut off even if the charging fails, there is no need to flow the commutation current. it is obtained so as not to output the closing command signal S ₂ to. Flowing the commutation current releases the energy stored in the commutation capacitor 31, so that it is possible to save energy by preventing the commutation current from flowing when not needed.
[0019]
Load current existence signal S ₅ is To it, a signal delayed by the delay element 443 (1) is outputted is inputted signal (2) to the AND element 463, the signal (2) is input to the AND element 464 . On the other hand, the signal S ₄ is similarly input to the AND element 464 as the signal (3) inverted by the inverting element 454. The output signal of the AND element 464 (4) is input to the AND element 462, this AND element 462, a fault detection signal S ₀ and the external shutoff signals S ₁ is inverted by the respective inversion element 452 and 453 Have been entered. Therefore, immediately after the turning-on operation, both the signal S ₀ and the signal S ₁ are Low, so both inverted signals are High. Therefore, when the output signal (4) of the AND element 464 is Low, the output signal of the AND element 462 is also Low. When the signal (4) is High, the output signal of the AND element 462 is also High. On the other hand, when either the signal S ₀ or the signal S ₁ is High, that is, when a cutoff command is issued to the vacuum circuit breaker 1, the inverted signal becomes Low, so that the signal (4) is High or Low. In either case, the output signal of the AND element 462 becomes Low. That is, the output signal of the AND element 462 becomes high when the signal S ₄ is turned on once and then turned off when the shut-off command is not issued immediately after turning on, and remains low otherwise. Even if (4) is erroneously set to High for some reason, the output signal of the AND element 462 does not become High when a shut-off command is issued.
[0020]
Figure 4 is a time chart for explaining the operation of the logic circuit of FIG. In this figure, the horizontal axis is time, and time t ₁ and time t ₂ are the same as those in FIG. In FIG. 2, the signal S ₂ is illustrated to rise at a time t ₃ that is slightly delayed from the time t ₂ when the signal S ₄ is turned off. This delay is, for example, the final of the logic circuit for generating the signal S _2. Since this occurs when the stage is shared with the logic circuit for generating the signal S ₂ during the shut-off operation, the point t ₃ in FIG. 2 is assumed to coincide with the time t ₂ in FIG. It is shown.
The operation of the logic circuit of FIG. 3 will be described with reference to FIG.
It is assumed that when a closing operation is performed at time t _{1 and} the main contact of the vacuum circuit breaker 1 is turned on, a load current flows from this time. This load current is measured by the DC current transformer 5 of FIG. 1 and is input to the control circuit 4. When the load current is smaller than a predetermined value, it is determined that the load current is substantially absent and is present when it is large. This determination circuit is also an item added in this embodiment, but will not be described in detail because it can be easily created within the scope of the prior art. Signal S ₅ is High when it is judged Low, there and when it is determined that the load current is not. The value for determining the presence or absence of the load current is set to about 1/100 of the rated load current. This value is smaller than the current that the vacuum circuit breaker 1 can cut off without a zero point. Therefore, when it is determined that there is no load current, the current is cut off by opening the main contact. There is no fear of breaking the vacuum circuit breaker 1 or spilling over to a ground fault.
[0021]
The signal S ₅ changes from Low to High at time t ₁ and is input to the AND element 463 as it is, and the signal (1) delayed by the delay element 443 is also input to the AND element 463. When the signal S ₅ continues to be high, the output signal (2) of the AND element 463 is the same as the signal (1) as shown in FIG. Signal (2) is inputted to the AND element 464, the inverted signal of the signal S ₄ to the AND element 464 (3) be input together, even time t ₂ the signal S ₄ is changed from High to Low signal the output signal of the aND element 464 when S ₅ maintains the status of the High (4) becomes High.
When the output signal of the AND element 462 becomes High, the signal is shaped by the monoste 422 and becomes the signal S ₂ .
The time T is determined by the mechanism shown in FIG. 6 and a mechanism not shown, but is about 20 milliseconds.
[0022]
The delay time T _D2 of the signal S ₅ by the delay element 443 is set to a value smaller than the time T, for example, about 10 milliseconds when the time T is about 20 milliseconds as described above. This delay time _TD2 is for actually determining “present” only after the load current of a magnitude that is determined as “present” continues to flow for a certain period of time.
However, since the phenomenon of failure of input is a very rare phenomenon, even if the load current flows for a short time, the commutation current is superimposed, that is, the signal S ₅ is omitted by omitting the delay element 443 and the AND element 463. In many cases, the circuit configuration of the signal (2) is acceptable.
[0023]
Note that FIG. 3 shown as a logic circuit for generating the input signal S ₂ for the commutation switch 33 is merely an example, and any circuit configuration is adopted within the scope of the prior art as long as it is not contrary to the object of the present invention. There is no problem.
[0024]
【The invention's effect】
As described above, according to the present invention, if it is detected that the main contact of the circuit breaker is opened after the closing operation and the commutation current is superimposed on the load current to generate the current zero point, the opened main contacts are short-circuited. Since the arc that has been generated disappears at this zero point and the load current is interrupted, the commutation type DC circuit breaker due to the arc continuing, and the ground fault accident caused by the ripple can be prevented in advance. The effect that it can be obtained.
[0025]
If the load current that flows after the charging is lost for a certain reason within a predetermined time, energy saving can be further achieved if the commutation current is not superimposed.
[Brief description of the drawings]
1 is a circuit diagram of a commutation type DC circuit breaker showing an embodiment of the present invention. FIG. 2 is a waveform diagram for explaining the operation of FIG. 1. FIG. 3 is a logic circuit for generating a signal S _{2 in} FIG. 4 is a time chart for explaining the operation of FIG. 3. FIG. 5 is a circuit diagram of a conventional commutation type DC circuit breaker. FIG. 6 is a diagram illustrating the principle of the vacuum circuit breaker of FIG.
200,210 ... commutation type DC blocking device, 1 ... vacuum circuit breaker, 2 ... non-linear resistance, 3 ... commutation circuit, 31 ... commutation capacitor, 32 ... commutation reactor, 33 ... commutation switch, S ₁ ... external Shut-off command signal, S ₂ ... Commutation switch input command signal, S ₄ ... Signal from auxiliary contact a, S ₅ ... Load current presence / absence signal, 4, 40 ... Control circuit, 100 ... DC power supply, 300 ... Load, 41 ... Auxiliary contact a, 422 ... Monoste, 441, 443 ... Delay element, 452, 453, 454 ... Inverting element, 462 463, 464 ... AND circuit

Claims (1)

A commutation circuit is provided in parallel with the circuit breaker, and a current zero point is generated by superimposing the commutation current generated by the commutation circuit during the breaking operation on the load current, and the current is interrupted at this zero point. In the flow type DC circuit breaker,
A commutation type DC circuit breaker characterized by detecting that the main contact of the circuit breaker has been reopened after the closing operation has failed and generating a zero current point by superimposing the commutating current on the load current. Because
A commutation type DC circuit breaker characterized by superimposing a commutation current on a load current when a load current flowing after charging exceeds a predetermined value and continues for a predetermined time .

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