Switch gear

Abstract

To provide a switch gear having a surge voltage suppression device at an inductive load open circuit that can be adopted to a circuit of a specific voltage.SOLUTION: A switch gear comprises a circuit having: a power source that supplies a current; an inductive load; a main switching device; an auxiliary switch; and a resistance. The inductive load is serially connected to the power source. The main switching device is serially connected to the inductive load, and controls a supply of a power to the inductive load from the power source. The auxiliary switch controls the supply of the power to the inductive load from the power source so as to be parallely connected to the main switching device. The resistance is serially connected to between the inductive load and the auxiliary switch.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to a switchgear.

Background Art

[0002] In a circuit having an inductive load such as an electric motor or a shunt reactor, it is known that a surge voltage is generated when an opener is opened.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a switchgear using a vacuum circuit breaker in a circuit with an extra-high voltage (voltage exceeding 7 kV), a device for suppressing the surge voltage when an inductive load is opened has not been put into practical use. Therefore, when a surge voltage occurs, there is a risk that a malfunction may occur in the electrical equipment due to the high voltage.

[0005] The problem to be solved by the present invention is to provide a switchgear provided with a surge voltage suppression device when an inductive load is opened, which can be applied to a circuit with an extra-high voltage.

Means for Solving the Problems

[0006] To achieve the above problems, the switchgear according to the present invention includes a circuit having a power supply for supplying current, an inductive load, a main switch, an auxiliary switch, and a resistor. The inductive load is connected in series to the power supply. The main switch is connected in series to the inductive load and controls the supply of power from the power supply to the inductive load. The auxiliary switch is connected in parallel to the main switch and controls the supply of power from the power supply to the inductive load. The resistor is connected in series between the inductive load and the auxiliary switch.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0008] [Embodiment] Hereinafter, an embodiment of the switch gear 1 will be described in detail with reference to the accompanying drawings. The configuration of the embodiment described below, as well as the actions and results (effects) brought about by the configuration, are merely examples and are not limited to the following description. In this specification, ordinal numbers are used only for distinguishing parts and members and do not indicate order or priority.

[0009] Figure 1 is a schematic configuration explanatory diagram of a circuit provided in a switch gear 1 according to one embodiment. The switch gear 1 is, for example, a device that houses electrical equipment in a grounded metal housing (not shown). The switch gear 1 has insulation performance with respect to the outside of the switch gear 1. As shown in Figure 1, the switch gear 1 in the present embodiment includes an inductive load 101 such as an electric motor and a shunt reactor, a circuit 11 having a switch, and a control device 12. Note that the circuit 11 of the switch gear 1 in the present embodiment is not limited to the example shown in Figure 1.

[0010] Circuit 11 includes a power source 100, an inductive load 101, a first switch S1, a second switch S2, and a resistor W1. The power source 100 is an AC power source that supplies special high-voltage power to circuit 11. The power source 100 is not limited to this, and it may be an AC power source that supplies high-voltage power with a voltage of 7 kV or less. The first switch S1 is an example of a main switch. The second switch S2 is an example of an auxiliary switch.

[0011] One end of the inductive load 101 is connected to the first switch S1 and the resistor W1, and the other end is connected to the power source 100. The inductive load 101 is connected in series with the power source 100. In the circuit 11 having the inductive load 101, a transient recovery voltage occurs immediately after the circuit 11 is opened by a switch or the like and the current flowing through the circuit 11 is interrupted. The inductive load 101 is, for example, a shunt reactor.

[0012] The inductive load 101 has an inductance L1 and a capacitance C1. The inductance L1 and the capacitance C1 are connected in parallel in the circuit 11 to form a resonance circuit. When a disconnection occurs in the circuit 11, energy remains in the inductance L1, and a surge voltage is generated by the resonance of the inductance L1 and the capacitance C1.

[0013] The first switch S1 is a switch that can interrupt the current flowing through the circuit 11 by opening and closing. The first switch S1 is connected in series with the inductive load 101 and controls the supply of power from the power source 100 to the inductive load 101. More specifically, the first switch S1 interrupts the current flowing through the circuit 11 based on an abnormality detection signal of a protection relay (not shown) such as an overcurrent relay.

[0014] The first switch S1 is, for example, a vacuum switch. The first switch S1 is not limited to a vacuum switch, and depending on the application, a draw-in switch or the like may be used as the switch.

[0015] The second switch S2 is a switch that can cut off the current flowing through the circuit 11 by opening and closing. The second switch S2 is connected in parallel to the first switch S1 and controls the supply of power from the power source 100 to the inductive load 101. More specifically, the second switch S2 cuts off the current flowing through the circuit 11 based on an abnormality detection signal from a protection relay (not shown) such as an overcurrent relay.

[0016] The second switch S2 is, for example, a vacuum switch. The second switch S2 is not limited to a vacuum switch, and depending on the application, a draw-out switch or the like can be used as the switch. Thus, the circuit 11 has two switches that can cut off the current flowing through the circuit 11.

[0017] Generally, a vacuum switch has a high maximum breaking current value. Therefore, when the first switch S1 and the second switch S2 are vacuum switches, the first switch S1 and the second switch S2 can cut off the current in the circuit 11 through which particularly high-voltage power flows. On the other hand, when a vacuum switch is used for opening and closing a circuit having an inductive load, a surge voltage is likely to occur for the reasons described above.

[0018] The resistor W1 is connected in series between the inductive load 101 (inductance L1 and capacitance C1) and the second switch S2. The resistor W1 reduces the current flowing through the resistor W1. Also, the resistor W1 improves the phase difference of the circuit 11 and increases the power factor. When the resistance value of the resistor W1 is large, the effect of improving the power factor becomes higher, and the effect of further reducing the current becomes higher.

[0019] The resistor W1 has a structure that can thermally withstand the current flowing through the resistor W1. Also, the resistor W1 has sufficient insulation performance with respect to the rated voltage of the circuit 11.

[0020] Circuit 11 further has a protection relay (not shown). The protection relay is connected to the first switch S1 and the second switch S2. The protection relay constantly monitors the presence or absence of fault current such as a short circuit in circuit 11. When the protection relay detects a fault current in circuit 11, the protection relay issues a control command to the first switch S1 and the second switch S2. Then, the first switch S1 and the second switch S2 that have received the control command quickly cut off the fault current flowing through circuit 11.

[0021] The control device 12 is connected to the first switch S1 and the second switch S2. The control device 12 performs control to open the first switch S1 after closing the second switch S2. Further, the control device 12 performs control to open the second switch S2 after opening the first switch S1. The control device 12 is fixed to the panel surface (not shown) of the switchgear 1, but is not limited thereto and may not be fixed to the panel surface of the switchgear 1. In this case, the control device 12 remotely controls the first switch S1 and the second switch S2 without being connected to the first switch S1 and the second switch S2. The control device 12 is an example of a control unit.

[0022] Hereinafter, with reference to FIGS. 2 to 5, the opening and closing procedures of the first switch S1 and the second switch S2 will be described. FIG. 2 is an explanatory diagram of a current path showing a state in which the first switch S1 and the second switch S2 of the switchgear 1 of the present embodiment are closed. FIG. 3 is an explanatory diagram of a current path showing a state in which the first switch S1 of the switchgear 1 of the present embodiment is opened and the second switch S2 is closed. FIG. 4 is an explanatory diagram of a current path showing a state in which the first switch S1 and the second switch S2 of the switchgear 1 of the present embodiment are opened. FIG. 5 is a flowchart showing the flow of the opening and closing process of the first switch S1 and the second switch S2. Note that the dashed line in FIG. 5 is an example of a portion corresponding to the control of the control device 12.

[0023] As shown in FIG. 1, during normal power-on, in circuit 11, the first switch S1 is in the closed state and the second switch S2 is in the open state. Therefore, the current flowing through circuit 11 flows through the first switch S1, and no current flows through the second switch S2.

[0024] As described above, in circuit 11, the protection relay constantly monitors the presence or absence of an accident current such as a short circuit (step S100). Also, the opening and closing of the first switch S1 and the second switch S2 shown below are controlled by the control device 12.

[0025] In step S100, when no accident current is generated in circuit 11, as shown in FIG. 2, first, the control device 12 closes the second switch S2 (step S101).

[0026] After the second switch S2 is closed by the control device 12, as shown in FIG. 3, the control device 12 opens the first switch S1 (step S102). At this time, in circuit 11, a series circuit of the inductive load 101, the second switch S2, and the resistor W1 is formed.

[0027] When steps S101 and S102 are executed by the control device 12 and current flows through the second switch S2, the power factor of circuit 11 is improved (increased) by the resistor W1, and the phase difference between the current and the voltage becomes smaller.

[0028] Next, as shown in FIG. 4, the control device 12 opens the second switch S2 and cuts off the current flowing through circuit 11 (step S103). Then, a transient recovery voltage is generated across the poles of the second switch S2. In steps S101 and S102, due to the action of the resistor W1, the phase difference between the current and the voltage of circuit 11 has become smaller. Therefore, in step S103, the transient recovery voltage generated when the current flowing through circuit 11 is cut off due to the opening of the second switch S2 is suppressed.

[0029] Also, generally, when an arc interruption phenomenon occurs in a circuit where the current is interrupted other than at the current zero point, a surge voltage is generated, the voltage between the poles of the switch exceeds the withstand voltage value, insulation breakdown occurs, and there is a risk of a reignition arc where current flows through the circuit again. However, in the circuit 11 of the present embodiment, the high-frequency current flowing through the circuit 11 when the reignition arc occurs is reduced by the resistor W1. Therefore, even when a reignition arc occurs in the circuit 11, the occurrence of high-frequency arc extinction is suppressed, and thus the occurrence of multiple reignition arcs is suppressed.

[0030] In step S100, when an accident current occurs in the circuit 11, the protection relay issues an accident removal command. Then, as shown in FIG. 4, the control device 12 that has received the accident removal command opens the first switch S1, and the interruption of the current flowing through the circuit 11 is completed (step S102).

[0031] Generally, since the current flowing through the circuit during an accident current occurrence is a large current, it is desirable to interrupt it as quickly as possible. Also, when interrupting a large current such as the one flowing through the circuit during an accident current occurrence, the arc interruption phenomenon is less likely to occur, and the probability of generating a surge voltage is also low.

[0032] Therefore, when an accident current occurs in the circuit 11, as described above, the steps of the control device 12 opening and closing the second switch S2 (steps S101 and S103) are omitted, and the current flowing through the circuit 11 is interrupted only by the control device 12 opening the first switch S1.

[0033] In other words, the procedure for the control device 12 to interrupt the current flowing through the circuit 11 when an accident current occurs is shorter than the procedure for the control device 12 to interrupt the current during normal power supply. Therefore, when an accident current occurs, the current flowing through the circuit 11 is quickly interrupted by the first switch S1, and the occurrence of fires and malfunctions of electrical equipment due to the accident current is suppressed.

[0034] In the above embodiment, the switch gear 1 includes a circuit 11 having a power source 100 that supplies current, an inductive load 101, a first switch S1, a second switch S2, and a resistor W1. The inductive load 101 is connected in series to the power source 100. The first switch S1 is connected in series to the inductive load 101 and controls the supply of power from the power source 100 to the inductive load 101. The second switch S2 is connected in parallel to the first switch S1 and controls the supply of power from the power source 100 to the inductive load 101. The resistor W1 is connected in series between the inductive load 101 and the second switch S2.

[0035] According to the above configuration, the current flowing through the circuit 11 can be selected by the opening and closing of the first switch S1 and the second switch S2 as to whether it flows through the first switch S1 or the second switch S2.

[0036] Also, in the present embodiment, the switch gear 1 has a control device 12 that controls to open the first switch S1 after closing the second switch S2.

[0037] According to the above configuration, during normal power supply of the circuit 11, since the inductive load 101 is not connected to the resistor W1, the resistance loss and heat generation of the first switch S1 are suppressed. On the other hand, when the control device 12 closes the second switch S2 and opens the first switch S1, a series circuit of the inductive load 101, the second switch S2, and the resistor W1 is formed. Therefore, the power factor of the circuit 11 increases, and the phase difference between the current and voltage in the circuit 11 becomes smaller.

[0038] Also, in the present embodiment, the control device 12 controls to open the second switch S2 after opening the first switch S1.

[0039] According to the above configuration, the control device 12 opens the second switch S2 in a state where the power factor of the circuit 11 has increased due to the resistor W1 and the phase difference between the current and voltage has become smaller. Therefore, when the control device 12 opens the second switch S2 and cuts off the current flowing through the circuit 11, the switch gear 1 can suppress the transient recovery voltage and surge voltage generated between the poles of the second switch S2.

[0040] Also, in this embodiment, the first switch S1 is a vacuum switch.

[0041] According to the above configuration, the switchgear 1 can cut off a larger current by opening the first switch S1.

[0042] Also, in this embodiment, the second switch S2 is a vacuum switch.

[0043] According to the above configuration, the switchgear 1 can cut off a larger current by opening the second switch S2.

[0044] Also, in this embodiment, the control device 12 performs control to open the first switch S1 without closing the second switch S2.

[0045] According to the above configuration, when an accident current such as a short circuit occurs, the step of the control device 12 opening and closing the second switch S2 is omitted, and only the step of the control device 12 opening the first switch S1 is executed. Therefore, the switchgear 1 can quickly cut off the current flowing through the circuit 11.

[0046] Also, in this embodiment, the inductive load 101 is a shunt reactor.

[0047] According to the above configuration, the leading reactive power flowing through the circuit 11 is compensated by the inductive load 101 which is a shunt reactor. Therefore, the switchgear 1 can suppress the voltage rise of the circuit 11 and stabilize the voltage.

[0048] As described above, several embodiments of the present invention have been explained. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Description of Reference Numerals

[0049] 1 Switch gear 11 Circuit 12 Control device 100 Power supply 101 Inductive load C1 Capacitance L1 Inductance S1 First switch S2 Second switch W1 Resistor

Claims

1. A power supply for supplying current, An inductive load connected in series to the power supply, A main switch connected in series to the inductive load for controlling the supply of power from the power supply to the inductive load, An auxiliary switch connected in parallel to the main switch for controlling the supply of power from the power supply to the inductive load, A resistor connected in series between the inductive load and the auxiliary switch, A switchgear comprising a circuit having the above.

2. Having a control unit for performing control to open the main switch after closing the auxiliary switch, The switchgear according to Claim 1.

3. The control unit performs control to open the auxiliary switch after opening the main switch, The switchgear according to Claim 2.

4. The main switch is a vacuum switch, The switchgear according to Claim 3.

5. The auxiliary switch is a vacuum switch, The switchgear according to Claim 4.

6. The control unit performs control to open the main switch without closing the auxiliary switch, The switchgear according to Claim 5.

7. The inductive load is a shunt reactor, The switchgear according to Claim 6.

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