Cut-off device system

Abstract

To determine capacitance of a capacitor in a cut-off device system which properly cuts off current in the event of an accident.SOLUTION: A cut-off device system (7) in a power system in which a shunt reactor (9) is installed comprises a capacitor (6) and a reactor (5) connected in parallel with the shunt reactor, and in series with each other. Capacitance of the capacitor satisfies a predetermined formula, in relation of zero-current point evaluation time, an angular frequency in the power system, and reactance of the cut-off device system.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a circuit breaker system. [Background technology]

[0002] Trading of electricity through grid interconnection has become common. When an accident such as a short circuit or a ground fault occurs in a grid-connected power system, it is necessary to quickly cut off the fault area in order to limit the area of ​​the fault.

[0003] In cable-based grid interconnection, shunt reactors are generally used to mitigate voltage fluctuations in the grid interconnection. In a power grid equipped with a shunt reactor, if an accident occurs, the sum of the charging current of the transmission line and the current through the shunt reactor will flow through the circuit breaker. As a result, a direct current is applied to the circuit breaker, causing a zero-point transition phenomenon in which the current does not cross zero, and the circuit breaker will not be able to interrupt the current even if it is opened.

[0004] In response to this, in Patent Document 1, in order to make the current applied to the shunt reactor cross zero, a capacitor is connected in series to the shunt reactor and the current flowing through the power system is resonated, thereby making the current cross zero. In particular, Patent Document 1 discloses a method for determining the capacitance of the capacitor for resonance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 5-22458 Summary of the Invention [Problem to be solved by the invention]

[0006] However, within the range of capacitances determined by the above-mentioned prior art methods, it may be possible to select a capacitance that does not cut off current quickly enough.

[0007] One aspect of the present invention is directed to determining the capacitance of a capacitor in a circuit breaker system that will properly interrupt current in the event of a fault. [Means for solving the problem]

[0008] In order to solve the above problems, a circuit breaker system according to one embodiment of the present invention is a circuit breaker system in a power system in which a shunt reactor is installed, comprising a capacitor and a reactor connected in parallel to the shunt reactor and in series with each other, an installed capacity of the circuit breaker system is greater than an installed capacity of the shunt reactor, and a capacitance C of the capacitor satisfies a predetermined equation in a relationship between a current zero evaluation time T, an angular frequency ω0 in the power system, and a reactance X of the circuit breaker system.

[0009] In order to solve the above problems, a circuit breaker system according to one embodiment of the present invention is a circuit breaker system in a power system, comprising a circuit breaker, a first capacitor and a first reactor connected in series to the circuit breaker and in series with each other, and a second capacitor and a second reactor connected in parallel to the first capacitor and the first reactor and in series with each other, wherein a capacitance C of the first capacitor and the second capacitor satisfies a predetermined equation in a relationship between a current zero evaluation time T, an angular frequency ω0 in the power system, and a reactance X of the circuit breaker system. Effect of the Invention

[0010] According to one aspect of the present invention, the capacitance of a capacitor in a breaker system that properly interrupts current in the event of a fault can be determined. [Brief description of the drawings]

[0011] [Figure 1] 1 is a circuit diagram showing a configuration of a main part of a power system according to a first embodiment. [Diagram 2] FIG. 2 is a model diagram showing a time series change in current caused by the breaker system according to the first embodiment. [Diagram 3] This is the result of a simulation of the current flowing through the target circuit breaker when three phases are short-circuited upstream of the target circuit breaker. [Figure 4] This is the result of a simulation of the current flowing through the target circuit breaker when two phases are short-circuited upstream of the target circuit breaker. [Diagram 5] FIG. 11 is a circuit diagram showing the configuration of a main part of a power system according to a second embodiment. [Figure 6] FIG. 11 is a model diagram showing a time series change in current caused by a breaker system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] [Embodiment 1] Hereinafter, an embodiment according to one aspect of the present invention (hereinafter, also referred to as "the present embodiment") will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0013] (Circuit configuration) 1 is a circuit diagram showing a configuration of a main part of a power system 100 according to the first embodiment. The power system 100 includes a three-phase power source 1, which supplies power to the power system 100. The power system 100 is connected to a transmission line 8 via a target circuit breaker 4 in a lower system of the three-phase power source 1. A load and a power generation facility are connected in parallel to the lower system of the transmission line 8.

[0014] A shunt reactor 9 is connected to one of the loads in the power system 100. That is, the shunt reactor 9 is connected in series to the target circuit breaker 4. A shunt reactor circuit breaker 10 is connected between the target circuit breaker 4 and the shunt reactor 9.

[0015] A capacitor 6 and a reactor 5 connected in series to one of the loads in the power system 100 are connected. That is, the capacitor 6 and the reactor 5 are connected in parallel to a shunt reactor 9. The capacitor 6 and the reactor 5 are collectively referred to as a circuit breaker system 7. A circuit breaker 11 for the circuit breaker system is connected upstream of the capacitor 6 and the reactor 5.

[0016] Although the shunt reactor 9 and the breaker system 7 are arranged at different locations, this is not limiting. In other words, the shunt reactor 9 and the breaker system 7 may be arranged at the same location.

[0017] (Operation in the event of an accident) The operation will be described in the case where an accident, for example, a short circuit accident occurs at a location P upstream of the target circuit breaker 4 in Fig. 1. The accident is not limited to a short circuit accident, but may also be a ground fault accident.

[0018] When a fault occurs, the shunt reactor 9 operates by switching the DC current i d In contrast, the circuit breaker system 7 generates a resonance determined by the capacitance C of the capacitor 6 and the inductance L of the reactor 5. In other words, the circuit breaker system 7 outputs an oscillating current i n will be output.

[0019] These currents are summed up and flow into the target circuit breaker 4. Therefore, the oscillating current i n The timing at which the current flowing into the target circuit breaker 4 crosses zero is determined depending on the period of the current zero evaluation time in the target circuit breaker 4. The current zero evaluation time in the target circuit breaker 4 is called T. During this current zero evaluation time T, the oscillating current i n It is necessary for the current to cross zero due to the current fluctuation caused by the contribution of the current zero point evaluation time T. Note that the current zero point evaluation time T does not include the relay time and the breaker opening time for the target breaker 4. In other words, the current zero point evaluation time T is the time when the current needs to cross zero when the target breaker 4 is physically in the open state.

[0020] (Determining the capacitance C of capacitor 6) The angular frequency in the power system 100 is ω0, and the voltage applied to the breaker system 7 is V L In this case, the oscillating current i n can be expressed as follows:

[0021]

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[0024]

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[0025]

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[0027]

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[0028]

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[0029] For example, to prevent resonance at the fundamental, the oscillating current i n If the resonance frequency f is set to be less than 50 [Hz], equation (9) becomes the following equation.

[0030]

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[0031] Although the equation has been modified to be related to the capacitance C, it may be modified to determine the selection conditions for the inductance L. In other words, the oscillation current i n The capacitance C of the capacitor 6 and / or the inductance L of the reactor 5 may be determined so as to shorten one period.

[0032] Furthermore, it is preferable to set the resonant frequency to less than 30 Hz. In this case, the condition for the capacitance C is as follows:

[0033]

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[0034] The sum of these currents (dotted line in FIG. 2) is the current that flows into the target circuit breaker 4. Therefore, when the target circuit breaker 4 is in a fully open state, the sum of the currents becomes zero, and the current is interrupted.

[0035] Before time T1, the total current flowing into the target circuit breaker 4 is approximately 0 [A] because the relationship between the transmission line 8 and the shunt reactor 9 is designed so that the reactive power balance is 0 [MVar].

[0036] Fig. 3 shows the simulation results of the current flowing through the target circuit breaker 4 when three phases are short-circuited upstream of the target circuit breaker 4. Fig. 4 shows the simulation results of the current flowing through the target circuit breaker 4 when two phases are short-circuited upstream of the target circuit breaker 4.

[0037] 3 and 4, until time T1, the target circuit breaker 4 passes a current that oscillates at a fundamental frequency. After time T1, the total current passing through the target circuit breaker 4 oscillates at a resonant frequency f.

[0038] At time T2, the target circuit breaker 4 is physically open, but the arc causes a state in which current continues to flow. After this state is reached, the current flowing through the target circuit breaker 4 becomes zero, allowing the current of the corresponding phase to be interrupted. In reality, the current interruption is completed at time T3. For example, time T3 is 68 [ms] in Figure 3 and 67 [ms] in Figure 4. Therefore, by determining capacitance C using equation (10) or equation (11), the current can be safely interrupted.

[0039] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals are given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0040] (Circuit configuration) Fig. 5 is a circuit diagram showing a configuration of a main part of a power system 101 according to embodiment 2. The power system 101 has a circuit breaker system 7 instead of the shunt reactor 9. That is, the power system 101 has a first circuit breaker system 7a and a second circuit breaker system 7b. Note that, although Fig. 5 shows two sets of circuit breaker systems 7, the present invention is not limited to this and may have three or more sets.

[0041] The first circuit breaker system 7a has a first reactor 5a and a first capacitor 6a connected in series, while the second circuit breaker system 7b has a second reactor 5b and a second capacitor 6b connected in series.

[0042] The first circuit breaker system 7a is located upstream of the power transmission line 8, and the second circuit breaker system 7b is located downstream of the power transmission line 8. In other words, the position of the circuit breaker system 7 is not limited.

[0043] (Operation in the event of an accident) In the second embodiment, since there is no reactor (the shunt reactor 9 in the first embodiment) that does not have a capacitor 6, resonance occurs in the breaker system 7 that is a set of all the capacitors 6 and the reactors 5.

[0044] Therefore, multiple oscillating currents i n The sum of the above flows into the target circuit breaker 4, and the DC current i d Therefore, the oscillating current i n Since the current becomes zero twice in one period, it is sufficient that the half period is shorter than the current zero point evaluation time T, as shown in equation (12).

[0045]

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[0047] In addition, although the circuit constants in the first circuit breaker system 7a and the circuit constants in the second circuit breaker system 7b are described as being equal, this is not limiting. In other words, the resonant frequency in the first circuit breaker system 7a and the resonant frequency in the second circuit breaker system 7b may be set to different values. If the resonant frequencies of the first circuit breaker system 7a and the second circuit breaker system 7b are equal, the range that the common capacitance C can take is expressed by formula (15).

[0048]

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[0049] As shown in FIG. 6, from the time T1 when the accident occurred, the current flowing from the circuit breaker system 7a to the target circuit breaker 4 (dotted line in FIG. 6) is an oscillating current i oscillating at a resonant frequency f whose frequency is changed from the fundamental wave. n Furthermore, the current flowing from the circuit breaker system 7b to the target circuit breaker 4 (solid line in FIG. 6) is an oscillating current i oscillating at a resonant frequency f whose frequency is changed from the fundamental wave. n It becomes.

[0050] The sum of these currents (dash line in FIG. 6) is the current that flows into the target circuit breaker 4. Therefore, when the target circuit breaker 4 is in a fully open state, the sum of the currents becomes zero, and the current is interrupted.

[0051] By connecting capacitors 6, whose capacitance C is determined by equation (15), to all reactors 5, it becomes possible to interrupt currents in the event of all accidents. This configuration also has the advantage that the compensation rate for the reactance of reactors 5 by capacitors 6 per set in the breaker system 7 can be reduced.

[0052] 〔summary〕 A circuit breaker system according to a first aspect of the present invention is a circuit breaker system in a power system in which a shunt reactor is installed, comprising a capacitor and a reactor connected in parallel to the shunt reactor and in series with each other, an installed capacity of the circuit breaker system is greater than an installed capacity of the shunt reactor, and a capacitance C of the capacitor satisfies equation (10) in a relationship between a current zero evaluation time T, an angular frequency ω0 in the power system, and a reactance X of the circuit breaker system.

[0053] According to the above configuration, the current can be appropriately interrupted in the event of an accident.

[0054] A circuit breaker system according to a second aspect of the present invention may be configured in such a manner that, in the first aspect, the capacitance C satisfies formula (11).

[0055] According to the above configuration, it is possible to reduce the risk of resonance with the fundamental wave and to properly cut off the current in the event of an accident.

[0056] A circuit breaker system according to a third aspect of the present invention is a circuit breaker system in a power system, comprising a circuit breaker, a first capacitor and a first reactor connected in series with the circuit breaker and in series with each other, and a second capacitor and a second reactor connected in parallel with the first capacitor and the first reactor and in series with each other, wherein in a relationship between a current zero evaluation time T, an angular frequency ω0 in the power system, and a reactance X of the circuit breaker system, capacitances C of the first capacitor and the second capacitor each satisfy equation (15).

[0057] According to the above configuration, the current can be appropriately interrupted in the event of an accident.

[0058] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0059] 1 3 phase power supply 4. Target circuit breaker 5 Reactor 5a 1st reactor 5b Second reactor 6 Capacitors 6a 1st capacitor 6b Second Capacitor 7 Circuit Breaker System 7a First circuit breaker system 7b Secondary circuit breaker system 8. Power Lines 9 Shunt reactor 10. Shunt reactor circuit breaker 11 Circuit breaker for circuit breaker system 100, 101 Power system

Claims

1. A circuit breaker system in an electric power system in which a shunt reactor is installed, a capacitor and a reactor connected in parallel to the shunt reactor and in series with each other, The installed capacity of the circuit breaker system is greater than the installed capacity of the shunt reactor, Current zero evaluation time T, angular frequency ω in the power system ０ and a reactance X of the circuit breaker system, the capacitance C of the capacitor satisfies the following equation. [0010]

2. 2. The circuit breaker system of claim 1, wherein the capacitance C satisfies the following equation: [0025]

3. A circuit breaker system in an electric power system, comprising: A circuit breaker; a first capacitor and a first reactor connected in series to the circuit breaker and in series with each other; a second capacitor and a second reactor connected in parallel to the first capacitor and the first reactor and in series to each other, Current zero evaluation time T, angular frequency ω in the power system ０ and a reactance X of the circuit breaker system, the capacitances C of the first capacitor and the second capacitor respectively satisfy the following equation. [0030]

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