JPH1040786A - Self-excited communication direct current breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small direct current breaker and improve the shutoff function by eliminating reactor of a commutator, simplify the structure of a breaker, lower the electric resistance of a commutating circuit, and heighten the magnification of electric current. SOLUTION: When arc contacts of a breaker 11 are parted and an electric current shutoff process is started, even if no reactor is installed in a commutating circuit, an arc is generated and since the arc itself has inductance, oscillation is started attributed to mutual functions of the arc and a capacitor 12. Various disturbances appear as slight fluctuations of the electric current and in the case the circuit condition is in an unstable region, the disturbances grow and the vibration is enlarged and current zero is obtained. In this way, by connecting a capacitor 12 in prescribed conditions with the commutating circuit, the vibration is enlarged and the electric current can be shut. Moreover, by connecting a surge absorber 14 in parallel with the capacitor 12, a surge absorber d.c. current breaker can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-commutated commutation system having a commutation circuit, a function of supplying a direct current of a power system, and a function of cutting off the direct current of a power system when an abnormality such as a ground fault or a short circuit occurs. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC cutoff device, and more particularly to a self-excited commutation type DC cutoff device having a commutation circuit composed of only parallel capacitors.

[0002]

2. Description of the Related Art FIGS. 2 and 3 show "Eleventh International Gas Discharge and its Application International Conference" No. FIG. 118 schematically shows a DC power transmission system using a self-excited commutation type DC circuit breaker shown in FIG. 118 (1995), and schematically shows a configuration of the self-excited commutation type DC circuit breaker.

The operation of the protection circuit breaker (DC circuit breaker) of the DC power transmission system shown in FIG. 2 is as follows.

[0004] The DC breaker (1) is open during normal operation. When a ground fault occurs in the neutral wire (2), the DC breaker (1) is closed and the ground fault current is reduced to the DC breaker (1).
To eliminate the neutral line (2) accident. After the insulation of the neutral line (2) is restored, the DC breaker (1) is opened to cut off the arc, and a DC current is commutated to the neutral line (2) to return to normal operation.

As shown in FIG. 3, this DC circuit breaker (1) is a circuit breaker (1) using an arc-extinguishing gas such as SF ₆ gas.
1), a commutation circuit including a capacitor (12) and a reactor (13) connected in parallel, and a capacitor (12) and a reactor (1) connected in series of the commutation circuit.
And 3) a surge absorber (14) made of a ZnO element or the like connected in parallel between them. FIG.
Shows a puffer-type gas circuit breaker (11), which is an embodiment of the DC circuit breaker (11), and includes a fixed contact (22) and a movable contact (23) for supplying a direct current to the DC circuit breaker. , The arc (28) generated between the fixed and movable contacts (22) and (23) when the electrode is opened,
A puffer piston (26) for blowing arc-extinguishing gas (27) such as F ₆ gas, and fixed and movable contacts (22);
(23) and an insulating nozzle (24) arranged so as to surround the contact end.

Next, the operation of this conventional example will be described. The current interruption process is started by opening the arc contacts (22, 23) of the circuit breaker (11). Various disturbances appear as minute fluctuations in the current, and when the circuit conditions are in an unstable region, the disturbance grows, the oscillation expands, and the current reaches the zero point. That is, when the fixed contact (22) and the movable contact (23) of the puffer type gas circuit breaker (11), which are energized with direct current, are opened, the fixed and movable contacts (22), (2) are opened in the same manner as in the AC interruption.
An arc (28) occurs during 3). Here, the reactor (13) and the capacitor (1) are connected in parallel with the circuit breaker (11).
2), the current is commutated to the commutation circuit, while the current of the arc is resonated to approach the zero point, and the SF ₆ gas (27) pressurized by the puffer piston (26)
Is blown from the insulating nozzle (24) to the arc (28) to extinguish the arc.

[0007]

In the self-excited commutation method, a parallel reactor and a parallel capacitor are used to expand and oscillate an arc current to perform commutation. In particular, what role does the parallel reactor play? It is not clear what type of parallel reactor and parallel capacitor should be provided depending on the current and the breaking current and the performance of the circuit breaker. In addition, since the arc itself generated between the fixed and movable contacts at the time of interruption has inductance,
Although it is thought that it is possible to cut off without using a parallel reactor, also in that case, depending on the breaking current and the performance of the circuit breaker,
It is not clear what type of parallel capacitor should be provided.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has a self-excited commutation type DC cutoff device in which a commutation circuit is constituted only by capacitors and an optimum capacitor capacity can be defined. The purpose is to provide.

[0009]

A self-commutated commutation type DC interrupter according to claim 1 of the present invention has a function of energizing DC of an electric power system and shuts off DC of an electric power system in the event of abnormality such as ground fault or short circuit. A commutation circuit consisting of only a capacitor connected in parallel to the circuit breaker, and a surge absorber connected in parallel to the capacitor of the commutation circuit.

According to a second aspect of the present invention, there is provided a self-excited commutation type DC interrupter, wherein the capacity Ce of a capacitor of the commutation circuit is Ce.
Is set to a value that satisfies the following equation (1). 15μF <Ce <90μF (1)

According to a third aspect of the present invention, there is provided a self-excited commutation type DC interrupter, wherein the capacity Ce of a capacitor of the commutation circuit is Ce.
Is set to a value that satisfies the following equation (2). 35μF <Ce <70μF (2)

According to a fourth aspect of the present invention, there is provided a self-excited commutation type DC interrupter, wherein the capacity Ce of a capacitor of the commutation circuit is Ce.
Is a DC current value io (A) interrupted by the circuit breaker.
And the relationship between the average energy loss n (W) and the average arc time constant θ (sec) when the capability of the circuit breaker is approximated by a Meyer type arc model is set to a value that satisfies the following equation (3). It is. 0.80 <io / (n ・ Ce / θ) ^1/2 <0.95 （３）

According to a fifth aspect of the present invention, there is provided a self-excited commutation type DC interrupter, wherein the capacity Ce of a capacitor of the commutation circuit is Ce.
Is a DC current value io (A) interrupted by the circuit breaker.
The relationship between the average energy loss n (W) and the average arc time constant θ (sec) when the capability of the circuit breaker is approximated by a Meyer type arc model is set to a value satisfying the following equation (4). It is. 0.80 <io / (n · Ce / θ) ^1/2 <0.85 (4)

According to a sixth aspect of the present invention, there is provided a self-excited commutation type DC interrupter, wherein the circuit breaker has a fixed contact and a movable contact for supplying a direct current, and the fixed and movable contacts are fixed and movable when the movable contact is opened. A puffer type gas circuit breaker comprising a puffer piston for blowing an arc-extinguishing gas to an arc generated between contacts, and an insulating nozzle arranged to surround the contact end of the fixed or movable contact. The value is io = 3500A
When the capacity of the circuit breaker is approximated by a Meyer type arc model, the average energy loss n of the circuit breaker is set to 8 to 15 MW, and the average arc time constant θ is set to 1
It is set to 5 to 50 μsec.

According to a seventh aspect of the present invention, in the self-excited commutation type DC interrupter, the average arc time constant θ of the circuit breaker is set to 2
It is set to 0 to 40 μsec.

In the present invention, the circuit breaker fixed, upon opening of the movable contact, the voltage of the arc generated between these contacts v _a - current i _a dynamic characteristics, Meier model equation (5), approximating I can do it. Where r _a is
Arc resistance. _{(1 / r a) · (} dr a / dt) = (1 / θ) · {1- (υ a · i a) / n} (5) In other words, in this Mayer model, breaker capability of the arc of the It is given by two constant parameters: energy loss n and arc time constant θ. Although the actual energy loss n of the arc and the time constant θ of the arc are not constants, the model can be approximated by using an average value. For example, FIG. 5 shows that the breaking current io = 840 A, the parallel reactor capacity Le = 225 μH, and the parallel capacitor capacity C
Arc voltage e in the breaking test when e = 5.1 μF
_a (= v _a) and the measurement results of the current i _a, and FIG. 6
Calculates this result as (1 / r _a ) · (d _a / dt) −e _a i _a
This is displayed in a plane. The data, as shown in FIG. 6, the intersection of the horizontal axis e _a i _a at the time of the linear approximation is arc loss n, the intersection of the longitudinal axis _{(1 / r a) · (} dr a / dt) Is the reciprocal 1 / θ of the arc time constant. That is,
From the interruption test results plotted in FIG. 6, the arc loss is n = 2 to 3.3 MW, and the reciprocal of the arc time constant θ = 10
The characteristic value of the circuit breaker of 20 μs can be read.

Next, a Meyer-type arc model of equation (5) approximated by two constant parameters (arc energy loss n and arc time constant θ) indicating the performance of the circuit breaker and a circuit equation (formula (described later) 6) to (8) show that the dynamic characteristics of the arc can be reproduced.

FIG. 7 shows that arc loss n = 2 MW, reciprocal of arc time constant θ = 18.5 μs, breaking current io = 840 A,
It is a reproduced waveform calculated when the parallel reactor capacity Le = 225 μH and the parallel capacitor capacity Ce = 5.1 μF. This calculation result is very similar to the interruption test result shown in FIG. That is, the validity of approximating the capability of the circuit breaker with the Meyer-type arc model is shown.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In order to clarify how the oscillation of the arc current expands and interrupts by the breaking current, the performance of the circuit breaker, and the parameters of the commutation circuit,
The theoretical calculation using the Meyer model and the test data were compared.

FIG. 1 is a circuit diagram showing a configuration of a DC cutoff device according to an embodiment of the present invention. In FIG.
A DC cutoff device according to the present invention is connected in parallel to a circuit breaker (11) such as an SF ₆ gas circuit breaker connected to a DC line, and a capacitor (12) having a capacity set according to the present invention.
And a surge absorber (14) composed of ZnO elements connected in parallel.

Next, the operation of the DC cutoff device will be described. The current interrupting process of this DC interrupter is similar to that shown in FIG. 2 and starts by opening the arc contacts of the circuit breaker (11). Even if a reactor is not provided in the commutation circuit, when an arc is generated, the arc itself has an inductance, so that an interaction with a capacitor causes vibration conditions. Various disturbances appear as minute fluctuations in the current, and when the circuit conditions are in an unstable region, the disturbance grows, the oscillation expands, and the current reaches the zero point. As described above, by connecting a capacitor under a certain condition to the commutation circuit, even a simple commutation circuit having no reactor can expand the vibration and cut off the current. Further, since there is no reactor, the stray resistance of the reactor cable is reduced, so that the current expansion rate is increased and the cutoff performance is improved.

Next, a theoretical analysis using a Meyer model is performed to determine what type of capacitor should be used. In this Meyer model, as mentioned above,
The performance of the circuit breaker is given by two constant parameters of an arc time constant θ and an arc loss n, and the arc is assumed to be a uniform cylindrical arc having a constant diameter and the energy loss n of the arc is constant. The present invention also uses this concept to define the capabilities of different gas circuit breakers.

The arc behavior of current i _a and the voltage v _a of the DC blocking device shown in FIG. 3, Mayer arc model equation (5) is given by the circuit equations of the formula (6) to (8).

The variables and circuit parameters appearing in the equations can be made dimensionless as follows. T = t / θ (Dimensionless time) (9) I = i / io (Dimensionless current) (10) V = υ / (n / io) (Dimensionless voltage) (11) R = r / (n / io ² ) (Dimensionless resistance) (12) L _N = L / (n ・ θ / io ² ) (Dimensionless reactance) (13) C _N = C / (i ²・ θ / n) (Dimensionless capacitance) (14) Ω = ω / (1 / θ) (Dimensionless angular frequency) (15)

Using the above dimensionless variables, the basic equations (5) to (8) can be rewritten as follows. (1 / R _a ) ・ (dR _a / dT) = 1-V _a・ I _a (16) dV _e / dT = (1 / C _Ne ) ・ (Io-I _a ) = (1 / C _Ne ) ・(1−I _a ) (17) L _Ne · (dI _a / dT) = V _e + R _e · (Io−I _a ) −V _a (18) V _a = R _a · I _a (19)

If the arc current is Ia = 1 (this is equivalent to the actual arc current value ia = io) and Va = 1, equation (16) is in equilibrium and the arc current voltage is
This value is constant. The response of the equation to the small variation ΔI _a of the arc current can be expressed as: The minute fluctuations appearing in the voltage are Δva, Δve
Notation. It is assumed that these minute fluctuations are sufficiently smaller than 1. I _a ≡I _a・ (1 + ΔI _a ) (20) V _a ≡V _a・ (1 + ΔV _a ) (21) V _e ≡V _e・ (1 + ΔV _e ) ≡V _a・ (1 + ΔV _e ) (22)

By substituting these minute fluctuations into the basic equation and ignoring higher-order minute quantities (Δ ² ), the following equations are obtained. _{(dΔV a / dT) - (} dΔI a / dT) = - ΔV a -ΔI a (23) V a · (dΔV e / dT) = - (I a / C Ne) · ΔI a (24) L Ne · I _a · (dΔI _a / dT) = V _a · ΔV _e -I _a · R _e · ΔI _a -V _a · ΔV _a (25)

From the above equation, the following linear differential equation for ΔIa can be obtained. L _Ne・ (d ³ ΔI _a / dT ³ ) + (R _e + _LNe +1) ・ (d ² ΔI _a / dT ² ) + {R _e + (1 / C _Ne ) -1} ・ (dΔI _a / dT) + 1 / C _Ne = 0 (26)

The characteristic equation of this differential equation has three real roots or one real root and two complex roots. ΔIa becomes an oscillating mode when it has two complex roots. If the real part of this complex root is positive,
ΔIa becomes an unstable solution and the vibration expands. If the characteristic equation of the differential equation has only real roots, this disturbance grows monotonically in a non-oscillation mode (when one real root is positive) or monotonically decays (when all real roots decay). If negative). Here, the phenomenon of expansion in the vibration mode is more important. This is because the actual machine level, in particular, the duty of interrupting a large current is in the normal vibration mode.

The general solution of equation (26) is given by: ΔI _a = Δo ・ expα ^oT + Δ1 ・ expα ^1T (sinΩT + Φ) (27)

Here, it is assumed that the characteristic equation of the equation (26) can be factorized as follows. (ρ-αo) ・ (ρ-α ₁ -jΩ) ・ (ρ-α ₁ + jΩ) = 0 (28)

Equation (26) was solved to evaluate the circuit parameter dependence of the constant α ₁ of the expansion rate of the arc current oscillation. The calculation result of the constant α ₁ of the expansion ratio of the current amplitude shown in FIG.
Breaking current io = 3500A, arc time constant θ = 40μ
s, arc loss n = 10 MW, and stray resistance Re of the commutation circuit R _e = 0.2Ω. To greet current zero point is essential that the amplitude of the vibration is sufficiently grown, the amplitude of the vibration is constant alpha ₁ magnification grows for positive only.

FIG. 8A shows only the case where the expansion factor constant α ₁ is positive with respect to the commutation capacitor and the reactor capacity. As can be seen from FIG. It can be seen that the magnification constant α ₁ is positive even with the capacitor capacity. That is, when the gas circuit breaker has an infinitely long shut-off time (when the SF ₆ gas can be blown indefinitely), by increasing the reactor capacity, the amplitude of the arc current is enlarged with a smaller capacitor capacity and finally. Means that it can be cut off at the zero point.

However, in an actual circuit breaker, since it is necessary to cut off within a predetermined time, the expansion rate of the vibration is not a sufficiently large value such that the current zero point can be reached within this time. Not be. Therefore, the constant α ₁ of the expansion rate of the vibration is closely related to the breaking performance of the circuit breaker.

FIGS. 9 (a) and 9 (b) correspond to (a) of FIG.
Out of the calculation results, the capacitor capacitance Ce = 20 μF,
A cross section of Ce = 30 μF is displayed (horizontal axis: reactor capacity,
(Vertical axis: magnification rate of vibration), and FIG. 9 also shows the results of the success or failure of the cutoff test under these circuit conditions. As is clear from these figures, the magnification of vibration under this condition is
It can be seen that there is a maximum value for a certain reactor capacity. Further, when these calculation results are compared with the interruption test data, the capacitor capacitances Ce = 20 μF and Ce = 30 μF
For both the F, it can be seen that the enlargement ratio alpha ₁ of the vibration has successfully blocked if 0.018 or more. That is,
In the circuit breaker used in the tests with a finite cutoff time, to greet current zero point within this time, clear that may be a commutation circuit condition enlargement ratio alpha ₁ of the vibration is 0.018 or more It became.

FIG. 8B shows that the constant α _{1 of the} enlargement ratio is 0.
The circuit conditions of 018 or more are shown for the commutation capacitor and the reactor capacity. From this, it can be seen from the theoretical calculation that there is an optimum reactor capacity that minimizes the capacitor capacity.

On the other hand, FIG. 10 shows the breaking current io = 3500
In the case of A, the results of the success or failure of the cutoff test under various commutation circuit conditions are shown for the commutation capacitors and the reactor capacities. It can be seen that a result substantially equal to the curve of the cutoff region obtained was obtained. That is, it is understood that the test results can be substantially predicted by the current theoretical calculation.

FIG. 11 shows the case where the stray resistance of the commutation circuit is increased, that is, the breaking current io = 3500
A, arc time constant θ = 40 μs, arc loss n = 10M
W, when the stray resistance R _e of the commutation circuit is 0.4Ω,
It is the result of calculating the circuit condition dependency in which the constant α ₁ of the expansion rate of the current amplitude is 0.018 or more.

It can be seen from this that the stray resistance of the commutation circuit has a large effect on the expansion rate of the vibration, and that an increase in the resistance value suppresses the growth of the vibration. That is, from the viewpoint of the stray resistance of the commutation circuit, it can be seen that the case where the reactor cable is short is more advantageous for interruption.

As described above, the expansion rate of the current oscillation is a good index for evaluating the performance of the circuit breaker. The magnification of the vibration is a function of the circuit parameters Ce, Le, Re, and the arc characteristics n, θ.

FIG. 12 shows the case where the capacitance of the capacitor is variously changed, that is, breaking current io = 3500 A, arc time constant θ = 40 μs, arc loss n = 10 MW, stray resistance Re of the commutation circuit Re = 0.2Ω, and capacitor Capacity Ce =
It is a result of calculating the reactor capacity dependence of the constant α ₁ of the current amplitude expansion rate in the case of 20 μF, 30 μF, 50 μF, and 70 μF.

It can be seen that the constant α of the current amplitude expansion rate
_It can be seen that, under the circuit condition where ₁ is 0.018 or more, the area of the reactor capacity becomes wider as the capacitor capacity becomes larger. In particular, the capacitor capacity Ce = 70 μF
In the case of, the reactor capacity Le = 0 μH, that is, it can be cut off without the parallel reactor.
As described above, the elimination of the parallel reactor not only simplifies the commutation circuit, but also lowers the stray resistance, which is very advantageous for interruption.

FIG. 13 shows an arbitrary breaking current io, an arc time constant θ = 20 to 40 μs, and an arc loss n = 5 to 10 M
W, when the stray resistance Re of the commutation circuit is Re = 0.2Ω, the capacitor capacity that can be cut off even when the reactor capacity is zero is io
It is a result calculated with respect to / (n / θ) ^1/2 .

It can be seen from this that the capacity of the capacitor that can be cut off without a reactor may be smaller as the arc time constant θ is smaller (the capacity of the circuit breaker is better).

The capacity of the capacitor Ce that can be cut off without the reactor is 15 when the cutoff current io = 3500 A.
μF <Ce <90 μF, more preferably 35 μF <C
e <70 μF. Further, for an arbitrary breaking current, the DC current value to be broken is defined as io (A), and when the capability of the circuit breaker is approximated by a Meyer type arc model, the average energy loss is defined as n (W). Constant θ
(Sec), the relationship of the capacitor capacity Ce that can be cut off without a reactor is expressed by the following equation (3), that is, 0.80 <io / (n · Ce / θ) ^1/2 <0.95 (3), and more preferably the following equation (3) 4), that is, a value that satisfies 0.80 <io / (n · Ce / θ) ^1/2 <0.85.

Further, when the breaker capacity when the breaking current io = 3500 A is approximated by a Meyer type arc model, the average energy loss n of the breaker is 8 to 15 MW, and the average arc loss is 8 to 15 MW. Time constant θ is 15 ~
It is set to 50 μsec, more preferably, 20 to 40 μsec.

[0047]

As described above, according to the present invention, the self-excited commutation type DC cut-off device has a function of energizing the DC of the power system and a function of cutting the DC of the power system in the event of an abnormality such as a ground fault or short circuit. , A commutation circuit consisting of only a capacitor connected in parallel to the circuit breaker, and a surge absorber connected in parallel to the capacitor of the commutation circuit. With such a configuration, since the reactor of the commutation circuit is eliminated, the structure of the device is simplified, the number of components is reduced, and a small DC cutoff device can be obtained. Further, since there is no reactor in the commutation circuit, the electric resistance of the commutation circuit (the stray resistance of the reactor cable of the commutation circuit) is reduced, the expansion rate of the current is increased, and the breaking capability is significantly improved.

Further, by setting the capacity of the capacitor of the commutation circuit to a value that satisfies a predetermined mathematical formula, the optimum value can be easily and easily set to an optimum value, which is combined with the fact that the reactor of the commutation circuit is omitted. As a result, it is possible to provide a compact and high-performance DC cutoff device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a DC cutoff device according to an embodiment of the present invention.

FIG. 2 is a schematic system diagram of a DC power transmission system using a self-excited commutation type DC circuit breaker.

FIG. 3 is a diagram showing a configuration of a DC blocking device according to a conventional example.

FIG. 4 is a diagram showing an embodiment of a DC breaker according to the present invention.

FIG. 5 is a waveform chart showing an example of arc voltage and current waveforms in a breaking test.

FIG. 6 shows the cutoff waveform as (1 / r _a ) · (d _a / dt) −
It is a diagram showing in e _a i _a plane.

FIG. 7 is a reproduced waveform diagram obtained by calculating an interruption waveform (arc voltage and current waveform).

FIG. 8 is a diagram showing a calculation result of circuit parameter dependence of a constant α ₁ of the magnification of current oscillation.

FIG. 9 is a diagram showing a reactor capacity dependency of a constant α ₁ of an enlargement ratio with respect to a capacitor capacity.

FIG. 10 is a diagram showing cut-off regions for various reactors and capacitor capacities.

FIG. 11 is a diagram showing a calculation result of circuit parameter dependence of a constant α ₁ of the magnification when the stray resistance of the commutation circuit is increased.

FIG. 12 is a diagram showing a reactor capacity dependence of a magnification constant α ₁ with respect to various capacitor capacities.

FIG. 13 is a diagram showing the capacity dependency of a circuit breaker on the capacity of a capacitor that can be cut off without a reactor.

[Explanation of symbols]

(11) Circuit breaker, (12) Capacitor (commutation circuit), (14) Surge absorber, (22) Fixed contact, (23) Movable contact, (26) Puffer piston, (24) Insulating nozzle.

Continued on the front page (72) Inventor Hiroki Ito 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Sueshin Hamano 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Inside (72) Inventor Etsuo Nitta 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Manabu Yokata 3-2-2 Nakanoshima, Kita-ku, Osaka-shi, Osaka Kansai Electric Power Co., Inc. Inside (72) Inventor Takaki Hashimoto 2-5 Marunouchi, Takamatsu City, Kagawa Prefecture Inside Shikoku Electric Power Company (72) Inventor Masayuki Hatano 6-15-1, Ginza, Chuo-ku, Tokyo Inside Power Development Co., Ltd.

Claims (7)

[Claims] 1. A circuit breaker having a function of energizing a direct current of a power system and a function of shutting off a direct current of the power system in the event of an abnormality such as a ground fault or short circuit, and an inverter comprising only a capacitor connected in parallel to the circuit breaker. A self-excited commutation type DC cutoff device, comprising: a current circuit; and a surge absorber connected in parallel to a capacitor of the commutation circuit. 2. The self-excited commutation type DC cutoff device according to claim 1, wherein the capacitance C of the capacitor of the commutation circuit is set to a value satisfying the following expression (1). 15μF <Ce <90μF (1) 3. The self-excited commutation type DC cutoff device according to claim 2, wherein the capacitance Ce of the capacitor of the commutation circuit is set to a value satisfying the following expression (2). 35μF <Ce <70μF (2) 4. The capacity Ce of a capacitor of the commutation circuit.
Is a DC current value io (A) interrupted by the circuit breaker.
And the relationship between the average energy loss n (W) and the average arc time constant θ (sec) when the capability of the circuit breaker is approximated by a Meyer type arc model is set to a value satisfying the following equation (3). The self-excited commutation type DC cutoff device according to claim 1, characterized in that: 0.80 <io / (n ・ Ce / θ) ^1/2 <0.95 （３） 5. The capacity Ce of a capacitor of the commutation circuit.
Is a DC current value io (A) interrupted by the circuit breaker.
And the relationship between the average energy loss n (W) and the average arc time constant θ (sec) when the capacity of the circuit breaker is approximated by a Meyer type arc model is set to a value satisfying the following equation (4). The self-excited commutation type DC cutoff device according to claim 4, characterized in that: 0.80 <io / (n · Ce / θ) ^1/2 <0.85 (4) 6. A circuit breaker comprising: a fixed contact and a movable contact for supplying a direct current; a puffer piston for blowing an arc-extinguishing gas to an arc generated between the fixed and the movable contact when the fixed and the movable contact are opened. ,
A puffer type gas circuit breaker comprising an insulating nozzle arranged so as to surround the contact end of the fixed or movable contact. When a direct current value to be cut off is io = 3500 A, the capability of the circuit breaker is a Meyer type. When approximated by the arc model, the average energy loss n of the circuit breaker is 8 to
15MW, and the average arc time constant θ is 15-50.
2. The self-excited commutation type DC cutoff device according to claim 1, wherein the DC cutoff device is set to μsec. 7. The circuit breaker has an average arc time constant θ of 20.
7. The self-excited commutation type DC cut-off device according to claim 6, wherein the DC cut-off device is set to a range of 40 to 40 [mu] sec.