JP3336443B2 - Capacitor bank protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor bank having a parallel circuit using a plurality of DC capacitors used for a power supply of an inverter for industrial equipment, for example.
More specifically, the present invention relates to a protective device for a capacitor bank for preventing leakage of an impregnating agent due to rupture of a case (breakdown of a unit capacitor) occurring at the time of destruction of a capacitor (single unit capacitor), or other accidents to other equipment attached thereto. is there.

[0002]

2. Description of the Related Art As a conventional example, a cut piece is used for a protection device for a capacitor, which cuts off a circuit between a single-unit capacitor and an external terminal by utilizing case expansion when an abnormality occurs.
For example, Japanese Utility Model Publication No. 58-18281 can be mentioned. In this conventional example, a single-unit capacitor and a cut piece are connected in series, and when an abnormality occurs in the single-unit capacitor, the internal pressure of the case increases and the case expands, so that the gap between the insulating support plates is increased. The fixed cut piece cuts off and cuts off the circuit,
This ensured safety. Such a conventional example is used only when the power supply is an AC power supply, and cannot be cut off safely when the power supply is a DC power supply. Therefore, it is not used when the power supply is a DC power supply.

FIG. 10 shows a circuit example of a large-capacity DC capacitor bank, which is composed of a large number of single-unit capacitors C _1.
· The C _n are connected in parallel, it is intended to smooth the rectified output of the rectifier 1 for rectifying an AC power source through a parallel circuit of the capacitor C ₁ .... Then, the smoothed DC voltage was supplied to the inverter 2, and the output of the inverter 2 was applied to the motor 3. Note the DC filter capacitor used in the inverter circuit and the like are those used by dozens parallel connection of single unit capacitor C ₁ ··· C _n. Here, when one unit capacitor (for example, the unit capacitor C ₁ shown in FIG. 10) out of several tens fails, the other unit capacitors C ₂ ... Connected in parallel and the power supply as shown in FIG arrow from fault current flows, decomposition gas is generated by the arc discharge in the inside of the single unit capacitor C _1,
The case may swell and rupture, which may spread to accidents such as oil blasts and fires.

[0004] As a method of preventing this, various methods have conventionally been used in DC capacitor banks. First, in the first method, as shown in FIG. 11, two unit capacitors C ₁ and C ₂ are connected in series, and a large number of the series circuits are connected in parallel, and one capacitor C ₁ is connected to one capacitor C ₁ . connect the voltmeter 4 in parallel, the terminal voltage of the capacitor C ₁ is measured, is to stop the voltage application to the fault capacitor C ₁ by detecting the change in the terminal voltage.

A second method is disclosed in JP-B-63-2373.
No. 8 discloses a method in which _two single-unit capacitors C ₁ and C ₂ are connected in parallel as shown in FIG. 12, and when one single-unit capacitor C ₁ fails. fault current from the other single unit capacitor C ₂ flows into, but the protection switch 5 for short-circuiting forced between the single unit capacitor C ₁ terminal is provided at this fault current, single unit capacitor C
By fault current ₁ is prevented from flowing, thereby preventing the rupture of a single vessel capacitor C _1.

[0006]

However, such a conventional method for protecting a large-capacity DC capacitor bank is disclosed in FIG.
In the case of (1), there is a problem that the voltmeter 4 and a system for processing the output of the voltmeter 4 and stopping the power application become complicated and costly.

Further, in the case of FIG. 12, one protection switch 5 is required for every two unit capacitors, which is like a large-capacity DC capacitor bank in which several tens of unit capacitors are connected in parallel and used. In such a case, there was a problem that the price was extremely high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional drawbacks, and an object of the present invention is to provide a capacitor bank capable of simplifying the configuration for protecting a large-capacity DC capacitor bank and achieving cost reduction. To provide a protection device.

[0009]

Therefore, a capacitor bank protection device according to the present invention provides a cutting piece 7 for cutting off a circuit by cutting using the expansion of a case due to an increase in internal pressure when an abnormality occurs, and a cutting piece 7 for cutting off the circuit. And a single unit capacitor C connected in series to form a capacitor body 6, connect a plurality of the capacitor bodies 6 to form a parallel circuit, connect a DC power source to one end of the parallel circuit, and On the side, a load is connected.

[0010]

The protection device for the capacitor bank operates as follows. First, when an abnormality occurs in the single-unit capacitor C, the inflow current from the single-unit capacitor C adjacent to the failed single-unit capacitor C and the fault current from the DC power supply flow. An arc discharge occurs, a decomposition gas is generated, and the internal pressure of the case increases. The cut piece 7 is cut by utilizing the case deformation due to expansion due to the pressure rise of the case. When the cut piece 7 is cut, in the case of the single-unit capacitor C, the cut piece 7 is cut off even if the cut piece 7 is cut. Since it is a power supply, an arc current is maintained, and it is difficult to cut off a fault current. However, even in a large-capacity DC capacitor bank, if another single-unit capacitor C is connected in parallel with the single-unit capacitor C, even if one single-unit capacitor C fails, the other single-unit capacitor C is connected. Thus, the arc current is absorbed by the other single-unit capacitor C, and the fault current can be reliably shut off. Therefore, the failed single-unit capacitor C is quickly and surely separated from the circuit, and the rupture of the case due to a fault current, oil injection, fire, and the like can be prevented. Moreover, since the single-unit capacitor C and the cutting piece 7 are connected in series, the configuration can be simplified and the cost can be reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a specific embodiment of the capacitor bank protection device of the present invention will be described in detail with reference to the drawings. The present invention is a protection device that constitutes a large-capacity DC capacitor bank by a large number of single-unit capacitors, and isolates a failed single-unit capacitor from a circuit when one of the single-unit capacitors fails. .

FIG. 1 shows a circuit example of a large-capacity DC capacitor bank used in a power supply section of, for example, an inverter for industrial equipment according to the present invention. A large number of capacitors are provided on the output side of a rectifier 1 for rectifying an AC power supply AC. A parallel circuit in which the main bodies 6 are connected in parallel is connected, and the inverter 2 is connected to the output side of this parallel circuit. The motor 3 is connected to the inverter 2. The capacitor body 6 constituting the large-capacity DC capacitor bank includes a single-unit capacitor C,
It is composed of this single-unit capacitor C and a cutting piece 7 connected in series. As shown in FIG. 3, the cut piece 7 is formed of a copper piece, and has a cut portion 10 whose central portion is bent in a substantially U-shape, and fixed pieces 8 on both sides of the cut portion 10.
Consists of The fixing piece 8 of the cutting piece 7 is provided with a hole 9 for screw insertion for mounting, and a notch 11 is formed at one end of the cutting part 10 for more reliable cutting.

FIG. 4 is a perspective view of a main part showing a mounted state of the cutting piece 7, and is held between an insulating support plate 12 made of an insulating material and a terminal 13 and fixed to a case (not shown). The cut piece 7 is pinched and fixed by 14.
Note that one terminal 13 is connected to the single-unit capacitor C, and the other terminal 13 is connected to the positive electrode side of the DC power supply.

FIG. 2 is an equivalent circuit diagram when one single-unit capacitor C fails, in which L indicates the inductance component of the circuit, and R indicates the resistance. Also, C on the right is
It shows another single-unit capacitor connected in parallel.
Here, when one single-unit capacitor C fails, there is an inflow current from the single-unit capacitor C of the capacitor body 6 adjacent to the failed single-unit capacitor C, and a fault current also flows from the DC power supply (the output terminal of the rectifier 1). Flows in. For this reason, an arc discharge occurs in a failure portion of the single-unit capacitor C, a decomposition gas is generated, and the internal pressure of the case increases. The cut portion 10 of the cut piece 7 is cut using the case deformation due to expansion due to the rise in pressure of the case.

At this time, since the current flowing through the single-unit capacitor C is a DC current, normally (when only one single-unit capacitor C is used, that is, when another single-unit capacitor C is not connected in parallel), the cut piece 7 is Even if it is cut, the arc current continues, and it is difficult to quickly shut off the fault current. However, when another unit capacitor C is connected in parallel to the failed unit capacitor C as in the present invention, the arc current is absorbed by the other unit capacitor C, and the fault current can be quickly and reliably removed. Can be shut off. As a result, the failed single-unit capacitor C is separated from the main circuit, and it is possible to prevent rupture of the capacitor case due to a fault current, oil injection, fire, and the like. Moreover, since the single-unit capacitor C and the cutting piece 7 are connected in series, the configuration can be simplified and the cost can be reduced.

FIG. 5 shows a schematic configuration of a measuring circuit for a capacitor bank according to the present invention. A 66 KV, 50 Hz AC high voltage power supply 21 is stepped down to 1200 V by a transformer 22, and a silicon rectifier 23 is operated to be used as a test power supply. . The DC power source (the silicon rectifier 23) is provided with a charging device 24,
A test was performed on the interruption of the fault current in the case where the series circuit of the backup DC circuit breaker 25 and the capacitor body 6 was connected in parallel, and the single capacitor was not connected to one capacitor body 6 and the case where the single capacitor was connected. .

The test was conducted as follows. That is, the breaking operation test of the capacitor protector (capacitor body 6)
An electric current flows in the capacitor body 6, and assuming thermal expansion, air pressure is sent to the capacitor processed for the test, and after a few seconds, a direct current of 1500 V is applied to perform an operation test of the capacitor body 6 at a certain constant current. The procedure is as follows.

(1) Preparation Confirmation of opening of DC input device 24 Setting of test capacitor (capacitor body 6) Input of backup DC circuit breaker 25 Input of AC high voltage power supply 21

(2) Test Air pressure supply DC input device 24 enters Capacitor body 6 (test device) After 5 to 9 seconds, backup DC breaker 25 is opened AC power source 21 is opened

In FIG. 5, reference numerals 31 and 32 denote analyzing recorders. One analyzing recorder 31 is used for continuous measurement (sampling time: 5.0 msec).
The other analyzing recorder 32 is used for measurement during a transition (sampling time 0.5 msec). At each of the points shown in FIG. 5, measurement is performed by the analyzing recorders 31 and 32.

FIGS. 8 and 9 show cutoff waveforms when a single capacitor is not connected in parallel to the capacitor body 6, FIG. 8 shows cutoff waveforms at the time of continuous measurement measured by the analyzing recorder 31, and FIG. Analyzing Recorder 32
3 shows a cut-off waveform at the time of transition measured in FIG. FIG. 8 (a)
Is the supply voltage, (b) is the gap voltage, (c) is the current in the main circuit, (d) is the case distortion voltage of the capacitor body 6, and (e) is air in the case of the capacitor body 6. The waveform to the valve signal to the solenoid valve to be sent is shown.

FIG. 9 shows the transient waveforms of the supply voltage, the gap voltage, the current, and the case distortion voltage. From the test results shown in FIG. 9, when the single-unit capacitors are not connected in parallel, the supply voltage is 1640 V, the conduction current is 490 A, the total inductance value is 15 mH, and the maximum arc voltage (electrode voltage) is 2550 V. The cutoff time is as long as about 170 msec.

On the other hand, when a single capacitor is connected to the capacitor body 6 in parallel, the cutoff time is very short as shown in FIGS. FIGS. 6 and 7 correspond to FIGS. 8 and 9, respectively. That is, when the single capacitors are connected in parallel, the supply voltage is 1630 V, the conduction current is 490 A, the total inductance value is 15 mH, the capacity of the single capacitors connected in parallel is 2100 μF, and the maximum arc voltage (electrode voltage) is 190
As shown in FIG. 7, the cutoff time is very short as compared with the case where no single-unit capacitor is connected in parallel.

As described above, according to the present invention, the protection method used for a capacitor in an AC power supply is conventionally considered to be impossible to use in a capacitor bank for a DC power supply. It has been made based on the finding that an experiment can quickly and reliably shut off a failure.

[0025]

As described above, according to the capacitor bank protection device of the present invention, since another single-unit capacitor is connected in parallel with the single-unit capacitor, even if one of the single-unit capacitors fails, Since the arc current is absorbed by the other single-unit capacitor, the fault current can be quickly and reliably shut off. For this reason, the failed single-unit capacitor is quickly and reliably separated from the circuit, so that rupture of the case due to a fault current, oil injection, fire, and the like can be prevented. In addition, since the single-unit capacitor and the cut piece are connected in series, the configuration can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit example of a capacitor bank according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram when the single-unit capacitor according to the embodiment of the present invention fails.

FIG. 3 is a perspective view of a cut piece according to the embodiment of the present invention.

FIG. 4 is a main part perspective view showing a state in which the cut pieces according to the embodiment of the present invention are provided.

FIG. 5 is a test and measurement circuit diagram according to the embodiment of the present invention.

FIG. 6 is a diagram showing a cutoff waveform at the time of continuous measurement when the single capacitors of the embodiment of the present invention are connected in parallel.

FIG. 7 is a diagram showing a cut-off waveform during a transition when the single capacitors of the embodiment of the present invention are connected in parallel.

FIG. 8 is a diagram showing a cut-off waveform at the time of continuous measurement when a single-unit capacitor is not connected in parallel.

FIG. 9 is a diagram showing a cut-off waveform during a transition when a single capacitor is not connected in parallel.

FIG. 10 is a diagram showing a circuit example of a conventional capacitor bank.

FIG. 11 is a circuit diagram showing a protection method in a conventional large-capacity DC capacitor bank.

FIG. 12 is a circuit diagram showing a protection method in another conventional large-capacity DC capacitor bank.

[Explanation of symbols]

 6 Capacitor body 7 Cutting piece C Single unit capacitor

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01G 2/14-2/18 H02H 7/16

Claims (1)

(57) [Claims] 1. A cutting piece (7) for interrupting a circuit by cutting by utilizing expansion of a case due to an increase in internal pressure when an abnormality occurs.
And the single piece capacitor (C) connected in series with the cut piece (7) to form a capacitor body (6). A plurality of the capacitor bodies (6) are connected to form a parallel circuit. A protection device for a capacitor bank, wherein a DC power supply is connected to one end of a circuit and a load is connected to the other end.