JPS6033716Y2 - capacitor bank protection device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a protection device for a capacitor bank that detects and protects a capacitor bank in which a plurality of unit capacitors are connected in series and parallel to each other.

For example, a DC capacitor bank used in an impulse current generator or the like is constructed by connecting a plurality of relatively small-capacity case-type capacitors in series and a plurality of series branches connected in parallel.

The total charging energy of such a capacitor bank is hundreds of kilojoules to megajoules.

Therefore, if dielectric breakdown occurs in even one capacitor during charging, there is a risk that, depending on the case, all the charging energy will be concentrated and consumed in the faulty capacitor, leading to a false capacitor case bursting accident.

For this reason, conventionally, in this type of capacitor bank, the electromagnetic force of the fault current is used to short-circuit the fault capacitor, or a current limiting fuse is used to cut off the fault current.

There is also a system in which several blocks of unit capacitors are connected in series to increase the bank actance, and to suppress the wraparound energy in the event of an accident to less than the unit capacitor's case destruction energy.

However, in the event of an accident, it is necessary to inspect the bank to find the faulty part, and it is difficult to install an interlock in some cases.

Furthermore, when the bypass energy is suppressed by increasing the bank glue actance, it is difficult to detect a faulty capacitor by visual inspection, and repair work becomes extremely difficult and troublesome.

For this reason, various protection devices have been considered.

FIG. 1 is a block diagram showing an example of a previously proposed protection device for a capacitor bank.

In the figure, 1 is a unit capacitor C11, C2X, C31...
This is a capacitor bank in which multiple C64 series branches are connected in parallel.

This capacitor bank 1 is connected to a power source (not shown) via a breaker 2 and charged.

Further, a series circuit including a switch 3 and a discharge resistor 4 is connected in parallel to the capacitor bank 1.

Further, the series branches of the unit capacitors of the capacitor bank 1 are divided into two sets, each center stage of each series branch is connected in parallel for each set, and these connection points a and b are connected to the AC input side of the rectifier 5. do.

A light emitting element 7 is connected to the DC output side of the rectifier 5 via an auxiliary circuit 6, and the light emitting element 7 is made to emit light in accordance with the output current corresponding to the potential difference between the stages of the series branch circuit of the capacitor bank. ing.

The light from the light emitting element 7 is then guided to the light receiving element 9 via an insulating light guide 8.

The output signal of the light receiving element 9 is applied to a relay circuit 10 to operate the breaker 2 and the switch 3 when a predetermined amount of light is received.

In this way, during normal operation of capacitor bank 1, unit capacitors C11, C21, C31...C64
Connection point a due to variations in capacitance during manufacturing.

A small potential difference E1 is generated between the terminals b.

Using this potential difference E, the light emitting element 7 can be caused to emit light via the auxiliary circuit 6, and the light can be transmitted to the light receiving element 9 via the light guide 8.

In this case, since the light emitted from the light emitting element 7 is weak, the relay circuit 10 is inoperative, and the breaker 2 maintains the closed circuit and the switch 3 maintains the open circuit.

If any of the unit capacitors suffers dielectric breakdown,
The potential difference E2 between the connection points a and b is extremely large compared to the potential difference E1 that occurs under normal conditions, and the amount of light from the light emitting element 7 also increases.

Therefore, the amount of light received by the light receiving element 9 also increases, and the relay circuit 1
0 operates, circuit breaker 2 opens and capacitor bank 1
is disconnected from a power source (not shown), and the switch 3 is closed to discharge the residual charge through the resistor 4.

Note that dielectric breakdown of any unit capacitor can be detected by making the input to the auxiliary circuit 6 unidirectional using the rectifier 5.

According to such a protection device for a capacitor bank, even if dielectric breakdown occurs in any of the unit capacitors, the potential difference E will always be maintained.
2 can be detected and the breaker 2 can be opened to prevent the accident from spreading.

Furthermore, since a fiber cable with good electrical insulation properties is used as the light guide, even if the light emitting element 7 side is charged to a high voltage, signals can be transmitted safely and reliably without using an insulating transformer or the like.

However, with such a device, it is not possible to detect a failure in the protection system of the light emitting element 7, the light receiving element 9, the light guide 8, etc.

Therefore, if an accident occurs in the capacitor bank 1 due to a failure in the maintenance system, there is a problem in that it is not possible to detect this and protect the capacitor bank 1.

The present invention has been devised in view of the above circumstances, and provides a capacitor bank protection device that can detect failures in the capacitor bank 7 and failures in the protection system itself with a simple configuration, and provides high reliability. The purpose is to

An embodiment of the present invention will be described below with reference to a block diagram shown in FIG. 2, in which the same parts as in FIG. 1 are given the same reference numerals.

In the figure, reference numerals 81 and 82 denote two light guides that guide the light emitted from the light emitting element 7 to the first and second light receiving elements 91 and 92, respectively.

Note that the light emitting element 7 is connected to the auxiliary circuit 6 between the connection points C and d.
It emits light with an amount of light that corresponds to the voltage applied through it.

Furthermore, the first light-receiving element 91 has relatively high sensitivity and is operated by the normal potential difference E3 between the connection points C and d of the capacitor bank 1, and provides its output signal to the relay control circuit 10.

Further, the second light receiving element 92 has relatively low sensitivity, operates by a relatively large potential difference E4 when any of the unit capacitors of the capacitor bank 1 fails, and provides its output signal to the relay control circuit 10.

The relay control circuit 10 determines that it is normal when the output signal is given only from the first light receiving element 91, and determines that the protection system is abnormal when the output signal of the first light receiving element 91 is deenergized.
If the output signal of the second light receiving element 92 is output, it is determined that the capacitor bank 1 is abnormal.

If it is determined to be normal, the breaker 2 is closed, each unit capacitor of the capacitor bank 1 is charged from a power source (not shown), and the switch 3 is opened.

If it is determined that there is an abnormality, the breaker 2 is opened to cut off the power source and the capacitor bank 1, and the switch 3 is closed to discharge the charge in the capacitor bank 1 via the discharge resistor 4.

Therefore, even if dielectric breakdown occurs in any of the unit capacitors, it is possible to reliably prevent the accident from expanding.

Furthermore, abnormalities in the protection systems of the light emitting element 7, the light receiving elements 91, 92, etc. can also be detected, and high reliability can be obtained.

In addition, in the conventional protection device shown in Figure 1, in order to confirm the operation of the protection system, it is necessary to put the capacitor bank into the same condition as when the capacitor dielectric breakdown occurred, making such a test extremely troublesome. Met.

On the other hand, according to the embodiment described above, by reducing the voltage applied to the capacitor bank 1, for example, the voltage applied to the light emitting element 7 is reduced, and the amount of light emitted by it is also reduced.

Therefore, even if the capacitor bank 1 is normal, the potential difference between the connection point C9d becomes low and the light emitting element 7
The amount of light emitted also decreases.

Therefore, the output of the first light receiving element 91 is deenergized, and the relay circuit 10 determines that there is an abnormality in the protection system, thereby making it possible to confirm the operation of the protection device.

Note that the present invention is not limited to the above embodiments,
For example, when an abnormality in the protection system is detected in the relay circuit 10, an appropriate failure display device may be operated.

As detailed above, the present invention applies the potential difference between appropriate series branches of a capacitor bank in which a plurality of unit capacitors are connected in series and parallel to the light emitting element via the auxiliary circuit L2, and uses this light emission as a light guide. A first light-receiving element that operates with a potential difference in normal conditions and a second light-receiving element that operates with a potential difference in abnormal conditions.
the light receiving element, and this output signal is given to the relay circuit.

When only the output signal of the first light receiving element is given, it is normal; When the output signal of the second photodetector is given, the capacitor bank is damaged. If the output signal of the second light-receiving element is deactivated, it is assumed that the protection system has failed.
In response to this failure detection, the capacitor bank is disconnected from the power supply.

Therefore, it is possible to protect the capacitor bank and to detect failures in the protection system itself, thereby providing a highly reliable capacitor bank protection device with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a previously proposed protection device, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1... Capacitor bank, 2... Breaker, 3... Switch, 4... Discharge resistor, 5... Rectifier, 6...Auxiliary circuit,
7... Light emitting element, 81, 82... Light guide, 91, 92... Light receiving element, 10...
...Relay circuit.

Claims (1)

[Scope of utility model registration request] In a capacitor bank in which a plurality of unit capacitors are connected in series and parallel, an auxiliary circuit that is given a potential difference between stages between appropriate series branches of this capacitor bank and outputs a voltage according to this potential difference, and an output of this auxiliary circuit. a light-emitting element to which a voltage is applied; an insulating light guide that guides the light emission of the light-emitting element; and a first light-receiving element that is supplied with light through the light guide and operates based on the above-mentioned potential difference during normal operation;
When light is applied through the light guide and only the output signal of the second light receiving element, which operates due to the above potential difference at the time of failure of the capacitor bank, and the first light receiving element is given, it is considered normal. When the output signal of the second light receiving element is given, it is assumed that the capacitor bank has failed.
A protection device for a capacitor bank, comprising: a relay circuit that considers the failure of the protection system when the output signal of the second light-receiving element is deactivated, and disconnects the capacitor bank from the power supply in response to the detection of the failure.