JP6788564B2 - High-voltage power supply equipment for decommissioned nuclear power plants - Google Patents

Description

The present invention relates to a high voltage power supply facility for a decommissioned nuclear power plant.

As described in Patent Document 1, a nuclear power plant has an in-house power supply system. The in-house power supply system of a nuclear power plant can be classified into an in-house transformer, a start-up transformer (spare transformer), a power supply system, and an instrumentation control power supply system. An in-house transformer is a transformer that steps down the voltage from a generator or switch to the voltage supplied to the facility.

The power supply system is classified into a high voltage power supply equipment system (6.9 kV system) and a low voltage power supply equipment system (480 V or 460 V). The high-pressure power supply system supplies power to large-capacity auxiliary equipment such as a circulating water pump, a low-pressure condensate pump, a high-pressure condensate pump, a reactor water supply pump, and a recirculation flow pump.

The circulating water pump is a pump that circulates seawater for cooling the steam generated in the nuclear reactor with a condenser after passing through a turbine. The low-pressure condensate pump, high-pressure condensate pump, and reactor water supply pump are pumps that supply condensate cooled from steam by a condenser to a high-pressure reactor. The recirculation flow rate pump is a pump that adjusts the flow rate of the reactor water in the reactor to adjust the output of the reactor and changes the output of the reactor.

The high-voltage power supply equipment system includes the high-voltage power supply equipment system (6.9 kV system) and the in-house transformer that supplies power to the high-voltage power supply equipment system (6.9 kV system), provided that the above-mentioned large-capacity auxiliary equipment is started and operated. A (spare) transformer is designed.

In recent years, decommissioning methods for aging nuclear power plants have been studied, but in the case of nuclear power plants, fuel remains in the reactor or fuel pool for several years even after the application for decommissioning. Even after the fuel is taken out, the dismantling work of the core, which is a high-concentration radioactive material, will continue every few decades.

In the situation where fuel is present and the situation where high-concentration radioactive material is present after that, as a nuclear power plant, fuel is used to maintain the negative pressure of the building and the environmental conditions (temperature, humidity, etc.). It is necessary to operate the cooling system and air conditioning system, and the facilities associated with them (cooling water supply, seawater heat exchange, etc.) will continue to operate. Therefore, it is necessary to maintain the power supply equipment that supplies power to the equipment related to the fuel cooling system, air conditioning system, and the like.

On the other hand, while the life of a nuclear power plant is 40 or 60 years, the expected life of electrical equipment applied to the on-site power supply system is generally about 20 years, and the on-site power supply even after decommissioning. Since the system is necessary, it is necessary to renew (replace) the power supply equipment even after the nuclear power plant is decommissioned.

Japanese Unexamined Patent Publication No. 2016-213985

Until now, decommissioning of nuclear power plants has been decided only for nuclear power plants with low output, such as research reactors and the first domestic unit, so the demand for cost reduction for renewal of power supply equipment was not so large.

However, in the future, it is expected that commercial reactors with relatively high output will be decommissioned due to the balance between the cost required to comply with the new regulations enforced after the so-called Fukushima accident and the remaining operating period. There is. In a commercial furnace with a large output, the operation pattern of the power load is significantly different between the case of operation and the case after the decommissioning is decided, so the required specifications for the high-voltage power supply equipment are also different. Furthermore, it is expected that the demand for cost reduction will increase.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a high-voltage power supply facility for a decommissioned nuclear power plant, which can reduce the cost of the high-voltage power supply facility.

In order to solve the above problems, from one viewpoint of the present invention, it is a high-voltage power supply facility of a decommissioned nuclear power plant, and a power receiving circuit breaker connecting the first transformer and the high-voltage power supply system and a power receiving circuit breaker. It is provided with an impedance increasing portion provided on the primary side of the vessel.

According to the present invention, the short-circuit current can be suppressed by providing the impedance increasing portion on the primary side of the power receiving circuit breaker, and as a result, the rated breaking current value of the power receiving circuit breaker can be reduced and the cost can be reduced. be able to.

It is an in-house power source composition diagram of a nuclear power plant at the time of commercial operation of a plant. It is an in-house power supply composition diagram of a nuclear power plant after decommissioning of a plant. Explanatory drawing which shows the voltage drop at the time of starting an electric motor in a high voltage power supply system. Explanatory drawing which shows the inflow path of the current at the time of a short circuit accident in a high voltage power supply system. Evaluation diagram of short-circuit impedance of major transformers (in-house transformer, starting transformer). The high-voltage power supply panel is shown, (a) shows the high-voltage power supply panel during commercial operation of the plant, and (b) shows the high-voltage power supply panel to which this embodiment is applied.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In a nuclear power plant, the on-site transformer and the start (spare) transformer, etc. can be renewed (replaced) because the life of the on-site transformer and the start (spare) transformer can be extended compared to the on-site power supply equipment and the replacement cost of the transformer is high. ) Is often 40 years or more.

Therefore, since the specifications of the transformer cannot be changed, it is necessary to install the same high-voltage power supply equipment (high-voltage power supply panel) as during plant operation even after the decommissioning is decided. However, high-voltage power supply equipment for nuclear power plants has high short-circuit current specifications for circuit breakers and has strict operational obligation requirements. Therefore, the circuit breaker is also required to be large and DC electromagnetically driven. Therefore, even after the decommissioning is decided, it is necessary to prepare a large-capacity DC power supply facility.

On the other hand, in the general industry, a small hybrid high-voltage circuit breaker that uses a capacitor and a spring as a drive system to significantly reduce the drive current of the circuit breaker is on the market. However, there is no general hybrid high-voltage circuit breaker with short-circuit current specifications required during normal operation of a nuclear power plant, and it is difficult to apply it to a nuclear power plant in operation.

Therefore, in the present embodiment, a high-voltage power supply that can be combined with an existing in-house transformer and a start (spare) transformer by combining a high-voltage power supply facility with a high-voltage reactor and limiting the short-circuit current at the time of an accident with the high-voltage reactor. Propose equipment. According to the high-voltage power supply equipment of the decommissioned nuclear power plant according to the present embodiment, a hybrid high-voltage circuit breaker used in the general industry is used instead of the DC electromagnetically driven circuit breaker dedicated to the nuclear power plant. Therefore, the cost at the time of replacement can be reduced. In addition, by using a hybrid high-voltage circuit breaker, ancillary equipment such as a large-capacity DC power supply equipment becomes unnecessary, and maintainability is improved.

That is, according to this embodiment, when only the high-voltage power supply equipment is renewed at the time of decommissioning, cost reduction, simplification of maintenance, and simplification of incidental equipment such as DC power supply equipment for driving the circuit breaker of the high-voltage power supply panel are realized. can do.

The first embodiment will be described with reference to FIGS. 1 to 6. FIG. 1 shows an in-house power supply configuration diagram of a nuclear power plant during commercial operation of a plant.

The in-house power supply system in the nuclear power plant is a circuit that supplies power generated from the generator 101 to the system side via the main transformer 102 and the switchyard 103, and a circuit that supplies power to the in-house load via the in-house transformer 104. And a starting transformer 105. When the power supply from the in-house transformer 104 is stopped due to the generator stop, the main circuit accident of the generator 101 or the main transformer 102, etc., the start transformer 105 is transmitted from the system side via the switchyard 103. It is a transformer for direct power supply. The in-house transformer 104 and the start-up transformer 105 are examples of the “first transformer”.

The in-house transformer 104 and the start-up transformer 105 are installed to step down the voltage on the generator 101 and switch 103 side to the rated voltage of 6.9 kV of the high-voltage power supply system (metal clad switch gear: M / C) 106, respectively. doing. Each of the transformers 104 and 105 is connected to the high voltage power supply system 106 via the high voltage circuit breaker 202A. Further, the in-house transformer 104 and the start transformer 105 have specifications (% impedance) that limit the short-circuit current to the breaking current of the circuit breaker 110 applied to the high-voltage power supply system or less when a short-circuit accident occurs in the high-voltage power supply system 106. have.

The high-pressure power supply system 106 includes a circulating water pump that cools with a condenser (not shown) after passing through a turbine, and a low-pressure condensate pump and a high-pressure condensate pump that supply condensate into a high-pressure reactor. , The reactor water supply pump and a large-capacity auxiliary machine 107 such as a condenser flow pump are connected. The recirculation flow rate pump is a pump that adjusts the flow rate of the reactor water in the reactor to adjust the output of the reactor (not shown) and changes the output of the reactor.

The low-voltage power supply system (power center: P / C, motor control center: MCC) 108 is connected to the high-voltage power supply system 106 via a circuit breaker 110 and a power transformer 109. The low voltage power supply system 108 is for supplying power to auxiliary equipment other than the large capacity auxiliary equipment 107, and is stepped down to a low voltage (480V or 460V) by the power transformer 109 which is an example of the "second transformer". Power is supplied.

The large-capacity auxiliary machine 107 such as the low-pressure condensate pump, the high-pressure condensate pump, the reactor water supply pump, and the circulating water pump connected to the high-pressure power supply system 106 has a capacity of 1000 kW to 7000 kW class. Since the drive motors of these pumps are induction motors, a starting current of about 6 to 7 times the rated current flows when the pumps are started. On the other hand, there is a limit to the drop in the input voltage at the time of starting, and the minimum starting voltage is generally about 80% of the rated voltage.

The effect of this starting current will be described with reference to FIG. 3A. Since the starting current at the time of starting the electric motor is supplied from the generator 101 or the switchyard 103 side via the in-house transformer 104 or the starting transformer 105, the short-circuit impedance (% Z) 301 of each of the transformers 104 and 105 is reached. The magnitude of the voltage drop changes depending on it.

The short-circuit impedance (% Z) 301 of the in-house transformer 104 and the starting transformer 105 is designed so that the starting current Ist1 302 at the time of starting the large-capacity motor can satisfy the minimum startable voltage of the motor (% Z 301 is set appropriately). There must be.

On the other hand, when a short-circuit accident occurs in the high-voltage power supply system 106, it is necessary to promptly cut off the short-circuit current Is so as not to affect other circuits (operation can be continued). FIG. 4A shows a schematic diagram thereof.

The short-circuit current Is1 401 is the sum of the inflow current IsL1 402 on each transformer side and the motor contribution Ism1 403 of the motor. The motor contribution Ism1 403 of the electric motor depends on the total capacity (total capacity) of the electric motors connected to the high-voltage power supply system 106. The inflow current IsL1 from each transformer will be limited by the short-circuit impedance (% Z) of the transformer, and it is necessary to design so as to keep it below the breaking current of the circuit breaker 110 applied in the high-voltage power supply system 106. is there.

As described above, the short-circuit impedance (% Z) 301 of the transformer is determined from the upper limit value (determined from the voltage drop) 501 and the lower limit value (short-circuit current value of the circuit breaker) 502. This content is illustrated as shown in FIG.

As shown in FIG. 5, the lower limit value 502 of the short-circuit impedance (% Z) 301 increases depending on the transformer capacity. Since the upper limit value 501 is not as high as the lower limit value 502, when the transformer capacity exceeds a certain capacity, the upper limit value and the lower limit value are reversed, and the transformer cannot be selected. That is, it is necessary to take measures such as increasing the number of transformers.

In a nuclear power plant, as described above, since there are many auxiliary machines 107 having a large capacity load, the capacities of the in-house transformer 104 and the starting transformer 105 also increase. For this reason, the circuit breaker 110 of the high-voltage power supply system 106 is often provided with a circuit breaker of 40 kA or 63 kA, which is expensive in terms of cost, and the number of transformers 104 in the facility is one or two. ..

Since the starting transformer 105 has selection conditions other than the above, it is not generally determined only by the capacitance and the short-circuit impedance (% Z) 301, but it is an important factor in selecting the specifications.

Further, since it may be necessary to quickly turn on the open circuit breaker, a direct current electromagnetically driven (MA) type circuit breaker 110 is used in the nuclear power plant. The DC electromagnetically driven circuit breaker 110 requires a large-capacity (input current: about 90 A) DC power supply.

Due to the above situation, the cost of the circuit breaker 110 is high, and the DC power supply system, which is ancillary equipment, also needs to have a large capacity. However, as described above, when the nuclear power plant is decommissioned, the operation of the auxiliary machine 107 that contributes to power generation becomes unnecessary, and the operation of the equipment 108 that is not directly related to power generation such as fuel management, cooling, ventilation and air conditioning of the building, etc. Maintenance is important. That is, it is important to continue stable operation of the device group of the low-voltage power supply system 108 for maintaining the environment of the power plant.

Even after decommissioning, if fuel removal, decontamination of radioactivity, dismantling, etc. are included, the decommissioning work will be on the order of several decades, so it is important to maintain the in-house power supply system including the high-voltage power supply system 106. .. On the other hand, since the large-capacity auxiliary machine 107 is not operated as described above, it is not necessary to apply an expensive circuit breaker 110 with a breaking current of 40 kA or 63 kA to the high-voltage power supply system 106, which makes maintenance easier. It is important to apply a circuit breaker 110 with a breaking current of 20 kA class or less, which also has merits. Currently, there is a circuit breaker called a hybrid type that combines a capacitor storage and a spring in the drive mechanism. When using a hybrid high-voltage circuit breaker, the DC power supply, which is ancillary equipment, requires a smaller capacity than the MA type.

However, in order to apply such a hybrid high-voltage circuit breaker having a small circuit breaker current to the high-voltage power supply system 106 of a nuclear power plant, the short-circuit impedance (% Z) 301 of the in-house transformer 104 and the start-up transformer 105 is changed. There is a need. This means that when a hybrid high voltage circuit breaker is used, these transformers 104 and 105 also need to be updated together.

However, transformers generally have a longer life than power panels, etc., and the remaining life can be diagnosed by maintenance, and it costs a lot to update the transformer. It is considered that there are many cases where it does not cooperate with the update time of the high-voltage power panel.

Therefore, FIG. 2 shows an in-house power supply configuration diagram according to this embodiment. FIG. 2 shows the in-house power supply configuration of a decommissioned nuclear power plant. The major difference between FIGS. 2 and 1 is that a high-voltage reactor 201 as an "impedance increasing portion" is added to the primary side of the power receiving circuit breaker 202 of the high-voltage power supply system. The high-voltage reactor 201 acts to suppress the current with respect to the reactive current, but has no particular effect on the active current.

FIG. 4B shows current flows 403 and 404 when a short-circuit accident occurs in the high-voltage power supply system 106 according to this embodiment. As described above, the short-circuit current 404 flowing from the system side depends on the short-circuit impedance (% Z) 301 of the transformer.

In the case of a large-capacity transformer such as a main transformer (in-house transformer 104, starting transformer 105), the resistance / reactor (R / X) is about 0.1, which is almost a reactor component, so that the short-circuit current Is. Is almost reactive current. Therefore, by using the high voltage reactor 201, the short circuit current Is can be limited by the short circuit impedance (% Z) 301 of the transformer and the high voltage reactor 201. By appropriately selecting the reactor value of the high-voltage reactor 201, it is possible to apply the 20 kA class circuit breaker 202 to the high-voltage power supply panel.

On the other hand, as shown in FIG. 3B, by inserting the high-voltage reactor 201 into the high-voltage power supply system 106, the voltage drop at the time of starting the electric motor becomes large. This is because the current at the time of starting the motor is large and a large amount of reactive current is contained. As described above, since it is not necessary to operate the auxiliary machine (electric motor) 107 having a large capacity load after decommissioning, there is no particular problem even if the high voltage reactor 201 is added in terms of voltage drop.

The results so far will be described again with reference to the upper limit value (determined from the voltage drop) and the lower limit value (short-circuit current value of the circuit breaker) of the short-circuit impedance (% Z) 301 of the transformer. The contents are shown in FIG.

If a 20 kA class circuit breaker 202 is applied to the high-voltage power supply panel, the range of the transformer short-circuit impedance (% Z) 301 that can be selected due to the short-circuit current limitation (dotted line 503) becomes narrow, and as a result, the transformer is updated. There is no other way.

On the other hand, in this embodiment, the high voltage reactor 201 is provided on the primary side of the power receiving circuit breaker 202, and the power receiving circuit breaker 202 and the transformers 104 and 105 are electrically connected via the high voltage reactor 201. Therefore, the short-circuit current can be reduced, and the 20 kA class circuit breaker 202 can be applied to the high-voltage power supply panel without updating the transformers 104 and 105.

Further, as an arrangement problem, it may be required not to change the panel size of the high-voltage power supply system 106 in order to divert the cable that supplies power to the load.

FIG. 6 shows a schematic outline view of the high-voltage power supply panel. The upper side of FIG. 6 shows a high-voltage power supply panel as a comparative example before applying this embodiment. In this high-voltage power supply panel, as shown in FIG. 1, a 63 kA class power receiving circuit breaker 202A is used.

The lower side of FIG. 6 shows a high-voltage power supply panel according to this embodiment. As described above, since a large capacity load is not required after decommissioning, in this embodiment, the high voltage reactor 201 is arranged on the primary side of the power receiving circuit breaker 202 so that the installation position of the power receiving circuit breaker 202 is not changed as much as possible. A high-voltage power panel can be configured.

Further, in this embodiment, in consideration of updating the transformers 104 and 105 to smaller transformers after decommissioning, a disconnection device 2011 as a "connection destination change device" is installed on the secondary side of the high-voltage reactor 201. To do. When updating the transformer, the specifications of the new transformer will be such that the 20 kA class power receiving circuit breaker 202 can be applied. Further, the disconnection device 2011 disconnects the high-voltage reactor 201 from the primary side of the power receiving circuit breaker 202, and directly connects the output of the new transformer to the power receiving circuit breaker 202 of the power supply panel of the high-voltage power supply system 106. By configuring the high-voltage reactor 201 so that it can be separated in this way, it is possible to handle the power supply panel of the high-voltage power supply system 106 without changing the configuration shown on the lower side of FIG. 6, and the usability is improved.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

101: Generator, 102: Main transformer, 103: Switchyard, 104: In-house transformer, 105: Starting transformer, 106: High-voltage power supply system, 107: Large-capacity load auxiliary machine, 108: Low-voltage power supply system, 110 : Circuit breaker, 201: High voltage reactor, 202, 202A: Power receiving circuit breaker, 2011: Disconnector

Claims (3)

High-voltage power supply equipment for a decommissioned nuclear power plant
A power receiving circuit breaker that connects the first transformer and the high-voltage power supply system,
An impedance increase unit provided on the primary side of the power receiving circuit breaker and
With
A low-voltage power supply system is connected to the high-voltage power supply system via a second transformer.
The low-voltage power supply system is connected to devices related to environmental maintenance in the power plant other than devices directly related to power generation in the nuclear power plant.
The impedance increasing portion is a high-voltage reactor.
A connection destination changing device for changing the connection destination of the primary side of the power receiving circuit breaker is further provided between the impedance increasing unit and the primary side of the power receiving circuit breaker.
When updating the first transformer to a new first transformer, the impedance increasing portion and the primary side of the power receiving circuit breaker are separated by operating the connection destination changing device. wherein to connect the new first transformer and the primary side of the power receiving circuit breaker,
High-voltage power supply equipment for a decommissioned nuclear power plant. The power receiving circuit breaker is a hybrid high-voltage circuit breaker provided with a drive mechanism that utilizes electricity storage by a capacitor and spring force.
High-voltage power supply equipment for a decommissioned nuclear power plant according to claim 1 . The breaking current of the power receiving circuit breaker is less than 63 kA.
The high-voltage power supply equipment of the decommissioned nuclear power plant according to claim 2 .

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