WO2016167251A1

WO2016167251A1 - Device for stabilizing failure in electrical power system and method for use in same

Info

Publication number: WO2016167251A1
Application number: PCT/JP2016/061812
Authority: WO
Inventors: 晃古谷
Original assignee: 株式会社東芝
Priority date: 2015-04-16
Filing date: 2016-04-12
Publication date: 2016-10-20
Also published as: JP2016208586A

Abstract

Provided is a feature for stabilizing failure in an electrical power system with which the power generation output can be maintained even when an instantaneous voltage drop over a long period due to a system failure is expected. The failure stabilization device is provided with: a bypass breaker installed between a power station and an external power transmission system fed with electrical power from the power station, the bypass breaker being capable of switching between supply, in which the power station and the external power transmission system are electrically connected, and open, in which the electrical connection is disestablished; a braking resistor connected in parallel to the bypass breaker, the braking resistor having a predetermined resistance value; a system information reception unit for receiving system information relating to the operational state of the external power transmission system; a first determining unit for determining whether or not the received system information satisfies a disturbance occurrence condition for detecting the incidence of a disturbance in the external power transmission system; and a control signal output unit for outputting, when the disturbance incidence condition is satisfied, an opening signal for opening the supplied bypass breaker.

Description

Accident stabilization device and method in power system

Embodiment of this invention is related with the accident stabilization technique in the electric power system for responding to the grid fault which generate | occur | produced in the external power transmission system.

A general power system is composed of a power plant and an external power transmission system that receives power from this power plant. In a power system with ample output adjustment capability at a power plant, a large scale system is established by disconnecting the generator to be stepped out and increasing the output of the generator when a system fault such as a short circuit accident or grounding accident occurs. It is controlled stably so that it does not develop into an unstable system.

On the other hand, in a power system with little margin for output adjustment capability, the degree of intervention for stable control by output adjustment is limited when a system fault occurs. In particular, since the transmittable capacity decreases as the distance from the center of the power transmission network decreases, there is less margin for output adjustment capability, and the stability of the power system decreases. In a power system with low stability, if a system fault occurs at the very end of the power plant, the generator may step out.

And, if the power plant output greatly increases or decreases due to the generator step-out, it becomes impossible to maintain the supply and demand balance, causing voltage collapse of the entire power system and large-scale power outage.

Conventionally, a power transmission system stabilization device has been introduced for the purpose of preventing step-out of a generator connected to an end of a power transmission network and performing stable control of the power transmission network in the event of a system failure.

For example, a technique is disclosed in which a gate circuit having a semiconductor switching element is turned on / off in accordance with the magnitude of a current to be transmitted, and the current flows to the braking resistor circuit. This technology suppresses the acceleration of the generator by passing a current through the braking resistor circuit and consuming electric power, thereby preventing the generator from stepping out and improving the transient stability of the transmission system.

JP 2002-17041 A

By the way, there are various power plants in the power system, and plants such as nuclear power plants and thermal power plants (steam power plants) generate power using a large-capacity synchronous generator. This synchronous generator has a strong synchronization force for maintaining synchronization with an external power transmission system, and has a large inertia. For this reason, the steam power plant is important in increasing the transient stability of the electric power system and increasing the resistance to system fluctuations caused by a system fault.

In this steam power plant, power is generated by rotating a steam turbine and rotating a synchronous generator connected to the steam turbine by steam generated by heating water with a heat source. For this reason, a large-scale pump for circulating water and steam used for power generation is installed in the steam power plant, and this large-scale pump is driven using an electric motor such as an induction motor or a variable speed inverter drive.

The electric motor for driving the pump is driven by feeding the electric power generated by the generator through the on-site power source. For this reason, when a system fault such as a short-circuit accident or a grounding accident occurs and a current flows into the point of the accident, a short-time instantaneous voltage drop occurs in the power plant, and the drive capability of the motor decreases. As a result, the steam flow used for power generation cannot be maintained, and the power generation output of the plant may be reduced.

Specifically, the induction motor generates torque is proportional to the square of the voltage. Therefore, when the voltage becomes half of the rated voltage due to instantaneous voltage drop, the induction motor generates torque at the rated output. To one-fourth of Since the output of the induction motor depends on the torque x number of rotations, the output of the induction motor decreases due to the pump load at the rated output, and the operation with a lower number of rotations is performed from the balance point between the load torque and the output during rated operation. Move to a point. For this reason, the rotational speed of the pump decreases.

When the speed of the pump is reduced, water and steam used for power generation cannot be circulated sufficiently, resulting in a decrease in power generation output. In particular, when a plurality of pumps are connected in series, when the rotational speed of the upstream pump decreases, the suction pressure of the downstream pump decreases, and the plant operation may not be continued.

In addition to the electric motor that drives the large pump, equipment necessary for plant operation such as a motorized valve and control panel is also supplied with power from the on-site power supply. For this reason, even when these on-site loads occur, if an instantaneous voltage drop occurs in the power plant, there is a possibility that the in-house load cannot be driven normally and the plant operation is affected.

Conventional accident stabilization technology improves the stability of the power system by dumping abnormal currents in the power grid. When an instantaneous voltage drop occurs in the power plant due to a grid fault, the load on the site such as the motor It does not take into account the influence on the driving of the power plant, and does not suppress a decrease in the power generation output of the plant.

The present invention has been made in view of such circumstances, and the accident stabilization technique in the power system that can maintain the power generation output even when a long-term instantaneous voltage drop is assumed in the power plant due to a system fault. The purpose is to provide.

In the accident stabilization apparatus in the electric power system according to the embodiment of the present invention, the input state is installed between the power plant and an external power transmission system that receives power supply from the power plant, and electrically connects between them. A bypass circuit breaker that can be switched to an open state that cuts off the electrical connection, a braking resistor that is connected in parallel to the bypass circuit breaker and has a predetermined resistance value, and an operation of the external power transmission system A system information receiving unit that receives system information related to a state, and a first determination that determines whether the received system information satisfies a disturbance occurrence condition set for detecting occurrence of a disturbance event in the external power transmission system And a control signal output unit that outputs an open signal that switches the bypass circuit breaker in the on state to the open state when the disturbance generation condition is satisfied. It is characterized in.

In the accident stabilization method in the electric power system according to the embodiment of the present invention, the input state that is installed between the power plant and an external power transmission system that receives power supply from the power plant, and electrically connects between them The external power transmission using a bypass circuit breaker that can be switched to an open state that interrupts electrical connection to the external circuit, and a braking resistor that is connected in parallel to the bypass circuit breaker and has a predetermined resistance value A step of receiving system information regarding the operating state of the system, and a step of determining whether or not the received system information satisfies a disturbance occurrence condition set for detecting occurrence of a disturbance event in the external power transmission system; Outputting an open signal for switching the bypass circuit breaker in the on state to the open state when the disturbance generating condition is satisfied, And butterflies.

The embodiment of the present invention provides an accident stabilization technique in an electric power system that can maintain a power generation output even when a long-term instantaneous voltage drop is assumed in a power plant due to a system fault.

The block diagram which shows the structure of the accident stabilization apparatus which concerns on 1st Embodiment installed between the power station and the external power transmission system. The figure explaining the setting method of the resistance value of the braking resistor applied to this embodiment. (A) The figure which shows the state of the accident stabilization apparatus at the normal time, (B) The figure explaining the state of the accident stabilization apparatus when the disturbance event occurs, (C) The accident stabilization after the disturbance event has converged The figure explaining the state of an apparatus. (A) Top view which shows the example of application of the accident stabilization apparatus which concerns on this embodiment in the case of transmitting electric power to an external electric power grid | system by 3-phase alternating current, (B) The external view of the accident stabilization apparatus which concerns on this embodiment. The flowchart which shows the control action of the accident stabilization apparatus which concerns on 1st Embodiment. (A) A graph comparing the output voltage of the generator terminal and the external power transmission system in this embodiment and the comparative example when a three-phase short-circuit accident occurs at the closest end of the power plant, (B) Comparison with this embodiment A graph comparing the internal phase difference angle of the main generator with an example. The block diagram which shows the structure of the accident stabilization apparatus which concerns on 2nd Embodiment installed between the power station and the external power transmission system. The flowchart which shows the control action of the accident stabilization apparatus which concerns on 2nd Embodiment. The block diagram which shows the structure of the accident stabilization apparatus which concerns on 3rd Embodiment installed between the power station and the external power transmission system. The block diagram which shows the modification of the accident stabilization apparatus which concerns on 3rd Embodiment installed between the power station and the external power transmission system. The figure which shows the structure of a general power plant and an external power transmission system (comparative example).

(First embodiment)
Hereinafter, this embodiment is described based on an accompanying drawing.
FIG. 1 shows a configuration of an accident stabilization device 10 (hereinafter, abbreviated as accident stabilization device 10) in the power system according to the first embodiment, installed between a power plant 11 and an external power transmission system 12. ing.

The accident stabilization apparatus 10 in the power system according to the present embodiment is installed between a power plant 11 and an external power transmission system 12 that receives power supply from the power plant 11, and electrically connects them. A bypass circuit breaker 13 that can be switched between an on-state and an open state that interrupts electrical connection, a braking resistor 14 that is connected in parallel to the bypass circuit breaker 13 and has a predetermined resistance value, and external power transmission The system information receiving unit 51 that receives the system information s regarding the operating state of the system 12 and whether or not the received system information s satisfies the disturbance occurrence condition set for detecting the occurrence of the disturbance event in the external power transmission system 12. And a control signal output unit 53 that outputs an open signal t that opens the bypass circuit breaker 13 that is turned on when a disturbance generation condition is satisfied. Equipped with a.

The power plant 11 is a steam power plant such as a thermal power plant or a nuclear power plant that generates steam with the generated thermal energy and rotates the turbine using the steam to generate power with the main generator 15. . The external power transmission system 12 means the entire power transmission network outside the power plant 11, including an external load that receives power generated by the power plant 11 through the power transmission line 28.

First, the configuration within the power plant 11 will be described.
The main generator 15 is connected to the main circuit phase separation bus 18 via the generator circuit breaker 17 and supplies the generated power to the main circuit phase separation bus 18. The automatic voltage regulator 16 performs field voltage control and keeps the terminal voltage of the main generator 15 constant.

The electric power supplied to the main circuit phase separation bus 18 branches to the in-house load side in the power plant 11 and the external power transmission system 12 side outside the power plant 11.

The electric power sent to the in-house load side is stepped down in voltage by the in-house transformer 19 and branches in two directions. The branched power is supplied to the _two local buses 21 (21 ₁ , 21 ₂ ) via the circuit breakers 20 (20 ₁ , 20 ₂ ). Various in-house loads are connected to the in-house bus 21 for power supply.

Plant bus 21 _1, feed water pump motor _{₂₂ (22} 1a, ₂₂ _1b) for driving a pump for water supply, condensate pump motor 23 ₁ for driving a pump for recovery of water, the generator auxiliary motor 24 _1, and the electric low bus load 26 _1, such as a valve or control panel is connected, and supplies power to the respective load. In addition, electric power is supplied to the feed water pump motor 22 _1a via the motor variable speed drive inverter 25 ₁ .

House bus 21 _2, feed water pump motor _{_{22 (22 2a, 22 2b)}} , a condensate pump motor 23 _2, the generator auxiliary motor 24 _2, and low pressure bus load 26 ₂ are connected, the power to each of the load Supply. Incidentally, a condensate pump motor 23 ₂ is supplied with power via the electric motor variable speed drive inverter 25 _2.

The in-house bus 21 serves as an in-house power source for supplying electric power to the in-house load, and the output of the power plant 11 can be maintained by maintaining the voltage of the in-house bus 21 at a certain level or higher. Is operated stably. The configuration of the load connected to the in-house bus 21 (21 ₁ , 21 ₂ ) is an example, and is not limited to this configuration.

On the other hand, the electric power transmitted to the external power transmission system 12 side is boosted in voltage by the main transformer 27 and externally transmitted via the accident stabilization device 10 installed between the power plant 11 and the external power transmission system 12. It is sent to the system 12.

The accident stabilization device 10 includes a bypass circuit breaker 13, a braking resistor 14, and a control device 50.

The bypass circuit breaker 13 is a circuit breaker installed between the power plant 11 and the external power transmission system 12, and switches between an on state in which these are electrically connected and an open state in which the electrical connection is interrupted. Is possible.

The bypass circuit breaker 13 is normally turned on and is switched to an open state when a disturbance event occurs. Switching on / off in the bypass circuit breaker 13 is performed using an open signal t output from the control device 50.

Here, the disturbance event means a system fault such as a short circuit accident or a ground fault, which occurs in the external power transmission system 12, or an unbalanced state of the voltage or current flowing through the external power transmission system 12. The disturbance event causes a voltage drop in the in-house bus 21 that affects the operation (drive) of the in-house load or a voltage drop in the external power transmission system 12 that may cause a step-out of the main generator 15.

In addition, about the insulation system of the bypass circuit breaker 13, the general-purpose goods currently used widely in an ultra high voltage power transmission system are applied, applying the existing insulation systems, such as an air insulation system and a gas insulation system. Thereby, the highly economical accident stabilization apparatus 10 can be comprised.

The braking resistor 14 is electrically connected in parallel to the bypass circuit breaker 13 and has a predetermined resistance value. Note that the resistance value of the braking resistor 14 needs to be set appropriately, and a method for setting the resistance value will be described later.

The brake resistor 14 may be a general-purpose product widely used in an ultra-high voltage power transmission system, but a high-resistance conductor (for example, iron) is installed in oil in a casing similar to an oil-filled transformer. A resistor of structure is preferred. The resistor having this structure can spread the heat load and saves space as compared with a case where a high-resistance conductor is directly installed in the atmosphere.

The braking resistor 14 is designed to have a sufficient heat capacity against the heat energy generated while acting as a resistance. In addition, when a plurality of continuous inputs are assumed, it is designed to have a sufficient heat capacity according to the total heat energy at the time of continuous inputs.

Since the braking resistor 14 is not frequently turned on for a short time, it hardly diffuses during the operation, and only the temperature rise of the conductor needs to be considered. For this reason, only cooling by natural circulation is sufficient for the cooling method of the braking resistor 14.

Normally, since the bypass circuit breaker 13 is turned on, only a small amount of current flows through the braking resistor 14 having a high resistance value, and most of the current flows through the bypass circuit breaker 13. On the other hand, when a disturbance event occurs, since the bypass circuit breaker 13 is opened, a current flows through the braking resistor 14.

The control device 50 includes a system information receiving unit 51, a first determination unit 52, and a control signal output unit 53. The function of each unit constituting the control device 50 may be realized by executing a predetermined program code in an electronic circuit such as a processor, and is not limited to such software processing. It may be realized by hardware processing using an electronic circuit, or may be realized by combining software processing and hardware processing.

The system information receiving unit 51 receives system information s output from an operation device (not shown) provided in the external power transmission system 12 via a transmission network that connects the external power transmission system 12 and the control device 50. .

The system information s is information related to the operating state of the external power transmission system 12, an accident detection signal output from the operation device when a system fault such as a short circuit accident or a ground fault occurs, and any arbitrary information in the external power transmission system 12. It includes voltage and current signals measured at the connection point. The accident detection signal includes information on the type of accident that occurred and the position where the accident occurred.

The first determination unit 52 determines whether or not a disturbance event has occurred in the external power transmission system 12 based on the system information s received by the system information reception unit 51. The first determination unit 52 presets a disturbance generation condition for detecting the presence or absence of a disturbance event using the system information s.

(1) As a typical disturbance generation condition, (1). Whether a short-circuit accident occurred in the immediate vicinity of the power plant 11, (2). Whether or not the voltage drops so as to hinder the maintenance of the voltage of the in-house bus 21 (3). Whether the main generator 15 has a voltage drop that may cause an acceleration step-out; (4). There are four conditions: whether there is a voltage or current imbalance that affects the operation of the on-site load.

The first determination unit 52 determines that the condition (1) satisfies the disturbance generation condition when the accident detection signal indicates a short-circuit accident at the closest end of the power plant 11 when the accident detection signal is received. .

For condition (2), the voltage value of the measured voltage signal is compared with the rated voltage value, and the disturbance generation condition is determined when a voltage drop that causes a problem in maintaining the voltage of the in-house bus 21 has occurred. It is determined that it satisfies. Alternatively, a reference value for detecting a voltage drop that would hinder the maintenance of the voltage of the in-house bus 21 is set in advance, and it is determined that the disturbance generation condition is satisfied when the measured voltage value falls below this reference value. May be.

In addition, the condition determination may be performed using the current value of the measured current signal, and the current increase is such that the voltage maintenance of the in-house bus 21 is disturbed by comparing the measured current value with the rated current. If it occurs, it may be determined that the disturbance generation condition is satisfied.

For condition (3), the voltage value of the measured voltage signal is compared with the rated voltage value, and the disturbance generating condition is determined when a voltage drop that may cause the main generator 15 to accelerate out of step occurs. It is determined that it satisfies.

For condition (4), the average value or deviation of the voltage value (or current value) of the measured voltage signal is measured to detect the degree of voltage value balance. Then, when the degree of balance exceeds a certain reference range, it is determined that a disturbance generation condition is satisfied, assuming that an unbalance has occurred.

The first determination unit 52 determines that the disturbance generation condition is satisfied when any one of the above-described conditions (1) to (4) is satisfied. On the other hand, when neither condition is satisfied, it is determined that the disturbance generation condition is not satisfied.

The disturbance occurrence conditions are not limited to the conditions (1) to (4). For example, the conditions may be set more finely based on the type of accident and position information included in the accident signal. By setting a plurality of disturbance generation conditions and making a determination based on a plurality of system information s (accident signal, voltage signal, and current signal), a disturbance event can be detected more accurately.

It should be noted that the degree of voltage drop, the reference value, and the degree of balance required to determine the disturbance event under the conditions (2), (3), and (4) are the internal voltage of the main generator 15, the internal impedance, Since it changes depending on the parameters of the power plant 11 and the external power transmission system 12 such as the load configuration and the load of the external power transmission system 12, the analysis is performed in advance and the result is set based on the result.

When the first determination unit 52 determines that the disturbance generation condition is satisfied, the control signal output unit 53 outputs an open signal t for switching the bypass circuit breaker 13 in the open state to the open state.

After that, when the disturbance event converges, that is, when the disturbance generation condition is not satisfied, the output of the release signal t is stopped. Thereby, the bypass circuit breaker 13 which has been in the open state is switched to the on state again.

Next, a method for setting the resistance value of the braking resistor 14 will be described with reference to FIG.
The resistance value of the braking resistor 14 needs to be set to an appropriate resistance value so as to achieve the function of maintaining the voltage of the in-house bus 21 and preventing the acceleration step-out of the main generator 15 when a disturbance event occurs. .

First, the resistance value is examined from the viewpoint of achieving the function of maintaining the voltage of the in-house bus 21.
The in-house bus 21 is connected to the main circuit phase separation bus 18 via the in-house transformer 19. Under normal conditions, the voltage of the main circuit phase separation bus 18 is maintained at a rating by controlling the main generator 15 by the automatic voltage regulator 16. And the voltage of the in-house bus 21 is kept at the rating by setting the operating voltage and adjusting the tap ratio of the in-house transformer 19.

When the voltage of the main circuit phase separation bus 18 decreases due to a system fault (for example, a short-circuit fault), the voltage of the in-house bus 21 also decreases.

At this time, when the voltage of the in-house bus 21 when the braking resistor 14 is turned on is examined by the unit method, the difference between the internal voltage of the main generator 15 and the voltage of the external power transmission system 12 is determined as the internal impedance of the main generator 15. The voltage of the external power transmission system 12 is added to the divided voltage of the impedance of the main transformer 27 and the impedance of the braking resistor 14.

From this relationship, when the expected rate of voltage drop in the external power transmission system 12 and the target value of the voltage of the in-house bus 21 (for example, 80% of the rated voltage) are determined, the minimum resistance value X _min of the braking resistor 14 is I want.

On the other hand, as for the maximum resistance value, as long as the voltage of the main generator 15 is controlled by the automatic voltage regulator 16, the voltage is kept substantially constant even when the resistance value is increased. Therefore, from the viewpoint of maintaining the voltage of the in-house bus 21, the range 101 where the minimum resistance value X _min or more is an appropriate resistance value range. The range 101 varies depending on the conditions of the main generator 15 and the external power transmission system 12.

Subsequently, the resistance value is examined from the viewpoint of preventing the acceleration failure of the main generator 15.
In order to prevent the accelerating step-out of the main generator 15, it is necessary to sufficiently consume energy by the braking resistor 14.

That is, the condition for preventing step-out is that the sum of the energy consumed by the braking resistor 14 and the power transmitted to the external power transmission system 12 is larger than the energy that must be consumed to prevent step-out.

Here, when the energy consumed by the braking resistor 14 is defined as P ₁ , the power transmitted to the transmission system: P ₂ , and the energy necessary for preventing step-out: P ₃ , in order to prevent step-out, the following Formula (1) becomes a condition.
P ₁ + P ₂ ≧ P ₃ Formula (1)

The resistance value of the braking resistor 14 R, if the current flowing through the braking resistor 14 was I, the energy consumed per unit time in the resistor becomes RI ^2. Since this what braking resistor is integrated in the period being turned is P _1, it is transformed into Equation (1), the following equation (2).
R ≧ (P ₃ −P ₂ ) / (integral value of I ² ) (2)

The current has an upper limit depending on the capacity of the main generator 15 and the impedance of the electric circuit, and the integral value is also a constant. From this relationship, the lower limit value Y _min of the resistance value selection range is determined.

On the other hand, when the voltage between the terminals of the braking resistor 14 is V, the energy consumed per unit time by the resistor is V ² / R, and this is obtained by integrating this during the period when the braking resistor is turned on. _1, and therefore, when the deformed substituted into (1), the following equation (3).
R ≦ (integral value of V ² ) / (P ₃ −P ₂ ) (3)

The terminal voltage has an upper limit because the voltage of the main generator 15 is controlled by the automatic voltage regulator 16, and the integrated value is also a constant. From this relationship, the maximum value Y _max of the resistance value selection range is obtained.

Therefore, from the viewpoint of preventing the acceleration step-out of the main generator 15, Y _min ≦ R ≦ Y _max (range 102) is an appropriate resistance value range. The range 102 varies depending on the voltage of the in-house bus 21 and the condition of the main transformer 27.

The resistance value range 103 determined based on the resistance value range 101 for maintaining the voltage of the in-house bus 21 and the resistance value range 102 for preventing the generator step-out is the voltage maintenance and main voltage of the in-house bus 21. An appropriate resistance value range that achieves the function of preventing the generator 15 from accelerating step-out is obtained. The resistance value of the braking resistor 14 is set within this range 103.

The operation of the present embodiment will be specifically described with reference to FIGS. In FIGS. 3A to 3C, the configuration of the in-house load connected to the in-house bus 21 is shown in a simplified manner.

FIG. 3A shows a configuration of the accident stabilization apparatus 10 in a normal state, and the electric power generated by the main generator 15 is supplied to the main circuit phase separation bus 18. Then, the power branched by the main circuit phase separation bus 18 is transmitted to the external power transmission system 12 through the main transformer 27, the bypass circuit breaker 13, and the power transmission line 28. Since the bypass circuit breaker 13 is in the on state at normal times, most of the current flows through the bypass circuit breaker 13.

The other power branched by the main circuit phase separation bus 18 is supplied to the in-house bus 21 via the in-house transformer 19. Power is supplied from the in-house bus 21 to the in-house load.

In this situation, when a short circuit accident occurs at the closest end of the power plant 11, power cannot be transmitted from the power plant 11 to the external power transmission system 12. For this reason, the load of the main generator 15 decreases rapidly, and an imbalance with the machine input to the main generator 15 occurs. At the same time, a short-circuit current flows from the main generator 15 to the accident point.

FIG. 3B shows the configuration of the accident stabilization apparatus 10 when a short-circuit accident occurs at the closest end of the power plant 11.

When the control device 50 always receives the system information s and receives an accident signal related to a short-circuit accident at the closest end of the power plant 11, the control device 50 determines that the disturbance generation condition is satisfied, and opens the bypass circuit breaker 13. t is output. Thereby, bypass circuit breaker 13 will be in an open state.

When the bypass circuit breaker 13 is opened, the braking resistor 14 is electrically inserted between the main transformer 27 and the external power transmission system 12.

Thus, the short-circuit current that has flowed to the point of failure through the bypass circuit breaker 13 flows through the braking resistor 14. Joule loss occurs in the braking resistor 14 depending on the magnitude of the flowing current and the resistance value of the braking resistor 14, and the braking resistor 14 functions as a load of the main generator 15.

Since the resistance value of the braking resistor 14 is set in advance assuming the output of the main generator 15 immediately before the occurrence of the short-circuit accident, the load of the braking resistor 14 and the mechanical input of the main generator 15 are set. And the acceleration of the main generator 15 is suppressed.

At the same time, the current passing through the braking resistor 14 causes a potential difference across the resistor. Since a potential difference is generated between both ends of the braking resistor 14, the electric power generated by the main generator 15 can be supplied to the external power transmission system 12 side and the in-house load side, so that the voltage of the in-house bus 21 is maintained. As a result, the in-house load that receives power from the in-house bus 21 can be driven without being affected by a short circuit accident.

FIG. 3C shows the configuration of the accident stabilization apparatus 10 after the short-circuit accident has converged.
When the short-circuit accident converges, the control device 50 stops outputting the release signal t because the disturbance generation condition is not satisfied. Thereby, the bypass circuit breaker 13 is switched from the open state to the closed state.

When the bypass circuit breaker 13 is turned on and returns to the normal state, most of the power transmitted to the external power transmission system 12 is transmitted again through the bypass circuit breaker 13.

FIG. 4A shows an application example of the accident stabilization apparatus 10 in the case where the electric power generated at the power plant 11 is transmitted by three-phase alternating current. FIG. 4B shows an external view of the accident stabilization apparatus 10 installed between the power plant 11 and the external power transmission system 12. In addition, since the structure of each function of the control apparatus 50 becomes the same as FIG. 1, description is abbreviate | omitted.

The electric power generated at the power plant 11 is transmitted to the external power transmission system 12 by three-phase alternating current via _three transmission lines 28 (28 ₁ , 28 ₂ , 28 ₃ ). The bypass circuit breaker 13 and the braking resistor 14 are installed for each of the three phases between the power plant 11 and the external power transmission system 12.

One control device 50 is provided for each of the three bypass circuit breakers 13, and controls the on / off operation of the bypass circuit breaker 13 in accordance with a disturbance event that occurs in the external power transmission system 12.

Specifically, first, the system information receiving unit 51 (FIG. 1) receives the system information s regarding the operating state of the external power transmission system 12 for each phase.

The first determination unit 52 determines for each phase whether or not the received system information s satisfies the disturbance occurrence condition. For example, when a three-phase short circuit accident occurs at the closest end of the power plant 11, it is determined that the above condition (1) is satisfied in all three phases.

When an accident other than a three-phase short circuit occurs, such as a one-phase ground fault, a two-phase ground fault, or a line short circuit, the voltage of the accident phase decreases and an unbalanced current flows depending on the load state. At this time, the phase satisfying the conditions (2) to (4) is determined to satisfy the disturbance generation condition.

The control signal output unit 53 outputs an open signal t to the bypass circuit breaker 13 corresponding to the phase that satisfies the disturbance generation condition. For example, the line between the short-circuit failure occurs, if a disturbance occurs condition is satisfied by the power phase of the

transmission lines

28 ₁ and 28 _3, and outputs an opening signal t to the

bypass breaker

13 ₁ and 13 _3.

FIG. 5 shows a flowchart showing the control operation of the accident stabilization apparatus 10 according to the first embodiment (see FIG. 1 as appropriate).

The system information receiving unit 51 receives system information s (accident signal, voltage signal, and current signal) from the external power transmission system 12 (S10). In addition, the system | strain information reception part 51 always performs reception of the system | strain information s.

And the 1st determination part 52 determines whether the received system | strain information s satisfy | fills the disturbance generation conditions preset in order to detect a disturbance event (S11). If the disturbance generation condition is not satisfied, the process ends (S11: NO).

The control signal output unit 53 outputs the release signal t when the disturbance generation condition is satisfied (S11: YES, S12).

The control signal output unit 53 continues to output the release signal t until the first determination unit 52 determines that the disturbance generation condition is not satisfied, in other words, until the disturbance event converges (S13: NO).

On the other hand, when the first determination unit 52 determines that the disturbance generation condition is not satisfied, that is, when the disturbance has converged, the output of the release signal t is stopped and the process ends (S13: NO, S14).

FIG. 6 is a comparison of the results of power system analysis in the case of simulating a three-phase short-circuit accident at the closest end of the power plant 11 between the present embodiment (FIG. 1) and the comparative example (FIG. 11). is there. As a configuration of the comparative example, as shown in FIG. 11, a general configuration in which a power plant 11 and an external power transmission system 12 are connected is used.

Here, a power system analysis is performed by simulating a state in which a three-phase short-circuit accident that occurred one second later lasts 250 ms. Further, in the case of applying this embodiment, it is assumed that the bypass circuit breaker 13 is opened 50 ms after the occurrence of the short-circuit accident and is turned on again immediately after the accident has converged.

FIG. 6 (A) is a graph showing the output of the generator terminal voltage and the external power transmission system voltage in each of the present embodiment and the comparative example.

When this embodiment is applied, the generator terminal voltage (reference numeral 301) is greatly reduced immediately after a short circuit accident (the residual voltage is mainly due to the impedance of the main transformer 27). However, as soon as the bypass circuit breaker 13 is opened, the voltage rises instantaneously to 80% or more, and it can be seen that a voltage sufficient for the operation of the in-house load connected to the in-house bus 21 is maintained.

Then, when the accident converges and the bypass circuit breaker 13 is turned on, the voltage is temporarily increased above the rated voltage by voltage compensation by the braking resistor 14, but then returns to the rated voltage or less, and the voltage stabilizes. . The voltage (reference numeral 302) of the external power transmission system 12 is also stabilized after the accident has converged.

On the other hand, in the configuration of the comparative example, as indicated by the generator terminal voltage (reference numeral 303), during the short-circuit accident, only the residual voltage due to the impedance of the main transformer 27 remains (30% or less), and the on-site load operation continues. Is in danger. The voltage (reference numeral 304) of the external power transmission system 12 is lowered by being dragged by the voltage of the in-house power supply, and the rated voltage cannot be maintained even if the accident is recovered.

FIG. 6B is a graph showing the behavior of the internal phase difference angle of the main generator 15 in each of the present embodiment and the comparative example.

In the present embodiment, it is shown that the internal phase difference angle (symbol 305) of the main generator 15 is suppressed to 100 ° or less after the short-circuit accident, and the operation of the main generator 15 can be continued.

On the other hand, as for the internal phase difference angle (reference numeral 306) of the main generator 15, the configuration of the comparative example shows an aspect of accelerated step-out exceeding 180 °.

In this way, even when a disturbance event that causes a long-time significant voltage drop occurs in the power plant 11, the bypass circuit breaker 13 is opened and the braking resistor 14 is inserted to compensate the voltage. Thus, the voltage of the in-house bus 21 is maintained, and the driving load of the in-house load is prevented. The time during which a significant voltage drop occurs in the in-house bus 21 is a short time until the bypass circuit breaker 13 operates regardless of the actual accident duration.

By preventing the driving load of the on-site load from being reduced, the steam flow used for power generation is maintained, and operation is possible at the plant output before the instantaneous voltage drop. At the same time, since the unbalance between the mechanical input and the electrical output of the main generator 15 is eliminated and the step-out is prevented, the main generator 15 is also maintained in the operating state.

For this reason, it is possible to overcome the influence of the instantaneous voltage drop in the entire power plant 11 and continue the steady operation without disconnecting the power plant 11 from the power system.

(Second Embodiment)
FIG. 7 is a configuration diagram illustrating the accident stabilization apparatus 10 according to the second embodiment. In addition, about the structure and part corresponding to 1st Embodiment (FIG. 1), the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

The accident stabilization device 10 of the second embodiment is different from the first embodiment in that a resistance information detector 29 detects the temperature and failure of the braking resistor 14 and outputs the temperature signal and the failure signal as resistance information u. And a resistance information receiving unit 54 that receives the output resistance information u, and a second determination unit 55 that determines whether or not the braking resistor 14 can be turned on based on the resistance information u. The output unit 53 is to output an open signal t when it is determined that the disturbance generation condition is satisfied and the braking resistor 14 can be turned on.

The resistance information detector 29 is installed in the vicinity of the braking resistor 14 or so as to accommodate the braking resistor 14 therein, and detects the temperature and failure of the braking resistor 14. The temperature of the braking resistor 14 is detected using a temperature detector such as a thermistor or a thermocouple. The failure of the braking resistor 14 is detected from abnormal heat generated using a temperature detector, abnormal gas generated at the time of failure, or a voltage value when a failure detection current is passed.

The resistance information detector 29 converts the detected temperature and failure into an electrical signal, and outputs the temperature signal and the failure signal to the resistance information receiving unit 54 as resistance information u. The failure signal is output only when a failure occurs.

The second determination unit 55 determines whether the braking resistor 14 can be turned on (energized) based on the resistance information u received by the resistance information receiving unit 54. Since the resistance value of the braking resistor 14 varies depending on the temperature, if the resistance value is not appropriate depending on the temperature state (see FIG. 2), it is determined that the braking resistor 14 cannot be turned on. Also, when a failure signal is received, it is determined that the input is impossible.

The control signal output unit 53 outputs the release signal t when it is determined that the disturbance generation condition is satisfied and the braking resistor 14 can be turned on. Therefore, the bypass circuit breaker 13 is opened and the braking resistor 14 is turned on only when the braking resistor 14 is in a state of normally functioning.

FIG. 8 shows a flowchart showing the control operation of the accident stabilization apparatus 10 according to the first embodiment (see FIG. 7 as appropriate).

The system information receiving unit 51 receives system information s (accident signal, voltage signal, and current signal) from the external power transmission system 12 (S20). Note that the system information receiving unit 51 always receives the system information s.

And the 1st determination part 52 determines whether the received system | strain information s satisfy | fills the disturbance generation conditions preset in order to detect a disturbance event (S21). If the disturbance generation condition is not satisfied, the process ends (S21: NO).

When the disturbance occurrence condition is satisfied, the resistance information receiving unit 54 receives the resistance information u output from the resistance information detector 29 (S22).

The second determination unit 55 determines whether or not the braking resistor 14 can be turned on (energized) based on the resistance information u received by the resistance information receiving unit 54 (S23). If the braking resistor 14 cannot be turned on, the process ends (S23: NO).

The control signal output unit 53 outputs the release signal t when the braking resistor 14 can be turned on (S23: YES, S24).

The control signal output unit 53 continues to output the release signal t until the first determination unit 52 determines that the disturbance generation condition is not satisfied (S25: NO).

On the other hand, when the first determination unit 52 determines that the disturbance generation condition is not satisfied, that is, when the disturbance has converged, the output of the release signal t is stopped and the process ends (S25: YES, S26).

As described above, when the temperature is high immediately after the operation and a sufficient effect cannot be obtained even when the resistor is opened, or when the resistor is broken, it is determined that the braking resistor 14 cannot be turned on and the bypass circuit breaker 13 is turned off. Do not perform release. Thereby, protection of the braking resistor 14 is realizable. In addition, it is good also as a structure which restrict | limits the open time of the bypass circuit breaker 13 with a timer as assistance when the determination operation by the 2nd determination part 55 does not function.

(Third embodiment)
FIG. 9 is a configuration diagram illustrating an accident stabilization apparatus 10 according to the third embodiment. In addition, about the structure and part corresponding to 1st Embodiment (FIG. 1), the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

The accident stabilizing device 10 of the third embodiment is different from the first embodiment in that an auxiliary resistor 30 (30 ₁ , 30 ₂ ,... 30 _n ) connected in parallel to the braking resistor 14 and an auxiliary resistor 30 and the switch 31 (31 ₁ , 31 ₂ ,... 31 _n ) for turning on / off the electrical connection between the brake resistor 14 and the brake resistor 14, and the switch 31 to switch between the brake resistor 14 and the auxiliary resistor 30. And a resistance value adjustment unit 56 that adjusts the resistance value of the combined resistance.

A plurality of auxiliary resistors 30 are connected in parallel to the braking resistor 14. By providing the auxiliary resistor 30, when the bypass circuit breaker 13 is opened, the current flows through the combined resistance of the braking resistor 14 and the auxiliary resistor 30.

The plurality of auxiliary resistors 30 may have the same resistance value, or may have different resistance values. It is desirable that the combined resistance of the braking resistor 14 and the auxiliary resistor 30 can take a wide range of resistance values.

The changeover switch 31 is a switch for turning on / off the electrical connection between the auxiliary resistor 30 and the braking resistor 14. By switching this switch, the number of parallel stages of the auxiliary resistor 30 connected to the braking resistor 14 can be changed, and the resistance value of the combined resistor can be adjusted.

Since the braking resistor 14 is always energized, the switch is turned on / off with a slight current flowing. For this reason, the changeover switch 31 uses a switch that can cut off the normal load current (the current in the state where the bypass circuit breaker 13 is turned on).

The resistance value adjusting unit 56 changes the number of parallel stages of the braking resistor 14 connected to the braking resistor 14 by switching the changeover switch 31 so that the set resistance value is obtained, and adjusts the resistance value of the combined resistance. . The resistance value is set by the user within an appropriate resistance value range (see FIG. 2) for achieving the function of maintaining the voltage of the in-house bus 21 and preventing the acceleration step-out of the main generator 15. Further, in the case of load following operation or the like, the resistance value of the combined resistance may be automatically set according to the output of the main generator 15.

In plants with operating conditions in which the output of the main generator 15 changes significantly, such as load following operation, there may be an operating region that cannot be handled with a fixed resistance value.

In this way, by making the resistance input when a disturbance event occurs variable, the resistance value can be adjusted so that the maximum effect can be achieved in maintaining the plant output, and the operating conditions can be flexibly handled.

FIG. 10 is a configuration diagram showing a modified example of the accident stabilization apparatus 10 according to the third embodiment. In addition, about the structure and part corresponding to 3rd Embodiment (FIG. 9), the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

In this modification, the resistance information detector 29 for detecting the temperature and failure of the braking resistor 14 and the resistance information receiving unit 54 for receiving the temperature signal of the braking resistor 14 shown in the second embodiment (FIG. 7) are used. To do.

The resistance value adjusting unit 56 inputs the temperature signal of the braking resistor 14 received by the resistance value receiving unit. Then, the resistance value of the combined resistance of the braking resistor 14 and the auxiliary resistor 30 is adjusted according to this temperature. The adjustment of the resistance value is performed within a range of an appropriate resistance value that achieves the function of maintaining the voltage of the in-house bus 21 and preventing the acceleration of the main generator 15 from being stepped out.

When the braking resistor 14 is premised on short-time insertion, the conductor temperature rises greatly and the resistance value changes greatly by one-time insertion. When the bypass circuit breaker 13 is switched in a short time and the braking resistor 14 is turned on a plurality of times, the temperature may not be lowered sufficiently and the turning on of the braking resistor 14 may be restricted due to an increase in the resistance value.

</ RTI> According to this modification, even when the temperature of the braking resistor 14 rises greatly and the resistance value changes, it can always be adjusted to an appropriate resistance value. For this reason, the restriction | limiting of the conditions which throw in the braking resistor 14 is eased significantly.

According to the accident stabilization device in the power system of each embodiment described above, between the power plant and the external power transmission system, a circuit breaker capable of switching between an on state and a cut-off state, and connected in parallel to this breaker Even when a disturbance event occurs, it is possible to switch the circuit breaker from the on state to the interrupted state when a disturbance event occurs. The power generation output can be maintained.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 ... Accident stabilization apparatus, 11 ... Power station, 12 ... External power transmission system, 13 ... Braking resistor, 14 ... Bypass circuit breaker, 15 ... Main generator, 16 ... Generator circuit breaker, 17 ... Automatic voltage regulator , 18 ... main circuit phase separation bus, 19 ... in-house transformer, 20 ... breaker, 21 (21 ₁ , 21 ₂ ) ... in-house bus, 22 (22 _1a , 22 _1b , 22 _2a , 22 _2b ) ... feed water pump motor , 23 (23 ₁ , 23 ₂ ) ... Condensate pump motor, 24 (24 ₁ , 24 ₂ ) ... Generator auxiliary motor, 25 (25 ₁ , 25 ₂ ) ... Motor variable speed drive inverter, 26 (26 ₁ , 26 ₂ ) ... Low-voltage bus load (electric valve, control panel, etc.), 27 ... Main transformer, 28 ... Power transmission line, 29 ... Resistance information detector, 30 (30 ₁ , 30 ₂ , ..., 30 _n ) ... auxiliary resistor, ₃₁ (31 1, ₃₁ 2, ... , 31 _n) ... changeover switch, 50 ... controller, 51 ... system information receiving unit, 52 ... first determination unit, 53 ... control signal output section, 54 ... resistance information receiving unit, 55 ... second determination unit, 56 ... Resistance value adjustment unit, s ... system information, t ... open signal, u ... resistance information.

Claims

A bypass installed between the power plant and an external power transmission system that receives power from this power plant, and can be switched between an on state in which the power is electrically connected and an open state in which the electrical connection is interrupted A circuit breaker,
A braking resistor connected in parallel to the bypass circuit breaker and having a predetermined resistance value;
A grid information receiving unit that receives grid information related to the operating state of the external power transmission system;
A first determination unit that determines whether or not the received grid information satisfies a disturbance occurrence condition set for detecting occurrence of a disturbance event in the external power transmission system;
An accident stabilization device in an electric power system, comprising: a control signal output unit that outputs an open signal that switches the bypass circuit breaker in the input state to the open state when the disturbance generation condition is satisfied.
The grid information is measured at an accident information transmitted from the external power transmission system when an accident occurs, a voltage signal measured at an arbitrary connection point in the external power transmission system, and an arbitrary connection point in the external power transmission system. The accident stabilization device for a power system according to claim 1, wherein the fault stabilization device is at least one of current signals.
The resistance value of the braking resistor is a range of resistance values that cause a potential difference necessary for maintaining the voltage of the in-house bus that supplies the power to the load in the power plant, and prevents accelerated step-out in the generator of the power plant. 2. The accident stabilization device for an electric power system according to claim 1, wherein the accident stabilization device is set based on a range of a resistance value that causes necessary energy consumption.
The bypass circuit breaker and the braking resistor are installed for each of the phases in the case of transmitting power by multiphase alternating current,
The system information receiving unit receives the system information related to the operating state of the external power transmission system for each phase,
The first determination unit determines, for each phase, whether the received system information satisfies the disturbance generation condition,
The accident stabilization apparatus for an electric power system according to claim 1, wherein the control signal output unit outputs the open signal to the bypass circuit breaker corresponding to a phase that satisfies the disturbance generation condition.
A resistance information detector for detecting the temperature and failure of the braking resistor and outputting the temperature signal and the failure signal as resistance information;
A resistance information receiving unit for receiving the output resistance information;
A second determination unit that determines whether or not the braking resistor can be turned on based on the resistance information;
2. The accident stability in the electric power system according to claim 1, wherein the control signal output unit outputs the release signal when it is determined that the disturbance generation condition is satisfied and the braking resistor can be turned on. Device.
An auxiliary resistor connected in parallel to the braking resistor;
A changeover switch for turning on / off the electrical connection between the auxiliary resistor and the braking resistor;
The accident in the electric power system according to claim 1, further comprising a resistance value adjusting unit that switches the changeover switch to adjust a resistance value of a combined resistance of the braking resistor and the auxiliary resistor. Stabilizer.
The accident in the electric power system according to claim 6, wherein the resistance value adjusting unit adjusts a resistance value of a combined resistance of the braking resistor and the auxiliary resistor according to a temperature of the braking resistor. Stabilizer.
A bypass installed between the power plant and an external power transmission system that receives power from this power plant, and can be switched between an on state in which the power is electrically connected and an open state in which the electrical connection is interrupted Using a circuit breaker and a braking resistor connected in parallel to the bypass circuit breaker and having a predetermined resistance value,
Receiving system information relating to the operating state of the external power transmission system;
Determining whether the received grid information satisfies a disturbance occurrence condition set in order to detect the occurrence of a disturbance event in the external power transmission system;
Outputting an open signal for switching the bypass circuit breaker in the on state to the open state when the disturbance generation condition is satisfied, and a method for stabilizing an accident in an electric power system.