JPS62160099A - Control circuit for exciter of turbine generator for atomic reactor - Google Patents

Abstract

PURPOSE:To continue the operation of an auxiliary machine in a power plant for a predetermined time by closing a field breaker for a predetermined time when a turbine is tripped. CONSTITUTION:When a defect occurs in a turbine generator 10 so that any of contacts 1a-1n is closed, an auxiliary relay 4 is excited to excite a trip coil 16TC of a field breaker 1b. Simultaneously, a thyristor gate block signal is output from an automatic voltage regulator 15 to a thyristor 12. After a contact 3 closed when a turbine trip is detected is closed when a turbine generator 10 is tripped, a predetermined time is elapsed by a relay 3X for a limited time to excite an auxiliary relay 4. Thus, after the turbine is tripped, the generator 10 is continuously operated for a predetermined time period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control circuit for an excitation device in a thyristor direct excitation type nuclear reactor turbine generator.

[Technical background of the invention and its problems] As shown in FIG. 4, in a conventional turbine generator for a thermal power plant or a nuclear power plant, the shaft of an AC exciter 20 is directly connected to the shaft of a turbine generator 10. This AC exciter 2
0 output is rectified by a rectifier 21 and applied to the field circuit 13 of the turbine generator 10. On the other hand, the output voltage of the turbine generator 10 is controlled by detecting the output voltage of the turbine generator 10 with the instrument transformer 14 and controlling the gate of the thyristor device 22 with the automatic voltage regulator (AVR) 15. The output voltage of the exciter 20 is controlled, so that the field circuit 1 of the turbine generator 10
3 was controlled to control its output voltage to a predetermined value.

In addition, when stopping the turbine generator 10, a field installed in the field circuit 24 of the AC excitation 1111120! When the output voltage of the AC exciter 20 is reduced by opening the circuit breaker 23, the current flowing through the field open circuit 13 of the turbine generator 1510 is reduced, so the output voltage of the turbine generator 10 is reduced, and finally the turbine Generator 10 stops.

By the way, in the conventional turbine generator 10, the field 1a
The reason why the circuit breaker 23 is provided in the field circuit 24 of the AC exciter 2o instead of the 10 field circuits 13 in the turbine power generation is that in the turbine power generation, the 10 field circuits 13 are high voltage and large current. This is because if a field circuit breaker is provided in the field circuit 13, the circuit breaker itself becomes large in size, which increases the equipment cost.

In this way, in the conventional turbine generator 10, the field circuit breaker 23 is provided in the field circuit 24 of the AC excitation circuit 20, so even if the turbine generator 10 has to be stopped in an emergency, the field circuit breaker 23 Even if the output voltage of the turbine generator 10 was opened, the output voltage of the turbine generator 10 did not immediately become zero.

The reason is that the AC exciter 20 is directly connected to the turbine generator 10, and because of their large inertia, even if the AC exciter 20 is no longer excited, the rotational speed decreases slowly. There was a problem in that even after 5 seconds had passed, about 70% of the voltage remained, and it took a considerable amount of time to stop the turbine generator 10.

Therefore, in recent turbine generators for thermal power plants or nuclear power plants, the cylindrical excitation system is increasingly being adopted in order to improve the control function of the output voltage.

As shown in FIG. 5, in the thyrisk direct excitation method, an excitation transformer 11 is provided on the output side of the turbine power generator IJ10, and a thyristor device 12 provided on the secondary side of this excitation transformer 11 performs rectification. , and is configured to supply this rectified current to the field winding 13 of the turbine generator 10.

In the turbine power generation, the output voltage is detected by the instrument transformer 14 installed on the output side of the turbine 10, and the automatic voltage regulator (A
When VR>15, the gate of the thyristor device 12 is controlled, thereby controlling the output voltage of the turbine generator 10 to a predetermined value.

In such a thyristor direct excitation method, in order to stop the turbine generator 10, the output voltage of the turbine generator 10 is reduced by opening the field circuit breaker 16 provided in the field circuit 13 of the turbine generator 10. I'm trying to lower it. Therefore, the thyristor direct excitation method can reduce the output voltage of the turbine generator 10 much more quickly than the AC exciter method shown in FIG.

For example, the output voltage of the field breaker 16 can be reduced to about 70% voltage in about 1 second.

Here, FIG. 3 shows a comparison of voltage drop characteristics when the turbine generator is stopped between the Cyrisk direct excitation method employed in recent turbine generators and the AC exciter method conventionally employed. The solid line (A) is a recent thyristor direct excitation system. The two-dot line (B) is a voltage drop characteristic curve when the turbine generator is stopped using a conventional AC exciter system.

As shown in Figure 3, the thyristor direct excitation method adopted in recent turbine generators prevents the spread of accidents in the event of a generator failure because the voltage drops quickly when the generator is stopped, as shown by the solid line (A). It is preferable to do so. However, even if a turbine trip occurs due to an accident in an external power transmission line and the generator is stopped, the voltage of the generator will drop quickly, which may be undesirable. For example, in a boiling water nuclear power plant, the power for the recirculation pump motor built into the reactor is supplied from the turbine generator during normal plant operation, and is supplied from the external power line when the plant starts or stops, or when the turbine power generation malfunctions. It is configured to be supplied from Therefore, if a fault occurs in the external power line, the turbine will be unloaded and trip the turbine to prevent overspeed, but at this time the voltage of the turbine generator will drop instantaneously and the recirculation pump will Since the input voltage of the in-furnace recirculation pump is extremely small, the rotational speed of the recirculation pump will drop rapidly. On the other hand, if the recirculation flow rate decreases rapidly before the reactor scrams, the core may become thermally severe.

In the case of the conventional AC exciter system, the voltage drop of the turbine generator is gradual, so even if an accident occurs on the external power line, the recirculation pump can continue to operate until the turbine trips and the reactor scrams. However, in the case of the recent Cyrisk direct excitation method, the voltage drop of the turbine generator is rapid, so the recirculation pump or
- It is assumed that there is a problem in which the recirculation flow rate suddenly decreases due to a rip.

In addition, in the case of an emergency shutdown of the turbine generator due to a turbine generator accident, the aforementioned in-furnace type recirculation pump motor can receive power from the external power line by switching the busbar, etc., so the above-mentioned problems will not occur. does not occur.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to maintain the output voltage of the generator for a certain period of time to provide compensation within the power plant in the event that the turbine trips due to an external power transmission line accident, etc. An object of the present invention is to provide a control circuit for an excitation device of a turbine generator for a nuclear reactor, which allows the machine to continue operating for a predetermined period of time.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a contact that closes due to various failures of the generator, a contact that closes for a certain period of time by a time-limited relay that is energized by the contact that closes when a turbine trips, and one of these contacts. an auxiliary relay that is energized when the contact of the auxiliary relay is closed; and a trip coil of a field breaker that is energized when the contact of the auxiliary relay is closed; Excitation 1a of a nuclear reactor turbine generator configured to output a thyristor gate block signal to a thyristor device controlling the
It is a control circuit for the device.

[Embodiments of the invention] Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a control circuit 5 for an excitation device of a turbine generator for a nuclear reactor according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a thyristor direct excitation system for a nuclear reactor turbine generator to which the control circuit of the present invention is applied.

In FIG. 1, 1a to 1n are contacts that close due to n types of failures in the turbine generator, and 2 is a contact of a manual switch that manually stops the turbine generator. 3 is a contact that closes when the turbine trips, and when this contact 3 closes, a time-limiting relay 3X is energized. Also, 3Xa is a time-limited relay 3X
It is a contact that closes for a certain period of time after it is energized. Contact 1
a to 1n, contact 2 or contact 3Xa are connected in parallel, and when any of these contacts closes, the auxiliary relay 4 is energized, and the energization of the auxiliary relay 4 opens the contact 4a and activates the field breaker. 16 trip coil 16TC is excited, and at the same time as the field breaker 16 shown in FIG. has been done.

Note that P indicates ten power supplies and N indicates one power supply.

Next, the operation of the above embodiment will be explained.

Now, if a failure occurs in the turbine generator 10, the contact 1a
~1n is closed, and the auxiliary relay 4 is energized. Further, when it is desired to manually emergency stop the turbine power generation unit 10, the contact point 2 is closed by operating the manual switch, and the auxiliary relay 4 is thereby excited. When the auxiliary relay 4 is energized by these factors, the 1-lip coil 161C of the field breaker 16 is energized, and at the same time as the field breaker 16 shown in FIG. regulator 15 to thyristor device 1
2 thyristor gate block signal is output, and the output voltage of the turbine generator 10 drops rapidly.

On the other hand, in the event of a turbine trip, which is an external factor for the turbine generator 10, the time limit relay 3X closes the contact 3 that closes when a turbine trip is detected, and the contact 3Xa closes after a certain period of time has elapsed. At the same time as the relay 4 is energized and the field breaker 16 is opened, the automatic voltage regulator (AVR) 15 outputs a thyristor gate block signal to the thyristor device 12, and the output voltage of the turbine generator 10 is reduced. After the turbine trip, the turbine generator 10 can continue to operate for a certain period of time. At this time, the turbine trip signal causes
Although the turbine trips, the rated rotational speed is maintained sufficiently for several seconds because the turbine's rotational speed is extremely large.

In FIG. 3, an output voltage drop characteristic curve at the time of turbine trip is shown by a dashed line (C) when the control circuit for an excitation device of a turbine generator for a nuclear reactor according to the present invention is employed.

A comparison with the output voltage drop characteristic curves (a) and (b) during turbine trip in the conventional case described above shows that the output voltage of the turbine generator is maintained at the rated voltage for several seconds.

Note that the control circuit for the excitation device of the turbine generator for nuclear reactors described above is an extremely important circuit for continuing operation of the turbine generator or for protection in the event of an accident, so it is possible to multiplex the circuit or use semiconductors. Of course, it may be configured with a circuit to ensure safety.

[Effects of the Invention] As explained above, according to the present invention, in the event of an accident with a turbine generator, the field circuit breaker is opened instantaneously to stop the turbine generator and prevent the accident from expanding, and also to prevent external transmission. In the event that the turbine trips due to a power line accident, etc., the field breaker is kept closed for a certain period of time, and the turbine's large inertia maintains the rotation speed, allowing the turbine generator to continue operating. The recirculation pump motor built into the reactor can continue to operate until the reactor is scrammed, thereby preventing the core from becoming thermally severe.

[Brief Description of the Drawings] Fig. 1 is a control circuit diagram for an excitation device of a turbine generator for a nuclear reactor according to an embodiment of the present invention, and Fig. 2 is a schematic diagram of a thyristor direct excitation system for a turbine generator adopting the present invention. 3 is a characteristic curve diagram comparing the output voltage change when the turbine generator of the present invention and the conventional turbine generator is stopped. FIG. 4 is a schematic diagram of the configuration of the AC exciter system of the conventional turbine generator. FIG. 5 is a diagram of the configuration. This is a schematic diagram of a thyristor direct excitation method for a turbine generator. 1a-in, 2.3... Contact 3X... Time-limited relay 3Xa... Contact 4 of time-limited relay 3X... Auxiliary relay 4a... Contact 5 of auxiliary relay 4... Control circuit for excitation device 16TC...Trip coil 1 of field vii circuit breaker 16
0...Turbine generator 11...Excitation transformer 12...Thyristor device 13...Field winding 15...VJ voltage regulator 16...Field circuit breaker. Agent Patent attorney Nori Chika Ken Yudo Mitsumata Hirofumi 1 Figure 2 Time 3 Sono? 2 Figure 4 Figure 5

Claims (1)

[Claims] A contact that closes due to various failures of the generator, a contact that closes for a certain period of time due to a time-limited relay that is energized by the contact that closes when the turbine trips, an auxiliary relay that is energized when any of these contacts closes, and the contact of this auxiliary relay. and a trip coil of a field breaker that is excited when the field breaker is closed, and is configured to output a thyristor gate block signal to a thyristor device that controls the excitation circuit of a turbine generator for a nuclear reactor at the same time as the field breaker is opened. A control circuit for an excitation device of a turbine generator for a nuclear reactor, characterized in that: