JPS6154822A - Method of controlling switching of bus in power plant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides an in-power station bus that switches the power supply to the in-power station bus from the main power transmission line to the standby power transmission line while minimizing shock to the electric motor. The present invention relates to a switching control method.

[Background of the invention]

The following methods have been known as busbar switching methods within a power plant, but the reality is that none of them are sufficient.

That is, the first method is as shown in Japanese Unexamined Patent Publication No. 139645/1983, when the voltage difference 5 phase difference between the main power transmission line system and the backup power transmission line system is within a predetermined range, instantaneous switching is determined by the determination device. This is a method in which time-limited switching is performed when the value is outside a predetermined range. Second, as shown in Japanese Unexamined Patent Publication No. 58-218830, the switching state can be changed in a timed or instantaneous manner depending on the voltage difference (1 phase difference) between the main power transmission line system and the backup power transmission line system, and the magnitude of the current used. This is a method of switching busbars so that power can be smoothly supplied to safety-related auxiliary equipment without impacting them.

Part 3, as shown in Japanese Patent Application Laid-open No. 57-91636, connects in series a parallel circuit of an inrush current suppression impedance and a short-circuit switch to short-circuit this impedance to the motor circuit, and temporarily In this method, the ratio e of the transient impedance value at the time of power supply system switching to the impedance value for suppressing the transient phenomenon at the time of switching is constant, and the power supply switching is performed smoothly.

The first two methods use voltage differences.

The purpose of this is to reduce the impact when switching power to the motor by reducing the phase difference, but these are all passive and switch will occur when the potential difference 1 phase difference decreases. It is.

On the other hand, the last method attempts to reduce the impact by inserting an impedance, but it has problems such as requiring an impedance and a short circuit switch.

By the way, nuclear power plants have the following special circumstances, and it is necessary to adopt an optimal method for switching the plant busbars.

That is, in boiling water nuclear reactors, an internal pump driven by a static variable frequency power supply device is used as a reactor recirculation pump. However, since this internal pump is installed within the reactor pressure vessel, the mechanical dimensions of each internal pump are limited due to the arrangement, and it is not possible to have a large inertia. For this reason, simultaneous loss of power for driving all internal pumps accelerates the decrease in the reactor coolant flow rate and reduces the thermal margin of the fuel rods. Therefore, it is necessary to reduce the possibility of a power outage when switching the station bus, and to minimize the impact caused by the 9 phase difference in voltage between the bus and the standby power transmission line during switching.

[Purpose of the invention]

An object of the present invention is to provide an in-power plant bus bar switching control method that enables smooth uninterrupted switching when switching from the main transmission line 11L to the backup transmission line in the event of a power outage on the main transmission line.

[Summary of the invention]

To this end, the present invention aims to eliminate the influence on the electric motor caused by the existence of a voltage difference of one phase when switching the power source of the power plant bus, by connecting the charger connected to the power plant bus to the electric power of the storage battery. By operating it as an inverter, it supplies power to the station bus during the power switching period, and also adjusts the voltage, frequency, and phase of the station bus to be synchronized with the backup power source being switched, and then connects the backup power source with a power receiving breaker. It was designed so that . This makes it possible to achieve the desired uninterruptible switching.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 1 to 4.

First, the power source configuration within a power plant according to the present invention will be explained.

FIG. 1 shows an example of the configuration. According to this, when the main generator 6 driven by the turbine 5 is operating normally, the circuit breakers 100a and 100b of the main power transmission line switchyard bus 3a are closed, and the main power generator 6 is operated by the main power transmission line 1. The generated power is transmitted through the main transformer 8. On the other hand, there are various electric motors 7 (7a to 7n) as auxiliary equipment in the power station, and the power generated by the main generator 6 is sent to these through the station transformer 9, station transformer power receiving breaker 15, and station motherboard A4. It is now sent via Therefore, under normal conditions, the station transformer power receiving breaker analyzer 15 is closed and the starting transformer power receiving breaker 16 is open.

By the way, the main generator 6 was stopped), the main power transmission line 1-! If the main power transmission line switchyard bus 3a becomes abnormal, power cannot be supplied to the electric motor a7 via the station transformer 9, so the station transformer power reception breaker 15 is opened and the starting transformer receives power. The breaker 16 is turned on, and this operation is called in-station bus switching. By this operation, j) the power to the motor 7 is sent via the backup transmission line 2, the breaker 200a, the closed bus 3b1 between the backup transmission lines, the breaker 200b, the starting transformer 10, and the station bus 4. However, of course, in this case, the station transformer power receiving breaker 15
is open, and the starting transformer power receiving breaker 16 is closed.

In these operations, there is no problem if the voltage and phase of the station bus a4 and the voltage and phase of the backup power transmission line 2 are exactly the same, but if the station transformer power receiving breaker 15 is opened, the
By the time the JJ transformer power receiving circuit breaker 16 is turned on, it is approximately 0.
．． The power supply is lost for about 2 seconds, resulting in a malfunction. When the power supply to the station bus 4 is cut off, the electric motor 7 supplies electric power to the station bus 4 through the action of a generator, but since there is no power source to drive the electric motor 7, its rotation is decelerated as the rotation of the electric motor 7 is released. As a result, both voltage and frequency will decrease. Figure 2 shows this situation in the form of a pie chart.

Here, with reference to FIG. 3, the state at the time of switching the local bus will be explained in detail. Figure 3 shows the change in the voltage on the station bus side with respect to the voltage on the standby transmission line and the voltage difference when switching the station bus, as well as the change in the secondary current of the station transformer and the starting transformer. . According to this, the station bus switching is performed when the standby power transmission line side voltage and the station bus side voltage are the same voltage and have the same phase frequency. As shown in the figure, the station bus 4
Since the voltage and phase of the starting transformer power receiving circuit breaker 1
6, a voltage difference and two phase differences occur between the power supply and the backup power transmission line 2. This acts as a large voltage difference for the electric rfIb machine 7, and as can be seen from the change in the secondary current of the starting transformer 10, an excessive current flows through the motor 7, giving it a shock.

The purpose of the present invention is to prevent such an impact, but in the present invention, a conversion device (charger) 12 for charging the storage battery 14 provided in the power plant is used for switching control. It looks like this. The converter 12 normally receives a negative force from the station bus 4, converts it into DC, charges the storage battery 14, and supplies power to the DC loads 18 (18a to 18n) via the DC bus 17. However, the idea is to use this as an inverter when switching bus lines. In order to control the operation as this inverter, the conversion control device 13 has an in-house bus 4.
Voltage and phase signals on the side of the standby power transmission line 2 are applied through the voltage transformer 11a, while voltage and phase signals on the side of the backup power transmission line 2 are applied through the voltage transformer 11b.

Now, suppose that it is necessary to open the in-station transformer power receiving breaker 15 and turn on the starting transformer power receiving breaker 16 due to a trip of the main generator 6, etc., and the bus bar switching control method according to this example is to be used at that time. The explanation is as follows.

That is, first, when the plant control device 19 detects a state such as a trip of the main generator 6, an open signal is given to the in-station transformer power reception breaker 15. The process up to this point is the same as the previous case, but the difference is that at the same time, the conversion control device 13 is instructed to start the local bus switching control.

Since the conversion device 12 and the conversion control device 13 are made of semiconductor devices, their operation is much faster than that of the in-station transformer power receiving circuit breaker 15.
The converter 12 is controlled as an inverter to keep the voltage and phase of the station bus 4 constant, and the power of the storage battery 14 is sent to the station bus 4, contrary to the normal case. As shown in FIG. 2, the motor 7 operates to prevent the motor 7 from being decelerated.

Next, the conversion control device 13 checks the status of the standby power transmission line 2 obtained via the voltage transformer 11b, and if it is healthy, the voltage and phase of the station bus a4 match with that voltage and phase. The converter 12 is then controlled, and when this control is completed, the starting transformer power receiving breaker 16 is turned on. By this operation, if the backup power transmission line 2 is healthy, the power source can be switched from the main generator 6 to the backup power transmission line 2 without interruption.

Although FIG. 4 shows the flow of control by the plant control device and the conversion control device, no particular explanation is required regarding this.

If the backup power transmission line also loses power, the starting transformer power receiving breaker will be prevented from turning on, and the operation will continue until the in-station transformer power receiving breaker is turned on after the main generator is restored, or the capacity of the storage battery will be reduced. By converting the power of the storage battery as much as possible using a converter and operating necessary auxiliary equipment, a power outage can be predicted and the plant can be stopped normally.

In addition, when starting the main generator, power is received from the backup power transmission line, but when switching to the main generator (main power transmission line), there is no restriction on switching time. The generator is adjusted to synchronize the main generator and the station bus, allowing for uninterrupted switching.

In Figure 1, we have explained only the switching from the station transformer power receiving breaker to the starting transformer power receiving breaker, but by adding the main generator voltage signal, it is possible to switch from the starting transformer power receiving breaker to the starting transformer power receiving breaker. Of course, the present invention is also applicable to switching to an in-station transformer power receiving breaker.

〔Effect of the invention〕

As explained above, the present invention has the advantage that switching from the main power transmission line to the backup power transmission line can be performed smoothly and without interruption.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a power supply configuration in a power plant according to the present invention, FIG. 2 is a diagram showing a temporal change in residual voltage of a motor when power supply is cut off, This figure shows the transient phenomenon at the time of switching the station busbars, and Figure 4 is a diagram showing the control 70- by the main device in FIG. 1. 1... Main power transmission line, 2... Backup power transmission line, 3a... Main power transmission line switchyard busbar, 31)... Backup power transmission line switchyard busbar, station busbar, 6... Main generator, 7 (7a-7n)...
- Electric motor, 9... Station transformer, 10... Starting transformer, lla. 11b... Instrument transformer, 12... Conversion device, 13
... Conversion control device, 14... Storage battery, 15... Station transformer power receiving breaker, 16... Starting transformer power receiving cutoff G117... DC bus, 19... Plant control device.

Claims (1)

[Claims] 1. The station busbar to which the conversion device for charging storage batteries is connected can be supplied with power from the main generator via the station transformer power receiving breaker and the station transformer, while the starting transformer power receiving breaker and the starting transformer When it is possible to supply power from the standby power transmission line through the power supply, the station bus switching signal opens the station transformer power receiving breaker, and the conversion device for charging the storage battery operates as an inverter to convert DC power from the storage battery to AC. A power plant bus switching control method characterized by adjusting the voltage and phase of the plant bus by converting it into electric power and turning on a power receiving breaker of a starting transformer in synchronization with the standby power transmission line side.