JPS607891B2 - Transformer tap position selection device - Google Patents

Description

[Detailed Description of the Invention] This invention is used, for example, in a power plant, etc., when the power generation system is connected to a system bus that receives power generated by multiple power generation systems and supplies it to a load all at once. This invention relates to improvements in transformer tap position selection devices.

In general, in large-capacity power plants that have multiple power generation systems, when connecting the power generation system to the load system bus due to an increase in load, the generation voltage of the power generation system is converted to a value close to the voltage of the load system bus using a transformer. A means of connecting is used.

FIG. 1 is a system connection diagram explaining the outline.

In the figure, 1 is a generator, 2 is an excitation device that supplies excitation power to the generator 1, and 3 is a field cutter and disconnector, and when the cutter is turned on, the output of the excitation device 2 is changed to the generator 1. is supplied to the field coil. 4 is an automatic voltage regulator, and the generated voltage of the generator 1 is controlled to a constant voltage by this automatic voltage regulator.

Reference numeral 5 denotes a transformer equipped with a tap changer, into which the generated voltage of the generator 1 is input.

The winding tap, that is, the transformation ratio of the transformer 5 can be arbitrarily set by setting the tap position.

The output of the transformer 5 is supplied to the load system by turning on the line breaker 6.

7 and 8 are both power generation system connection buses, and 9 is a load system bus.

In the power generation system configured as described above, when the generator 1 is started and its rotational speed reaches a specified value, the field magnet and disconnector 3 are turned on, and the excitation power from the excitation device 2 is supplied to generate electricity. Machine 1 starts generating electricity.

Electric power generated by the generator 1 is transferred to the transformer 5 via the connection bus 7.
is input. Then, the input voltage from the generator 1 is converted to a value close to the voltage of the load system bus 9 by a tap switching device provided in the transformer 5. After this voltage conversion, the disconnector 6 is turned on and the power generation system is connected to the load system. Thereafter, the output of the generator 1 is increased to supply power to the load system. However, as a condition for turning on the above-mentioned breaker 6,
It is required that the potential difference and phase difference between the connection bus 8, ie, the input side of the shield breaker 6, and the load system bus 9, ie, the output side of the shield breaker 6, are within specified values.

Conventionally, a transformer tap position control device as shown in FIGS. 2 and 3 is used as a system connection control means that detects the potential difference between the power generation system and the load system bus 9, which is one element of the closing condition of the breaker 6. was used. FIG. 2 shows a transformer tap position selection device for manually connecting a power generation system to a load system.

In the figure, the potential of the power generation system is detected by a first detection device, that is, a voltage transformer 11 and a voltmeter 12, and the potential of a load system bus 9 is detected by a second detection device, that is, a voltage transformer 13 and a voltmeter 14. be done. Then, the potentials detected by both detection devices are visually confirmed by the power plant operator, and the potential difference is calculated. The tap switching control device 10 is operated so as to obtain a transformation ratio that is approximately equal to the calculated potential difference between the two systems, and in response to a command from the control device 10, the tap switching device of the transformer 5 is set to the commanded tap position. It works as expected. Then, the winding ratio of the transformer 5 is adjusted to a value that is approximately equal to the voltage ratio of both systems. After this tap adjustment is completed, the disconnector 6 is turned on and the power generation system is connected to the load system. Further, FIG. 3 shows a transformer tap position selection control device that is automatically controlled so that the transformation ratio of the transformer 5 becomes a predetermined value. In the case of FIG. 3, it is assumed that the output voltage of the generator 1 is held constant by the automatic voltage regulator 4, and that the voltage of the system bus 9 hardly changes. The tap position of the transformer 5 corresponding to the voltage is stored.

When the field generator or disconnector 3 is turned on, a closing signal is sent from the field generator or disconnector 3 to the tap position selection device 15.

Then, the tap position selection device 15 is actuated by this signal, and the tap changeover control device 10 operates the tap changeover device of the transformer 5 so that the tap position is set to the stored tap position, and the transformer 5 is operated at a predetermined transformation ratio. can be switched to When this tap switching of the transformer 5 is completed, a signal indicating that the tap position selection device 15 and the disconnector 6 can be turned on is sent out. Then, when this signal is inputted, a breaker control device (not shown) closes the breaker 6 and connects the power generation system to the load system. It should be noted that the operation of the tap position selection device 15 is locked by turning on the shroud breaker 6, and subsequent control of the tap changeover device is automatically performed by the tap position control device 101. However, with the manual control method shown in Figure 2, it is possible to control the voltage of the power generation system to a value closest to the voltage of the load system bus, but visual confirmation of the potential difference and tap switching control operations are all performed during operation. This has to be done by an operator, which has drawbacks such as the risk of misidentification of the indicating voltmeter and the difficulty of saving labor. Further, in the automatic control system shown in FIG. 3, the tap position of the transformer 5 stored in the tap position selection device 15 is a value determined theoretically and empirically, and the tap position of the transformer 5 is stored in the tap position selection device 15, and the tap position of the transformer 5 is a value determined theoretically and empirically, and the tap position of the transformer 5 is stored in the tap position selection device 15. The potential difference between the potential of the system bus 9 and the voltage of the power generation system, that is, the output voltage of the transformer 5 may become large.

If the circuit breaker 6 is turned on when this potential difference is large,
This results in a large electrical or mechanical shock being applied to the generator 1, which is an undesirable drawback in terms of operation. This invention was made to eliminate the above-mentioned conventional drawbacks, and includes a transformer that detects the potential of the load system bus and operates to bring the potential of the connected power generation system close to the potential of the load system bus. The object of the present invention is to provide a device tap position selection control device.

A transformer tap position selection control device according to an embodiment of the present invention will be described below with reference to FIGS. 4 and 5.

In the device shown in FIG.
Since it is similar to the figure, the explanation will be omitted.

Reference numeral 13 denotes a voltage detection device, such as a voltage transformer, by which the potential of the load system bus 9 is detected.

16 is a tap position selection device based on the present invention, into which the detection signal detected by the voltage detection device 13 is inputted.

When the input signal for the field breaker or disconnector 3 is input, the voltage detection device 13 input to the tap position selection device 16
With the voltage signal, a signal for switching to the tap position corresponding to the signal is issued, and the tap switching device of the transformer 5 is switched by the tap switching control device 10 operated by this signal. When the switching of the tap position of the transformer 5 is completed, a completion signal is sent from the tap switching control device 10. Upon receiving the signal from the tap switching control device 10, the capacitor breaker control device (not shown) operates to close the capacitor breaker 6 and connect the power generation system at a voltage approximately equal to the voltage of the load system bus 9. be done. When the field shield breaker 6 is turned on, its closing signal is input to the tap position selection device 16, and this signal cancels the signal input when the field shield breaker 3 is turned on. Then the tap switching control device 1 of the transformer 5
0, control is performed automatically. The tap position selection device 16 will be explained in detail with reference to FIG. 5.

18 is a terminal for applying the system bus voltage stepped down by a voltage transformer, 19 is an AC-DC converter, and voltage detector 13
The AC voltage of the load system bus 9 detected and stepped down is inputted, converted to DC voltage, and output.

20 is a voltage-to-frequency converter, which is equipped with a high frequency oscillator and receives the DC voltage from the AC-DC converter 19;
The frequency of the high frequency wave oscillated is controlled by this DC voltage.

Reference numeral 21 denotes an oscillator, which oscillates a square wave with an extremely stable frequency using a crystal resonator or the like.

22 is a first frequency divider, into which the square wave signal oscillated by the oscillator 21 is inputted, and this square wave signal is frequency-divided and shaped.

23 is a first adjustment switch, and the frequency division ratio of the square wave signal is set by operating this adjustment switch.

24 is a gate that allows the signal from the voltage-to-frequency converter 20 to pass only when the square wave signal voltage frequency-divided and shaped by the first frequency divider 22 is positive (or negative).

25 is a second frequency divider, and the signal passing through the gate 24 is divided by this frequency divider.

A second adjustment switch 26 changes the frequency division ratio of the second frequency divider 25. Note that the first adjustment switch 23 and the second adjustment switch 26 are provided so as to be interlocked with each other. For example, when the first adjustment switch 23 is set so that the frequency division ratio of the first frequency divider 22 is 1/n, the frequency division ratio of the second frequency divider 25 is set to 1. The second adjustment switch 26 is set by changing the setting of the first adjustment switch 23 so that the frequency division ratio of the first frequency divider 22 becomes k/n. The relationship is such that the setting of the second adjustment switch 26 is changed so that the frequency division ratio of the frequency divider 25 becomes 1/k. However, this relationship assumes that the frequency of the output signal of the voltage-to-frequency converter 20 is much higher than the frequency of the output signal of the first frequency divider 22. 27 is a counter, The number of pulses of the square wave signal output from 25 is counted.

Therefore, if the number of pulses counted by the counter 27 is adjusted in advance using the voltage-to-frequency converter 20 or the like in accordance with the voltage signal input to the AC-DC converter 19, the number of pulses counted by the counter 27 can be adjusted in advance. It becomes possible to read the voltage value detected by the voltage detector 13 based on the count value. Note that 19 above
27, the detection device 16a is formed. Reference numeral 28 denotes a conversion device which selects the tap position of the tap switching device according to the count value of the counter 27, detects the corresponding tap position, and sends out the tap position signal.

A closing signal for the field shield breaker 3 and a closing signal for the connecting shield breaker 6 are input to the shield breaker condition input terminal 29.

This terminal 29 is connected to a locking circuit device 301. The locking circuit device 30 holds the signal from the distributor 28 at the time when the field cutter 3 is turned on, energizes and holds only the auxiliary relay corresponding to the signal, and energizes and holds the auxiliary relay corresponding to the signal. Locked to prevent energization. 31
A plurality of auxiliary relays are provided corresponding to the number of taps of the transformer 5, and are controlled by the locking device 30.

32 is a contact of the auxiliary relay 31, and the signal from the distributor 28 is transmitted to the tap switching control device 1 via this contact.

The above 30 to 32 form the storage device 16b. Reference numeral 34 denotes a power supply circuit to which power necessary for each of the above-mentioned elements is supplied via the terminal 33.

Note that the voltage of the load system bus 9 changes from moment to moment, and even if, for example, a ground fault or the like occurs in a far part of the system and the system bus voltage momentarily drops, the tap position selection device 16 will immediately switch off. Since it is not preferable to respond, the frequency division ratio of the first frequency divider 22 is set to respond to the average voltage at each predetermined time interval.

That is, as the frequency of the signal output from the first frequency divider 22 becomes higher, it responds more sensitively to fluctuations in the voltage signal input to the AC-DC converter 19. Therefore, it also responds to instantaneous voltage fluctuations in the load system bus 9, which are unnecessary for controlling the tap changer. Therefore, by setting an appropriate frequency, for example, the pulse width of the output signal of the first frequency divider 22, to about 5 seconds, a response is made to the average value of the load system bus voltage for 5 seconds. Moreover, since the pulse width can be adjusted by the first adjustment switch 23, it is possible to set the pulse width to an appropriate time period in consideration of the fluctuation speed of the load system bus voltage, etc. However, when the output pulses of the first frequency divider 22 are directly counted by the counter 27, even if the voltage applied to the terminal 18 is constant, the first adjustment switch 23 By changing the frequency division ratio, the count value of the counter 27 changes.

In order to prevent this, a second frequency divider 25 is connected between the gate 24 and the counter 27, and the second frequency divider 25 is connected between the gate 24 and the counter 27. The frequency division ratio of the counter 25 is changed to correct the value of the counter 27 to be constant. Since the present invention is configured as described above, the potential of the load system bus is detected moment by moment at the average value over a predetermined period of time, and the power generation instruction signal of the power generation system for connection to the load system is input, and the power generation instruction signal is detected at the time when power generation starts. A tap position signal corresponding to the load system bus voltage of The power generation system is connected to the load system without causing harmful shock to the load system.

Further, in the above embodiment, the time limit is adjusted using the first adjustment switch 23 and the second adjustment switch 26, but when the rate of change of voltage fluctuation in the power system is almost constant, the second adjustment switch Even if the frequency divider 25, the first adjustment switch 23, and the second adjustment switch 28 are omitted and the time limit is fixed, the same effect as in the above embodiment can be obtained.

As described above, the transformer tap position selection device according to the present invention is suitable for connecting a generator to a power system, which is a load system bus, by operating a switchgear of a transformer having a tap changer. a detection device that detects the voltage of the system voltage of the voltage system; a conversion device that converts the detected voltage signal into a tap signal corresponding to the tap of the transformer; and a generator that stores the input tap position signal. A tap position selection device is constructed with a storage device that sends the tap position signal to the tap switching device according to the voltage signal of Not only is the connection extremely stable, but it also provides great benefits such as labor-saving connection operations.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram for explaining the system connection, FIGS. 2 and 3 are connection diagrams showing a conventional device, and FIG. 4 is a connection diagram showing a transformer tap position selection control device according to an embodiment of the present invention. ,
FIG. 5 is a block diagram illustrating the main parts of FIG. 4. The same reference numerals in the figures indicate the same or corresponding parts. In the figure, 5 is a transformer, 6 is a switchgear, 7 and 8 are connection buses, 9 is a system bus, 13 is a voltage detection device, 16 is a tap position selection device, 16a is a detection device, 16b is a storage device, 2
8 is a conversion device. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. After switching the tap position of the transformer with a tap changer to a position suitable for connection between the generator and the power system, which is the load system bus, the switchgear is turned on and power is transferred between the generator and the power grid via the transformer. In systems that connect systems,
a detection device that detects the voltage of the power system and sends out a voltage signal; a conversion device that receives the voltage signal and converts it into a tap position signal of the transformer corresponding to the voltage signal; A transformer tap position selection device comprising a storage device that stores the voltage signal of the generator and sends the stored tap position signal as an operation signal for the tap changer upon input of the voltage signal of the generator input to the transformer. .