JPH0469802B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an improvement in a load tap switching device using a thyristor switch.

[Conventional technology]

FIG. 9 shows the structure of a conventional load tap switching device disclosed in Japanese Patent Application Laid-Open No. 16921/1982. In the figure, when switching the connecting contacts 8 and 9 that are in contact with the output terminal 113 of the transformer winding 10 to the output terminal 114 or 112, a switching device that is linked to the drive mechanism of the connecting contacts 8 and 9 (not shown) is used. 29
The rotary switch 39 rotates and the contacts 41, 42,
43 and 44 and the movable contact 30, and the protrusion 20 which rotates along with the rotary switch 39 operates the micro switches 17, 18 and 19 arranged in the switching device 29, thereby opening and closing the thyristors 31, 44 and the movable contact 30. It is configured to control the ignition of terminals 32, 33 and 34 to switch to a predetermined output terminal.

[Problem that the invention seeks to solve]

Conventional on-load tap switching devices using thyristor switches use mechanical switches such as micro switches and rotary switches, so if they are used frequently, they tend to fail due to contact wear, etc., resulting in low reliability and poor reliability. Ta. Further, since tap switching is performed based on signals from a microswitch that is opened and closed by the drive shaft of the rotary switch, there is a problem in that sufficiently accurate timing cannot be obtained.

[Means for solving problems]

The on-load tap switching device of the present invention has voltage detection means connected in parallel to two sets of thyristor switches each constructed by connecting thyristors in antiparallel, and a current detection means connected in series, and based on their detection signals, the above-mentioned It is configured to control two sets of thyristor switches.

[Effect]

A firing signal for firing a predetermined thyristor switch is output by performing a logical operation on the detection signals of the voltage detecting means and the current detecting means.

〔Example〕

FIG. 1 shows a circuit diagram of an embodiment of the present invention. In the figure, a load 7 is connected to a current carrying contact 65. Current-carrying contact 65 contacts a tap on transformer winding 10, such as tap 69 in FIG. Thyristor element 3
1 and 32 are connected in antiparallel to form a thyristor switch 61, and thyristor elements 33 and 3
4 is connected in antiparallel to the thyristor switch 62
It consists of

In parallel to the thyristor switch 61, for example, PT
A voltage sensor 76 and a nonlinear resistance element 78 are connected, one end of which is connected to a tap selector 67. The other end of the thyristor switch 61 is connected to a current-carrying contact 65 via a current sensor 73 such as a CT. Further, a voltage sensor 75 is connected in parallel to the thyristor switch 61, and one end of the voltage sensor 75 is connected to a tap selector 66. The other end of the thyristor switch 61 is connected to a current carrying contact 65 via a current sensor 72. A plurality of taps are provided on the transformer winding 10. For example, in FIG.
8, 69, and 70 are illustrated. Current sensor 7
2 and 73 and the detection outputs of the voltage sensors 75 and 76 are input to the control circuit 71 and the in-phase determination circuit 79, and the output of the in-phase determination circuit 79 is input to the control circuit 71. The thyristor firing signal outputted by the control circuit 71 is configured to be applied to each of the thyristor elements 31, 32, 33, and 34 through wiring not shown. Drive mechanism 77
is the current-carrying contact 65 and the tap selectors 66, 67.
The detailed mechanism is not shown in the drawings.

Next, the operation will be explained. FIG. 2 shows the transition process when the tap is switched from a low potential tap to a high potential tap.

FIG. 2a shows the state in which the tap 69 is selected through the current carrying contact 65. Figure 2b
The drive mechanism 77 is activated by a switching signal to the high voltage tap.
operates, the tap selector 67 connects the energizing contact 65 to the tap 70, and the tap selector 66 connects the tap 69.
is in contact with. FIG. 2c shows a state in which the firing signal is applied to the thyristor switch 61 in the state shown in FIG. 2b. FIG. 2d shows a state in which the tap selectors 66 and 67 are in contact with the taps 69 and 70, respectively, and the current-carrying contact 65 is separated from the tap 69. Figure 2 e shows thyristor switch 6.
By applying a predetermined ignition signal to each of taps 1 and 62, the tap is switched from tap 69 to tap 70. FIG.
The tap selector 66 is connected to the tap selector 66. Second
Figure g shows a state in which only the current-carrying contact 65 is in contact with the tap 70, and the tap switching to a high potential has been completed. The load current flows through the current-carrying contact 65 during the period from a to c in FIG. 2, and the current-carrying contact 65 flows through the tap 6 during the switching process from
9, the current is commutated to the tap selector 66 side, and remains in that state until FIG. do. Figure 3 is the same as Figure 2 a to g.
The output states of each voltage sensor 75, 76 and current sensor 72, 73 in each state are shown. Current sensor 7
Reference numerals 2 and 73 indicate currents i ₁ and i ₂ flowing through the thyristor switches 61 and 62, respectively, and voltage sensors 75 and 76 indicate the voltages applied to the thyristor switches 61 and 62, respectively.
E ₁ and E ₂ are detected. All sensor outputs are assumed to produce positive polarity outputs when the currents are shown in the arrow directions i ₁ , i ₂ and the voltage polarities are shown as E ₁ , E ₂ in FIG.

In the figure, the display of "0" in each column indicates that the detection output of the sensor is zero. Drive mechanism 77
When the state shown in FIG. 2a changes to that shown in FIG. 2b due to the operation, the outputs of each sensor become as shown in FIGS. 3a to 3b. If the ignition signal is not input to the thyristor switch 61 when moving from this state to the state shown in FIG. This will generate an arc. To avoid this, the control circuit 71
The sensor output in FIG. 3b, that is, when only the voltage sensor 76 of the thyristor switch 62 detects the voltage between the taps, it gives an ignition signal to the thyristors 31 and 32 of the thyristor switch 61. From the above, when the current-carrying contact 65 separates from the tap 69 during the transition from FIG. 3c to FIG. 3d, the load current commutates from the current-carrying contact 65 to the thyristor switch 61.

In order to carry out the natural commutation from the thyristor switch 61 to 62 in the state e in FIG. , when the output of the current sensor 72 is positive, an ignition signal is given to the thyristor 34 to make the thyristor 34 conductive, thereby causing natural commutation from the thyristor 32 to the thyristor 34. Further, after the thyristor 32 is turned off, a firing signal is given to the thyristor 33 to make the thyristor switch 62 conductive and to turn off the thyristor switch 61. Thereafter, by the operation of the drive mechanism 77, the third
It will be in the state shown in Figure g.

Next, the process of switching from a high potential tap to a low potential tap is shown in FIGS. 4a to 4g. Further, FIG. 5 shows the output states of each voltage and current sensor in each state of FIGS. 4a to 4g. Each state in Figure 4 a to g is tap 6.
8, 69, 70, tap selectors 66, 67, and current-carrying contacts 65 are connected differently in Fig. 2a.
The order is reverse to the switching of ~g. Therefore, the combinations of sensor output states are in the opposite order in FIGS. 3 and 5. However, when switching the low potential tap of a pure resistance load, the sensor output differs from that shown in Figure 5, so a separate
This will be explained with a diagram. The present invention utilizes such a difference in the sensor output state when switching from a high potential to a positive potential or from a low potential to a high potential tap.

In other words, when comparing the sensor output states in the respective processes of FIGS. 2 b to d and 4 b to d, there are no identical states, and the thyristor switches 61 and 62 are controlled based on this sensor output state. Thyristor switch 61 at the time of FIG. 2 d to e and FIG. 4 d to e,
The switching of thyristor switches 61 and 62 is the same in FIG. 2 d and FIG. 4 e, and since the sensor output states in FIG. 2 e and FIG.
Since it is not possible to specify and switch the thyristor switches 61 and 62 in the states shown in Fig. 2b and Fig. 4b,
The configuration is such that ignition signals are not given to both at the same time.

In the process of switching to a low potential tap in the case of a phase leading or lagging load, the thyristor switch may be controlled in accordance with the output signal of each sensor in the same manner as in the case of switching to a high potential tap.

The operation of switching to a low potential tap in the case of a purely resistive load (common mode load) will now be explained. At this time, the in-phase determination circuit 79 detects that the load is in-phase, and outputs a determination signal indicating that the load is in-phase to the control circuit 71. The tap switching process operates in the same way as when there is no common mode load up to FIG. 4d. Based on the difference in the output states of the sensors shown in FIG. 3b and FIG. 5b, the control circuit 71 detects the signal state shown in FIG. 3b, determines that it is switching to a low potential tap, and stores it. .

Figure 7 shows the current and voltage curves during in-phase operation.

In the figure, if the state shown in FIG. 4 d is present at time t ₁ in FIG. 7, the control circuit 71 controls the thyristors 31, 32, 3
and stop the ignition signal of 34. At time _t2 in FIG. 7, the load current il becomes zero. At this time, thyristor 3
Since the ignition signal is not applied to the thyristors 1 to 34, the thyristors 31 to 34 are turned off. Therefore, a circuit voltage is applied to the thyristor switches 61 and 62. However, due to the voltage/current characteristics shown in FIG. 6 of the nonlinear resistor 78 connected in parallel to the thyristor switch 62, the entire load current flows through the nonlinear resistor 78.
The voltage applied to the thyristors 33 and 34 is _V2 ,
The voltage applied to the thyristors 31 and 32 is limited to the sum of V ₂ and the tap-to-tap potential. Voltage
Since V ₂ is approximately 5% of the circuit voltage, the effect of the voltage drop due to the nonlinear resistor 78 on the load can be ignored. Since this voltage V ₂ is approximately twice the peak value V ₀ of the voltage between taps, this voltage V ₂ is detected by the sensor 75 or 76 and the control circuit 71
Compare the levels using thyristors 31 and 3.
2, 33, and 34 can be controlled.
That is, as shown in FIG.
If the T ₂ period is approximately 1.2 times the maximum turn-off time of the thyristors 33 and 34, the thyristors 33 and 34 are completely turned off at the time t ₃ . Therefore, at time t ₃ , control circuit 71 applies firing signals to thyristors 31 and 32 to select tap 68 . From time _t3 to time _t4 , a forward voltage is applied to the thyristor 31, and a forward current flows, so the thyristor 31 becomes conductive. Thereafter, the thyristor 32 becomes conductive. As a result of the above, the control circuit 7
After the operation of step 1 is completed, the operation of the drive mechanism 77 brings the state to the final state shown in FIG. 4g.

The state of the above operation is shown in FIG. E ₁ in the figure,
E ₂ , i ₂ and i ₂ are voltages and currents detected by the respective voltage detection means and current detection means.

In the above embodiment, a nonlinear resistor is provided in parallel with the thyristor switch, but if the withstand voltage of the thyristor switch permits, a resistor with a high resistance value may be used, and the same effect as in the above embodiment can be obtained. Furthermore, although the embodiment has shown a case in which a nonlinear resistance element is used in parallel with the thyristor switch, the same effect can be produced even if the nonlinear resistance element is used in the other thyristor switch or provided in both thyristor switches. However, when switching to a low-potential tap with a pure resistance load, as in the case of the nonlinear resistance element described above, the resistor must be set so that a voltage of 1.2 times or more of the peak voltage between the taps is applied to the high-resistance resistor for a period of _T2 or more. You need to choose a value.

〔Effect of the invention〕

According to the present invention, since the current and voltage flowing through the thyristor switch are detected and the firing of the thyristor switch is controlled based on the detection signal, a changeover switch and a mechanical detection contact are not required, resulting in a highly reliable and low-cost switch. An on-load tap switching device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a diagram showing the state when switching from a low potential tap to a high potential tap in an embodiment of the present invention, and FIG. 3 is a diagram showing a state when switching from a low potential tap to a high potential tap. FIG. 4 is a diagram showing the states of the detection signals of the voltage and current sensors in each state shown in FIG. 2 when switching from a high potential tap to a low potential tap in an embodiment of the present invention. , Fig. 5 is a diagram showing the state of the detection signal of the voltage and current sensor in each state shown in Fig. 4 when switching from a high potential tap to a low potential tap, and Fig. 6 shows the voltage-current characteristics of the nonlinear resistance element. Figure 7 is a diagram showing the current voltage waveform and thyristor voltage and current in the case of a pure resistance load, Figure 8 is a diagram showing the state of the detection signal of the voltage and current sensor in the case of a pure resistance load, and Figure 9 The figure is a circuit diagram of a conventional on-load tap switching device. 61...Second thyristor switch, 62...
First thyristor switch, 72... Second current detection means, 73... First current detection means, 75...
... second voltage detection means, 76 ... first voltage detection means, 71 ... control circuit, 79 ... in-phase determination circuit.

Claims (1)

[Scope of Claims] 1. A first thyristor switch and a second thyristor switch configured by connecting thyristors in antiparallel, and a first voltage detection means and a second voltage detection means connected in parallel to each of the thyristor switches. means, a first current detecting means and a second current detecting means connected in series with each of the above-mentioned thyristor switches, and an in-phase determination circuit that outputs a signal when the phases of the current and voltage are in the same phase; When switching to a high potential tap, the second thyristor switch is activated when the first voltage detection means detects a voltage or when both the first voltage detection means and the second current detection means detect a voltage and a current, respectively. is turned on, and the first thyristor switch is controlled so as to be turned on when both the second voltage detection means and the first current detection means detect voltage and current, respectively, and the switch is switched from a high potential tap to a low potential tap. At the time of switching, the first thyristor switch is turned on when the second voltage detection means or the second voltage detection means and the first current detection means respectively detect voltage and current, and the first thyristor switch turns on. An on-load tap switching device having a control means for controlling the second thyristor switch to turn on when both the voltage detection means and the second current detection means detect voltage and current, respectively. 2 When the in-phase determination circuit outputs a signal,
When both the second voltage detection means and the first current detection means respectively detect voltage and current, the second thyristor switch is turned off, and both the first and second voltage detection means detect at least the turn-off time voltage of the thyristor switch. 2. The on-load tap switching device according to claim 1, further comprising control means for controlling the first thyristor switch to be turned on when the first thyristor switch is detected.