JPH0584523B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thyristor switch-type on-load tap changer that uses a thyristor switch as a changeover switch.

[Conventional technology]

A conventional device of this type is shown in FIG. In the figure, 1 is a transformer tap winding having a plurality of taps, 2 is an upper fixed contact connected to an upper tap at an arbitrary position of the transformer tap winding 1, and 3 is an upper fixed contact 2 Each of the fixed contacts 2 and 3 is a lower fixed contact connected to a tap adjacent to the lower one connected to the tap.
are fixed at predetermined intervals. Reference numeral 6 denotes a tap selector, which includes a pair of first and second movable contacts 4, which select a tap by contacting the fixed contacts 2, 3.
5, a thyristor switch 8 in which a pair of thyristor elements are connected in antiparallel to each other is connected between the first movable contact 4 and the output terminal, and a thyristor switch 8 is connected between the second movable contact 5 and the output terminal. is connected to a nonlinear resistor 9 whose main component is zinc oxide, and the first movable contact 2 and the second movable contact 3 are connected to the fixed contacts 4 and 5.
The distance that bridges the gap is maintained. The nonlinear resistor 9 is selected to have voltage-current characteristics shown in FIG. 5, and whose limiting voltage is higher than the voltage between adjacent taps and lower than the ground potential of each tap. 10
12 is an ignition device that controls the ignition of the thyristor switch 8, and is equipped with an auxiliary contact 11. When the auxiliary contact 11 is closed, the thyristor switch 8 is outputs the ignition signal. The energizing switch 10 and the auxiliary contact 11 are the movable contact 4,
5 to operate at a predetermined position.

Next, the operation will be explained. FIG. 6 shows the switching order during the switching operation of the conventional device. 1 to 5 and 8 to 10 in the figure are the same as in FIG. 4.

Further, FIG. 7 is a sequence diagram showing the open/close states of each contactor and switch at the time of switching. In FIG. 6, a indicates a steady state of contact at an arbitrary tap position. In the figure, the flow path of the load current I _L is indicated by a thick line (the same applies hereafter), and the tap winding 1
→ Fixed contact 2 connected to the upper voltage tap →
The first movable contact 4 is output via the energization switch 10. Now, when there is a tap change command and the position of the voltage tap is to be changed to a lower tap, the tap selector 6 moves as shown in Fig. 6b, and the second movable contact 5 moves to the upper fixed contact. It separates from the child 2 and comes into contact with the lower fixed contact 3. By contacting the nonlinear resistor 9, the voltage between the taps (hereinafter referred to as
Auxiliary contact 1 is added at this position (referred to as U _S ).
1 is closed, an ignition signal is output from the ignition device 12 to the thyristor switch 8, and the thyristor switch 8 becomes conductive, resulting in the state shown in FIG. 6c. Next, the energizing switch 10 is opened, resulting in the state shown in _FIG . The state shown in FIG. 6e is reached, which is output via the second movable contact 5 and the nonlinear resistor 9.

Further, the tap selector moves, and the first movable contact 4 separates from the upper fixed contact 2 and contacts the lower fixed contact 3, resulting in the state shown in FIG. 6f. Then the auxiliary contact 11 closes again and the ignition device 12
The ignition signal is output from the thyristor switch 8, and the thyristor switch 8 becomes conductive, resulting in the state shown in Fig. 6g.Then, the energizing switch 10 is closed, resulting in the state shown in Fig. 6h, and the load current I _L flows from the lower tap. Lower fixed contact 3, first movable contact 4, energizing switch 1
Output via 0. After that, auxiliary contact 11
is opened, the ignition signal of the ignition control device disappears, the thyristor switch 8 is turned off, and the load current I _L
is output from the lower tap via the lower fixed contact 3 connected to the lower tap, the first movable contact 4, and the energization switch 10, and the state shown in Figure 6i is reached, completing the switching of one tap. do.

The energizing switch 10 opens during the transition from state c to d in Figure 6 during tap switching, but the voltage between the terminals of the energizing switch 10 at this time is about 1 to 2 volts, and the contact opens with almost no firing. can. Also,
In Fig. 6, at the stage of transition to c or d, the nonlinear resistor 9
A voltage is applied between the taps, but since the limiting voltage is selected so that almost no current flows at this voltage, there will be no short circuit between the taps.

[Problem that the invention seeks to solve]

The conventional thyristor-type tap changer on load is configured as described above, and by opening and closing the auxiliary contact,
Since the opening and closing of the thyristor switch 8 is controlled, if a series of switching operations is performed at high speed, it will be difficult to obtain accurate timing for the opening and closing operations of the auxiliary contact.To avoid this, it is necessary to perform a series of switching operations at low speed. When the load current flows through the nonlinear resistor for a longer period of time, the amount of heat generated by the nonlinear resistor increases accordingly, requiring a large and expensive nonlinear resistor with high heat resistance. In addition, the auxiliary contact is
Although it is a mechanical contact, the reliability of the tap changer is greatly affected by its quality, so it requires a highly reliable one, which poses problems such as making it more expensive.

This invention was made in order to solve the above problems, and the opening/closing control of the thyristor switch is performed using the voltage across the thyristor switch and the voltage between the first movable contact and the second movable contact. This is done electrically, which not only eliminates the need for expensive auxiliary contacts, but also makes it possible to accurately control the thyristor switch even when switching is performed at high speed, and the current flowing through the nonlinear resistor increases accordingly. It is an object of the present invention to provide an on-load tap changer in which the time during which the load current is applied is shortened, thereby reducing the heat generation of a nonlinear resistor and making the switch compact.

[Means to resolve the problem]

The thyristor type on-load tap changer according to the present invention includes a first voltage detection device that detects the potential difference between both ends of the thyristor switch, and a second voltage detection device that detects the potential difference between a pair of movable contacts of the tap selector. , and an ignition control device for controlling ignition of the thyristor switch in response to voltage signals from the first and second voltage detection devices.

[Effect]

In the thyristor-type on-load tap changer according to the present invention, when the first voltage detection device detects voltage and the second voltage detection device detects no voltage, the ignition device ignites the thyristor switch.

〔Example〕

Examples of the present invention will be described below. FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the embodiment, and FIG. 3 is a switching sequence diagram. In the figure, numerals 1 to 6 and 8 to 10 are the same as or have the same functions as conventional ones, and their explanations will be omitted. 13 is a first voltage detection device that detects the potential difference between both ends of the thyristor switch 8 (hereinafter referred to as _VTH ); 14 is a first movable contact 4;
and the second movable contact 5 (hereinafter referred to as V _STEP
A second voltage detection device 15 outputs an ignition signal to the thyristor switch 8 when the second voltage detection device 14 detects no voltage and the first voltage detection device 13 detects _VTH . However, when the second voltage detection device 14 is detecting V _STEP , the ignition device is configured not to output an ignition signal even if the voltage detection device 13 detects V _TH .

The first movable contact 4 and the second movable contact 5 move while maintaining a bridging distance between the fixed contacts 2 and 3, and the first A thyristor switch 8 is connected to the movable contact 4, a nonlinear resistor 9 is connected to the second movable contact 5, and the second movable contact moves in advance.

The energization switch 10 is configured to open and close at a predetermined position in conjunction with the movement of the second movable contact 5. The nonlinear resistor 9 has the same characteristics as in the conventional example as shown in FIG. 5, and its limiting voltage is higher than the voltage between adjacent voltage taps V _STEP and lower than the ground voltage of each voltage tap. .

Next, the operation will be explained. FIG. 2a shows a state in which the tap selector selects an arbitrary tap and is in a steady state. In this state, the thyristor switch 8 is open, the energizing switch 10 is closed, and the load current I _L is tap winding 1 → fixed contact 2 connected to any tap → first movable contact 4 →
It is output via the energization switch 10. When a tap switching command is issued in this state, the tap selector 6 moves to the lower position, and first the second movable contact 5 moves and separates from the upper fixed contact 2. Second
The energizing switch 10 is opened before the movable contact 5 moves and comes into contact with the lower fixed contact 3. When the energizing switch 10 is opened and an attempt is made to cut off I _L , a voltage appears between the terminals of the thyristor switch 8.
V _TH is generated, the first voltage detection device 13 detects this, and the thyristor switch 8 is activated by the ignition device 15.
When the ignition signal is output to the thyristor switch 8, the thyristor switch 8 becomes energized, and the load current I _L is commutated to the thyristor switch 8 and comes into contact with the lower fixed contact 3, the second voltage detection device 14 detects V _STEP. is detected, the ignition signal output from the ignition device 15 to the thyristor switch 8 is stopped, and the thyristor switch 8 is opened. By opening the thyristor switch 8, the load current I _L decreases to the lower tap→
The current is commutated to the circuit via the lower fixed contact 3 → second movable contact 5 → nonlinear resistor 9, resulting in the state shown in FIG. 2c. In this switching process, a voltage of V _STEP is applied to the nonlinear resistor 9, but since its limiting voltage is set higher than the maximum value of V _STEP , the bridge current between the taps does not become large.

Next, the tap selector 6 moves to separate the first movable contact 4 from the first fixed contact 2, and then moves further to bring the first movable contact 4 into contact with the lower fixed contact 3. . When the first movable contact 4 contacts the lower fixed contact 3, the first voltage detection device 13
detects the voltage V _TH corresponding to the voltage drop of the load current I _L flowing through the nonlinear resistor 9, and activates the ignition device 1.
5 outputs an ignition signal to the thyristor switch 8, and the thyristor switch 8 becomes energized, resulting in the state shown in FIG. 2d.

When the tap selector 6 reaches the normal position after changing the tap, the energizing switch 10 closes and the first voltage detection device 13 detects zero voltage, which is output from the ignition device 15 to the thyristor switch 8. The ignition signal that was being used stops, the thyristor switch 8 becomes open, and the load current I _L that was flowing through the thyristor switch 8 is diverted to the energization switch 10, and the third
The state shown in FIG. f is reached, and one operation of tap switching is completed.

〔Effect of the invention〕

As described above, according to the present invention, the opening and closing of the thyristor switch is controlled by the presence or absence of V _TH and V _STEP , so even if a series of switching operations is performed at high speed, the opening and closing of the thyristor switch can be performed accurately. This enables highly reliable high-speed switching operation, reduces the time required to commutate the load current to the nonlinear resistor, and reduces power consumption in the nonlinear resistor, making it possible to use a small and inexpensive nonlinear resistor. The effect is that it can be used.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the configuration of FIG. 1, and FIG. 3 is a switching sequence diagram of the configuration of FIG. 1. Figure 4 is a conventional configuration diagram, and Figure 5 is the voltage of the nonlinear resistor.
Current characteristic diagram, Figure 6 is an explanatory diagram of the operation of the conventional configuration,
FIG. 7 is a conventional switching sequence diagram. In the figure, 1 is a tap winding, 2 and 3 are fixed contacts, 4 and 5 are movable contacts, 6 is a tap selector, and 8
is a thyristor switch, 9 is a nonlinear resistor, 10 is
1 is an energization switch, 13 is a first voltage detection device, 1
4 is a second voltage detection device, and 15 is an ignition device.

Claims (1)

[Claims] 1 A plurality of fixed contacts are connected to each tap of a transformer tap winding having a plurality of taps and are arranged at equal intervals keeping a predetermined distance, and a tap is selected by contacting the fixed contacts. It has a pair of movable contacts, one end of a thyristor switch in which a pair of thyristor elements are connected in antiparallel to each other is connected to one first movable contact, and a limited voltage is connected to the other second movable contact. One end of a nonlinear resistor whose value is higher than the voltage between adjacent taps and lower than the ground voltage of any tap is connected, and the other end of the thyristor switch and the other end of the nonlinear resistor are connected in common to load the thyristor switch. The first movable contact and the second movable contact are configured to output current, and during the movement process, the second movable contact leads while maintaining a distance that bridges the adjacent fixed contacts. a tap selector configured to move with the thyristor switch; and an energization switch connected in parallel with the thyristor switch;
a first voltage detection device that detects a potential difference between terminals of the thyristor switch; a second voltage detection device that detects a potential difference between the first movable contact and the second movable contact; The energizing switch includes an ignition device that outputs an ignition signal to the thyristor switch based on the detection voltage of the first voltage detection device and the detection voltage of the second voltage detection device, and the energization switch After the second movable contact is separated from the upper fixed contact and before it contacts the lower fixed contact, the contact is opened, and the first and second movable contacts contact the lower fixed contact. The ignition device closes when the first voltage detection device detects voltage and the second voltage detection device does not detect voltage. A thyristor switch type on-load tap changer characterized by outputting to a thyristor switch.