JP6535594B2 - Automatic voltage regulator - Google Patents

Description

  The present invention relates to an indirect-switching type automatic voltage regulator installed in a power system.

  An indirect-switching automatic voltage regulator has a series transformer in which a secondary winding is connected in series to a line and a regulated voltage is applied between primary terminals, and a tap winding including a plurality of taps. Between the primary terminal of the series transformer and the tap winding of the adjustment transformer, the adjustment transformer generating a regulated voltage between the taps of the tap windings, which supplies the voltage of the input as the input between the primary terminals of the series transformer The on-load tap changer (OLTC << On Load Tap Changer >>, hereinafter referred to simply as the tap changer) for switching the tap of the tap winding which outputs the adjustment voltage to be applied to the series transformer, and the voltage of the line are set. And a controller for controlling the tap changer so as to maintain the range.

  The tap changer has an output terminal connected to the primary terminal of the series transformer, and is connected between a plurality of tap selection switches provided between the plurality of taps of the tap winding and the output terminal and the output terminal. A bridge switch is connected via a current limiting resistor, and the primary side of the series transformer is opened by temporarily turning on the bridge switch in the process of switching the tap. The switch for selecting the tap to be turned on is switched while the switch is turned on, and the current-carrying tap of the tap winding (the tap for outputting the adjustment voltage given to the series transformer) is switched.

  As an automatic voltage regulator of this type, for example, as disclosed in Patent Document 1, a thyristor-type automatic voltage regulator having a tap selection switch and a bridge switch composed of bidirectional thyristor switches is known. Are known. The bi-directional thyristor switch can be configured by a pair of anti-parallel connected thyristors or bi-directional thyristors (triacs).

  In this type of automatic voltage regulator, if there is a contact failure at the connection connecting the switches of the tap changer and the tap of the adjustment transformer, or if the thyristors that constitute each switch fail or When a malfunction occurs, an accident may occur in which the primary terminals of the series transformer are opened. If an accident occurs in which the primary terminals of the series transformer are opened, the load current flowing through the secondary side (grid side) of the series transformer becomes all the excitation current, so the primary winding of the series transformer is abnormal. Overvoltage occurs. If this abnormal overvoltage is applied to both ends of the thyristor switch in the off state in the tap changer, the thyristors constituting the thyristor switch may be damaged.

  Therefore, in this type of automatic voltage regulator, when an accident occurs in which the primary side of the series transformer is opened, a protection operation is performed to suppress the voltage applied to the circuit on the tap switch side from the primary side of the series transformer. A protective device is provided to The protection device conventionally used is the level of the voltage between the output terminal of the tap changer and the shorting switch connected in parallel between the output terminals of the tap changer (voltage between the primary terminals of the series transformers) And a switch control unit that turns on the shorting switch when the set over voltage determination level (a level suitable for detecting an abnormal over voltage generated when the primary side of the series transformer is opened) Thus, the circuit on the tap changer side is protected from overvoltage by turning on the shorting switch when an accident occurs in which the primary side of the series transformer is opened. A magnetic contactor is usually used as a shorting switch.

JP, 2014-115770, A

  The protection device provided in the indirect-switching type automatic voltage regulator compares the voltage on the primary side of the series transformer with the over voltage determination level, and as a result of the comparison, an open accident occurs on the primary side of the series transformer. When it is determined that the resulting overvoltage is occurring, a drive command is given to a driver circuit for driving the shorting switch connected between the output terminals of the tap changer, and the shorting switch is turned on. Therefore, it can not be avoided that a certain delay time elapses between the occurrence of abnormal overvoltage on the primary side of the series transformer and the actual implementation of the protection operation. During this delay time, the inside of the tap changer There has been a problem that a high voltage is continuously applied to the thyristors constituting the thyristor switch in the off state, and the thyristors are excessively stressed.

  Further, in order to prevent the malfunction of the protection device, it is preferable to perform the protection operation when it is detected that the voltage level on the primary side of the series transformer has reached the overvoltage determination level more than once. In order to do so, it is necessary to continue the state where the overvoltage occurs over multiple cycles, but if the overvoltage is generated many times, the time during which the overvoltage is applied to the tap changer will be longer, so the tap changer The stress on the thyristor which is in the off state is further excessive, and the thyristor is more likely to be broken.

  The object of the present invention is to tap the level of the voltage applied from the series transformer to the tap changer before the protective device performs a full-scale protection operation when an overvoltage occurs on the primary side of the series transformer. Indirect switching that can prevent the thyristor in the tap changer from being overstressed in the event of an open accident by keeping the circuit in the changer at a safe level that will not destroy it. To provide an automatic voltage regulator of the formula.

The present invention discloses at least the following first to eighth inventions to achieve the above object.
<First Invention>
The present invention has a series transformer in which a secondary winding is connected in series to a line, and a regulated voltage is input to the primary side, and a tap winding including a plurality of taps, and the line voltage is used as an input. A conditioning transformer generating a plurality of voltages used as a regulating voltage between the taps of the winding, and an output terminal connected to the primary terminal of the series transformer, and between the plurality of taps of the tap winding and the output terminal A plurality of tap selection switches provided and a bridge switch connected via a current limiting resistor between output terminals, and series transformation is performed with on / off operation of the tap selection switch and the bridge switch. The tap switch which switches the tap of the tap winding that outputs the adjustment voltage to be supplied to the converter, and the overvoltage check to determine that the abnormal overvoltage is induced on the primary side of the series transformer by the voltage between the output terminals of the tap switch. Equipped with a protection device that performs control to turn on the shorting switch connected between the output terminals when it detects that the level has been reached, and suppresses the overvoltage applied to the tap changer from the series transformer. Automatic voltage regulator. In the automatic voltage regulator targeted by the present invention, the tap selection switch and the bridge switch are thyristor switches.

  In the present invention, among the tap selection switches, a pair of tap selection switches provided to short the output terminals of the tap changer when simultaneously turned on is selected as the immediate protection switch. A trigger element consisting of a semiconductor element which is turned on when the voltage applied across the both ends reaches a prescribed operating voltage is connected between the anode and gate of each of the thyristors constituting the instant protection switch. The level of the operating voltage of the trigger element is set to be higher than the level of the voltage applied across the trigger element when the voltage level between the output terminals of the tap changer reaches the over voltage determination level, and the series transformation When an abnormal overvoltage is induced on the primary side of the device, the trigger element is turned on, and the instant protection switch is turned on.

  With the above configuration, when an overvoltage is induced on the primary side of the series transformer, the switch for immediate protection is turned on from the first cycle of the overvoltage, and the series transformer applies the voltage to the tap changer. When an overvoltage occurs on the primary side of the series transformer, before performing a full-scale protection operation, closing the shorting switch connected between the output terminals of the tap changer. A preliminary protective action can be performed to suppress the level of the voltage applied from the series transformer to the circuit on the tap changer side to prevent the tap changer from being applied with an excessive voltage. . Therefore, when an overvoltage occurs on the primary side of the series transformer, the stress applied to each thyristor can be reduced, and the life of the tap changer can be extended and the reliability can be improved. Also, even if overvoltage is generated over multiple cycles on the primary side of the series transformer before the protective device performs full-scale protection operation, the level of voltage applied from the series transformer to the tap changer is suppressed during that time It is possible to accurately check that the overvoltage has occurred due to an open accident without giving excessive stress to the thyristor in the tap changer, so that the protection operation of the protection device can be performed. Reliability can be improved.

  Also, as described above, when a tap selection switch is used as an instant protection switch used to perform a preliminary protection operation when an overvoltage occurs on the primary side of the series transformer, a special semiconductor switch is used. It is possible to secure security until the full-scale protection operation is performed without adding the

  If, for any reason, the tap selection switch selected as the instant protection switch is accidentally broken and the primary side of the series transformer is opened, the above-mentioned preliminary protection operation is performed. In the automatic voltage regulator targeted by the present invention, the shorting switch connected between the output terminals of the tap changer is turned on when an abnormal overvoltage is induced on the primary side of the series transformer. Since the protection device is provided to perform the protection operation to suppress the overvoltage applied to the tap changer from the series transformer, the probability of the tap selection switch being broken is extremely low. Also, even if the tap selection switch selected as the immediate protection switch is broken and the preliminary protection operation is not performed, the protection device finally turns on the shorting switch for protection. Since the operation is performed, there is no possibility that the other tap selection switches of the tap changer will be damaged. According to the present invention, when an accident occurs in which the primary side of the series transformer is opened, in most cases a preliminary protective action is performed to overstress the thyristor in the tap changer. Can improve the reliability of the tap changer.

<Second invention>
The present invention is applied to the first invention, and in the present invention, one end is connected in common and the other end is connected to one and the other of the output terminals forming a pair of tap changers. The tap selection switch is selected as the immediate protection switch.

  As described above, when a pair of tap selection switches, one end of which is commonly connected and the other end of which is connected to one and the other of the output terminals forming a pair of tap changers, is selected as the immediate protection switch, When an abnormal overvoltage is induced on the primary side of the series transformer, it is possible to simultaneously turn on the pair of tap selection switches selected as the immediate protection switches and directly short between the output terminals of the tap changer. The preliminary protection operation can be properly performed.

<Third Invention>
The present invention is applied to the second invention, and in the present invention, a pair of tap selection switches which are turned on when selecting the through holes is selected as the instant protection switch.

  In the event of an open accident on the primary side of the series transformer, it is necessary to perform a protective action to short the primary side of the series transformer, and to make the tap changer be in the selected tap state. If a pair of tap selection switches which are turned on when selecting the through tap is made to be an instant protection switch, control of the tap changer for selecting the through tap is facilitated. be able to.

<The fourth invention>
The present invention is applied to an automatic voltage regulator similar to the automatic voltage regulator targeted by the first invention. In the present invention, a trigger element consisting of a semiconductor element which is turned on when the voltage applied across the both ends reaches a prescribed operating voltage is connected between the anode and gate of each thyristor constituting the bridging switch. . That is, in the present invention, the bridging switch is used as the immediate protection switch. Also in this case, the level of the operating voltage of the trigger element is set higher than the level of the voltage applied across the trigger element when the voltage level between the output terminals of the tap changer reaches the over voltage determination level. When an abnormal overvoltage is induced on the primary side of the transformer, the trigger element is turned on to turn on the bridge switch.

  Even when configured as described above, when an abnormal overvoltage occurs on the primary side of the series transformer, the switch for bridging is turned on by the function of the trigger element from the first cycle of the overvoltage, and the output of the tap changer Since the voltage between the terminals can be suppressed, the tap changer can be protected from overvoltage until the protection device performs the protection operation.

<Fifth Invention>
Generally, a plurality of tap selection switches provided in the tap changer have one end commonly connected to one tap of the tap winding and the other end connected to one and the other of the output terminals forming the pair of tap changers. It includes a pair of switches for selecting through taps which are connected and simultaneously turned on when selecting through taps. In the fifth aspect of the invention, there is provided a semiconductor which is turned on when a voltage applied across the thyristors of the thyristor switches constituting the pair of through-hole tap selecting switches reaches a prescribed operating voltage. A trigger element consisting of elements is connected. Also in this case, the level of the operating voltage of the trigger element is set higher than the level of the voltage applied across the trigger element when the voltage level between the output terminals of the tap changer reaches the over voltage determination level. When the abnormal overvoltage is induced on the primary side of the series transformer, the trigger element is turned on to turn on the pair of through hole tap selection switches. In this case, the protection device is configured to perform an operation to turn on the shorting switch after turning on the bridging switch when it is detected that an abnormal overvoltage has occurred on the primary side of the series transformer. There is.

  With the above configuration, when an abnormal overvoltage occurs on the primary side of the series transformer, the switch for bridging is turned on by the function of the trigger element from the first cycle of the overvoltage, and the output terminal of the tap changer is Therefore, it is possible to suppress the thyristor in the tap changer and allow the protection device to accurately confirm that the overvoltage has occurred due to an open accident, without causing excessive stress to the thyristor in the tap changer. The reliability of the protection operation can be enhanced.

<Sixth Invention>
The present invention is directed to an automatic voltage regulator similar to the automatic voltage regulator targeted by the fifth invention. In the present invention, the protective device generates an abnormal overvoltage on the primary side of the series transformer. When it is detected, the bridge switch is turned on, and then the shorting switch is turned on while maintaining the on state of the threading tap selection switch turned on by the action of the trigger element. Be done. The other configuration is the same as that of the fifth invention.

  When configured as described above, when it is detected that an abnormal overvoltage has occurred on the primary side of the series transformer, a short circuit occurs in a state in which the threading tap selection switch turned on by the function of the trigger element is maintained in the on state Since the switch can be turned on to shift to full-scale protection operation, protection of the tap changer can be continued until the short circuit accident is eliminated, and protection of the tap changer can be ensured. .

<Seventh Invention>
The present invention is applied to the fifth invention or the sixth invention, and in the present invention, from the overvoltage induced on the primary side of the series transformer when an accident occurs in which the primary side of the series transformer is opened. Not only the tap changer is protected, but also a protection action is performed to protect the tap changer and the tap winding from the overcurrent flowing to the primary side of the series transformer when a short circuit accident occurs in the system. When a short circuit fault occurs in the system, a short circuit current flows in the secondary winding of the series transformer connected in series to the line. At this time, if the tap changer selects a tap other than the pure tap, a large current flows from the primary side of the series transformer through the tap selection switch and the tap winding in the on state, and the tap winding is damaged. There is a fear. In addition, when a short circuit fault occurs in the system, if the bridge switch of the tap changer is in the on state, an overcurrent may flow through the current limiting resistor and the current limiting resistor may be burned. In order to prevent these accidents, it is necessary to perform a protective action to turn on the shorting switch that shorts between the output terminals of the tap changer even when a short circuit accident occurs in the system. When generated, no high voltage is induced on the primary side of the series transformer. Therefore, by configuring the protection device as in the fifth or sixth invention, protection of the tap winding and the current limiting resistor is achieved. I can not do it.

In the seventh invention, a relay is provided which generates a protection command when it is detected that a short circuit accident has occurred in a system in which a line is provided. In this case, the protection device is configured to perform the following protection operations (1) and (2) in addition to the protection operation performed by the protection device in the fifth invention or the sixth invention.
(1) When the relay issues a protection command in a state where the pair of through hole tap selection switches is on, control is performed to turn on the shorting switch while maintaining the on state of the pair of through hole tap selection switches I do.
(2) When the relay generates a protection command in the state where the pair of through hole tap selection switches is off, once all tap selection switches on the tap changer and the bridge switches are turned off to perform series transformation After the trigger element is turned on by generating an abnormal overvoltage on the primary side of the switch to turn on the pair of threading tap selection switches, the bridging switch is maintained in the OFF state to select the pair of threading taps Control is performed to turn on the shorting switch while maintaining the switch for the on state.

  When a short circuit accident occurs in the system with the through hole tap selected and the through hole tap selection switch turned on, the pair of through hole tap selection in which the current flowing through the primary side of the series transformer is in the on state The bypass current does not flow in the tap winding since it is bypassed from the tap winding through the switch. Also, at this time, since the bridging switch is in the off state, no overcurrent flows through the current limiting resistor. Therefore, when the relay issues a protection command in a state in which the threading tap is selected, the tap winding is performed by performing control to turn on the shorting switch while maintaining the on state of the pair of threading tap selection switches. And protection of the current limiting resistor.

  When a short circuit accident occurs in the system with taps other than the through taps selected and the through tap selection switch turned off, taps through the tap selection switches that are on from the primary side of the series transformer An overcurrent flows in the winding. In addition, when the bridging switch is turned on at the occurrence of a short circuit accident, an overcurrent flows from the primary side of the series transformer to the current limiting resistor. In these cases also, it is necessary to turn on the shorting switch to perform the protection operation, but since a high voltage is not induced on the primary side of the series transformer when a short circuit accident occurs, the voltage on the primary side of the series transformer ( The method of turning on the shorting switch when the voltage between the output terminals of the tap changer reaches the over voltage determination level can not perform the protection operation.

  Therefore, in the seventh invention, when the relay generates a protection command in a state in which a tap other than the through threading tap is selected (when a short circuit accident occurs in the system in a state in which the through threading tap selection switch is off) ) Temporarily turn off all tap selection switches and bridge switches of the tap changer, intentionally generate an abnormal overvoltage on the primary side of the series transformer, and configure a pair of through hole tap selection switches The trigger element connected between the anode gates of the thyristors of the thyristor switches is immediately turned on to turn on the pass-through tap selection switch. As a result, the current flowing on the primary side of the series transformer at the time of occurrence of a short circuit is bypassed from the tap winding to promptly protect the tap winding. Also, switching to the full-scale protection operation by turning on the shorting switch while keeping the bridging switch in the off state and keeping the pair of through hole tap selection switches in the on state, a short circuit accident occurs. The protection operation is continued until it is eliminated.

  As described above, according to the seventh aspect of the invention, not only can the tap changer be protected from an abnormal overvoltage that occurs when an accident occurs in which the primary side of the series transformer is opened, a short circuit accident occurs in the system. Since the tap changer and the tap winding can be protected from the current flowing in the primary side of the series transformer when it occurs, the protection of the automatic voltage regulator can be ensured. Further, in the event of a short circuit, it is possible to prevent damage to the current limiting resistor due to an overcurrent by keeping the bridge switch in the OFF state.

<The eighth invention>
The eighth invention is applied to any one of the first invention to the sixth invention, and in the present invention, the level of the operating voltage of the trigger element and the voltage level between the output terminals of the tap changer The tap switcher is set to a level below the level of the voltage applied across the trigger element when it reaches a level that causes the thyristor in the off state to break down.

  When configured in this manner, the level of the voltage applied to the tap changer is a safe level that does not cause breakdown of the thyristor when an overvoltage-induced open accident occurs on the primary side of the series transformer. Therefore, it is possible to ensure protection of the thyristor in the tap changer.

  According to the present invention, when an overvoltage occurs on the primary side of the series transformer, it is possible to start the series transformer before performing the full-scale protection operation of turning on the shorting switch connected between the output terminals of the tap changer. A preliminary protection operation can be performed to suppress the level of the voltage applied to the circuit on the tap changer side to a safe level that is not likely to break the circuit in the tap changer. Therefore, when an overvoltage occurs on the primary side of the series transformer, it is possible to prevent each thyristor from being overstressed, and it is possible to extend the life of the tap changer and to improve the reliability.

  Further, according to the present invention, even if overvoltage is generated over a plurality of cycles on the primary side of the series transformer before the protective device performs full-scale protection operation, the overvoltage is applied from the series transformer to the tap changer during that time. Voltage level can be maintained at a safe level, so that it is possible to accurately confirm that an overvoltage accident has occurred due to an open accident without giving excessive stress to the thyristor in the tap changer. The reliability of the protection operation by the device can be enhanced.

  Further, according to the present invention, when an overvoltage occurs on the primary side of the series transformer, a reserve for keeping the level of the voltage applied to the tap changer at a safe level until the protection device performs full-scale protection operation. The switches used to perform the typical protection operation are configured using the tap selection switch, so preliminary protection before the full-scale protection operation is performed without adding a special semiconductor switch You can make it work.

  In particular, according to the seventh invention, not only can the tap changer be protected from an overvoltage that occurs when an accident occurs in which the primary side of the series transformer is opened, but also when a short circuit accident occurs in the system Since the protection operation of protecting the tap changer and the tap winding from overcurrent flowing on the primary side of the transformer can also be performed, protection of the tap changer can be ensured.

FIG. 1 is a circuit diagram schematically showing a configuration of an embodiment of the present invention. In one embodiment of the present invention, it is the circuit diagram showing the state where the trigger element was connected to each thyristor of the thyristor switch which constitutes the switch for immediate protection. It is a circuit diagram for explaining the operation of one embodiment of the present invention. FIG. 7 is another circuit diagram for explaining the operation of an embodiment of the present invention. FIG. 10 is yet another circuit diagram for explaining the operation of an embodiment of the present invention. FIG. 10 is yet another circuit diagram for explaining the operation of an embodiment of the present invention. FIG. 10 is yet another circuit diagram for explaining the operation of an embodiment of the present invention. FIG. 10 is yet another circuit diagram for explaining the operation of an embodiment of the present invention. FIG. 10 is yet another circuit diagram for explaining the operation of an embodiment of the present invention. FIG. 10 is yet another circuit diagram for explaining the operation of an embodiment of the present invention. FIG. 10 is yet another circuit diagram for explaining the operation of an embodiment of the present invention. FIG. 6 is a waveform diagram showing a waveform of a voltage applied between output terminals of the tap changer in an embodiment of the present invention. It is the circuit diagram which showed roughly the structure of other embodiment of this invention.

  FIG. 1 shows the configuration of the first embodiment of the present invention. In FIG. 1, the secondary winding is connected in series to the three-phase lines Lu to Lw of the power system, and adjustment is made to the primary side. The series transformer 2 into which a voltage is inputted, 2 has a primary winding connected in parallel to the lines Lu to Lw, has a tap winding on the secondary side, and the primary side of the series transformer 1 from between the taps of the tap winding 3 is a tap changer provided between the tap winding of the adjustment transformer 2 and the primary terminal of the series transformer 1.

  The series transformer 1 comprises a first unit series transformer TSu, a second unit series transformer TSv and a third unit series transformer TSw, and a secondary winding of the first unit series transformer TSu. Csu, the secondary winding Csv of the second unit series transformer TSv, and the secondary winding Csw of the third unit series transformer TSw are connected in series to the three-phase lines Lu to Lw, respectively. The primary windings Cpu to Cpw of the first to third unit series transformers TSu to TSw are three-phase Y-connected by connecting one ends thereof to the neutral point N. Three-phase primary terminals 1u to 1w are drawn from the other ends of the primary windings Cpu to Cpw, respectively.

  The regulating transformer 2 consists of a first unit regulating transformer TS1 and a second unit regulating transformer TS2. The primary winding Cp1 of the first unit adjustment transformer and the primary winding Cp2 of the second unit adjustment transformer are three-phase V-connected by one end of each being commonly connected, and the primary winding Cp2 is Three-phase input terminals 2u to 2w are drawn out from the other end, the common connection point of primary windings Cp1 and Cp2 and the other end of primary winding Cp2, and these input terminals are connected to lines Lu to Lw, respectively. .

  The respective secondary windings Cs1 and Cs2 of the first unit adjustment transformer TS1 and the second unit adjustment transformer TS2 are tap windings, and taps t11 and t11 are respectively connected from one end and the other end of the tap winding Cs1. t13 is drawn out, and the tap t12 is drawn out from the portion near the other end of the tap winding Cs1. Further, the taps t21 and t23 are drawn out from one end and the other end of the tap winding Cs2, respectively, and the tap t22 is drawn out from a portion near the other end of the tap winding Cs2.

  The tap changer 3 has output terminals 3u to 3w connected to primary terminals 1u to 1w of the series transformer 1, respectively, and between a plurality of taps of the tap windings Cs1 and Cs2 and the output terminals 3u to 3w A plurality of tap selection switches Th1 (1) to Th3 (1), ThA (1) to ThC (1), Th1 (2) to Th3 (2) and ThA (2) to ThC (2) provided, A bridging switch ThS (1) connected between the output terminals 3w and 3v via a current limiting resistor R (1) and a current limiting resistor R (2) between the output terminals 3u and 3v And the bridge switch ThS (2) to switch the tap of the tap winding for outputting the adjustment voltage to be applied to the series transformer 1 with the on / off operation of the tap selection switch and the bridge switch. Each tap selection switch and the bridge switch are composed of a bidirectional thyristor switch using a thyristor as a switching element.

  In the illustrated example, one end of each of the tap selection switches Th1 (1) to Th3 (1) is commonly connected to the output terminal 3w, and the other end is tap of the tap winding of the first unit adjustment transformer. It is connected to t13, t12 and t11. Further, one end of each of the tap selection switches ThA (1) to ThC (1) is commonly connected to the output terminal 3v, and the other end of each of these tap selection switches is the tap winding Cs1 of the first unit adjustment transformer. Are connected to the taps t11, t12 and t13. The tap selection circuit 3A (1) on the first unit adjustment transformer side is configured by the tap selection switches Th1 (1) to Th3 (1) and the tap selection switches ThA (1) to ThC (1). .

  In addition, one end of tap selection switches Th1 (2) to Th3 (2) is commonly connected to the output terminal 3u, and the other ends of these tap selection switches are taps of the tap winding Cs2 of the second unit adjustment transformer. It is connected to t23, t22 and t21. Furthermore, one end of tap selection switches ThA (2) to ThC (2) is connected to the output terminal 3v, and the other ends of these tap selection switches are tap t21 of the tap winding of the second unit adjustment transformer TS2. , T22 and t23. Tap selection switches Th1 (2) to Th3 (2) and tap selection switches ThA (2) to ThC (2) constitute the tap selection circuit 3A (2) on the second unit adjustment transformer side, and the taps A tap changer 3 is configured by selection circuits 3A (1) and 3A (2), current limiting resistors R (1), R (2), and switches for bridging ThS (1), Ths (2). ing.

  In the present embodiment, the first unit adjustment transformer side tap selection circuit 3A (1) and the second unit adjustment transformer side tap selection circuit 3A (2) share the output terminal 3v, so that the first unit adjustment transformer side tap selection circuit 3A (1) The secondary sides of the unit adjustment transformer TS1 and the second unit adjustment transformer TS2 are three-phase V-connected, and the output terminal 3v is grounded.

  In the tap changer 3 used in the present embodiment, one end of the tap selection switches ThA (1) to ThC (1) whose one end is commonly connected to the output terminal 3v and one end is common to the output terminal 3w By turning on one of the connected tap selection switches Th1 (1) to Th3 (1), two of the three taps provided on the tap winding Cs1 are energized. And is configured to apply a voltage between the two selected current application taps between the primary terminals 1v and 1w of the series transformer 1 through the output terminals 3v and 3w, and for selecting a tap to be turned on A tap winding used as an adjustment voltage by changing a combination of one of the switches ThA (1) to ThC (1) and one of the tap selection switches Th1 (1) to Th3 (1) to be turned on. Switching the magnitude and phase of the voltage between taps of line Cs1 Accordingly, as the position of the tap (current taps) for outputting a regulated voltage, to achieve a seven tap position including plain tap position.

  Similarly, one of the tap selection switches ThA (2) to ThC (2) whose one end is commonly connected to the output terminal 3v and the tap selection switch Th1 (2) whose one end is commonly connected to the output terminal 3u By turning on one of ~ Th3 (2), two taps of the three taps provided on the tap winding Cs2 are selected as the energizing taps, and the selected two energizing taps Between the primary terminals 1v and 1u of the series transformer 1 through the output terminals 3v and 3u, and the tap selection switches ThA (2) to ThC (2) to be turned on. The magnitude and phase of the inter-tap voltage of the tap winding Cs2 used as the adjustment voltage by changing the combination of one of them and one of the tap selection switches Th1 (2) to Th3 (2) to be turned on. Tap to output the adjustment voltage by switching As the position of the tap), to achieve a seven tap position including plain tap position.

  The voltages between the three phase output terminals 3u and 3v, between 3v and 3w and between 3w and 3u of the tap changer 3 are respectively between the primary terminals 1u and 1v of the three phases of the series transformer 1, between 1v and 1w and 1w, It is input as a 3-phase adjustment voltage between 1u.

The first unit adjustment transformer-side tap selection circuit 3A (1) and the second unit adjustment transformer-side tap selection circuit 3A (2) output the adjustment voltage to be applied between the primary terminals of the series transformer 1 The position of the tap is switched in seven steps from tap position 1 to tap position 7 so that seven types of adjustment voltages can be applied to the primary side of the series transformer 1. For example, when selecting tap position 1, on the tap selection circuit 3A (1) side, the tap selection switches ThC (1) and Th1 (1) shown in FIG. As a result, on the tap selection circuit 3A (2) side, the tap selection switches ThC (2) and Th1 (2) are turned on. Further, when selecting the through tap, on the tap selection circuit 3A (1) side, the tap selection switch ThA (1) and the tap selection switch Th1 (1) are turned on, and the tap selection circuit 3A (2) is turned on. On the) side, the tap selection switch ThA (2) and the tap selection switch Th1 (2) are turned on. The relationship between the tap position 1 to the tap position 7 and the tap selection switches (thyristor switches) turned on to realize the respective tap positions is summarized in Table 1 below.

  In Table 1, in order to distinguish between the first unit adjustment transformer side tap selection circuit 3A and the second unit adjustment transformer side tap selection circuit 3B in FIG. The suffixes (1) and (2) added at the end are omitted. Among the tap position 1 to the tap position 7, the tap position 4 is the position of the transparent tap. When tap position 4 is selected, tap selection switches ThA (1) and Th1 (1), one end of which is connected in common to tap t11 and the other end connected to output terminals 3v and 3w, are simultaneously turned on. The tap selection switches ThA (2) and Th1 (2), one end of which is commonly connected to the tap t21 and the other end respectively connected to the output terminals 3v and 3u, are simultaneously turned on. As a result, without shorting between the taps of the tap windings Cs1 and Cs2 of the adjustment transformer 2, the output terminals 3v, 3w and 3v, 3u of the tap changer 3 are shorted, and thus the series transformer The adjustment voltage applied between the primary terminals of each phase of 1 is zero.

  Although not shown, the tap selection switch and the bridge switch of the tap changer 3 are controlled to switch the tap position so that the line voltage returns to the specified range when the line voltage deviates from the specified range. A tap changer controller is provided. This control device detects the line voltage and controls the tap selection switch and the bridge switch on / off so that the tap changer 3 performs tap switching operation when it is necessary to adjust the line voltage. A digital relay for tap changer control is provided, and when it becomes necessary to adjust the line voltage by the function of this digital relay, the switches for bridging ThS (1) and ThS (2) are temporarily turned on. An operation to turn off the tap selection switch which has selected the tap position up to now, and a new tap position while preventing the open state between the output terminals 3v and 3w and between 3v and 3u in the state And an operation of turning on a tap selection switch for selecting the tap position to switch the tap position from the previous position to the new position.

  In the illustrated automatic voltage regulator, contact failure may occur at the connection connecting between each switch of the tap changer 3 and the tap of the adjustment transformer 2, or an on state may be used to select a predetermined tap position. When the tap selection switch in the above is broken and turned off, an accident (open accident) occurs in which the primary terminals of the series transformer 1 are opened. When an open accident occurs, of the load currents Iu, Iv and Iw flowing through the secondary side (grid side) of the series transformer 1, the load current of the phase in which the open accident occurs becomes the exciting current of the series transformer 1. , An abnormal overvoltage occurs between the open primary terminals of the series transformer 1. If this abnormal overvoltage is applied to the thyristor in the tap changer 3 which is in the off state and constitutes the tap selection switch, the thyristor may be damaged.

  Therefore, in the automatic voltage regulator according to the present embodiment, it is determined whether an open accident has occurred by comparing the voltage level on the primary side of the series transformer 1 with the overvoltage determination level, and an open accident has occurred. When it is determined, the tap switch 3 is first operated to select the through tap by the function of the digital relay, and then the short circuit switch connected between the output terminals of the tap switch 3 is closed. A protection device is provided to short-circuit between the output terminals 3 and to protect the tap changer 3 from overvoltage.

  In the example shown in FIG. 1, the magnetic contactors MC (1) and MC (2) controlled by digital relays (not shown) are connected between the output terminals 3v and 3w of the tap changer 3 and 3v and 3u respectively. Of the tap windings Cs1 and Cs2 when it is detected that the voltage level between the output terminals 3v and 3w and 3v and 3u has reached the set overvoltage determination level. Switch to make the tap switch 3 perform the through tap selection operation with the through hole as the through tap position, then give a command to a digital relay (not shown) to turn on the electromagnetic contactors MC (1) and MC (2) A control unit 5 (1), 5 (2) is provided, and the above protective device is constituted by the electromagnetic contactors MC (1) and MC (2), and the switch control units 5 (1) and 5 (2). ing.

  The above overvoltage determination level is a level suitable for reliably detecting an overvoltage induced between the primary terminals of the series transformer 1 when the primary side of the series transformer 1 is opened, and is turned off in the tap changer 3 It is set lower than the voltage level which may cause the thyristor in the state to break down. This overvoltage determination level is determined to an appropriate value based on the experimental result.

  The switch control units 5 (1) and 5 (2) are monitored by, for example, a voltage monitoring unit that constantly monitors voltages between the output terminals 3v and 3u and between 3v and 3w of the tap switch 3. When the voltage level between the output terminals 3v and 3u and the voltage level between the output terminals 3v and 3w are compared with the overvoltage determination level, and it is determined that the voltage level between any output terminals becomes equal to or higher than the overvoltage determination level In order to cause the tap changer 3 to perform the through tap selecting operation in which the energizing tap position of the tap winding Cs1 and the energizing tap position of the tap winding Cs2 are both passed through, the tap changer control device is given a transparent tap selection command. It has been confirmed that the transparent tap selection command generation unit and the tap changer control device perform control to set the tap position selected by the tap changer 3 as the transparent tap position in response to this command. At the same time, an electromagnetic contactor drive unit can be configured to issue an instruction to a digital relay (not shown) to cause the digital relay to perform an operation of closing the electromagnetic contactors MC (1) and MC (2).

In switch control units 5 (1) and 5 (2), only one of the voltage level between the output terminals 3v and 3u of the tap changer and the voltage level between the output terminals 3v and 3w is higher than the over voltage determination level Even in this case, the energizing tap positions of both of the tap windings Cs1 and Cs2 are set as the through-tapping positions, and both of the magnetic contactors MC (1) and MC (2) are closed.

  In the case of the above protective device, the period from the occurrence of an abnormal overvoltage on the primary side of the series transformer 1 to the closing of the magnetic contactors MC (1) and MC (2) (shorting switch) It is inevitable that some delay time will elapse. During this delay time, abnormal overvoltage is continuously applied from the series transformer 1 to the tap changer 3, so that the thyristors constituting the thyristor switch in the off state in the tap changer 3 are stressed.

  In addition, in order to prevent the malfunction of the protection device, the protection device may be configured to perform the protection operation when detecting that the voltage level on the primary side of the series transformer 1 has exceeded the overvoltage determination level multiple times. preferable. For that purpose, it is necessary to continue the state where the overvoltage occurs over a plurality of cycles, but when the overvoltage is generated many times, the time during which the overvoltage is applied to the tap changer 3 becomes longer, so the tap changer The stress applied to the thyristor in the off state within 3 may be excessive, and the thyristor may be destroyed.

  Therefore, in the present embodiment, tap selection switches Th1 (1) to Th3 (1), ThA (1) to ThC (1), Th1 (2) to Th3 (2) provided in the tap changer 3. And ThA (2) to ThC (2), a pair of tap selection switches provided in such a positional relationship as to short between the output terminals of the tap changer 3 when made conductive simultaneously. Is selected as an instant protection switch, and the anode of each thyristor constituting the instant protection switch is a trigger element composed of a semiconductor element which is turned on when the voltage applied across the both ends reaches a specified operating voltage.・ Connect between gates. Then, the level of the operating voltage of the trigger element is higher than the level of the voltage applied across the trigger element when the voltage level between the output terminals of the tap switch 3 reaches the over voltage determination level, and the tap switch The primary side of the series transformer 1 is set lower than the level of the voltage applied to the trigger element when the voltage between the three output terminals reaches a level that causes the thyristor constituting the tap selection switch to break down. As soon as the level of the induced voltage exceeds the over voltage determination level, the trigger element is turned on and the instant protection switch is automatically turned on, whereby the series switch 1 is applied to the tap changer 3. In the tap changer 3, a preliminary protection operation is performed to suppress the voltage of the tap switch 3 to a level that does not cause destruction of the thyristor in the off state.

  On the tap selection circuit 3A side, a pair of tap selection switches ThA (1) and Th1 (1), a pair of tap selection switches ThB (1) and Th2 (1), and a tap selection switch as the above-mentioned immediate protection switches Any of the ThC (1) and Th3 (1) pairs can be selected as the instant protection switch. Further, on the tap selection circuit 3B side, a pair of tap selection switches ThA (2) and Th1 (2), a pair of tap selection switches ThB (2) and Th2 (2), and a tap selection switch ThC (2) and Th3. One of the pairs of (2) can be selected as the immediate protection switch.

  In the present embodiment, in order to facilitate transition to the through tap performed at the time of the protection operation, a pair of tap selection switches ThA (1) and Th1 (1) for through tap selection and tap selection for the same through tap selection as well. Switch pairs ThA (2) and Th1 (2) are selected as the immediate protection switches.

  FIG. 2 shows switches for tap selection (in the present embodiment, tap selection switches ThA (1), Th1 (1), ThA (2) and Th1 (2)) for use as an instant protection switch. It shows an example of the thyristor switch which comprises. In this example, a thyristor switch is configured by a pair of thyristors Tha and Thb having unidirectionality which are reverse-parallel-connected (parallel-connected in different directions). The gates of the thyristors Thah and Thb are connected to the trigger signal output terminal of the tap changer controller (not shown), and when the tap changer controller gives a trigger signal to the gates of the thyristors Thah and Thb, the thyristors Thah and Thb Among them, the thyristor to which a forward voltage is applied between the anode and the cathode is turned on. Here, when a positive half-wave voltage is applied to tap selection switches ThA (1), Th1 (1), ThA (2) and Th1 (2) selected as the immediate protection switches A forward voltage is applied between the anode and the cathode of the thyristor Tha forming the switch, and negative half-wave voltage is applied to the tap selection switches ThA (1), Th1 (1), ThA (2) and Th1 (2). When applied, it is assumed that a forward voltage is applied between the anode and the cathode of the thyristor Thb constituting each switch.

  When the thyristor switch selected as the instantaneous protection switch comprises a pair of anti-parallel connected thyristors Tha and Thb as shown in FIG. 2, the anode of the thyristor Tha and the anode of the thyristor Thb Trigger elements 5a and 5b are connected between the gates, respectively. The trigger elements 5a and 5b are composed of voltage-responsive semiconductor elements (switching elements) that are turned on when the voltage applied to both ends reaches a specified operating voltage.

  The semiconductor elements constituting the trigger elements 5a and 5b maintain the off state when the voltage applied to both ends is less than the specified operating voltage, and are automatically turned on when the applied voltage reaches the specified operating voltage. Any semiconductor element to be in a state may be selected as long as it can select an operating voltage suitable for turning on the instant protection switch at an appropriate timing.

  As this semiconductor element, for example, a non-gate two-terminal thyristor (thyristor not having a gate) configured to be self-triggered and turned on when the voltage applied between the anode and the cathode reaches a prescribed voltage. Can be used. As the gateless two-terminal thyristor, for example, one marketed under the trade name of SIDAC (registered trademark) can be used. Sidac has two-way characteristics and one having unidirectional characteristics, but any of these may be used in the present invention.

  In addition, as a semiconductor element constituting the trigger element, a trigger diode (trade name: diac) which is a diode that is turned on when a prescribed operating voltage is applied to both ends, or the level of the applied voltage is It is also conceivable to use a Zener diode or the like that breaks down when reaching a specified level.

  The level of the operating voltage of the trigger element is higher than the level of the voltage applied across the trigger elements 5a and 5b when the voltage level between the output terminals of the tap switch 3 reaches the over voltage determination level, and the tap The voltage level between the output terminals of the switch 3 is set to a level lower than the level of the voltage applied across the trigger element when the voltage level across the tap switch 3 reaches a level that causes the thyristor in the off state to break down. Is preferred.

  Next, the operation when an accident occurs in which the primary side of the series transformer 1 is opened in the automatic voltage regulator according to the present embodiment will be described with reference to FIGS. 3 to 11. In FIG. 3 to FIG. 11, the block showing the tap selection switch in the off state is shown in white and the block showing the tap selection switch in the on state is shown in light black. In FIGS. 3 to 11, the switch control units 5 (1) and 5 (2) are not shown.

  As shown in FIG. 1, with tap selection switches Th1 (1), ThC (1), Th1 (2) and ThC (2) turned on and tap position 1 is selected, as shown in FIG. It is assumed that the tap selection switch ThC (1) has failed and is turned off as indicated by an X mark. At this time, since the primary terminals 1v and 1w of the series transformer 1 are open, load currents Iv and Iw of the V phase and W phase become excitation currents of the series transformer 1, and the series transformer 1 An abnormal overvoltage Vov occurs between the primary terminals 1v and 1w, and the overvoltage Vov is applied between the output terminals 3v and 3w of the tap changer 3 as shown in FIG.

  In the present embodiment, as described above, when an open accident occurs on the primary side of the series transformer 1 and an overvoltage occurs between the primary terminals of the series transformer 1, the protection device is an electromagnetic contactor (shorting switch ) Before turning on MC (1) and MC (2) and performing full-scale protection operation, turn on the pair of through-hole tap selection switches ThA, Th1 selected as the immediate protection switches to turn them on. By short-circuiting the output terminals of the tap changer 3 by the switch, a preliminary protection operation is performed to prevent an excessive voltage from being applied to the circuit in the tap changer 3.

  As shown in FIG. 3, when the tap selection switches Th1 (1), ThC (1), Th1 (2), ThC (2) are turned on and "tap position 1" is selected, an open accident occurs. In the case where the tap selection switch ThA (1) and Th1 (1) have been generated, the tap selection switch Th1 (1) is already in the ON state, and thus the other through-tap selection switch ThA ( By turning on only 1), it is possible to short-circuit the output terminals of the tap changer 3 by turning on both the through-hole tap selection switches ThA (1) and Th1 (1).

  Here, it is assumed that the overvoltage Vov applied between the series transformer 1 side and the output terminals 3v and 3w of the tap changer 3 has a waveform shown by a broken line in FIG. In FIG. 12, Vn indicates the level of the rated voltage between the output terminals of the tap changer 3, and Va indicates the level of the overvoltage Vov to determine that an open accident has occurred in which the primary side of the series transformer 1 is opened. Shows the over voltage determination level to be compared with. Also, V s is between the output terminals of the tap changer 3 when the voltage applied across the trigger element connected between the anode and gate of the thyristor forming the through tap selection switch reaches a prescribed operating voltage. It shows the level of the applied voltage (this level will be referred to as a trigger element operation level).

  When an open accident occurs while tap position 1 is selected, an overvoltage Vov applied between the primary terminals 1v and 1w of the series transformer 1 and between the output terminals 3v and 3w of the tap switch 3 is The tap selection switch Th1 (1) in the on state is applied to the threading tap selection switch ThA (1) in the off state. Trigger elements 5a and 5b (see FIG. 2) are connected between the anodes and gates of the thyristors Tha and Thb constituting the through hole tap selection switch ThA (1).

  As shown in FIG. 12, when the level of the positive half wave of the overvoltage Vov reaches the trigger element operation level Vs, a pair of thyristor Tha constituting the tap selection switch TA (1) which has been in the off state until then. , Thb, and the forward voltage is applied in the positive half wave of overvoltage, and the trigger element 5a connected between the anode and the gate of the thyristor Tha is turned on to trigger the one thyristor Tha. As a result, the tap selection switch ThA (1) which has been in the off state is turned on, and both of the tap selection switches ThA (1) and Th1 (1) are turned on. The output terminals 3v and 3w of the switch 3 are short-circuited, and as shown in FIG. 6, the voltage between the output terminals 3v and 3w of the tap switch 3 is reduced to almost 0V.

  While the voltage between the output terminals 3v and 3w of the tap changer 3 decreases to 0 V, the trigger element 5a connected between the anode and the gate of the thyristor Tha of the tap selection switch TA (1) is turned off. Since the thyristor Tha maintains the on state, the tap selection switches ThA (1) and Th1 (1) for the through tap selection maintain the on state until the positive half wave of the overvoltage Vov ends. Do.

  When the negative half-wave of the overvoltage Vov is started, the voltage of the negative half-wave appears between the output terminals of the tap changer 3, but when this voltage reaches the operating level -Vs of the trigger element The trigger element 5b connected between the anode and the gate of the other thyristor Thb forming the switch ThA (1) is turned on to turn on both tap selection switches ThA (1) and Th1 (1). Is turned on, the output terminals 3v and 3w of the tap changer 3 are short-circuited, and as shown in FIG. 6, the voltage between the output terminals 3v and 3u of the tap changer 3 is made approximately 0V. In FIG. 6, the dotted arrow shown on the right of Vov indicates that the voltage Vov applied up to now has disappeared.

  Since these operations are continued while an overvoltage is induced on the primary side of the series transformer 1, the tap changer 3 in the case where the protection switch for immediate protection is performed as in this embodiment. The waveform of the voltage between the output terminals of is as shown by the solid line in FIG. 12, and the voltage applied to the tap switch 3 is suppressed to the trigger element operating level Vs or less. Since the trigger element operating level Vs is set higher than the overvoltage determination level Va, it is determined that the overvoltage is equal to or higher than the overvoltage determination level while the preliminary protection operation is being performed (an open accident occurs) Confirmation of what you are doing can be done without problems.

  As described above, while the preliminary protection operation is performed to suppress the voltage applied between the output terminals of the tap changer 3 by the conduction of the immediate protection switches Th1 (1) and ThA (1), the series operation is performed. The voltage applied from the transformer 1 to the tap changer 3 is limited to the operating level Vs or less of the trigger element. Therefore, if the trigger element operation level Vs is set to a level lower than the level that causes the thyristor in the off state to break down in the tap switch 3, the tap switch 3 is performed while the preliminary protection operation is performed. It is possible to prevent excessive stress on the inner thyristors. Therefore, before the protective device turns on the magnetic contactors (short circuit switches) MC (1) and MC (2) to perform full-scale protection operation, the overvoltage induced on the primary side of the series transformer 1 is judged as an overvoltage Even if it is determined over a plurality of cycles whether the level is higher than the level, the level of the voltage applied from the series transformer 1 to the tap changer 3 can be maintained at a safe level. Therefore, the reliability of the protection operation by the protection device can be enhanced by accurately confirming that the overvoltage has occurred due to the open accident without giving excessive stress to the thyristor in the tap changer 3. .

  The protection device is set when it is confirmed that an opening accident on the primary side of the series transformer 1 has occurred while the preliminary protection operation is being performed (for example, the overvoltage Vov has exceeded the overvoltage determination level When the number of times of detection is detected, a command is given to a digital relay not shown to first turn on the bridging switches ThS (1) and ThS (2) as shown in FIG. 7 and then show in FIG. Thus, after all the tap selection switches of the tap changer 3 are turned off, as shown in FIG. 9, the transparent tap selection switches Th1 (1), ThA (1), Th1 (2), ThA ( 2) Turn on the state and select the pass-through tap position 4. Next, after instructing the digital relay from switch control units 5 (1) and 5 (2) to perform operations of closing electromagnetic contactors MC (1) and MC (2) as shown in FIG. 10, By the operation of the digital relay, as shown in FIG. 11, the bridge switches ThS (1) and ThS (2) are turned off, and all the tap selection switches are turned off to over-voltage the tap changer 3. Be protected from

  In the above description, as shown in FIG. 8, after all the tap selection switches of the tap changer 3 are turned off, as shown in FIG. 9, the pass-through tap selection switches Th1 (1), ThA (1 And Th1 (2), ThA (2) are turned on to select the through-hole tap position 4, but in the process shown in FIG. 7, the bridging switches ThS (1) and ThS (2) are turned on. Since the voltage on the primary side of the series transformer 1 is already suppressed by being put into the state, as shown in FIG. 8, after all the tap selection switches of the tap changer 3 are turned off, the diagram As shown in 9, the control for turning on the through hole tap selection switches Th1 (1), ThA (1) and Th1 (2), ThA (2) is not essential. That is, the protection device turns on the bridging switches ThS (1) and ThS (2) when it is detected that an abnormal overvoltage occurs on the primary side of the series transformer, and then turns on by the function of the trigger element. Operation of turning on the magnetic contactors MC (1) and MC (2) (shorting switch) while maintaining the on state of the through-hole tap selection switch, the bridge switch, and all tap selection switches And may be configured to perform an action of turning off.

  In the above description, when an opening accident occurs in which the primary side of the series transformer 1 is opened, one tap of the tap selection switches Th1 (1) and ThA (1) that happens to constitute the instant protection switch Although it is assumed that the selection switch Th1 (1) is in the on state, an immediate protection switch is configured when an open accident occurs and an overvoltage Vov is applied between the output terminals 3v and 3w of the tap switch 3. When both of the tap selection switch pairs Th1 (1) and ThA (1) are in the off state, the voltage Vov across the output terminals 3v and 3w of the tap switch 3 has reached the trigger element operating level Vs. When the trigger element connected between the anode and the gate of the thyristor forming each of the tap selection switches Th1 (1) and ThA (1) that form the instant protection switch is turned on, both taps Selection switch Th1 (1) By ThA (1) to the ON state, the preliminary protection operation output pin 3 v, the inter-3w shorted.

  In the above description, although the case where the overvoltage is applied between the output terminals 3v and 3w of the tap switch 3 is taken as an example, the above case is also applied when the overvoltage is applied between the output terminals 3v and 3u of the tap switch 3. Similar to the above, the preliminary protection operation is performed.

  In the above embodiment, among the plurality of tap selection switches, a pair of tap selection switches (in the above embodiment, provided to short between the output terminals of the tap changer when they are simultaneously turned on) The tap selection switches Th1 (1), ThA (1), Th1 (2), ThA (2)) are selected as the instant protection switches, and the anode-gate between the thyristors constituting these instant protection switches is selected. However, the bridge switches Ths (1) and Ths (2) are selected as the immediate protection switches, and the anode and gate of each of the thyristors constituting these bridge switches are connected. The trigger element may be connected to Also in this case, the level of the operating voltage of the trigger element is set higher than the level of the voltage applied across the trigger element when the voltage level between the output terminals of the tap changer reaches the over voltage determination level. When an abnormal overvoltage is induced on the primary side of the transformer (between terminals 1v and 1w and between 1u and 1w), the trigger element is turned on to turn on the bridging switches Ths (1) and Ths (2) Configured to be

  Also in this configuration, when an abnormal overvoltage occurs on the primary side of the series transformer, the switch for bridging is turned on by the function of the trigger element from the first cycle of the overvoltage, and the output terminal of the tap changer Since the voltage between them can be suppressed, the tap changer can be protected from overvoltage until the protection device performs a full-scale protection operation.

  In the above embodiment, the protection device is configured to protect the tap changer 3 from abnormal overvoltage induced on the primary side of the series transformer when an accident occurs such that the primary side of the series transformer 1 is opened. However, in addition to the protection operation that protects the tap changer from the overvoltage induced on the primary side of the series transformer when an accident occurs in which the primary side of the series transformer is opened, a system in which a line is provided The protection device is configured to perform a protection operation to protect the tap changer and the tap winding from the overcurrent flowing to the primary side of the series transformer when a short circuit current occurs in the line and a short circuit current flows in the line. It can also be done. When a short circuit accident occurs in the system, the voltage induced on the primary side of the series transformer 1 does not increase and does not reach the over voltage determination level, so the protection device is configured as in the above embodiment. Then, the protection operation can not be performed.

  In the case where a protection operation is also performed to protect the tap changer 3 and the tap winding from overcurrent flowing to the primary side of the series transformer 1 when a short circuit fault occurs in the system and a short circuit current flows in the line, As in the above embodiment, the trigger element is connected between the anode and the gate of each thyristor of the thyristor switches constituting the through hole tap selection switches Th1 (1), ThA (1) and Th1 (2), ThA (2). The current flowing through the line is constantly monitored, and the monitored line current is higher than the system short circuit current threshold (minimum value of the short circuit current flowing through the line when a short circuit accident occurs in the system). A digital relay for short circuit protection that generates a protection command when it is detected is provided in the automatic voltage regulator, and in addition to the protection operation performed in the above embodiment, the protection device is further performed to perform the following protection operation. Configure.

  When it is detected by the digital relay that a short circuit accident has occurred in the system, as shown in the following (1) and (2), taps other than the pass through taps are selected when the pass through tap is selected by the tap changer. In the case where is selected, different protection operations are performed.

(1) When a threading tap is selected when a short circuit accident occurs in the system and the digital relay generates a protection command (a threading tap selection switch Th1 (1), ThA (1) and Th1 (2) , ThA (2) is turned on), the tap changer control digital relay functions as a through tap selection switch Th1 (1), ThA (1) and Th1 (2), ThA (2). After turning on the magnetic contactors MC (1) and MC (2) (shorting switch) while maintaining the on state of the switch, the tap relay control digital relay functions to execute the through tap selection switch Th1 (1), ThA (1) and Th1 (2), ThA (2) are turned off (all tap selection switches are turned off) to complete the protection operation.

(2) When a short circuit accident occurs in the system and the digital relay generates a protection command, a tap other than the through-passage tap is selected (through-through tap selection switch Th1 (1), ThA (1) and Th1 (2) When ThA (2) is off), the tap selector control digital relay functions to temporarily turn off all tap selection switches and the bridge switch of tap selector 3. The trigger element connected between the anode and gate of each thyristor of the thyristor switch that constitutes the switch for selecting through taps is turned on by intentionally generating abnormal overvoltage on the primary side of the series transformer 1 At the same time, the through hole tap selection switches Th1 (1), ThA (1) and Th1 (2), ThA (2) are turned on. Then, while holding the bridge switch in the off state, the digital relay for tap changer control is triggered to the switches for selecting the transparent taps Th1 (1), ThA (1), Th1 (2), ThA (2) After turning on the magnetic contactors MC (1) and MC (2) (shorting switch) in a state in which these tap selection switches are maintained in the on state by applying a signal, the pass-through tap selection switch Th1 (1) , ThA (1) and Th1 (2), ThA (2) are turned off (all tap selection switches of the tap changer are turned off) to complete the protection operation.

  As described above, when it is detected that a short circuit accident has occurred in the system in a state where the threading tap selection switch is off, all tap selection switches for the tap changer and the bridging switch When an abnormal overvoltage is intentionally generated on the primary side of the series transformer in the off state, the switch for selecting through-hole taps is turned on by the function of the trigger element, and the current flowing through the primary side of the series transformer is In order to shift to the full protection state by turning on the shorting switch while holding the through tap selection switch in the on state by the function of the digital switch for tap changer control. It is possible to prevent the tap winding from being damaged when an overcurrent occurs in the tap winding when a short circuit accident occurs in the system.

  When a short circuit accident occurs in the system, the electromagnetic contactor MC (1) is turned on with the bridge switches ThS (1) and ThS (2) turned on to limit the voltage applied to the tap changer 3. , MC (2) may be turned on. However, when the bridging switch ThS (1) or ThS (2) is turned on when a short circuit accident occurs in the system, the current limiting resistor R (1) , R (2) may cause a large current to flow and cause the current limiting resistors to burn out. Therefore, in the protection operation performed when a short circuit accident occurs in the system, the shorting switch MC in the state in which the transparent tap selection switch (instant protection switch) is on without turning on the bridging switch. (1) It is necessary to control to turn on the MC (2).

  The tap changer 3 used in the automatic voltage regulator to which the present invention is applied has an output terminal connected to the primary terminal of the series transformer 1 and a plurality of taps of the tap winding and the output terminal of the tap changer 3. And a bridge switch ThS connected via a current limiting resistor R between a plurality of tap selection switches provided between them and an output terminal of the tap changer 3 for a tap selection switch and a bridge. It may be configured to switch the tap (energization tap) of the tap winding that outputs the adjustment voltage to be applied to the series transformer 1 along with the on / off operation of the switch, and the specific configuration is shown in FIG. It is not limited to the example.

  For example, as shown in FIG. 13, tap selection switches ThA (1) and ThB (three taps including one end tap of the tap winding Cs 1 of the adjustment transformer 2 and the output terminal 3 w respectively) 1) and ThC (1), and tap selection is made between the other end tap of the tap winding Cs1 and the output terminal 3v and between one end tap of the tap winding Cs1 and the output terminal 3v By providing switches Th1 (1) and Th2 (1), the tap selection circuit 3A (1) on the tap winding Cs1 side is configured, including one end tap of the tap winding Cs2 of the adjustment transformer 2 Tap selection switches ThA (2), ThB (2) and ThC (2) are provided between the three taps and the output terminal 3u, and the other end tap of the tap winding Cs2 and the output terminal 3v And between one end tap of one of the tap windings Cs2 and the output terminal 3v By providing the tap selection switch Th1, respectively (2) and Th2 (2), can also be used tap changer 3 which constitutes a tap selection circuit 3A tap winding Cs2 side (2). Since the tap selection circuits 3A (1) and 3A (2) constituting the tap changer 3 shown in FIG. 13 are already known as shown in Patent Document 1, their operation will be described I omit it.

  When the tap changer 3 having the configuration shown in FIG. 13 is used, a pair of the tap selection switch ThA (1) and the tap selection switch Th2 (1) and the tap selection switch ThA (2) and the tap selection are used. The pair of switches Th2 (2) can be selected as the instant protection switch.

  In each of the above-described embodiments, although the adjustment transformer 2 and the tap changer 3 are three-phase V-connected, adjustment is performed using the adjustment transformer 2 having three primary and secondary windings. Of course, the present invention can be applied to the case where a configuration in which the transformer 2 and the tap changer 3 are three-phase Y-connected or three-phase Δ-connected is employed.

  In each of the above embodiments, an isolation transformer having a primary winding and a secondary winding (tap winding) isolated from each other is used as the adjustment transformer 2. However, as the adjustment transformer 2, a shunt winding is used. The present invention can also be applied to the case where an autotransformer having a tap is used.

1 series transformer 1u, 1v, 1w primary terminal of series transformer 2 adjustment transformer 2u, 2v, 2w input terminal of adjustment transformer 3 tap changer 3u, 3v, 3w output terminal of tap changer 3A (1) tap Selection circuit 3A (2) Tap selection circuit Cs1, Cs2 Tap winding ThA (1) to ThC (1) Tap selection switch Th1 (1) to T3 (1) Tap selection switch ThA (2) to ThC (2) Tap selection switch Th1 (2) to T3 (2) Tap selection switch ThS (1), ThS (2) Bridge switch R (1), R (2) Current limiting resistor MC (1), MC ( 2) Magnetic contactor

Claims (4)

A secondary winding is connected in series to a line, and a series transformer to which an adjustment voltage is input on the primary side, and a tap winding provided with a plurality of taps, the voltage of the line being an input, the tap winding Control transformer for generating a plurality of voltages to be used as the adjustment voltage between the taps, and an output terminal connected to a primary terminal of the series transformer, and a plurality of taps of the tap winding and the output terminal A plurality of tap selection switches provided therebetween and a bridge switch connected via the current limiting resistor between the output terminals, for on / off operation of the tap selection switch and the bridge switch The tap switch which switches the tap of the tap winding which outputs the adjustment voltage given to the series transformer along with it, and the voltage between the output terminals of the tap switch is an abnormal overcharge on the primary side of the series transformer. Control is performed to turn on the shorting switch connected between the output terminals when it is detected that the over voltage determination level has been reached to determine that an induction has occurred, and the series transformer applies to the tap changer. An automatic voltage regulator comprising: a protection device for performing a protection operation for suppressing an overvoltage and the tap selection switch and the bridge switch being thyristor switches;
A trigger element consisting of a semiconductor element which is turned on when a voltage applied to both ends reaches a prescribed operating voltage is connected between the anode and gate of each of the thyristors constituting the bridge switch,
The level of the operating voltage of the trigger element is set higher than the level of the voltage applied across the trigger element when the voltage level between the output terminals of the tap changer reaches the overvoltage determination level. The trigger element is turned on when the abnormal overvoltage is induced on the primary side of the series transformer, and the bridge switch is turned on;
Automatic voltage regulator characterized by. A secondary winding is connected in series to a line, and a series transformer to which an adjustment voltage is input on the primary side, and a tap winding provided with a plurality of taps, the voltage of the line being an input, the tap winding Control transformer for generating a plurality of voltages to be used as the adjustment voltage between the taps, and an output terminal connected to a primary terminal of the series transformer, and a plurality of taps of the tap winding and the output terminal A plurality of tap selection switches provided therebetween and a bridge switch connected via the current limiting resistor between the output terminals, for on / off operation of the tap selection switch and the bridge switch The tap switch which switches the tap of the tap winding which outputs the adjustment voltage given to the series transformer along with it, and the voltage between the output terminals of the tap switch is an abnormal overcharge on the primary side of the series transformer. Control is performed to turn on the shorting switch connected between the output terminals when it is detected that the over voltage determination level has been reached to determine that an induction has occurred, and the series transformer applies to the tap changer. And a plurality of tap selection switches, one end of which is commonly connected to one tap of the tap winding and the other end of which is a pair of tap changers. A pair of through hole tap selection switches connected to one and the other of the output terminals to be turned on simultaneously when selecting the through hole taps, wherein the tap selection switch and the bridge switch are thyristor switches In the automatic voltage regulator,
A relay is provided that generates a protection command when it is detected that a short circuit accident has occurred in a system in which the line is provided,
A trigger element composed of a semiconductor element which is turned on when the voltage applied to both ends reaches a prescribed operating voltage between the anode and gate of each thyristor of the thyristor switches constituting the pair of through hole tap selection switches Connected and
The level of the operating voltage of the trigger element is set higher than the level of the voltage applied across the trigger element when the voltage level between the output terminals of the tap changer reaches the overvoltage determination level. The trigger element is turned on when an abnormal overvoltage is induced on the primary side of the series transformer, and the pair of threading tap selection switches are turned on;
The protection device is configured to perform an operation of turning on the shorting switch after turning on the bridging switch when it is detected that the abnormal overvoltage has occurred on the primary side of the series transformer. And the switch for shorting with the pair of threading tap selection switches maintained in the on state when the relay issues a protection command with the pair of threading tap selection switches being on. When the relay issues a protection command while the pair of threading tap selection switches are off, all tap selection switches for the tap changer and the bridge switches are turned on. To cause the trigger element to perform an on operation by generating the abnormal overvoltage on the primary side of the series transformer. After turning on the switch for pin selection, the switch for bridging is kept in the off state, and the switch for shorting is turned on in the state where the pair of switches for tap selection are kept in the on state Be configured to
Automatic voltage regulator characterized by . A secondary winding is connected in series to a line, and a series transformer to which an adjustment voltage is input on the primary side, and a tap winding provided with a plurality of taps, the voltage of the line being an input, the tap winding Control transformer for generating a plurality of voltages to be used as the adjustment voltage between the taps, and an output terminal connected to a primary terminal of the series transformer, and a plurality of taps of the tap winding and the output terminal A plurality of tap selection switches provided therebetween and a bridge switch connected via the current limiting resistor between the output terminals, for on / off operation of the tap selection switch and the bridge switch The tap switch which switches the tap of the tap winding which outputs the adjustment voltage given to the series transformer along with it, and the voltage between the output terminals of the tap switch is an abnormal overvoltage on the primary side of the series transformer. Control is performed to turn on the shorting switch connected between the output terminals when it is detected that the over voltage determination level for determining induced has been reached, and applied to the tap changer from the series transformer And a plurality of tap selection switches, one end of which is commonly connected to one tap of the tap winding and the other end forms a pair of tap changers. It includes a pair of through tap selection switches connected to one and the other of the output terminals to be turned on simultaneously when selecting the through taps, and the tap selection switch and the bridge switch are composed of thyristor switches. In the automatic voltage regulator,
A relay is provided that generates a protection command when it is detected that a short circuit accident has occurred in a system in which the line is provided,
A trigger element composed of a semiconductor element which is turned on when the voltage applied to both ends reaches a prescribed operating voltage between the anode and gate of each thyristor of the thyristor switches constituting the pair of through hole tap selection switches Connected and
The level of the operating voltage of the trigger element is set higher than the level of the voltage applied across the trigger element when the voltage level between the output terminals of the tap changer reaches the overvoltage determination level. The trigger element is turned on when an abnormal overvoltage is induced on the primary side of the series transformer, and the pair of threading tap selection switches are turned on;
The protective device turns on the bridging switch when it is detected that the abnormal overvoltage has occurred on the primary side of the series transformer, and then turns on the pass through which is turned on by the action of the trigger element. The relay is configured to turn on the shorting switch while maintaining the on state of the tap selection switch, and the relay generates a protection command when the pair of threading tap selection switches are on. When the pair of threading tap selection switches is maintained in the on state, the short circuit switch is turned on, and when the pair of threading tap selection switches is off, the relay receives a protection command. When it occurs, once turn off all tap selection switches and bridge switches of the tap changer, and turn it on the primary side of the series transformer. Note that after the trigger element is caused to perform an on operation to generate the abnormal over voltage to turn on the pair of threading tap selection switches, the bridging switch is maintained in the off state to select the pair of threading taps. Control for turning on the shorting switch in a state in which the switch is kept on;
Automatic voltage regulator characterized by . The level of the operating voltage of the trigger element is applied across the trigger element when the voltage level between the output terminals of the tap changer reaches a level that causes the thyristor in the off state to break down in the tap changer. 4. The automatic voltage regulator according to claim 1, wherein the voltage is set to a level lower than that of the voltage.

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