JP3206692B2 - Runaway monitoring device for tap changer under load - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor for driving a load tap changer (hereinafter abbreviated as LTC) of a transformer.
(Hereinafter, referred to as an LTC drive) relates to a tap runaway monitoring device for monitoring that normal forward or reverse drive is normally performed according to an operation command.

[0002]

2. Description of the Related Art A motor used for an LTC drive is generally a three-phase AC motor, and forward rotation and reverse rotation are performed by exchanging two of three connection wires of three phases. That is, as is well known, the phase sequence of the motor at the time of normal rotation is R, S, T, and the R sequence and the T phase are exchanged, and the phase sequence is T,
In the order of S and R, the inversion is used.

FIG. 3 is a circuit diagram showing an LTC drive and its main circuit. In this figure, a U-, V-, and W-phase three-phase electric wire is connected to a three-phase AC motor 1 that is an LTC drive, while a three-phase AC power supply of R, S, and T phases is It is connected to U-, V-, and W-phase three-phase electric wires via the diversion switch 3 and the reverse rotation switch 4. The forward switch 30 includes two switches, one for opening and closing between the R and U phases and the other for opening and closing between the T and W phases, and the reverse switch 40 between the R and W phases. Switch that opens and closes the switch and switch that opens and closes between the T and U phases
Consists of two switches.

At the time of forward rotation, both of the two switches of the forward rotation switch 30 are "closed", and both of the two switches of the reverse rotation switch 40 are "open". The phase sequence of the connected three-phase AC motors 1 is R, S, and T. On the other hand, in the reverse rotation, on the other hand,
The three switches are both "open" and the two switches of the reverse rotation switch 40 are both "closed", the wires of the RW and TU phases are connected, and the phase sequence of the three-phase AC motor 1 is T , S,
It becomes R.

As described above, the forward rotation switch 30 is opened.
When the switch 40 for normal rotation and reverse rotation is "open", the rotation is reversed, and neither of the switches is simultaneously turned "open" or "closed". In a transformer provided with an LTC, a tap winding from which a plurality of tap terminals are drawn is provided, these tap terminals are connected to the LTC, one tap terminal is selected and connected to a circuit, and the tap terminal is connected to the LTC terminal. The primary voltage is converted to a secondary voltage based on the corresponding transformation ratio. By switching the tap terminal while the load current is flowing, the secondary voltage can be increased or decreased. Whether the secondary voltage needs to be changed or not is determined based on the determination that the signal measured by the instrument transformer provided in the secondary circuit is input to the control device and various conditions are taken into account, or the boost command or A step-down command is issued, and based on these operation commands, the LTC drive rotates forward based on the step-up command, and reversely rotates based on the step-down command to drive the LTC and switch the tap.

In order to reliably switch taps, 1
Control is performed so that only one tap is changed for one operation command. Such a control method is called “one command and one operation”. If an abnormality occurs for some reason, "1 command 1
If the "operation" is not observed, tap runaway will occur, and the secondary voltage of the transformer will rise or fall more than necessary, seriously affecting the power system, so to monitor such tap runaway In addition, a timer 2 for detecting whether the normal rotation switch 30 and the reverse rotation switch 40 are operating normally is provided.

The timer 2 is inserted between the U-phase and W-phase wires, and a voltage is applied between these wires.
That is, while the three-phase AC motor 1 is being driven, a signal _ST is output as a repetitive pulse that alternates between High and Low at a constant cycle. This signal _ST is L (not shown).
The number of pulses is counted in the TC control device, and when the pulse number exceeds a preset value, the circuit is cut off by the circuit breaker 6 so as to prevent the abnormality from further expanding. Since the number of pulses of the signal S _T is proportional to the elapsed time, which means that the number is that is larger than the set value driving time forward or reverse rotation of the three-phase AC motor 1 is continued too long, it It is appropriate to judge that a tap runaway has occurred, such as two or more taps moving continuously.

[0008]

Since the tap runaway abnormality has a serious ripple effect as described above, it is necessary to reliably detect and take appropriate measures.
There is a problem that monitoring with the timer 2 alone is not always sufficient. An object of the present invention is to provide an LTC tap runaway monitoring device which solves such a problem and doubles the detection of tap runaway to improve the reliability of the device.

[0009]

According to the present invention, a forward rotation switch and a reverse rotation switch are provided between a three-phase AC motor driving a tap changer and its power supply. In a tap runaway monitoring device of a load tap changer in which forward rotation or reverse rotation is controlled by exchanging two phases by turning them on and off, a voltage monitoring unit is provided between terminals of a forward rotation switch and a reverse rotation switch, respectively. It is determined that tap runaway has occurred when a predetermined time set in advance by the signal output from the voltage monitoring unit has elapsed during the forward rotation or the reverse rotation. And a light-emitting element and a light-receiving element that receives light emitted by the light-emitting element and outputs an electric signal. It is a non-contact switch composed of semiconductor switching elements connected in opposite polarities, and a timer for monitoring normal / reverse rotation is provided between the two phases on the three-phase AC motor side that are switched by the forward rotation switch and the reverse rotation switch. It is assumed that the set time for judging the abnormality detection by the voltage monitoring unit is set shorter than the set time of the timer.

[0010]

In the configuration of the present invention, the three-phase AC motor is driven with the forward rotation switch or the reverse rotation switch being "closed" by providing a voltage monitoring section between the terminals of the forward rotation switch and the reverse rotation switch. In this state, the voltage monitoring unit outputs a signal indicating that there is no voltage. Therefore, it is possible to determine that tap runaway has occurred when the value of the period is measured and the value is longer than a preset time. By configuring the voltage monitoring unit with a light emitting element connected in reverse polarity and a light receiving element that receives light emitted from the light emitting element, converts the light into an electric signal, and outputs the electric signal, the light emitting element can be configured such that the forward or reverse switch is closed. In this case, no light is emitted because no voltage is applied to the voltage monitoring unit, and a low signal is output from the light receiving element, indicating that the three-phase AC motor is being driven.

[0011] Further, the forward and reverse switches are constituted by non-contact switches comprising two semiconductor switching elements connected in opposite polarities, so that they can be integrated with the voltage monitoring unit. In addition, in a configuration in which a voltage monitoring unit is added to the conventional circuit configuration in which a timer for monitoring forward and reverse rotation is provided between two phases to be exchanged, the time set for the output signal of the voltage monitoring unit is output by the timer. By setting it shorter than the time set for the signal,
If there is a tap runaway, the voltage monitor detects the tap runaway first and the timer detects it only when the voltage monitor fails. Limited to backup function in case of failure.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
FIG. 1 is a circuit diagram showing an LTC drive and a main circuit thereof according to an embodiment of the present invention, and complicated circuit components are shown by blocks. This figure is similar to FIG. 3, and the same components are denoted by the same reference numerals and detailed description is omitted. In addition, the illustration of the circuit breaker 6 in FIG. 3 is omitted.

[0013] forward rotation switch 3 consists of two non-contact switches 31 and 32 to be "closed" by the operation signal S _L of forward, reverse switch 4 is "closed" by the operation signal S _R of the reverse 2 The non-contact switches 41 and 42 each include a voltage monitoring unit 33 and 3
4,43,44 is plugged in parallel, the voltage signal S _VL or S _VR is output when a voltage is detected. Examples of these specific circuit configurations will be described later.

The forward switch 3 connects RU and TV similarly to the forward switch 30 of FIG. 3 so that the phase sequence of the three-phase AC motor 1 becomes R, S, and T. , The non-contact switch 31 is RU, and the non-contact switch 32 is TW
Responsible for each connection. The reverse rotation switch 4 connects RW and TU similarly to the reverse rotation switch 40 of FIG. 3, and connects the three-phase AC motor 1 so that the phase sequence of the three-phase AC motor 1 becomes T, S, and R. The contactless switch 41 is responsible for RW connection, and the contactless switch 42 is responsible for TU connection, respectively. Forward switch 30 and reverse switch 40 of FIG.
Although a mechanical contact is illustrated as a contact constituting the device and is illustrated as a non-contact switch in FIG. 1, the present invention is not limited to one contact.

The voltage monitor 33 is connected in parallel to the contactless switch 31. Therefore, the contactless switch 31
Is "closed", the voltage between the terminals is zero, so the output signal _SVL of the voltage monitoring unit 33 is low, and when the non-contact switch 31 is "open", a voltage is applied between the terminals.
_VL becomes High. Voltage monitoring units 33, 34, 43, 44
Similarly, according to the "closed" and "open" states of the contactless switches 32, 41 and 42 which are connected in parallel,
Or, output High signal.

A method for detecting a runaway tap will be described by taking the contactless switch 31 and the voltage monitor 33 as examples. Proximity switch 31 is in a state of "closed" from the "open" by the operation command by the normal signal S _L with proximity switch 32. When the contactless switch 31 is closed, the voltage signal S _VL output by the voltage monitoring unit 31 becomes High.
State changes to Low and the non-contact switch 31 is closed.
Is detected. The duration of the non-contact switch 31 in the “closed” state is measured as the duration of the state in which the voltage signal S _VL is low, and if the value exceeds a preset time, it is determined that a tap runaway has occurred. .
This is similar to the detection of tap runaway by the timer 2 in FIG.

The voltage signal _SVL output from the voltage monitoring section 34 is essentially the same as that of the voltage monitoring section 33, so only one of them may be used. However, in order to provide redundancy and improve reliability, it is preferable to provide a voltage monitoring unit 34 as shown in the figure. Furthermore, by comparing these two signals that are supposed to be the same, it is also possible to use the signals for detecting an abnormality other than tap runaway. The detection of the tap runaway by the voltage monitoring units 33 and 34 is performed only at the time of forward rotation, and cannot be detected at the time of reverse rotation. The reason why the forward rotation switch 3 is in the "open" state is that the LTC drive is not only at the time of reverse rotation but also at the time of stop. The runaway of the tap at the time of reverse rotation is performed by voltage monitoring units 43 and 44 provided in the switch 4 for reverse rotation. The operation is similar to that at the time of the normal rotation described above, and the description is omitted.

The timer 2 for tap runaway monitoring is used as it is and used together with monitoring by the voltage monitoring units 33, 34, 43 and 44. By using them together, the devices are duplicated, and even if one device fails, it can be covered by the other device, and the reliability of the monitoring function is improved. FIG. 2 is a circuit diagram showing an example of the configuration of the non-contact switch 31 and the voltage monitoring unit 33. The other non-contact switches and the voltage monitoring unit shown in FIG. 1 have the same circuit configuration. The non-contact switch 31 is configured by connecting two non-contact switches 311 and 312 in parallel, and adopts a configuration that ensures high reliability so that operation can be continued even if one of the non-contact switches 3 fails. Have been.
The non-contact switch 311 is composed of optical thyristors 56 and 57 as optical semiconductor switching elements connected in anti-parallel and a light emitting diode 55 for emitting an optical gate signal thereto. Emitting diode 55 as a light emitting element is emitted by turning on the optical thyristor 56 when a current as operation signal S _L flows. In the drawing, N on the cathode side of the light emitting element 55 indicates that this circuit is connected to the N pole of the power supply. The non-contact switch 312 is also a non-contact switch 311
Since the same operation is performed with exactly the same configuration as that of FIG.

The voltage monitoring unit 33 includes light emitting diodes 51 and 52 as light emitting elements connected in anti-parallel via a resistor 53.
And a phototransistor 54 as a light receiving element for receiving light emitted from the phototransistor. The collector of the phototransistor 54 is connected to the P pole of the power supply, and the voltage signal S
_VL is output. When an AC voltage is applied to the light emitting diodes 51 and 52, one of them becomes conductive and emits light, and this light is converted into an electric signal by the phototransistor 54 and becomes a voltage signal _SVL .

The reason why both the non-contact switch 31 and the voltage monitoring unit 33 input and output signals via light is to insulate the signal circuit from the main circuit of the LTC drive, and to achieve the same object, it is necessary to use the optical switch. Instead of using a signal as a medium, a configuration using an isolation transformer or an isolation amplifier can be adopted. In order to ensure high reliability, it is suitable to use a non-contact type using a semiconductor element for a switch or a detector.
In addition, by using a semiconductor element as shown in the drawing and using optical transmission, the non-contact switch 31 and the voltage monitoring unit 33 are integrated to reduce the cost and size. .

The processing unit for monitoring a tap runaway in which the output signal S _V of the voltage monitoring unit 31 based on the inclusion in the control unit for outputting an operation signal. When the control unit is processed in a software and digital manner using a programmable controller or the like, the processing of the voltage signal _SVL output from the voltage monitoring unit 31 is also processed in a software or digital manner by the same programmable controller. It is appropriate to do.

The time set in advance for detecting the tap runaway by the voltage monitoring units 33, 34, 43, and 44 is set shorter than the time set in the timer 2, and the tap runaway by the voltage monitoring unit is always performed in a normal state. Is detected. Since the timer 2 conventionally used is of the contact type and the contactless type is superior in terms of reliability, it is more reliable to provide the timer 2 only as a backup as a device. improves.

[0023]

As described above, according to the present invention, by providing a voltage monitoring section between the terminals of the forward rotation switch and the reverse rotation switch, the motor is driven when the forward rotation switch or the reverse rotation switch is closed. In this state, the voltage monitoring unit outputs a signal indicating that the voltage is zero.Therefore, it is necessary to measure the period and determine that tap runaway has occurred when the value is greater than the preset time. This makes it possible to obtain an effect that the reliability of monitoring is improved by using a double monitoring method with a timer provided for monitoring a tap runaway in the related art.

Further, the voltage monitoring section is composed of a light emitting element and a light receiving element which receives light emitted from the light emitting element, converts the light into an electric signal, and outputs the electric signal, so that the two light emitting diodes have a forward switch or a reverse switch. When "closed", no light is emitted because no voltage is applied to the voltage monitoring unit, so that the output signal from the light receiving element becomes low, indicating that the three-phase AC motor is being driven. Since all of the elements used are semiconductor elements, the effect of being a highly reliable voltage monitoring unit is obtained.

In addition, by constructing the forward rotation switch and the reverse rotation switch by a non-contact switch composed of two semiconductor switching elements connected in opposite polarities, the reliability of these switches is improved, and Can be integrated with the voltage monitoring unit used, so that cost reduction and compactness can be achieved. In addition, in a configuration in which a voltage monitoring unit is added to the conventional circuit configuration in which a timer for monitoring a tap runaway is provided between two phases to be exchanged, the set time for abnormality detection by the voltage monitoring unit is set to the set time in the case of a timer. By setting it shorter, the voltage monitor always monitors tap runaway, and the timer is used as a monitoring device by limiting the function of the highly reliable voltage monitor to only a backup function in case of failure. The effect is that the overall reliability of is improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an LTC drive and a main circuit thereof showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of the contactless switch and the voltage monitoring unit of FIG. 1;

FIG. 3 is a circuit diagram of an LTC drive and its main circuit showing an example of a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Three-phase AC motor 2 Timer 6 Circuit breaker 3,30 Forward rotation switch 4,40 Reverse rotation switch 31,32,41,42 Non-contact switch 311,312 Non-contact switch 33,34,43,44 Voltage monitoring unit 51, 52, 55 Light emitting diode (light emitting element) 54 Phototransistor (light receiving element) 56, 57 Optical thyristor (optical semiconductor switching element)

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02H 7/055 H01F 29/02 H01F 29/04

Claims (4)

(57) [Claims] A forward rotation switch and a reverse rotation switch are provided between a three-phase AC motor driving a tap changer and its power supply, and these two phases are switched by turning on and off to perform forward rotation or reverse rotation. In a tap runaway monitoring device of a controlled tap changer under load, a voltage monitoring unit is provided between terminals of a forward rotation switch and a reverse rotation switch, respectively, and a forward or reverse rotation is driven by a signal output from the voltage monitoring unit. A tap runaway monitoring device for a load tap changer, wherein it is determined that tap runaway has occurred when a continuation time exceeds a predetermined time set in advance. 2. The tap of an on-load tap changer according to claim 1, wherein the voltage monitor comprises a light emitting element and a light receiving element for receiving light emitted from the light emitting element and outputting an electric signal. Runaway monitor. 3. The tap runaway monitoring device for a load tap changer according to claim 2, wherein the forward rotation switch and the reverse rotation switch are non-contact switches comprising semiconductor switching elements connected in reverse polarity. . 4. A timer for monitoring forward / reverse rotation is provided between two phases on the three-phase AC motor side which are switched by the forward / reverse switch and the reverse rotation switch, and a set time for judging abnormality detection by the voltage monitoring unit is provided. 4. The tap runaway monitoring device for a load tap changer according to claim 1, wherein the set time is set shorter than a set time of a timer.