JPH0259608B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormality detection device for an on-load tap changer in which the changeover switch is composed of a thyristor, and particularly to an abnormality detection device for an on-load tap changer applied to a thyristor changeover switch. The present invention relates to an abnormality detection device that can detect various types of abnormalities within half a cycle with relatively little information by making a determination based on the forward voltage application status of a thyristor.

Conventionally, in order to detect abnormalities in on-load tap changers that have contacts in the changeover switch, it is necessary to detect a large amount of high-energy arcing due to an abnormality or disconnection of the changeover switch (not shown). Insulating oil decomposes and evaporates, and an increase in pressure is used to detect abnormalities. By the way, the failure mode of an on-load tap changer in which a thyristor or the like is used as a changeover switch is generally either an open circuit or a short circuit between the anode and cathode of the thyristor. In particular, short circuit phenomena are often observed.
When such a short circuit occurs, an arc will not occur until the thyristor is externally damaged by the short circuit energy. Therefore, the detection of the abnormality will be delayed by that amount, and the countermeasures will also be delayed by that amount. There were drawbacks to this. In addition, with the conventional abnormality detection means described above, abnormality detection is performed in an indirect manner by detecting an increase in pressure due to decomposition and vaporization of insulating oil. inevitably had its limits.

The present invention was made in order to eliminate the drawbacks of the conventional means as described above, and determines whether the thyristors are normal or abnormal based on the application status of forward voltage to each of the plurality of thyristors used. It is an object of the present invention to provide an on-load tap changer abnormality detection device with improved abnormality detection speed.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 schematically shows the apparatus of the present invention, in which 1 is a transformer, and a primary side terminal 2, a secondary side output terminal 3, and a plurality of secondary side voltage taps are provided. It is being A voltage tap 5 is set one step lower in potential than any voltage tap 4 among them. Reference numeral 6 denotes a switching switch of a load tap changer, which includes a first pair of thyristors 7 and 8 connected in anti-parallel to each other, and a second pair of thyristors 7 and 8 also connected in anti-parallel to each other. 11,1
2, a first nonlinear resistor 9, and a second nonlinear resistor 10. First nonlinear resistance 9
is to protect the first pair of thyristors 7, 8 from overvoltage and to allow current to flow to the load when all the thyristors 7, 8, 11, 12 are non-conducting. They are connected in parallel, and one end is connected to voltage tap 4 of transformer 1.
The other end is connected to the secondary output terminal 3, respectively. The second nonlinear resistor 10 protects the second pair of thyristors 11, 12 from overvoltage and allows current to flow through the load when all the thyristors 7, 8, 11, 12 are non-conducting. It is connected in parallel to the pair of thyristors 11 and 12, and one end thereof is connected to the voltage tap 5 of the transformer 1.
The other ends are respectively connected to the same secondary output terminal 3 as the first nonlinear resistor 9. 13 is the first
A first forward voltage detection device 14 is for detecting the forward voltage of the pair of thyristors 7 and 8, and 14 is a second forward voltage detection device for detecting the forward voltage of the second pair of thyristors 11 and 12.
This is a forward voltage detection device. 15 is a state monitoring device for detecting the switching switch 6 from the forward voltage application state of all the thyristors 7, 8, 11, and 12. 16 and 17 are signal transmission lines, and the first
This is for transmitting a signal regarding the presence or absence of forward voltage of the pair of thyristors 7 and 8 from the first forward voltage detection device 13 to the condition monitoring device 15.
Reference numerals 8 and 19 denote signal transmission lines, which transmit signals regarding the presence or absence of forward voltage of the second pair of thyristors 11 and 12 from the second forward voltage detection device 14 to the condition monitoring device 15.
It is intended for transmission to. The nonlinear resistors 9 and 10 used here are made of, for example, zinc oxide, and their current-voltage characteristics are appropriately as shown in FIG. 2. It is also assumed that the limiting voltages of the nonlinear resistors 9 and 10 are sufficiently smaller than the minimum secondary tap voltage of the transformer 1 in FIG. 1 and larger than the voltages of the voltage taps 4 and 5.

Figures 3a and 3b respectively show the first
This figure shows an example of the forward voltage detection device 13 and the second forward voltage detection device 14. In FIG. 3a, 20 and 21 are the first forward voltage detection device 13.
One input terminal 20 is connected to the anode of thyristor 7 and the cathode of thyristor 8 in FIG. 1, and the other input terminal 21 is connected to the cathode of thyristor 7 and the anode of thyristor 8. There is. 22 and 23 are light emitting diodes, which are connected in antiparallel to the input terminals 20 and 21. 24,2
5 is a protection diode for protecting the light emitting diodes 22 and 23 from reverse voltage, 26,
27 are constant voltage diodes, each of which has the following characteristics:
When the forward voltage of the first pair of thyristors 7 and 8 in FIG. 1 exceeds the forward voltage in the thyristor conduction state (hereinafter referred to as thyristor ON voltage), conduction occurs in the reverse direction. It is. Further, 28 and 29 are current limiting resistors for protecting the light emitting diodes 22 and 23 from overcurrent, respectively. Reference numerals 16 and 17 are signal transmission lines for transmitting the light emission signals of the light emitting diodes 22 and 23, respectively, to the status monitoring device 15 in FIG. 1, and these are made of, for example, optical fibers. Similarly, in FIG. 3b, 30 and 31 are input terminals of the second forward voltage detection device 14, and one input terminal 30 is connected to the anode of the thyristor 11 and the cathode of the thyristor 12 in FIG. The other input terminal 31 is connected to the cathode of the thyristor 11 and the anode of the thyristor 12. 32,3
3 is a light emitting diode, and input terminals 30, 3
1 are connected in antiparallel to each other. 3
4 and 35 are light emitting diodes 32 and 33, respectively.
protection diode to protect from reverse voltage,
36 and 37 are constant voltage diodes, which correspond to the second pair of thyristors 11 and 11 in FIG. 1, respectively.
When the forward voltage of 12 becomes equal to or higher than the thyristor ON voltage, conduction occurs in the reverse direction. Further, 38 and 39 are current limiting resistors for protecting the light emitting diodes 32 and 33 from overcurrent, respectively, and 18 and 19 are signal transmission lines that transmit the light emission signals of the light emitting diodes 32 and 33, respectively. This is for transmitting to the condition monitoring device 15 in FIG. 1, and these are constructed of, for example, optical fibers.

The operation of the embodiment of the apparatus of the invention shown in FIG. 1 will now be described. Now, let the potentials of voltage taps 4 and 5 be E ₄ and E ₅ respectively.
If the voltage between the taps is E _S , then E _S = E ₄ − _{E 5}
It is assumed that this E _S is sufficiently larger than the thyristor ON voltage. Further, it is assumed that the current supplied from the output terminal 3 to the load (not shown) is _IL .

Now, current is flowing from voltage tap 4 of transformer 1 to the load.
When I _L is supplied, the second pair of thyristors 11, 12 are non-conducting; for the first pair of thyristors, thyristor 7 is conducting when I _L is positive; thyristor 8 is conducting when I _L is positive; Since the voltage between the anode and cathode of the second pair of thyristors 11 and 12 is approximately equal to the tap-to-tap voltage E _S , the anode-cathode voltage of the thyristors 7 and 8 of the first pair is conductive when・The voltage between the cathodes is equal to the thyristor ON voltage. At this time, if E _S is positive, the light emitting diode 33 in the forward voltage detection device 14 emits light, and if E _S is negative, the light emitting diode 33 emits light.
2 emits light (see Figure 3b). Similarly, when the current I _L is supplied from the voltage tap 5 of the transformer 1 to the load, if E _S is positive, the light emitting diode 22 in the first forward voltage detection device 13 emits light; If E _S is negative, the light emitting diode 23
emits light (see Figure 3a).

4a and 4b are timing waveform diagrams showing the light emission timing of these light emitting diodes during normal operation, and in FIG. 3a, the potential of the terminal 20 with respect to the terminal 21 is e ₁ , Figure 3b
, the potential of the terminal 30 with respect to the terminal 31 is
e ₂ , from voltage tap 4 to output terminal 3 in Figure 1
The current flowing from the voltage tap 5 to the output terminal 3 is i ₁ , and the current flowing from the voltage tap 5 to the output terminal 3 is i ₂ .

If thyristors 7 and 12 in FIG. 1 are turned on at the same time when E _S is positive, voltage taps 4 and 5 will be short-circuited,
If the short circuit current at this time is extremely small and does not cause any abnormality to the characteristics of the thyristors 7 and 12, all the light emitting diodes of the first forward voltage detection device 13 and the second forward voltage detection device 14 are simultaneously quenched. However, when the short circuit current is extremely large and exceeds the predetermined standard values of thyristors 7 and 12,
When the thyristors 7 and 12 are conductive, the forward voltage increases, and the light emitting diode 2 in FIG.
The light emitting diodes 33 in FIG. 2 and FIG. 3b emit light at the same time.

On the other hand, if thyristors 8 and 11 in FIG. 1 become conductive at the same time when E _S is negative, if the short circuit current is small, all of the light emitted by quench at the same time,
In addition, if the short circuit current is large, the light emitting diode 23
(FIG. 3a) and the light emitting diode 32 (FIG. 3b) will emit light at the same time.

Furthermore, when current is being supplied from the voltage tap 4 to the load, if E _S is positive and the thyristor 7 in FIG. 1 is misfired, then e ₁
and e ₂ are each nonlinear resistance 9 in phase with E _S
and 10, so that the third
Light emitting diode 22 in figure a and figure 3b
The light emitting diodes 32 at the same time emit light.
Furthermore, if E _S is negative and thyristor 8 in FIG.
The light emitting diode 23 in Figure a and the light emitting diode 33 in Figure 3b emit light at the same time.

When current is being supplied from the voltage tap 5 to the load, assuming that E _S is positive and the thyristor 11 in FIG. 1 has lost its arc, e ₁ and e ₂
are in phase and limited by the nonlinear resistors 9 and 10, respectively, so that the light emitting diode 22 in FIG. 3a and the light emitting diode 32 in FIG. 3b
and emit light at the same time, and if E _S is negative and the thyristor 12 is misfired, similarly, the light emitting diode 23 of FIG. 3a and the light emitting diode 33 of FIG. 3b They emit light at the same time.

In addition, when current is supplied from the voltage tap 4 to the load, if the light emitting diode 22 or 23 in Figure 3a emits light, the characteristics of the thyristor 7 or 8 in Figure 1 will deteriorate. Therefore, it is appropriate to consider that the forward voltage increases when it is in a conductive state.Similarly, when current is supplied from the voltage tap 5 to the load, the light emitting diode shown in Fig. 3b If 32 or 33 emits light, it is appropriate to consider that thyristor 11 or 12 in FIG. 1 has deteriorated. Note that the light emitting diodes 22 and 2 in FIG.
3, or the light emitting diodes 32 and 33 of FIG. 3b.
In principle, it is impossible for the two to emit light at the same time.

If the state of the thyristor in each light emission situation is summarized in a table based on the above, it will be shown in FIG. Here, the light emitting diode is represented by 1 in the light emitting state and 0 in the extinction state.

FIG. 6 illustrates the state monitoring device 15 in FIG. 1. 16 to 19 are signal transmission lines composed of, for example, optical fibers, as shown in Fig. 3a.
and the light emitting diode 22, 2 in FIG. 3b.
Light emission signals from 3, 32, and 33 are transmitted. 4
0 to 43 are phototransistors for converting this light emission signal into electrical signals; 44 to 47 are resistors; 4
8 to 51 are inverters, 52 to 60 are AND gates, and 61 is a display/alarm circuit for displaying/alarming.

In such a condition monitoring device 15, the first forward voltage detection device 13, the second forward voltage detection device 14
(FIG. 1) is introduced through signal transmission lines 16-19 and phototransistors 40-43 and resistor 4.
4 to 47 into electrical signals. That is, the phototransistors 40 to 43 are turned on when an optical signal is input, and their collector voltages are low due to the corresponding resistors 44 to 47.
If no optical signal is incident, the phototransistor is in an OFF state and its collector voltage becomes a high potential. Here, if the low potential state is logic "0" and the high potential state is logic "1", the outputs of the phototransistors 40 to 43 correspond to the light emitting diodes 22 in FIGS. 3a and 3b, respectively. ,23,3
Therefore, the outputs of the inverters 48 to 51 correspond to the light emitting states of the light emitting diodes 22, 23, 32, and 33, respectively. is equivalent to the corresponding logical state. Therefore,
AND gates 52 to 60 have light emission states of 0000, 0001, 0010, 0100, 0000, 0001, 0010, 0100,
At 0101, 0110, 1000, 1001 and 1010, the output becomes "1" and a predetermined signal is applied to the display/alarm circuit 61. Display/alarm circuit 61
is from a thyristor ignition device (not shown),
Based on the voltage tap information currently supplying current to the load and the information sent from the AND gates 52 to 60, the status of the thyristor is determined to be abnormal, normal, or abnormal, and display/alarm is issued if necessary. At the same time, signals are sent to other external devices (not shown), such as thyristor firing control devices, protection devices, etc.

In the above embodiment, the forward voltage detection device used has the configuration shown in FIG. 3a or 3b;
Alternatively, it is possible to use the configuration shown in FIG. Can be done.

Referring now to Figures 7a and 7b,
FIG. 7a shows the first forward voltage detection device 13', the seventh
In figure b a second forward voltage detection device 14' is shown, in both figures 20, 21, 30 and 3
1 are the same as those represented using the same reference numerals in FIGS. 3a and 3b. Also, 62,
72 is a transformer with a center tap on the secondary side;
63, 64, 73, 74 are diodes, 65, 6
6, 75, 76 are constant voltage diodes, 67, 6
8, 77, 78 are resistances, 69, 70, 79, 80
are thyristors 7, 8, 11, 12 in Fig. 1.
Condition monitoring device 1 sends a signal regarding the presence or absence of forward voltage of
71 is a common line for signal transmission lines 69 and 70, and 81 is a common line for signal transmission lines 69 and 80.

First, considering the device shown in FIG. 7a, if E _S is positive and thyristor 7 in FIG. 1 is conducting, terminals 20 and 21
The ON voltage of the thyristor is applied to the transformer 6.
A voltage is induced on the secondary side of the resistor 67, but if the Zener voltage of the constant voltage diode 65 is set higher than the peak value of the induced voltage mentioned above, this induced voltage can be applied to the resistor 67. Therefore, the output of the signal transmission line 69 is connected to the common line 71.
In contrast, the potential is almost 0. On the other hand, thyristor 7
When the thyristor is non-conducting, the voltage between the taps is applied to the terminals 20 and 21, and a sufficiently larger voltage is induced on the secondary side of the transformer 62 than when the thyristor is conducting. Mostly resistance 6
7, and the potential of the signal transmission line 69 takes a positive value. Further, when E _S is positive and the thyristor 12 in FIG. 1 is non-conductive, a positive voltage is generated in the signal transmission line 80, and when _E 8 or 1
1 is non-conductive, the signal transmission line 70 or 7
A positive voltage will be generated at 9. At this time, if the state in which a positive voltage is generated in the signal transmission lines 69, 70, 79, and 80 is defined as logic "1", and the state in which the signal transmission lines 69, 70, 79, and 80 are at zero potential is defined as logic "0", then FIG. This corresponds to the light emitting situation of the light emitting diode in the device shown in FIG. b.

Although the above-described embodiments of the present invention have been described with respect to a tap changer under load, the present invention can also be applied to a tap changer under no load, and the same effects as in the above embodiments can be obtained.

As explained above, according to the present invention, it is possible to detect an abnormality in the on-load tap changer based on the application status of the forward voltage to the thyristor. This method has the remarkable effect of being able to accurately detect abnormalities in a short period of time.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the device according to the present invention, FIG. 2 is a current-voltage characteristic diagram of a nonlinear resistor used in the embodiment of the present invention, and FIG.
Figures a and 3b are circuit diagrams showing a configuration example of the forward voltage detection device in Figure 1, and Figures 4a and 4b are circuit diagrams showing the ignition of the light emitting diode in the forward voltage detection device during normal operation. FIG. 5 is a timing waveform diagram showing the situation. FIG. 5 is a diagram showing the relationship between the light emitting situation of the light emitting diode and the state of the thyristor in the embodiment of the present invention. FIG. 6 is a diagram showing the configuration example of the condition monitoring device in FIG. 1. The schematic diagram shown, and FIGS. 7a and 7b are circuit diagrams showing other configuration examples of the forward voltage detection device in FIG. 1. 1...Transformer, 4 and 5...Voltage tap, 6...
switching switch, 7 and 8... first pair of thyristors;
11 and 12...second pair of thyristors, 9...first nonlinear resistance, 10...second nonlinear resistance, 1
3 and 13'...first forward voltage detection device, 14 and 1
4'...Second forward voltage detection device, 15...State monitoring device, 22, 23, 32, and 33...Light emitting diodes, 61...Display alarm circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A first nonlinear resistor connected in parallel to a first pair of thyristors connected antiparallel to each other is connected to one of a plurality of voltage taps in a transformer secondary winding. and a second non-linear resistor connected in parallel to a second pair of thyristors connected in anti-parallel to each other is connected one stage from the one of the plurality of voltage taps in the secondary winding of the transformer. In the abnormality detection device for an on-load tap changer, the first and second nonlinear resistors are connected to an output terminal of the transformer, and the first and second nonlinear resistors are connected to an output terminal of the transformer. a first forward voltage detection device that detects the presence or absence of forward voltage for each of the thyristors of the pair; and a second forward voltage detection device that detects the presence or absence of forward voltage for each of the thyristors of the second pair; To monitor the operating status of each thyristor based on the forward voltage application status of each of the plurality of thyristors from these forward voltage detection devices, and to perform a corresponding display/alarm operation when an abnormality is detected. An on-load tap changer abnormality detection device comprising a condition monitoring device. 2. The forward voltage detection device consists of a pair of antiparallel light emitting diodes connected in parallel to a pair of thyristors connected in antiparallel, and is adapted to detect the presence or absence of output light from these light emitting diodes. An on-load tap changer abnormality detection device according to claim 1. 3. The on-load tap changer abnormality detection device according to claim 2, wherein the means for transmitting the signal from the forward voltage detection device to the condition monitoring device is an optical fiber.