JP2013135129A - Abnormality detection method of instrument transformer and protection method of circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormality detection method of instrument transformers capable of quickly and accurately detecting internal abnormality of the instrument transformers, and further to provide a protection method of a circuit capable of appropriately protecting the circuit when the abnormality occurs inside the instrument transformer.SOLUTION: An abnormality detection method of instrument transformers comprises the steps of: connecting at least two instrument transformers with respect to one circuit; comparing output voltages of individual ones of the instrument transformers; and detecting abnormality of one instrument transformer on the basis of a variation in the output voltage of one of the individual ones of the instrument transformers. A protection method of the circuit connects a circuit breaker for cutting off power supply to the instrument transformers and an actuator that operates the circuit breaker while being input with the output voltages of the instrument transformers to the circuit. When detecting the abnormality of the instrument transformer, the actuator operates the circuit breaker and cuts off the power supply to the instrument transformer in which the abnormality is detected.

Description

  Embodiments described herein relate generally to an abnormality detection method for an instrument transformer and a circuit protection method.

  Generally, in a circuit having a power receiving / transforming facility, an instrument transformer is used for protection and voltage measurement. In this case, for example, if a fault occurs inside an instrument transformer, it may lead to a short circuit or a ground fault, and as a result, the fault is removed even though the substation equipment is normal. During this time, there was a risk of causing a power outage of the circuit for a long time. In order to avoid such a power failure of the circuit, when an abnormality occurs in the instrument transformer, it is necessary to quickly identify the abnormality and remove the failure.

  However, in general, the coil of an instrument transformer is composed of a thinner winding than the coil of a power transformer, and the winding resistance is relatively large. Therefore, for example, when a short circuit occurs in the primary coil and a circulating current is generated in the primary coil, the primary coil does not burn immediately even if the circulating current occurs, and gradually takes several minutes to several tens of minutes. Leads to burnout. In other words, such an internal abnormality of an instrument transformer is hard to be detected until the coil is burned out, the primary coil is burned out, and the abnormality of the instrument transformer is often detected only after the circuit is interrupted. There was a situation.

Japanese Patent Laid-Open No. 8-1553639

  Therefore, an abnormality detection method for an instrument transformer that can quickly and accurately detect the occurrence of an abnormality inside the instrument transformer, and an appropriate circuit when an abnormality occurs inside the instrument transformer. A circuit protection method that can be protected is provided.

According to the abnormality detection method for an instrument transformer of the present embodiment, at least two instrument transformers are connected to one circuit, output voltages of the instrument transformers are compared, and the instrument transformers are compared. The abnormality of the one instrument transformer is detected based on the fact that the output voltage of one of the instrument transformers varies.
The circuit protection method according to the present embodiment includes at least two instrument transformers, a circuit breaker that cuts off power supply to the instrument transformer, and an output voltage of the instrument transformer. And an operating device for operating the circuit breaker on the basis of. When the controller detects an abnormality in the instrument transformer, the controller operates the circuit breaker to interrupt power supply to the instrument transformer in which the abnormality is detected.

The figure which shows the connection aspect of the instrument transformer with respect to the circuit by 1st embodiment FIG. 1 equivalent diagram according to the second embodiment FIG. 1 equivalent diagram according to the third embodiment FIG. 1 equivalent diagram according to the fourth embodiment FIG. 1 equivalent diagram according to the fifth embodiment FIG. 1 equivalent diagram according to the sixth embodiment FIG. 1 equivalent diagram according to the seventh embodiment It shows the concept of the winding of the primary coil of a general instrument transformer, (a) is a diagram showing a normal state, (b) is a diagram showing a state in which the ends are short-circuited

  Hereinafter, a plurality of embodiments will be described with reference to the drawings. In addition, in each embodiment, the same code | symbol is attached | subjected to the substantially same component, and description is abbreviate | omitted.

(First embodiment)
First, with reference to FIG. 8, the abnormality which arises inside an instrument transformer is demonstrated. An instrument transformer is configured by winding a primary coil and a secondary coil having different numbers of turns around an iron core. This primary coil is set to a higher number of turns than the secondary coil by a thin winding in order to accurately step down the high voltage input to the primary coil with a predetermined transformation ratio and output it to the secondary coil. . FIG. 8 shows a winding form of a general primary coil 1. The primary coil 1 is formed by winding the primary winding 2 along the outer periphery of the iron core 3 as indicated by a solid arrow C in FIG. A plurality of layers, that is, N layers in this case are overlapped from the inner peripheral side to the outer peripheral side while folding back within a predetermined range of the iron core 3.

  As an abnormality that occurs inside the instrument transformer, there is a dielectric breakdown that occurs in the primary coil 1. In this case, dielectric breakdown is likely to occur at both ends of the adjacent two layers centering on the folded portion, that is, at the beginning and end of winding between the two layers. For example, in FIG. 8A, between the (N-1) layer and the (N) layer, an end A that is the winding start of the (N-1) layer, and the winding end of the (N) layer, It is easy for dielectric breakdown to occur between the end B. This is because, between the (N-1) layer and the (N) layer, the potential difference between the end A and the end B, which are both ends, is the largest.

Since the primary winding 2 is composed of a thin wire and has a relatively large resistance, when the end A and the end B are short-circuited, the current flowing through the primary coil 1 is as shown in FIG. , (N-1) layer and (N) layer flow between both end portions A and B, and a circulating current is generated in the winding indicated by a thick broken line D. In this case, it can be considered that the substantial number of layers of the primary coil 1 is reduced by the number of short-circuited layers, in this case, two layers. That is, when the output voltage in a normal case where no breakdown occurs in the primary coil 1 is V0, the output voltage V1 when the end A of the (N-1) layer and the end B of the (N) layer are short-circuited. Is represented by the following equation (1).
V1 = V0 × N / (N−2) (1)

  As shown in FIG. 1, the circuit 10 of the first embodiment is configured by connecting a load 13 such as a power receiving / transforming facility to distribution lines 11 and 12 connected to a single-phase AC power source (not shown). Yes. In addition, two instrument transformers, that is, a first instrument transformer 14 and a second instrument transformer 15 are connected to the one circuit 10. The instrument transformers 14 and 15 have the same configuration, and are configured by a general instrument transformer as shown in FIG. The instrument transformers 14 and 15 are respectively connected to the distribution lines 11 and 12 on the primary coils 141 and 151 side, that is, the input side. The secondary coils 142 and 152, that is, the output side, are connected to a voltage measuring instrument (not shown). Here, a voltage input to both ends of the primary coils 141 and 151 is set as an input voltage, and a voltage generated at both ends of the secondary coils 142 and 152 is set as an output voltage.

  In this configuration, an abnormality inside the instrument transformers 14 and 15, that is, an abnormality caused by a short circuit of the primary coils 141 and 151, causes the output voltage of the first instrument transformer 14 and the output voltage of the second instrument transformer 15 to be In comparison, it is detected based on a change in either output voltage. That is, if both the first instrument transformer 14 and the second instrument transformer 15 are operating normally, the output voltage of the first instrument transformer 14 and the output voltage of the second instrument transformer 15 Are almost the same value. Therefore, if the output voltage of the first instrument transformer 14 and the output voltage of the second instrument transformer 15 show substantially the same value, the first instrument transformer 14 and the second instrument transformer 15 are normal. It can be determined that it is operating.

  For example, if the output voltages of the instrument transformers 14 and 15 both fluctuate, but both show substantially the same value, it can be determined that both the instrument transformers 14 and 15 are operating normally. Therefore, it can be determined that the fluctuation in the output voltage is caused by the fluctuation in the voltage of the circuit 10. Thus, by monitoring the output voltages of the instrument transformers 14 and 15, it is possible to detect that an abnormality has occurred in the circuit 10. In this case, the circuit 10 can be appropriately protected by removing the abnormality that has occurred in the circuit 10 by repair or the like.

  On the other hand, when only one of the output voltages of the instrument transformers 14 and 15 changes, it can be determined that at least one of the instrument transformers 14 and 15 is not operating normally. In this case, if the cause of the abnormality is due to a short circuit of the primary coil 141 or the primary coil 151, only the output voltage of the instrument transformer in which the internal abnormality has occurred increases with a tendency according to the equation (1). Therefore, it is possible to specify that an internal abnormality has occurred in the instrument transformer on the side where the output voltage has increased among the instrument transformers 14 and 15. In this way, by comparing the output voltages of the instrument transformers 14 and 15, when the difference becomes larger than a predetermined value, an internal abnormality occurs in the instrument transformer whose output voltage has increased. Can be determined.

According to this, it is possible to quickly and accurately detect that an internal abnormality has occurred in one of the instrument transformers 14 and 15 due to a short circuit of the primary coils 141 and 151. In addition, since it is possible to quickly identify the faulty instrument transformer, it is possible to quickly remove the fault. As a result, when one of the instrument transformers 14 and 15 has an internal fault. However, the circuit 10 can be appropriately protected.
In addition, the structure which provides three or more instrument transformers may be sufficient, In this case, the internal abnormality of each instrument transformer can be detected by comparing the output voltage of each instrument transformer.

(Second embodiment)
Next, a second embodiment will be described with reference to FIG.
In the second embodiment, in addition to the configuration of the first embodiment, the first instrument transformer 14 and the second instrument transformer 15 are connected in series so that their output voltages cancel each other. That is, the high potential sides of the secondary coils 142 and 152 of the instrument transformers 14 and 15 are connected by the connection line 16. On the other hand, the lead wire 17 is connected to the low potential side of the secondary coil 142, and the lead wire 18 is connected to the low potential side of the secondary coil 152.
Thus, the secondary coil 142 of the first instrument transformer 14 and the secondary coil 152 of the second instrument transformer 15 are connected in antiparallel. Then, the potential difference between both ends of the secondary coils 142 and 152 connected in series, that is, between the lead wires 17 and 18 is measured. Based on the fact that the potential difference fluctuates, that is, the potential difference becomes larger than a predetermined value. The internal abnormality of the instrument transformers 14 and 15 is detected.

According to the second embodiment, the same effect as that of the first embodiment can be obtained. Furthermore, an internal abnormality in one of the instrument transformers 14 and 15 appears as a potential difference between the lead wires 17 and 18. Therefore, since the internal abnormality of the instrument transformers 14 and 15 can be detected by monitoring the potential difference between the lead wires 17 and 18, the configuration can be simplified.
Convenience is improved.

(Third embodiment)
Next, a third embodiment will be described with reference to FIG.
In the third embodiment, a single-phase circuit breaker 19 and an operating device 20 are connected to the circuit 10 in addition to the configuration of the first embodiment shown in FIG. The single-phase circuit breaker 19 is provided on the high-voltage power supply side (not shown), that is, on the opposite side of the load 13 with respect to the instrument transformers 14 and 15, and interrupts the circuit 10 to the instrument transformers 14 and 15. Shut off the power supply. The operating device 20 receives the output voltages of the instrument transformers 14 and 15 and operates the single-phase circuit breaker 19 based on the output voltages. That is, the operating device 20 is connected to the secondary coils 142 and 152 by the connection lines 21 and the output voltages of the instrument transformers 14 and 15 are input. And the operating device 20 detects the internal abnormality of the instrument transformers 14 and 15 by the method shown in 1st embodiment, and operates the single phase circuit breaker 19 based on the detection result.

  In this case, the controller 20 detects an internal abnormality in one of the instrument transformers 14 and 15, that is, an internal abnormality occurs in one of the instrument transformers 14 and 15, resulting in a difference in output voltage. When this is detected, the single-phase circuit breaker 19 is operated or tripped. Thereby, the circuit 10 is interrupted and the power supply to the instrument transformers 14 and 15 is interrupted.

  According to the third embodiment, when an internal abnormality occurs in either one of the instrument transformers 14 and 15, the operation device 20 detects the abnormality and trips the single-phase circuit breaker 19 to cause a circuit. By shutting off 10, power supply to the instrument transformers 14 and 15 can be shut off. In this case, since the circuit 10 is interrupted and the power supply to the instrument transformers 14 and 15 is interrupted, the primary coils 141 and 151 can be prevented from being burned out by the circulating current. Thereby, the influence of the internal abnormality of the instrument transformers 14 and 15 can be suppressed, and the circuit 10 can be protected quickly and appropriately.

  In this case, as in the second embodiment shown in FIG. 2, the secondary coils 142 and 152 are connected in antiparallel, and the voltage difference between the secondary coils 142 and 152 generated at both ends thereof is directly input to the controller 20. The structure which connects, ie, the leader lines 17 and 18 to the operation device 20 may be sufficient. In this case, since the differential voltage of the secondary coils 142 and 152 is output from the leader lines 17 and 18 in a state of comparison, the controller 20 only needs to monitor the potential difference between the leader lines 17 and 18. As a result, the operation device 20 can have a simple configuration.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIG.
In the fourth embodiment, a first circuit breaker 22 and a second circuit breaker 23 having the same configuration are connected to the circuit 10 instead of the single-phase circuit breaker 19 of the third embodiment shown in FIG. In this case, the first circuit breaker 22 is connected between the distribution lines 11 and 12 of the circuit 10 and the primary coil 141 of the first instrument transformer 14. The second circuit breaker 23 is connected between the distribution lines 11 and 12 of the circuit 10 and the primary coil 151 of the second instrument transformer 15.

  In this configuration, when the controller 20 detects an internal abnormality of either one of the instrument transformers 14 and 15, the controller 20 trips the circuit breaker 22 or the circuit breaker 23 so that the abnormality occurs. Disconnect the transformer from the circuit 10. That is, for example, when an internal abnormality occurs in the first instrument transformer 14, only the output voltage of the first instrument transformer 14 increases. The controller 20 detects that an internal abnormality has occurred in the first instrument transformer 14 based on the fluctuation of the output voltage, and trips the first circuit breaker 22. Then, the circuit 10 and the first instrument transformer 14 are disconnected, and the first instrument transformer 14 is disconnected from the circuit 10. Thereby, the power supply to the first instrument transformer 14 in which the internal abnormality has occurred is cut off. At this time, since the second circuit breaker 23 is not tripped, the power supply of the second instrument transformer 15 is continued without being disconnected from the circuit 10.

  According to the fourth embodiment, when an internal abnormality occurs in one of the instrument transformers 14 and 15, the controller 20 detects the abnormality, and the malfunctioning instrument transformer is disconnected. 22 and 23 can be separated from the circuit 10. In this case, since only the power supply to the instrument transformer in which the internal abnormality has occurred is interrupted among the instrument transformers 14 and 15, the shorted primary coil of the primary coils 141 and 151 is burned by the circulating current. This can be avoided appropriately. Thereby, the influence of the internal abnormality of the instrument transformers 14 and 15 can be suppressed, and the circuit 10 can be protected quickly and appropriately.

  Furthermore, in this case, even if one of the instrument transformers 14 and 15 in which an abnormality has occurred is disconnected from the circuit 10, the other instrument transformer in which no abnormality has occurred is connected to the circuit 10. Has been. Therefore, by using the other instrument transformer in which no abnormality has occurred, the circuit 10 can be continuously operated without stopping even if the failure is removed.

(Fifth embodiment)
Next, a fifth embodiment will be described with reference to FIG.
In the fifth embodiment, the circuit 30 is configured by connecting a load 34 such as a power receiving / transforming facility to U, V, and W phase distribution lines 31, 32, and 33 connected to a three-phase AC high-voltage power supply (not shown). It is configured. Further, three instrument transformers, that is, a third instrument transformer 35, a fourth instrument transformer 36, and a fifth instrument transformer 37 are connected to the one circuit 30. These instrument transformers 35, 36, and 37 have the same configuration and are connected between the phases of the three-phase circuit 30.

  Specifically, a primary coil 351, that is, an input side of the third instrument transformer 35 is connected to the U-phase distribution line 31 and the V-phase distribution line 32. Therefore, the interphase voltage between the U phase and the V phase is stepped down and output to the secondary coil 352 of the third instrument transformer 35, that is, the outputs u1 and v1. In the fourth instrument transformer 36, the primary coil 361 is connected to the V-phase distribution line 32 and the W-phase distribution line 33. Therefore, the interphase voltage between the V phase and the W phase is stepped down and output to the secondary coil 362 of the fourth instrument transformer 36, that is, the outputs v2 and w2. Further, in the fifth instrument transformer 37, the primary coil 371 is connected to the W-phase distribution line 33 and the V-phase distribution line 31. Therefore, the interphase voltage between the W phase and the V phase is stepped down and output to the secondary coil 372 of the fifth instrument transformer 37, that is, the outputs w3 and u3.

  Here, if all of the three-instrument transformers 35, 36, and 37 are operating normally, and the output voltages of the instrument transformers 35, 36, and 37 including the phase difference are combined, the result is A value of almost zero is shown. Therefore, when the output voltages of the three instrument transformers 35, 36, and 37 are combined including the phase difference, if the result shows a value of almost zero, these instrument transformers 35, 36, 37 can be determined to be operating normally.

  For example, when the output voltages of the instrument transformers 35, 36, and 37 fluctuate, but the result of the synthesis including the phase difference of each output voltage shows a value of almost zero, the instrument transformers 35, It can be determined that 36 and 37 are operating normally. Therefore, it can be determined that the variation in the output voltage is caused by the variation in the voltage of the circuit 30. In this case, since it can be determined that an abnormality has occurred in the circuit 30, the circuit 30 can be appropriately protected by removing the abnormality by repair or the like.

  On the other hand, when the combined result of the output voltages of the instrument transformers 35, 36, and 37 indicates a non-zero value, at least one of the instrument transformers 35, 36, and 37 is not operating normally. It can be judged. In this case, if the cause of the abnormality is due to a short circuit of one of the primary coils 351, 361, 371, only the output voltage of the instrument transformer in which the internal abnormality has occurred among the instrument transformers 35, 36, 37. Rises according to equation (1).

  Here, if the instrument transformers 35, 36, and 37 are operating normally, the combined result of these output voltages is 0, so that the output voltage of any two, for example, the instrument transformers 35, 36, can be obtained. The output voltage of the remaining one instrument transformer 37 obtained from the above and the actual output voltage of the remaining one instrument transformer 37 show substantially the same value. However, for example, when an internal abnormality occurs in the instrument transformer 37 and its output voltage rises, the actual output voltage of the instrument transformer 37 is determined from the output voltage of the instrument transformers 35 and 36. The value is larger than the output voltage of the device 37.

  That is, the actual output voltage of one instrument transformer 37 is larger than the output voltage of one instrument transformer 37 calculated from the output voltages of the other two instrument transformers 35 and 36. If it is, it can be determined that an internal abnormality has occurred in the one instrument transformer 37. Thus, among the three instrument transformers 35, 36, and 37 connected between the three phases, the remaining one of the instrument transformers obtained from the output voltage of the two instrument transformers is used. Based on the fact that the actual output voltage of the remaining one instrument transformer has increased, it is detected that an internal abnormality has occurred in the remaining one instrument transformer.

According to the fifth embodiment, it is possible to quickly and accurately detect that an internal abnormality has occurred in any one of the instrument transformers 35, 36, and 37 connected to the three-phase circuit 30. . In addition, since the faulty instrument transformer can be quickly identified, it is possible to quickly remove the fault. As a result, any one of the instrument transformers 35, 36, 36 has an internal fault. Even if it occurs, the circuit 30 can be appropriately protected.
In addition, the structure which provides four or more transformers for instruments may be sufficient. In this case, by comparing the output voltages of the two instrument transformers connected in the same phase with each other, it is possible to detect an internal abnormality of either one of the two instrument transformers.

(Sixth embodiment)
Next, a sixth embodiment will be described with reference to FIG.
In the sixth embodiment, a three-phase circuit breaker 38 and an operating device 39 are connected to the circuit 30 in addition to the configuration of the fifth embodiment. The three-phase circuit breaker 38 is provided on the high voltage power source side (not shown), that is, on the side opposite to the load 34 with respect to the instrument transformers 35, 36, and 37. The power supply to 36 and 37 is cut off. The operating device 39 receives the output voltages of the instrument transformers 35, 36, and 37, and operates the three-phase circuit breaker 38 based on the output voltages. That is, the operating device 39 is connected to each secondary coil 352, 362, 372 by each connection line 40, and the output voltage of the instrument transformers 35, 36, 37 is input. And the operating device 39 detects the internal abnormality of the instrument transformers 35, 36, and 37 by the method shown in the fifth embodiment, and operates the three-phase circuit breaker 38 based on the detection result.

  In this configuration, the controller 39 detects an internal abnormality in any one of the instrument transformers 35, 36, 37, that is, an internal abnormality has occurred in any one of the instrument transformers 35, 36, 37. When it occurs, the three-phase circuit breaker 38 is tripped and the circuit 30 is cut off to cut off the power supply to the instrument transformers 35, 36, and 37.

  According to the sixth embodiment, when an internal abnormality occurs in any one of the instrument transformers 35, 36, and 37 in the three-phase circuit 30, the operation device 39 detects the abnormality, By tripping the phase circuit breaker 38 and cutting off the circuit 30, the power supply to the instrument transformers 35, 36, and 37 can be cut off. In this case, since the circuit 30 is interrupted and the power supply to the instrument transformers 35, 36, and 37 is interrupted, it is possible to avoid the primary coils 351, 361, and 371 from being burned by the circulating current. Thereby, the influence of the internal abnormality of the instrument transformers 35, 36, and 37 can be suppressed, and the circuit 30 can be protected quickly and appropriately.

(Seventh embodiment)
Next, a seventh embodiment will be described with reference to FIG.
In the seventh embodiment, instead of the three-phase circuit breaker 38 of the third embodiment shown in FIG. 6, a third breaker 41, a fourth breaker 42, and a fifth breaker 43 having the same configuration are arranged in a circuit. 30. In this case, the third circuit breaker 41 is connected between the distribution lines 31 and 32 of the circuit 30 and the primary coil 351 of the third instrument transformer 35. The fourth circuit breaker 42 is connected between the distribution lines 32 and 33 of the circuit 30 and the primary coil 361 of the fourth instrument transformer 36. The fifth circuit breaker 43 is connected between the distribution lines 33 and 31 of the circuit 30 and the primary coil 371 of the fifth instrument transformer 37.

  In this configuration, when the controller 39 detects an internal abnormality in any one of the instrument transformers 35, 36, and 37, the controller 39 trips one of the circuit breakers 41, 42, and 43, and an abnormality occurs. Disconnect the instrument transformer from the circuit 30. That is, the operating device 39 trips the fifth circuit breaker 43 when detecting that an internal abnormality has occurred in the fifth instrument transformer 37, for example. Then, the circuit 30 and the fifth instrument transformer 37 are disconnected, and the fifth instrument transformer 37 is disconnected from the circuit 30. Thereby, the power supply to the fifth instrument transformer 37 in which the internal abnormality has occurred is cut off. At this time, since the third circuit breaker 41 and the fourth circuit breaker 42 are not tripped, the third instrument transformer 35 and the fourth instrument transformer 36 are not disconnected from the circuit 30 and the power supply is continued.

  According to the seventh embodiment, when an internal abnormality occurs in any one of the instrument transformers 35, 36, and 37 in the three-phase circuit 30, the controller 39 detects the abnormality, The instrumental transformer in which this occurs can be disconnected from the circuit 30 by the circuit breakers 41, 42, 43. In this case, only the power supply to the instrument transformer in which the internal abnormality has occurred is interrupted among the instrument transformers 35, 36, and 37, so that the shorted primary coil of the primary coils 351, 361, and 371 is the circulating current. Therefore, it is possible to appropriately avoid burning. Thereby, the influence of the internal abnormality of the instrument transformers 35, 36, and 37 can be suppressed, and the circuit 30 can be protected quickly and appropriately.

  Further, in this case, even if one of the instrument transformers 35, 36, 37 is disconnected from the circuit 30, the remaining two instrument transformers having no abnormality are the circuits. 30. Therefore, by using the remaining two instrument transformers in which no abnormality has occurred, operation can be continued without stopping the circuit 30 even during the period until the failure is removed.

  According to the abnormality detection method for an instrument transformer in the embodiment described above, the internal abnormality of the instrument transformer is detected by comparing the output voltages of at least two instrument transformers connected to one circuit. can do. Thereby, it is possible to quickly and accurately detect that an internal abnormality has occurred in the instrument transformer connected to the circuit. Furthermore, since the instrument transformer in which an abnormality has occurred can be quickly identified, it is possible to quickly remove the failure.

  Further, according to the circuit protection method in the embodiment described above, when an internal abnormality occurs in the instrument transformer, the power supply to the instrument transformer in which the abnormality has occurred is interrupted by the operation unit and the circuit breaker. The As a result, when an internal abnormality occurs in the instrument transformer, the influence of the internal abnormality can be suppressed and the circuit can be protected quickly and appropriately.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and equivalents thereof.

  In the drawing, 10 is a circuit, 14 is a first instrument transformer (instrument transformer), 15 is a second instrument transformer (instrument transformer), 19 is a single-phase circuit breaker (breaker), 20 Is an operating device, 22 is a first circuit breaker (breaker), 23 is a second circuit breaker (breaker), 30 is a circuit, 35 is a third instrument transformer (instrument transformer), and 36 is a fourth instrument. Transformer (instrument transformer), 37 is a fifth instrument transformer (instrument transformer), 38 is a three-phase circuit breaker (breaker), 39 is an operating device, 41 is a third breaker (breaker) ), 42 is a fourth circuit breaker (breaker), and 43 is a fifth circuit breaker (breaker).

Claims (6)

  At least two instrument transformers are connected to one circuit, the output voltages of the instrument transformers are compared, and the output voltage of one of the instrument transformers fluctuates. An abnormality detection method for an instrument transformer, comprising detecting an abnormality of the one instrument transformer based on the above.   Two instrument transformers are connected in series so that output voltages cancel each other, and the instrument transformer connected to the high voltage side of the difference voltage based on the difference in the difference voltage between the two ends connected in series. An abnormality detection method for an instrument transformer according to claim 1, wherein an abnormality of the instrument is detected.   The circuit is a three-phase circuit, in which three instrument transformers are connected between the three phases, respectively, and the remaining one of the three instrument transformers is obtained from the output voltage of two instrument transformers. An abnormality of the remaining one instrument transformer is detected based on an increase in an actual output voltage of the remaining one instrument transformer with respect to an output voltage of one instrument transformer. An abnormality detection method for an instrument transformer according to claim 1. For one circuit, at least two instrument transformers, a circuit breaker that cuts off power supply to the instrument transformer, and an operator that operates the circuit breaker based on an output voltage of the instrument transformer; Connect,
When the controller detects an abnormality of the instrument transformer using the abnormality detection method of the instrument transformer according to any one of claims 1 to 3, the controller operates the circuit breaker, A method for protecting a circuit, characterized in that power supply to an instrument transformer in which an abnormality is detected is cut off.   5. The circuit protection method according to claim 4, wherein the circuit breaker interrupts the circuit.   5. The circuit protection method according to claim 4, wherein the circuit breaker is provided between the circuit and the instrument transformer and separates the instrument transformer from the circuit.

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