JP6927892B2 - Electric circuit failure detection device - Google Patents

Description

The present invention relates to an electric circuit failure detection device.

As a technique for detecting an electric circuit opening failure on the primary side of a transformer, claim 1 of Patent Document 1 below states that "a logo installed on the neutral wire of the Y connection on the primary side of a standby transformer used in a nuclear power plant". Rogoski Coil; A reference set in which the current induced in the Rogoski coil is equal to or higher than the set reference value in a state where the secondary side circuit breaker of the standby transformer is opened. If it is maintained for a certain period of time or longer, a phase loss detection unit that determines that a phase loss has occurred on the primary side and generates an alarm signal; and an alarm signal provided by the phase loss detection unit displays an alarm to the administrator. A phase open detection device for connecting lines of standby transformers in a nuclear power plant, which comprises a main control unit;

Further, in the abstract of Patent Document 2 below, "The protection relay device is an input means for receiving an input of a three-phase load current output to the load side of a three-phase transformer composed of a YY-Δ connection. And a judgment means for judging whether or not the effective value of the load current of at least one phase out of the load currents of the three phases is equal to or less than the reference current value, and a switch provided on the tertiary winding based on the judgment result. The output means includes an output means for outputting a control signal for opening and closing, and a detection means for detecting an imbalance of the load current of three phases. The output means has an effective value of the load current of at least one phase equal to or less than the reference current value. In that case, a control signal for opening the switch is output, and when the effective values of all the three-phase load currents are larger than the reference current value, a control signal for closing the switch is output. " ing.

Further, in the specification of Patent Document 3 below, paragraph 0018, "It is difficult to detect the open phase of the primary side when the secondary side of the transformer connected to the transmission line or the distribution line is in a no-load state because the current is small. Although it is a thing, there is a feature that it takes a sufficient time to detect the open phase state because it is sufficient if the load can be detected before it is connected and put into use. The present inventor utilizes this feature. We have devised a phase loss detector that can detect phase loss with high accuracy by detecting a minute current over a sufficient period of time. "

Japanese Patent No. 5976959 Japanese Unexamined Patent Publication No. 2016-46972 Japanese Patent No. 5926419

The technique described in Patent Document 1 is to attach a Rogowski coil to a neutral point grounding electric circuit of a transformer and capture a change in behavior at a low load. However, it is difficult to attach the Rogowski coil itself when the transformer is not grounded due to the electric circuit configuration. Further, the technique described in Patent Document 2 is premised on applying a transformer having a YY-Δ connection, that is, a transformer having a tertiary winding, and cannot be applied to other transformers. be. Further, the technique described in Patent Document 3 is based on the premise that the detection accuracy can be improved by lengthening the measurement time of the current value. However, it is considered that the noise component may not be sufficiently removed even if the measurement time is lengthened due to the electric circuit state (unbalance, capacitance) of the external system and the lengthening of the measurement electric circuit.

Further, all of the techniques described in Patent Documents 1 to 3 are intended for one-phase open events on the primary side of the transformer, and it is difficult to apply them as they are for detecting two-phase open. Conceivable. As described above, all of the techniques described in Patent Documents 1 to 3 have a problem that the applicable circuit and the accident aspect are limited.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric circuit failure detecting device capable of reliably detecting an electric circuit opening failure.

In order to solve the above problems, the electric circuit failure detection device of the present invention includes a current sensor that measures the primary side current flowing in the electric circuit connected between the primary winding of the three-phase transformer and the power source, and the transformer. A control unit that determines the presence or absence of an open failure in the electric circuit based on the voltage sensor that measures the secondary side voltage of the transformer, the phase relationship of the primary side current, and the secondary side voltage, and outputs the determination result. When there is a ratio between the amplitude values of the respective phases in the secondary voltage of the transformer that is equal to or higher than a predetermined phase voltage deviation detection rate, the control unit is opened. It is characterized by outputting a determination signal indicating that a failure has occurred.

According to the present invention, it is possible to reliably detect an electric circuit opening failure.

It is a block diagram of the electric circuit failure detection apparatus by one Embodiment of this invention. It is operation explanatory drawing when the primary side open failure occurs. It is a block diagram of the control part in one Embodiment. It is a waveform diagram of the primary side current in one embodiment. It is another waveform diagram of the primary side current in one embodiment. It is another waveform diagram of the primary side current in one embodiment. It is a waveform diagram of the secondary side voltage in one embodiment. It is another waveform diagram of the secondary side voltage in one embodiment.

<Overall configuration of one embodiment>
FIG. 1 is a block diagram of an electric circuit failure detection device A according to an embodiment of the present invention.
In FIG. 1, the power system 150 is, for example, a commercial power system. The three-phase transformer 156 includes a primary winding 156a and a secondary winding 156b. The primary winding 156a is connected to the power system 150 via a circuit breaker 152 and an electric circuit 154. Here, the electric circuit 154 has an R-phase electric circuit 154r, an S-phase electric circuit 154s, and a T-phase electric circuit 154t. The circuit breaker 152 turns on / off the connection between the power system 150 and the transformer 156, and outputs the on / off state as a circuit breaker state signal Sb. The transformer 156 converts the voltage supplied from the power system 150 (for example, steps down) and supplies the power to the load device 160 via the electric circuit 158.

The electric circuit failure detection device A includes a winding type optical fiber current sensor 101 (current sensor), an optical fiber 102, voltage sensors 112 and 114, a signal processing unit 133, and a control unit 200. The current sensor 101, together with the signal processing unit 133, detects the primary side currents ir, is, and it of the R phase, S phase, and T phase flowing in the electric circuit 154.

The current sensor 101 is formed in a flexible rod shape. When the current sensor 101 is mounted on the electric circuit 154, it is not necessary to disconnect or disassemble the conductive portion of the electric circuit 154, and the current sensor 101 can be mounted only by winding the current sensor 101 around the conductive portion. The optical fiber 102 transmits the detection result of the current sensor 101 as an optical signal. The voltage sensor 112 detects the primary voltage vr, vs, vt in the power system 150. Further, the voltage sensor 114 detects the secondary voltage vu, vv, vw of the transformer 156.

The signal processing unit 133 has a light source (not shown) and outputs light to the current sensor 101 via the optical fiber 102. A mirror (not shown) that reflects the transmitted light is attached to the tip of the current sensor 101. The light reflected by the mirror returns to the signal processing unit 133. Here, a magnetic field is generated around the electric circuit 154 due to the current flowing through the electric circuit 154, and the light in the current sensor 101 is polarized according to the magnetic field due to the Faraday effect. Therefore, the signal processing unit 133 detects the primary side currents ir, is, and it based on the amount of polarization, and outputs the result. Further, the primary side voltages vr, vs, vit are input to the signal processing unit 133 for correction of the detection result of the primary side currents ir, is, it.

Further, the control unit 200 includes a circuit breaker status signal Sb output from the circuit breaker 152, primary side currents ir, is, it detected by the signal processing unit 133, and a secondary current detected by the voltage sensor 114. The side voltages vu, vv, vw and so on are received. The control unit 200 determines whether or not a failure has occurred in the electric circuit 154 based on these received signals and an algorithm described later, and outputs the result as a determination signal Sj. The determination signal Sj may be in the form of "alarm" or "trip output".

<Problems related to transformer primary side open failure>
Here, a problem will be described when an open failure occurs on the primary side of the transformer 156, that is, the electric circuit 154.
FIG. 2 is an operation explanatory diagram when this open failure occurs. As shown, it is assumed that the primary winding 156a of the transformer 156 is a star-shaped connection grounded at the neutral point and the secondary winding 156b is a triangular connection. Then, it is assumed that an open failure occurs in the R phase electric path 154r at the open failure point 170. The electric circuit 154 has a length of, for example, several hundred meters to several kilometers. The electric circuit 154 has a relatively large charging capacity with the ground potential. In FIG. 2, this charging capacity is indicated by a broken line capacitor (unsigned).

In FIG. 2, the vectors Vr, Vs, and Vt correspond to the primary side voltages vr, vs, and vt, and the vectors Vu, Vv, and Vw correspond to the secondary side voltages vu, vv, and vw. Then, it is assumed that the R-phase, S-phase, and T-phase windings in the primary winding 156a are wound corresponding to the U-phase, V-phase, and W-phase windings in the secondary winding 156b, respectively. ..

In FIG. 2, the V-phase and W-phase voltage vectors Vv and Vw are generated in the secondary winding 156b by the S-phase and T-phase voltage vectors Vs and Vt that are not the open phase. Then, the U-phase voltage vector Vu is generated in the secondary winding 156b by the V-phase and W-phase voltage vectors Vv and Vw. When the U-phase voltage vector Vu is generated, the R-phase voltage vector Vr is generated in the primary winding 156a. As described above, it can be seen that the change in the primary / secondary voltage relationship in the transformer 156 becomes small before and after the occurrence of the primary side open failure.

Further, the secondary current flowing through the secondary winding 156b is determined by the secondary side voltages vu, vv, vw (see FIG. 1) and the load impedance of the load device 160. Therefore, assuming that the secondary voltage vu, vv, vw does not change before the failure occurs, the magnitude and phase change of the secondary current also do not change. In reality, there is a slight change in the amount of electricity on the secondary side before and after the primary side open failure, but it is often difficult to detect the primary side open failure due to this change.

On the other hand, when the primary side open failure of the transformer 156 occurs, a significant change appears in the primary side currents ir, is, it of the transformer 156. That is, the amplitude value of the primary side current ir related to the open phase becomes almost zero, but the amplitude value of the remaining primary side currents is and it becomes larger than that before the failure occurred. The circuit breaker 152 shown in FIG. 1 is provided to protect the transformer 156 against overload, short circuit, etc., and any one of the primary side currents ir, is, and it exceeds a predetermined current threshold value. And, it is configured to turn off all phases. Therefore, it is conceivable to detect a change in the primary side current by a protective device (not shown) of the circuit breaker 152 to detect a primary side open failure. However, in general, in the protection device provided for current protection, the current threshold value for performing the breaking operation is set to a relatively high value. Therefore, when an open failure occurs on the primary side of the transformer in a low load state, it is difficult for the circuit breaker 152 to detect the open failure.

Further, in the present embodiment, as described above, the winding type optical fiber current sensor 101 is provided on the primary side of the transformer 156, but in a normal transformer, an iron core type current transformer for current measurement (FIG. (Not shown) is often applied. In this type of iron core type current transformer, the rated current on the primary side of the transformer is made to correspond to a predetermined secondary side current (for example, about 5A or 1A). Therefore, when the transformer is in a no-load or low-load state, the secondary side current of the iron core type current transformer becomes a minute value. Therefore, when the transformer is in a no-load or low-load state, it is often difficult to detect an open failure on the primary side of the transformer by an iron core current transformer.

When the primary side open failure occurs in the transformer 156, if the load device 160 is connected to the secondary side of the transformer 156, the degree varies depending on the grounding state of the neutral point on the primary side, the winding configuration, etc. The next-side voltages vu, vv, and vw become unbalanced. When the load device 160 includes, for example, an induction motor, the phase currents of the induction motor become unbalanced, causing abnormal noise and vibration, and in some cases, the induction motor burns out. Therefore, when a primary side open failure of the transformer 156 occurs, it is desired to detect it at an early stage and let the operator grasp it. In particular, in recent years, the load device 160 applied to ancillary equipment such as a nuclear power plant is strongly required to be protected against this event.

<Structure of control unit 200>
FIG. 3 is a block diagram of the control unit 200. The control unit 200 is composed of a relay circuit or the like.
The control unit 200 includes a phase current deviation detection unit 202, a line current deviation detection unit 204, a primary side current detection unit 206, a phase current phase difference detection unit 208, a phase voltage deviation detection unit 210, and an undervoltage detection. A unit 212, an AND circuit 222, 224, 234, 240, an OR circuit 226, 230, 232, 244, a NOT circuit 220, 228, 238, and a time-up circuit 236, 242 are provided.

(Phase current deviation detection unit 202)
The phase current deviation detection unit 202 obtains the amplitude values of the primary side currents ir, is, and it, and if there is a ratio between these amplitude values that is equal to or higher than the predetermined phase current deviation detection rate, "1". The phase current deviation signal S2 becomes "0" in other cases.
Here, an operation example of the phase current deviation detection unit 202 will be described.
In FIG. 4, (a) the load device 160 (see FIG. 1) has equipment including an induction motor and the equipment is in operation, and (b) the primary winding 156a (see FIG. 1) is neutral. It is a waveform diagram of the primary side current ir, is, it under the condition that it is a grounded star-shaped connection.
In any of the waveform groups G31, G32, and G33, the horizontal axis is time and the vertical axis is the current value. The primary side currents ir, is, and it are drawn by solid lines, dotted lines, and broken lines, respectively.

The waveform group G31 is a current waveform when the primary side open failure does not occur, and the amplitude values of the primary side currents ir, is, and it are substantially equal. In this case, the phase current deviation detection unit 202 sets the phase current deviation signal S2 to “0”. Further, the waveform group G32 is a current waveform when a one-phase (T-phase) primary side open failure occurs. In the illustrated example, the amplitude value of the primary side current it is significantly smaller than the amplitude value of the other primary side currents ir, is. In this case, the phase current deviation detection unit 202 sets the phase current deviation signal S2 to “1”. The amplitude value of the primary side current it is not completely zero because the charging capacity exists in each part of the electric circuit 154 and the transformer 156. Further, the waveform group G33 is a current waveform when a two-phase primary side open failure occurs, and the current in the open phase (R phase, T phase) is significantly smaller. Also in this case, the phase current deviation detection unit 202 sets the phase current deviation signal S2 to “1”.

Further, with reference to FIG. 5, another operation example of the phase current deviation detection unit 202 will be described. Here, FIG. 5 is a waveform diagram of the primary side currents ir, is, and it under the same conditions as those in FIG. However, in FIG. 5, it is assumed that the induction motor included in the load device 160 is operated at a low output. The waveform group G61 is a current waveform when the primary side open failure does not occur, and the amplitude values of the primary side currents ir, is, and it are substantially the same. Further, the waveform group G62 is a current waveform when a two-phase primary side open failure occurs. In this case, the amplitude value of the primary side current ir is significantly larger than the amplitude value of the primary side currents is and it.
Therefore, the phase current deviation detection unit 202 can output an accurate phase current deviation signal S2 even when the load device 160 includes an induction motor.

As shown in FIGS. 4 and 5, the one-phase open event can be basically detected by the deviation of each phase current value. However, when the transformer 156 is in a no-load or low-load state, the primary side currents ir, is, it are substantially equal to the transformer 156n exciting current. Then, in FIG. 2, when the charging capacity between the open failure point 170 and the transformer 156 is large, there may be a case where the deviation of each phase of the exciting current does not remarkably appear due to the charging current flowing through the charging capacity.

Here, when the neutral point of the primary winding 156a is not grounded, the neutral point moves due to the one-phase opening event, so that the secondary side voltages vu, vv, vw (see FIG. 1) are more than the current deviation. ) Deviation is more pronounced. Further, when the neutral point of the primary winding 156a is not grounded and a two-phase open event occurs, the effective voltage vector applied to the transformer 156 disappears, so that the current energizing current of the transformer and the second The next voltage tends to decrease in all three phases, and no effective interphase deviation appears.

As described above, there are various cases of the voltage and current aspects at the time of the primary side open failure of the transformer 156. Therefore, in the present embodiment, an algorithm effective for each mode of open failure is selected by other components shown in FIG. 3 (details will be described later), and the algorithm is implemented in parallel (OR operation is performed). Is going). As a result, regardless of the connection type of the transformer 156, the grounding method, and the electric circuit condition on the system side, the one-phase open and two-phase open failures that occur on the primary side during the no-load to rated load of the transformer 156 can be accurately detected. It becomes possible to detect.

(Phase current phase difference detector 208)
Returning to FIG. 3, the phase current phase difference detection unit 208 detects the primary side open failure based on the phase relationship of the primary side currents ir, is, and it. That is, the phase current phase difference detection unit 208 calculates the phase difference between the primary side currents ir, is, and it. Here, if the primary side current is in a three-phase equilibrium state, the phase difference between the primary side currents is 120 °. Therefore, considering the calculation error in this phase difference 120 °, the phase difference detection unit 208 is set to “0” if the phase difference between the primary side currents is in the range of 120 ° ± α (α is a predetermined constant). Is output, and the phase difference detection signal S8 which becomes “1” in other cases is output.

Here, an operation example of the phase current phase difference detection unit 208 will be described.
FIG. 6 shows that (a) the load device 160 (see FIG. 1) is unloaded, and (b) the primary winding 156a is a star-shaped connection grounded to a neutral point, (c) a triangle on the transformer 156. It is a waveform diagram of the primary side current ir, is, it under the condition that the connection is included. In the present embodiment, since the secondary winding 156b has a triangular connection, the above condition (c) is satisfied.
The waveform group G41 is a current waveform, that is, a waveform of an exciting current when a primary side open failure does not occur. As shown, the primary side currents ir, is, it have a phase difference of approximately 120 ° from each other. In this case, the phase current phase difference detection unit 208 sets the phase difference detection signal S8 to “0”.

Further, the waveform group G42 is a current waveform when a primary side open failure occurs. As described above, it is assumed that each electric circuit 154 (see FIG. 1) has a relatively long distance and has a large charging capacity with the ground potential. Then, when an open failure occurs in any of the phases on the primary side, a closed loop is formed through the charging capacity and the neutral point on the primary side of the transformer 156 by the voltage induced in the electric circuit 154 of the open phase, and the charging current returns. .. Since this charging current energizes the open phase of the primary winding 156a, the corresponding current is induced in the secondary winding 156b of the transformer 156. The current induced in the secondary winding 156b recirculates in the secondary winding which is a triangular connection, and as a result, is induced in each phase of the primary winding 156a. In FIG. 2, when the distance from the open failure point 170 to the transformer 156 is long and the charging capacity is large, the charging current becomes dominant over the exciting current. As a result, as shown in the waveform group G42, the primary side currents ir, is, and it are substantially in phase and have substantially the same current value. In this case, the phase current phase difference detection unit 208 sets the phase difference detection signal S8 to “1”.

(Line current deviation detection unit 204)
When the primary winding 156a is a star-shaped connection grounded at the neutral point, a zero-phase current flows through the primary winding 156a through the neutral point. Here, when the primary side currents ir, is, it are relatively small, the ratio of the zero-phase current to the primary side currents ir, is, it, which is the phase current, depending on the state of the transmission system such as the electric circuit 154. May increase. When the ratio of the zero-phase current increases, the phase relationship between the primary side currents ir, is, and it breaks down even if the primary side open failure does not occur, and the above-mentioned phase difference detection signal S8 may become “1”. There is sex. Under such circumstances, when determining the presence or absence of a primary side open failure based on the above-mentioned phase difference detection signal S8, it is necessary to consider the influence of the zero-phase current.

In FIG. 3, the line current deviation detection unit 204 is provided to determine whether or not the influence of the zero-phase current is large. First, the line current deviation detection unit 204 obtains the amplitude values of the line currents ir-is, ir-it, and is-it. Further, the line current deviation detection unit 204 becomes "1" when there is a ratio between these amplitude values that is equal to or higher than a predetermined line current deviation detection rate, and "1" in other cases. The line current deviation signal S4 which becomes 0 ”is output.

(Primary side current detector 206)
As described above, the line current deviation detection unit 204 can determine that the influence of the zero-phase current is excluded from the amplitude values of the line currents ir-is, ir-it, and is-it. However, since the exclusion of the influence of the zero-phase current is for preventing malfunction when detecting the current phase difference when an open failure does not occur, the primary side current ir, is, when the transformer 156 is unloaded. It is applied only in the small current region corresponding to it.

The primary side current detection unit 206 is provided to determine whether or not the primary side currents ir, is, and it are equivalent to no-load current. That is, the primary side current detection unit 206 becomes “0” when the amplitude value of any of the primary side currents ir, is, and it becomes equal to or higher than the predetermined primary side current detection threshold value, and “1” in other cases. Outputs the primary side current detection signal S6.

(Phase voltage deviation detection unit 210)
In FIG. 3, the phase voltage deviation detection unit 210 obtains the amplitude values of the secondary voltage vu, vv, vw of the transformer 156. Further, the phase voltage deviation detection unit 210 becomes “1” when there is a ratio between these amplitude values that is equal to or higher than the predetermined phase voltage deviation detection rate, and “0” in other cases. The phase voltage deviation signal S10 is output.

Here, an operation example of the phase voltage deviation detection unit 210 will be described.
FIG. 7 shows the secondary voltage under the condition that (a) the load device 160 (see FIG. 1) is in a no-load state, and (b) the primary winding 156a is a star-shaped connection with the neutral point ungrounded. It is a waveform diagram of vu, vv, vw. In other words, the phase voltage deviation detection unit 210 is provided for the case where the primary winding 156a is not grounded at the neutral point.
The waveform group G51 is a waveform of the secondary side voltages vu, vv, vw when the primary side open failure does not occur, and these amplitude values are substantially equal. In this case, the phase voltage deviation detection unit 210 sets the phase voltage deviation signal S10 to “0”.

Further, the waveform group G52 is a waveform of the secondary side voltages vu, vv, vw when a primary side open failure occurs, and it can be seen that the difference in voltage amplitude is large. In this case, the phase voltage deviation detection unit 210 sets the phase voltage deviation signal S10 to “1”.
As described above, in the no-load state where the neutral point of the primary winding 156a is ungrounded, the phase voltage deviation signal S10 based on the amplitude deviation of the secondary side voltages vu, vv, vw causes the primary side open failure. The presence or absence can be determined.

(Undervoltage detector 212)
Returning to FIG. 3, the undervoltage detection unit 212 obtains the amplitude values of the secondary side voltages vu, vv, and vw of the transformer 156, and obtains the amplitude values of these past amplitude values (in other words, the amplitude values at the normal time). Find the ratio, that is, the amplitude ratio. Then, the undervoltage detection unit 212 sets the undervoltage detection signal to "1" when any of these amplitude ratios is equal to or lower than the predetermined undervoltage detection rate β, and becomes "0" in other cases. Output S12.

Here, an operation example of the undervoltage detection unit 212 will be described.
8 shows that (a) the load device 160 (see FIG. 1) includes an induction motor and the induction motor is operating at low power, and (b) the primary winding 156a (see FIG. 1) is neutral. It is a waveform diagram of the secondary side voltage vu, vv, vw under the condition that it is a non-grounded star-shaped connection. In other words, the undervoltage detection unit 212 is also provided for the case where the primary winding 156a is not grounded at the neutral point.
The waveform group G71 is a waveform of the secondary voltage vu, vv, vw when the primary side open failure does not occur. Here, if a primary side open failure occurs in the two phases of the electric circuit 154, power is not supplied to the induction motor from the transformer 156. However, while the induction motor continues to rotate by coasting, within a relatively short time (for example, about several hundred milliseconds), the output voltage, that is, the secondary voltage vu, vv, vw is gradually reduced while the "induction generator". Functions as.

The waveform group G72 is a waveform of secondary side voltages vu, vv, vw in which the output voltage is lowered. As shown in the figure, the amplitude values of the secondary side voltages vu, vv, and vw in the waveform groups G71 and G72 are different. The undervoltage detection unit 212 detects changes in the amplitude values of the output voltage of the induction motor, that is, the secondary voltage vu, vv, vw. Then, the undervoltage detection unit 212 becomes “0” when the current value of any of the secondary side voltages vu, vv, and vw is “1 / β” or more of these normal values. , When it is less than "1 / β", the undervoltage detection signal S12 which becomes "1" is output. The undervoltage detection rate β is a predetermined constant exceeding “1”.

(Circuit after components 202 to 212)
Hereinafter, the circuit configuration of the subsequent stages of the components 202 to 212 will be described. In the following description, the logical sum is represented by "+", the logical product is represented by "x", and the logical negation is represented by "-".
First, the AND circuit 222 outputs the logical product “S4 × S6” of the line current deviation signal S4 and the primary side current detection signal S6 as the signal S22, and the OR circuit 226 outputs the signal S22 and the primary side current detection signal S6. The logical sum "S22 + (-S6)" with the logical denial of is output as the signal S26. Further, the AND circuit 224 outputs the logical product “S26 × S8 = (S4 × S6 + (−S6)) × S8” of the signal S26 and the signal S8 as the signal S24. That is, the signal S24 output by the AND circuit 224 has "a large deviation of the line current (S4 = 1)", "a relatively small primary side current ir, is, it (S6 = 1)", and "phase". If the deviation between the two is larger than 120 ° ± α (S8 = 1), or if the primary currents ir, is, it are relatively large (S6 = 0) and the deviation between the phases is This is a signal that becomes “1” when “greater than 120 ° ± α (S8 = 1)”. Then, the OR circuit 230 outputs a signal S30 that becomes “S2 + S24”. That is, the signal S30 is a signal indicating that a primary side open failure has occurred under the condition that the neutral point of the primary winding 156a is grounded.

Further, the OR circuit 232 outputs a signal S32 which is “S2 + S10 + S12”. The signal S32 is a signal indicating that a primary side open failure has occurred under the condition that the neutral point of the primary winding 156a is not grounded. Further, the NOT circuit 220 outputs the logic negation "-Sb" of the circuit breaker state signal Sb. Here, the circuit breaker state signal Sb is a signal that becomes “1” when the circuit breaker 152 is in the off state and “0” when the circuit breaker 152 is in the on state.
Further, the neutral point grounded state signal Se is a signal that becomes “1” when the neutral point of the primary winding 156a of the transformer 156 is grounded and “0” when the neutral point is not grounded. The reason why the neutral point grounding state signal Se is interposed is to make the detection device correctly determine the operating state (presence or absence of neutral point grounding) of the transformer 156.

The AND circuit 234 outputs a signal S34 which is “Se × (−Sb) × S30”. That is, in the signal S34, "the neutral point of the primary winding 156a is grounded (Se = 1)", "the circuit breaker 152 is on (Sb = 0)", and "the neutral point is grounded". If so, it becomes "1" under the condition that "a primary side open failure has occurred (S30 = 1)".

Further, the AND circuit 240 outputs a signal S40 which is “(−Se) × (−Sb) × S32”. That is, the signal S40 is "the neutral point of the primary winding 156a is ungrounded (Se = 0)", "the circuit breaker 152 is on (Sb = 0)", and "the neutral point is not". If it is grounded, it becomes "1" under the condition that "a primary side open failure has occurred (S32 = 1)".

The time-up circuit 236 outputs the signal S36 which becomes “1” if the signal S34 is continuously “1” for a predetermined time or longer. Similarly, the time-up circuit 242 outputs a signal S42 which becomes “1” if the signal S40 is continuously “1” for a predetermined time or longer. Then, the OR circuit 244 outputs the logical sum of the signals S36 and S42 as the determination signal Sj. As a result, the determination signal Sj becomes a signal that becomes "1" when an open failure occurs in the electric path 154, and becomes "0" in other cases.

<Effect of one embodiment>
As described above, according to the present embodiment, the primary side current (154) flowing in the electric circuit (154) connected between the primary winding (156a) of the three-phase transformer (156) and the power source (150). A current sensor (101) that measures ir, is, it), a voltage sensor (114) that measures the secondary voltage (vu, vv, vw) of the transformer (156), and a primary current (ir, is). , It), the secondary voltage (vu, vv, vw), and the control unit (200) that determines the presence or absence of an open failure in the electric circuit (154) and outputs the determination result. It is characterized by having.
Thereby, the electric circuit failure can be accurately detected based on the phase relationship of the primary side current and the secondary side voltage.

Further, the current sensor (101) is a winding type optical fiber current sensor having a function of reflecting incident light, outputs light to the current sensor (101), and reflects light from the current sensor (101). The signal processing unit (133) that detects the primary side current (ir, is, it) by receiving the current sensor (101) and the optical fiber (102) that connects the current sensor (101) and the signal processing unit (133). Have more.
This makes it possible to measure the primary side current (ir, is, it) with high accuracy.

Further, when the control unit (200) exists in the ratio between the amplitude values of the primary side currents (ir, is, it) of each phase, which is equal to or higher than the predetermined phase current deviation detection rate (S2 =). 1) Or, when the phase difference between the primary side currents (ir, is, it) of each phase is out of the predetermined range (120 ° ± α) (S8 = 1), an open failure has occurred. A determination signal (Sj = 1) indicating the above is output.
Thereby, the electric circuit failure can be detected more accurately based on the amplitude value and the phase of the primary side current (ir, is, it).

Further, the control unit (200) is equal to or higher than a predetermined phase voltage deviation detection rate among the ratios of the amplitude values of the respective phases in the secondary voltage (vu, vv, vw) of the transformer (156). If an object exists (S10 = 1), a determination signal (Sj = 1) indicating that an open failure has occurred is output.
As a result, the electric circuit failure can be detected more accurately based on the amplitude value of the secondary voltage.

Further, in the control unit (200), the ratio of the past value and the current value of the voltage in the secondary side voltage (vu, vv, vw) of the transformer (156) is equal to or less than the predetermined undervoltage detection rate ( In the case of S12 = 1), a determination signal (Sj = 1) indicating that an open failure has occurred is output.
Thereby, the electric circuit failure can be detected more accurately based on the voltage of the primary side voltage or the secondary side voltage.

Further, in the control unit (200), the phase difference between the primary side currents (ir, is, it) of each phase is out of a predetermined range (120 ° ± α) (S8 = 1), and the transformer is transformed. The ratios of the amplitude values of the line currents (ir-is, ir-it, is-it) on the primary side of the device (156) are all equal to or higher than the predetermined line current deviation detection rate (S4 = 1). And, when all the amplitude values of the primary side currents (ir, is, it) are less than the predetermined primary side current detection threshold (S6 = 1), or when the primary side currents (ir, is, it) of each phase are present. ) Are outside the predetermined range (120 ° ± α) (S8 = 1), and all the amplitude values of the primary side currents (ir, is, it) are on the predetermined primary side. When the current detection threshold value is equal to or higher than the current detection threshold value (S6 = 0), a determination signal (Sj = 1) indicating that an open failure has occurred is output.
Thereby, the electric circuit failure can be detected more accurately based on the phase of the primary side current, the amplitude value of the line current, and the amplitude value of the primary side current.

<Modification example>
The present invention is not limited to the above-described embodiment, and various modifications are possible. The above-described embodiments are exemplified for the purpose of explaining the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Further, another configuration may be added to the configuration of the above embodiment, and a part of the configuration may be replaced with another configuration. In addition, the control lines and information lines shown in the figure show what is considered necessary for explanation, and do not necessarily show all the control lines and information lines necessary for the product. In practice, it can be considered that almost all configurations are interconnected. Possible modifications to the above embodiment are, for example, as follows.

In the above embodiment, the control unit 200 is configured by a relay circuit or the like, but the control unit 200 is a general computer such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). Those with hardware may be applied.

101 Winding type optical fiber current sensor (current sensor)
102 Optical fiber 133 Signal processing unit 150 Power system (power source)
154 Electric circuit 156 Transformer 156a Primary winding 156b Secondary winding 160 Load device 200 Control unit A Electric circuit failure detection device ir, is, it Primary side current vr, vs, vt Primary side voltage vu, vv, vw Secondary side voltage

Claims (5)

A current sensor that measures the primary current flowing through the primary winding of a three-phase transformer and the electric circuit connected to the power source.
A voltage sensor that measures the secondary voltage of the transformer,
It has a control unit that determines the presence or absence of an open failure in the electric circuit based on the phase relationship of the primary side current and the secondary side voltage, and outputs the determination result .
The control unit indicates that the open failure has occurred if there is a ratio between the amplitude values of the respective phases in the secondary voltage of the transformer that is equal to or higher than the predetermined phase voltage deviation detection rate. An electric circuit failure detection device characterized by outputting the determination signal shown. The current sensor is a winding type optical fiber current sensor having a function of reflecting incident light.
A signal processing unit that outputs light to the current sensor and detects the primary side current by receiving the light reflected from the current sensor.
An optical fiber that connects the current sensor and the signal processing unit,
The electric circuit failure detection device according to claim 1, further comprising. When the control unit has a ratio between the amplitude values of the primary currents of each phase that is equal to or higher than a predetermined phase current deviation detection rate, or between the primary currents of each phase. The electric current failure detection device according to claim 1, wherein when the phase difference between the two is out of a predetermined range, a determination signal indicating that the open failure has occurred is output. The control unit is a determination signal indicating that the open failure has occurred when the ratio of the past value and the current value of the voltage at the secondary side voltage of the transformer is equal to or less than a predetermined undervoltage detection rate. The electric circuit failure detection device according to claim 1, further comprising outputting. A current sensor that measures the primary current flowing through the primary winding of a three-phase transformer and the electric circuit connected to the power source.
A voltage sensor that measures the secondary voltage of the transformer,
It has a control unit that determines the presence or absence of an open failure in the electric circuit based on the phase relationship of the primary side current and the secondary side voltage, and outputs the determination result.
In the control unit, even when the phase difference between the primary side currents of each phase is out of a predetermined range, the ratio of the amplitude values of the line currents on the primary side of the transformer is increased. When the line current deviation detection rate is less than the predetermined line current deviation detection rate and all the amplitude values of the primary side current are less than the predetermined primary side current detection threshold value, a determination signal indicating that the open failure has occurred is output. An electric current failure detection device characterized by not outputting.

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