JP2015118001A - Current detection circuit and current detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detection device capable of outputting an output voltage of a level corresponding to a level of current flowing through each of first through third power feeder lines.SOLUTION: A current detection device includes first through third output circuits 61, 62, 63, each of which uses a second current generated by respective one of first through third current transformers CT1, CT2, CT3 in response to a first current fed to respective one of first through third three-phase power feeder lines L1, L2, L3 to output an output voltage of a level corresponding to the first current flowing through the respective one of the first through third power feeder lines. Each of the first through third output circuits includes: rectifier circuits D1, D2 for rectifying the second current; capacitors C1, C2 which are charged by the second current rectified by the rectifier circuits; and a first resistor R20 for generating, from voltage across the capacitors, an output voltage that falls within an input voltage range of an analog-to-digital converter for obtaining the level of the first current flowing through respective one of the first through third power feeder lines.

Description

  The present invention relates to a current detection circuit and a current detection device.

  For example, an output circuit that outputs a voltage having a value corresponding to a current value supplied to a transmission line is known (for example, Patent Document 1).

JP 2011-30301 A

  The output circuit of Patent Literature 1 outputs a voltage having a value corresponding to the current value of the one-phase transmission line in the three-phase transmission line. For this reason, it may be difficult to detect the current value of each of the three-phase transmission lines based on the voltage output from the output circuit.

  The main present invention for solving the above-described problems is the first to third current transformers in which the second current is generated in response to the first current supplied to each of the three-phase first to third transmission lines. First to third output circuits, each of which outputs an output voltage having a value corresponding to the value of the first current of the first to third transmission lines based on a second current, and the first to third Each of the output circuits includes a rectifier circuit that rectifies the second current, a capacitor that is charged based on the second current rectified by the rectifier circuit, and the first current of each of the first to third transmission lines. A first resistor for outputting the output voltage within an input voltage range in an analog-to-digital converter for obtaining the value of the value based on a voltage across the capacitor; is there.

  Other features of the present invention will become apparent from the accompanying drawings and the description of this specification.

  According to the present invention, it is possible to output an output voltage having a value corresponding to the current value of each of the first to third transmission lines.

It is a figure which shows the power transmission system in 1st Embodiment of this invention. It is a figure which shows the output circuit in 1st Embodiment of this invention. It is a figure for demonstrating the 1st time constant when a capacitor is charged. It is a figure for demonstrating the 2nd time constant when a capacitor is discharged. It is a figure which shows the electric current of the power transmission line in 1st Embodiment of this invention, and the voltage output from an output circuit. It is a figure for demonstrating the detection error by the output circuit in 1st Embodiment of this invention. It is a figure which shows the electric current of the power transmission line when the direct-current component is superimposed at the time of the accident in 1st Embodiment of this invention, and the voltage output from an output circuit. It is a figure which shows the power transmission system in 2nd Embodiment of this invention. It is a figure which shows the output circuit in 2nd Embodiment of this invention.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings.

[First embodiment]
=== Power transmission system ===
Hereinafter, the power transmission system in the present embodiment will be described with reference to FIG. FIG. 1 is a diagram showing a power transmission system in the present embodiment.

  The power transmission system 100 includes a power transmission line L100, circuit breakers B1, B2, B3, current transformers CT1, CT2, CT3, auxiliary current transformer ST1 (first current transformer), auxiliary current transformer ST2 (second current transformer). ), Auxiliary current transformer ST3 (third current transformer), relay device 101, and cumulative interruption amount counter 6 (current detection device). Note that the cumulative cutoff amount counter 6 and the auxiliary current transformers ST1, ST2, and ST3 may correspond to a current detection device.

  The power transmission line L100 is a three-phase power transmission line, and has power transmission lines L1, L2, and L3 as power transmission lines for each phase. The power transmission lines L1 to L3 are provided with circuit breakers B1 to B3, respectively.

  The circuit breakers B1 to B3 block the positions where the circuit breakers B1 to B3 are provided in the power transmission lines L1 to L3 when the circuit breaker signal S1 is received. The circuit breakers B1 to B3 connect the positions where the circuit breakers B1 to B3 are provided in the power transmission lines L1 to L3 when a connection signal (not shown) is received.

  The current transformers CT1 to CT3 are provided in the transmission lines L1 to L3, respectively, and currents corresponding to the currents supplied to the transmission lines L1 to L3 are generated. Current transformers CT1, CT2, and CT3 are connected to relay device 101 via conductive lines L11, L12, and L13, respectively. The current generated by the current transformers CT1 to CT3 is supplied to the relay device 101.

  The relay device 101 detects a short circuit accident, a ground fault (also referred to as a “transmission line accident”), or the like of the transmission lines L1 to L3 based on the current supplied from the current transformers CT1 to CT3. When the relay device 101 detects a power transmission line accident, the relay device 101 outputs a cut-off signal S1. The interruption signal S1 is supplied to the circuit breakers B1 to B3 and the cumulative interruption amount counter 6. When the relay device 101 does not detect a power transmission line accident, the relay device 101 does not output the cutoff signal S1.

  The auxiliary current transformers ST1 to ST3 are provided on the conductive lines L11 to L13, respectively, and an alternating current corresponding to the current supplied from the current transformers CT1 to CT3 to the relay device 101 is generated. That is, the auxiliary current transformers ST1 to ST3 generate an alternating current (second current) according to the alternating current (first current) supplied to the transmission lines L1 to L3, respectively.

  The cumulative cutoff amount counter 6 is a device that calculates the cumulative cutoff amount based on the current generated by the auxiliary current transformers ST1 to ST3 and the cutoff signal S1. Note that the cumulative breaking amount is an index used as a guideline for checking the wear of the contacts of the breakers B1 to B3 due to the breaking of the breakers B1 to B3. The cumulative interruption amount is calculated based on the number of interruptions of the circuit breakers B1 to B3 and the magnitude of the accident current interrupted in the circuit breakers B1 to B3. The magnitude of the interrupted fault current indicates a value corresponding to the peak-to-peak value of the current of the transmission lines L1 to L3 when the transmission lines L1 to L3 are cut off after the transmission line accident occurs. Suppose that

=== Cumulative cutoff amount counter ===
Hereinafter, the cumulative cutoff amount counter in the present embodiment will be described with reference to FIG.

  The cumulative cutoff amount counter 6 has first input terminals T1, T2, second input terminals T3, T4, third input terminals T5, T6, a fourth input terminal T7, and an output terminal T8.

  Both ends of the auxiliary current transformer ST1 are connected to the first input terminals T1 and T2. Both ends of the auxiliary current transformer ST2 are connected to the second input terminals T3 and T4. Both ends of the auxiliary current transformer ST3 are connected to the third input terminals T5 and T6. The cutoff signal S1 is input to the fourth input terminal T7. The output terminal T8 is a terminal for outputting information about the cumulative cutoff amount.

  The cumulative cutoff amount counter 6 further includes a first output circuit 61, a second output circuit 62, a third output circuit 63, a processing device 71, an input device 72, an output device 73, a display device 74, a timing device 75, and a storage device 76. Have The first output circuit 61, the second output circuit 62, and the third output circuit 63 correspond to a current detection circuit.

  The first output circuit 61, the second output circuit 62, and the third output circuit 63 are respectively input with alternating current from the auxiliary current transformers ST1, ST2, and ST3, and have values corresponding to the peak-to-peak values of the alternating current. This circuit outputs a DC voltage.

  The processing device 71 is, for example, a CPU (Central Processing Unit) that calculates a cumulative cutoff amount and controls the cumulative cutoff amount counter 6 by executing a program stored in the storage device 76.

  The input device 72 is, for example, an operation switch for inputting a control command to the processing device 71. The output device 73 is a device that outputs information indicating the cumulative cutoff amount calculated by the processing device 71. The display device 74 is, for example, a light-emitting diode for displaying the status of the cumulative cutoff amount counter 6. The time measuring device 75 is, for example, a real time clock.

=== Output circuit ===
Hereinafter, the output circuit in the present embodiment will be described with reference to FIG. FIG. 2 is a diagram showing an output circuit in the present embodiment. Since the configuration of the first output circuit 61 is the same as the configuration of the second output circuit 62 and the configuration of the third output circuit 63, a circuit diagram of the first output circuit 61 is shown for convenience of explanation. The circuit diagram of the second output circuit 62 and the circuit diagram of the third output circuit 63 are omitted.

  The first output circuit 61 is a circuit that receives an alternating current from the auxiliary current transformer ST1 and outputs a direct current voltage having a value corresponding to the peak-to-peak value of the alternating current from the output terminals T11 and T12. The DC voltage output from the output terminals T11 and T12 is supplied to an analog / digital conversion device (not shown) of the processing device 71. This analog-to-digital conversion device is a device for obtaining the current value of each of the transmission lines L1 to L3. The first output circuit 61 includes a resistor R0, a first series connection resistor R10 (second resistor), diodes D1 and D2 (rectifier circuit), capacitors C1 and C2, a second series connection resistor R20 (third resistor), a third resistor A series connection resistor R30 (first resistor, third resistor), a series connection body R40 (filter circuit), and diodes D3 and D4 are included.

<Each element>
The resistor R0 is a fixed resistor for converting an alternating current input to the first input terminals T1 and T2 into an alternating voltage. The resistor R0 functions as an input impedance of the first output circuit 61, for example.

  The first series connection resistor R10 is a resistor for adjusting (setting) the first time constant as the time constant of the voltages at both ends P1 and P2 of the capacitors C1 and C2 when the capacitors C1 and C2 are charged. The first series connection resistor R10 includes a resistor R1 as a fixed resistor and a resistor R2 as a variable resistor.

  The diodes D1 and D2 are a pair of diodes that convert an alternating current input to the first input terminals T1 and T2 into a direct current. For example, the diodes D1 and D2 may be Schottky barrier type diodes.

  The capacitors C1 and C2 are a pair of capacitors that are charged based on the alternating current input to the first input terminals T1 and T2. A voltage having a value corresponding to the value of the alternating current input to the first input terminals T1 and T2 is generated at both ends P1 and P2 of the capacitors C1 and C2. That is, a voltage having a value corresponding to the value of the alternating current supplied to the power transmission line L1 is generated at both ends P1 and P2 of the capacitors C1 and C2. For example, each of the capacitors C1 and C2 may be formed by connecting a plurality of capacitors such as four capacitors.

  The second series connection resistor R20 and the third series connection resistor R30 are resistors for discharging the capacitors C1 and C2. The second series connection resistor R20 and the third series connection resistor R30 adjust (set) the second time constant as the time constant of the voltages at both ends P1, P2 of the capacitors C1, C2 when the capacitors C1, C2 are discharged. It also functions as a resistor for The third series connection resistor R30 also functions as a gain adjustment resistor for adjusting the level of the DC voltage generated between the output terminals T11 and T12. The second series connection resistor R20 has a resistor R3 as a variable resistor and a resistor R4 as a fixed resistor. The third series connection resistor R30 includes resistors R5 and R7 as fixed resistors and a resistor R6 as a variable resistor. The resistance values of the resistors R5, R6, and R7 are set so that the level of the DC voltage generated between the output terminals T11 and T12 is within the input voltage range in the analog-digital conversion device of the processing device 71. The input voltage range is a voltage range determined in advance based on the specifications of the analog-digital converter. The resistor R6 is a tapped resistor to which one end of the resistor R8 is connected.

  The serial connection R40 smoothes the DC voltage generated between the output terminals T11 and T12. That is, the series connection body R40 functions as a low-pass filter for preventing noise from being superimposed on the DC voltage generated between the output terminals T11 and T12. The series connection R40 includes a resistor R8 as a fixed resistor and a capacitor C3.

  The diodes D3 and D4 are a pair of protective diodes for preventing an overvoltage from occurring between the output terminals T11 and T12. The overvoltage indicates, for example, a voltage that is higher than the power supply voltage VCC and may damage the processing device 71 when applied to the processing device 71.

<Connection of each element>
Both ends of the resistor R0 are connected to the first input terminals T1 and T2. One end of the first series connection resistor R10 is commonly connected to one end of the resistor R0 and the first input terminal T1. The other end of the first series connection resistor R10 is connected in common with the anode of the diode D1 and the cathode of the diode D2. That is, the first direct contact resistor R10 is connected in series with the capacitor C1 through the diode D1, and is connected in series with the capacitor C2 through the diode D2. The diodes D1 and D2 are connected in series between the conductive lines 103 and 102 so that the direction from the conductive line 103 to the conductive line 102 is the forward direction. The capacitors C1 and C2 are connected in series between the conductive lines 102 and 103. The second series connection resistor R20 and the third series connection resistor R30 are connected between the conductive lines 102 and 103, respectively. That is, the second series connection resistor R20 and the third series connection resistor R30 are connected in parallel to the capacitors C1 and C2. One end of the resistor R8 is connected to the variable tap of the resistor R6 as described above. The other end of the resistor R8 is commonly connected to one end of the capacitor C3, the cathode of the diode D4, the anode of the diode D3, and the output terminal T11. The other end of the capacitor C3 is connected to the conductive line 103. Note that one end of the conductive wire 103 is connected to the output terminal T12. The anode of the diode D4 is connected to the conductive line 103. A power supply voltage VCC is applied to the cathode of the diode D3. The power supply voltage VCC is, for example, a voltage for operating the cumulative cutoff amount counter 6.

<Operation>
= Capacitor charging =
When the potential of the first input terminal T1 is higher than the potential of the first input terminal T2, a current (also referred to as “first input current”) flows from the first input terminal T1. The first input current is supplied in the order of the first series connection resistor R10, the connection point P0, the diode D1, the connection point P1, the capacitor C1, the connection point P3, and the first input terminal T2. At this time, the capacitor C1 is charged by the first input current. A voltage is generated at both ends of the capacitor C1 such that one end on the connection point P1 side has a higher level than the other end on the connection point P3 side.

  When the potential of the first input terminal T1 is lower than the potential of the first input terminal T2, a current (also referred to as “second input current”) flows from the first input terminal T2. The second input current is supplied in the order of the connection point P3, the capacitor C2, the connection point P2, the diode D2, the connection point P0, the first series connection resistor R10, and the first input terminal T1. At this time, the capacitor C2 is charged by the second input current. A voltage is generated at both ends of the capacitor C2 such that one end on the connection point P3 side has a higher level than the other end on the connection point P2 side.

  Therefore, when the capacitors C1 and C2 are charged, the voltages at both ends P1 and P2 of the capacitors C1 and C2 increase. And the voltage of the value according to the value of the voltage of both ends P1 and P2 of the capacitors C1 and C2 is generated between the output terminals T11 and T12. That is, between the output terminals T11 and T12, a direct current having a value corresponding to the peak-to-peak value of the alternating current supplied to the transmission line L1 (difference between the maximum value and the minimum value of the current value of the transmission line L1). A voltage will be generated.

= Capacitor discharge =
The capacitors C1 and C2 are discharged through the second series connection resistor R20 and the third series connection resistor R30. When the capacitors C1 and C2 are discharged, the voltages at both ends P1 and P2 of the capacitors C1 and C2 decrease. By adjusting the first time constant and the second time constant described above, a DC voltage having a value corresponding to the peak-to-peak value of the AC current supplied to the transmission line L1 is generated between the output terminals T11 and T12. It is possible to continue.

  Since a fixed resistor is used as the resistor R0, a compact resistor R0 as a component of the cumulative cutoff amount counter 6 can be obtained relatively easily and at a relatively low price. In addition, since a relatively small value of current is supplied to the third series connection resistor R30, the resistors R5, R6, and R7 as components of the cumulative cutoff amount counter 6 are relatively easy and relatively inexpensive. It becomes possible to obtain at. Therefore, the compact cumulative cutoff amount counter 6 can be provided relatively easily at a relatively low cost. In addition, since a variable resistor is used as the resistor R2, the first time constant can be finely adjusted. In addition, since variable resistors are used as the resistors R3 and R6, the second time constant can be finely adjusted.

  Note that the configurations of the second output circuit 62 and the third output circuit 63 are the same as the configuration of the first output circuit 61, and thus detailed description thereof will be omitted. The second output circuit 62 outputs a DC voltage having a value corresponding to the peak-to-peak value of the AC current supplied to the power transmission line L2 to an analog-digital conversion device (not shown) of the processing device 71. The third output circuit 63 outputs a DC voltage having a value corresponding to the peak-to-peak value of the AC current supplied to the power transmission line L3 to an analog / digital conversion device (not shown) of the processing device 71.

=== First and second time constants ===
Hereinafter, the first and second time constants in the present embodiment will be described with reference to FIGS. FIG. 3 is a diagram for explaining the first time constant when the capacitor is charged. FIG. 4 is a diagram for explaining the second time constant when the capacitor is discharged. Fig.5 (a) is a figure which shows the electric current of the power transmission line in this embodiment. FIG. 5B is a diagram illustrating a voltage output from the output circuit in the present embodiment. FIG. 6 is a diagram for explaining a detection error by the output circuit in the present embodiment. Fig.7 (a) is a figure which shows the electric current of the power transmission line when a direct-current component is superimposed at the time of the accident in this embodiment. FIG. 7B is a diagram illustrating a voltage output from the output circuit when a DC component is superimposed at the time of an accident in the present embodiment.

  For convenience of explanation, it is assumed that a power transmission line accident has occurred in the power transmission line L1. The current of the power transmission line in FIGS. 5A and 7A indicates the value of the current of the power transmission line L1. The voltage when the output circuit in FIGS. 5B, 6 and 7B is not applied is a predetermined resistance without connecting the first output circuit 61 to the input terminals T1 and T2. It is assumed that the voltage value generated at both ends of the resistor when a value resistor (not shown) is connected is shown.

  In FIGS. 5 to 7, time t1 indicates the time when a power transmission line accident occurs, and time t2 indicates the time after the cutoff time has elapsed from time t1.

<Capacitor charging / discharging and time constant>
When the capacitor C is charged (FIG. 3), as the time constant increases, the rising speed (rising speed) of the voltage V1 across the capacitor C decreases. In addition, when the capacitor C is discharged (FIG. 4), the rate of decrease (speed of falling) of the voltage V1 across the capacitor C becomes slower as the time constant increases.

<Time constant setting>
The first and second time constants are set based on a cutoff time corresponding to a time from time t1 (FIG. 5) at which a transmission line accident occurs to time t2 when the transmission line L1 is cut off by the circuit breaker B1. Is done. The interruption time is the total time of the relay operation time and the breaker interruption time. The relay operation time is the time from when the relay device 101 detects a power transmission line accident to when the cutoff signal S1 is output. The breaker breaking time is the time from when the breaker B1 receives the breaking signal S1 to when the power transmission line L1 is broken. The interruption time is determined based on the specifications of the relay device 101 and the circuit breaker B1.

  The first and second time constants are set to values such that the DC voltage between the output terminals T11 and T12 of the first output circuit 61 saturates from when the transmission line accident occurs until when the interruption time elapses. Is set. That is, in the first and second time constants, the value of the DC voltage between the output terminals T11 and T12 is a value corresponding to the difference (peak-to-peak value) between the maximum value and the minimum value of the current of the transmission line L1. Is set as follows. When the DC voltage between the output terminals T11 and T12 is saturated, when the value of the current supplied to the transmission line L1 (for example, the peak-to-peak value) is substantially the same, the output voltage between the output terminals T11 and T12 is increased over time. It shows that the value of the DC voltage does not change substantially. The fact that the value of the DC voltage between the output terminals T11 and T12 does not substantially change indicates that the fluctuation range of the voltage value is within approximately 10% in a predetermined time such as a plurality of periods, for example. By setting the first and second time constants, the peak-to-peak value of the current of the transmission line L1 when the transmission line L1 is interrupted is detected instead of the peak-to-peak value of the current of the transmission line L1 when the transmission line accident occurs. It becomes possible.

  Further, the second time constant is determined after a voltage of a value corresponding to the value of the DC voltage between the output terminals T11 and T12 in a saturated state has elapsed after 16.7 ms corresponding to one cycle of the current of the transmission line L1. For example, it is set to a value that decreases by about 10% or less.

  Note that the setting of the time constants of the second output circuit 62 and the third output circuit 63 is the same as the setting of the time constant of the first output circuit 61, and therefore the description thereof is omitted.

<Example of time constant setting>
= Time constant setting =
The first and second time constants are set to values at which the voltage saturates when, for example, 65 ms has elapsed as a shutoff time from the time of the accident. Further, the second time constant is set to a value that results in a voltage drop of 10% 17 ms after voltage saturation. These settings result in an average error of 95% (minimum 90%) (FIG. 6).

= Ground for 65ms =
The main target circuit breaker on which the cumulative interruption amount counter 6 is installed is 120 kV or less, and the relay operation time is 15 ms according to the JEC (Japanese Electrotechnical Committee) standard (JEC2300-P35). The circuit breaker breaking time is 3 cycles. Therefore, the target circuit breaker is cut off when 65 ms (≈15 ms + 16.7 ms × 3 cycles) has elapsed since the occurrence of the accident.

  For example, a 5-cycle circuit breaker of 66 kV or less has a relay operation time of 30 ms, which is about 113 ms (≈30 ms + 16.7 ms × 5 cycles), and the output voltage is sufficiently saturated even when used with the same time constant. There is no problem.

  Note that a 2-cycle circuit breaker of 240 kV or higher is slightly shortened to 48 ms (≈15 ms + 16.7 ms × 2 cycles), but the same system or higher is an effective grounding system, and the system time constant is small and the DC component is relatively small. Therefore, there are few cases that cause problems. The voltage may be saturated at about 50 ms.

  Since the first and second time constants are set based on the cutoff time, the peak-to-peak of the alternating current supplied to the transmission line L1 is also obtained when the DC component is superimposed when an accident occurs (FIG. 7). A DC voltage having a value corresponding to the value is generated between the output terminals T11 and T12.

  The setting of the first and second time constants in each of the second output circuit 62 and the third output circuit 63 is the same as the setting of the first and second time constants of the first output circuit 61. Is omitted.

=== Operation of cumulative cutoff amount counter ===
Hereinafter, with reference to FIGS. 1 and 5, the operation of the cumulative cutoff amount counter in the present embodiment will be described.

  When a power transmission line accident occurs (time t1), the relay device 101 detects the occurrence of the accident and outputs a cutoff signal S1. The interruption signal S1 is input to the circuit breakers B1 to B3 and the fourth input terminal T7 of the cumulative interruption amount counter 6. The cumulative cutoff amount counter 6 AD-converts a DC voltage supplied from each of the first output circuit 61, the second output circuit 62, and the third output circuit 63 to the analog-digital converter (described above) using the cutoff signal S1 as a trigger. . The cumulative cutoff amount counter 6 includes a DC voltage output from the first output circuit 61 (also referred to as “first DC voltage”) and a DC voltage output from the second output circuit 62 after the cutoff time has elapsed from time t1. (Also referred to as “second DC voltage”) and DC voltage (also referred to as “third DC voltage”) output from the third output circuit 63 are AD-converted to obtain values of the first to third DC voltages. .

  The cumulative cutoff amount counter 6 calculates the peak-to-peak values of the currents of the transmission lines L1 to L3 as the cutoff currents of the circuit breakers B1 to B3 based on the values of the first to third DC voltages, respectively, The cumulative cutoff amount of each of the devices B1 to B3 is calculated. That is, the cumulative cutoff amount counter 6 detects the currents of the transmission lines L1 to L3 as cutoff currents, and calculates the cumulative cutoff amount based on the detection result. At this time, the first output circuit 61 and the second output circuit 62 function as current detection circuits for the third output circuit 63 to detect the currents of the transmission lines L1 to L3 as the cutoff currents. For example, the cumulative cutoff amount counter 6 uses the cumulative values of the first to third DC voltages each time a power transmission line accident occurs as the cumulative cutoff amount. Therefore, the cumulative interruption amount counter 6 can obtain the cumulative interruption amount for each of the circuit breakers B1 to B3.

  As described above, the first output circuit 61, the second output circuit 62, and the third output circuit 63 function as a current detection circuit for detecting the currents of the transmission lines L1 to L3 as the cutoff currents. The first output circuit 61 is based on the current in the auxiliary current transformer ST1 that generates current according to the current supplied to the power transmission line L1, and has a DC voltage (output corresponding to the current value of the power transmission line L1). Voltage) is output from the output terminals T11 and T12. The first output circuit 61 includes diodes D1 and D2, capacitors C1 and C2, and a third series connection resistor R30. The diodes D1 and D2 rectify the current in the auxiliary current transformer ST1. The capacitors C1 and C2 are charged based on the current rectified by the diodes D1 and D2. The third series connection resistor R30 outputs a voltage within the input voltage range in the analog-to-digital converter for obtaining the value of the current of the transmission line L1, based on the voltage between both ends P1, P2 of the capacitors C1, C2. For resistance. The configurations of the second output circuit 62 and the third output circuit 63 are the same as the configuration of the first output circuit 61. Accordingly, the first output circuit 61, the second output circuit 62, and the third output circuit 63 can output output voltages having values corresponding to the current values of the power transmission lines L1, L2, and L3. Therefore, based on the output voltages output from the first output circuit 61, the second output circuit 62, and the third output circuit 63, it is possible to detect the current values of the power transmission lines L1, L2, and L3.

  The first output circuit 61 has a first series connection resistor R10 for setting a first time constant when the capacitors C1 and C2 are charged. Each of the second output circuit 62 and the third output circuit 63 also has a first series connection resistor having a configuration similar to that of the first series connection resistor R10. Therefore, it is possible to set the response speed of the output voltage of the first output circuit 61 with respect to the fluctuation of the current of the transmission line L1. Therefore, for example, the output voltage is prevented from fluctuating relatively abruptly based on a relatively abrupt fluctuation in the current of the transmission line L1 immediately after the time when the transmission line accident occurs (time t1 in FIG. 7). be able to. Therefore, the current detection accuracy in each of the power transmission lines L1, L2, and L3 can be improved.

  The first output circuit 61 has a second series connection resistor R20 for setting a second time constant when the capacitors C1 and C2 are discharged. Each of the second output circuit 62 and the third output circuit 63 also has a second series connection resistor having a configuration similar to that of the second series connection resistor R20. Therefore, it is possible to set the response speed of the output voltage of the first output circuit 61 with respect to the fluctuation of the current of the transmission line L1. Therefore, the current detection accuracy in each of the power transmission lines L1, L2, and L3 can be improved.

  Further, the first and second time constants of the first output circuit 61 are such that the value of the DC voltage output from the output terminals T11 and T12 is a value corresponding to the difference between the maximum value and the minimum value of the current of the transmission line L1. Is set as follows. The first and second time constants of the second output circuit 62 and the third output circuit 63 are set in the same manner as the first and second time constants of the first output circuit 61. Therefore, based on the output voltage of the first output circuit 61, it is possible to detect a value corresponding to the peak-to-peak value in the currents of the transmission lines L1, L2, and L3.

  The first output circuit 61 has a series connection R40 for smoothing the DC voltage output from the output terminals T11 and T12. Each of the second output circuit 62 and the third output circuit 63 also has a series connection body having the same configuration as the series connection body R40. Therefore, for example, high frequency noise can be prevented from being superimposed on the output voltage.

  The cumulative cutoff amount counter 6 includes a first output circuit 61, a second output circuit 62, a third output circuit 63, and an analog / digital converter. Accordingly, the current values of the transmission lines L1 to L3 can be obtained based on the output voltages of the first output circuit 61, the second output circuit 62, and the third output circuit 63, respectively. Since a DC voltage is output as an output voltage from each of the first output circuit 61, the second output circuit 62, and the third output circuit 63, the cumulative cutoff amount counter 6 is connected to the transmission lines L1 to L3 as cutoff currents. It is possible to reliably determine the current value. Therefore, when obtaining the cut-off current, for example, a relatively expensive oscilloscope (not shown) having a relatively high sampling frequency for measuring the alternating currents of the transmission lines L1 to L3 is not necessary. For this reason, the cost for calculating | requiring the interruption | blocking current of power transmission line L1 thru | or L3 can be reduced. Further, the cumulative interruption amount counter 6 can directly obtain the interruption current. Therefore, for example, current information indicating the current values of the power transmission lines L1 to L3 is stored in the storage device, and calculation work for calculating the cutoff current based on the current information stored in the storage device is not necessary. Therefore, the interruption current can be obtained relatively easily using the cumulative interruption amount counter 6.

[Second Embodiment]
In the cumulative cutoff amount counter 6B in the second embodiment, the first output circuit 61, the second output circuit 62, and the third output circuit 63 in the first embodiment are changed to the output circuit 61B, and the processing device 71 is changed to the processing device 71B. It has been changed. The configuration of the cumulative cutoff amount counter 6B other than the output circuit 61B and the processing device 71B is the same as the configuration of the cumulative cutoff amount counter 6.

=== Power transmission system, cumulative cutoff amount counter ===
Hereinafter, the power transmission system and the cumulative cutoff amount counter in the present embodiment will be described with reference to FIGS. 8 and 9. FIG. 8 is a diagram showing a power transmission system in the present embodiment. In addition, the same code | symbol is attached | subjected to the structure similar to the structure of FIG. 1, and the description is abbreviate | omitted. FIG. 9 is a diagram showing an output circuit in the present embodiment. The same reference numerals are given to the same components as those in FIG. 2, and the description thereof will be omitted.

  The power transmission system 100B includes a cumulative cutoff amount counter 6B. The cumulative cutoff amount counter 6B includes an output circuit 61B and a processing device 71B. The processing device 71B calculates a cumulative cutoff amount or performs overall control of the cumulative cutoff amount counter 6B. The output circuit 61B outputs a DC voltage having a value corresponding to the maximum peak-to-peak value among the peak-to-peak values of the currents of the transmission lines L1 to L3.

  The output circuit 61B (FIG. 9) includes a first circuit 201, a second circuit 202, a third circuit 203, diodes D7, D8, D9, and a series connection R40.

<Each element>
The configuration of the first circuit 201 is the same as the configuration of the first output circuit 61 (first embodiment) other than the serial connection R40 and the diodes D3 and D4. The configuration of the second circuit 202 and the configuration of the third circuit 203 are the same as the configuration of the first circuit 201. Note that one end of the conductive line 103B of the second circuit 202 and one end of the conductive line 103C of the third circuit 203 are connected to the conductive line 103A extending from the first circuit 201, respectively.

  The diode D7 is a diode for preventing the current supplied from the second circuit 202 and the third circuit 203 from flowing backward to the first circuit 201 side. The anode of the diode D7 is connected to the variable tap of the resistor R6 in the first circuit 201. The cathode of the diode D7 is connected to one end of the resistor R8. The diodes D8 and D9 are diodes having the same function as the diode D7. The anode of the diode D8 is connected to the variable tap of the resistor R6 in the second circuit 202. The anode of the diode D9 is connected to the variable tap of the resistor R6 in the third circuit 203. The cathodes of the diodes D8 and D9 are connected to one end of the resistor R8.

<Operation>
The capacitors C1 and C2 of the first circuit 201 are charged by the alternating current input to the first circuit 201. A voltage corresponding to the peak-to-peak value of the alternating current input to the first circuit 201 is generated between both ends P1 and P2 of the capacitors C1 and C2 of the first circuit 201. In addition, the capacitors C 1 and C 2 of the second circuit 202 are charged by an alternating current input to the second circuit 202. A voltage corresponding to the peak-to-peak value of the alternating current input to the second circuit 202 is generated between both ends P1 and P2 of the capacitors C1 and C2 of the second circuit 202. Further, the capacitors C1 and C2 of the third circuit 203 are charged by the alternating current input to the third circuit 203. A voltage corresponding to the peak-to-peak value of the alternating current input to the third circuit 203 is generated between both ends P1 and P2 of the capacitors C1 and C2 of the third circuit 203.

  Thereafter, a voltage generated between both ends P1 and P2 of the capacitors C1 and C2 of the first circuit 201, a voltage generated between both ends P1 and P2 of the capacitors C1 and C2 of the second circuit 202, A DC voltage having a value corresponding to the maximum voltage value among the voltages generated between both ends P1 and P2 of the capacitors C1 and C2 is generated between the output terminals T13 and T14.

  The cumulative cutoff amount counter 6B calculates the cumulative cutoff amount based on the value of the DC voltage generated between the output terminals T13 and T14.

  In the output circuit 61B, since the elements after the serial connection R40 are shared, the number of parts (number of elements) can be reduced by the number of shared elements. That is, the manufacturing cost of the cumulative cutoff amount counter 6B can be reduced, or a compact cumulative cutoff amount counter 6B can be provided.

  The first and second embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  In the first embodiment, the auxiliary current transformers ST1 to ST3 are directly connected to the cumulative cutoff amount counter 6, but the present invention is not limited to this. For example, the auxiliary current transformers ST1 to ST3 may be connected to the cumulative cutoff amount counter 6 via a full-wave rectifier circuit (not shown).

6, 6B Cumulative cutoff amount counter 61 First output circuit 62 Second output circuit 63 Third output circuit 71, 71B Processing device C1, C2 Capacitor D1, D2 Diodes L1, L2, L3, L100 Transmission line R20 Second series connection resistance R30 Third series connection resistor R40 Series connection body ST1, ST2, ST3 Auxiliary current transformer

Claims (7)

Based on the second currents in the first to third current transformers in which the second currents are generated in response to the first currents supplied to the three-phase first to third transmission lines, respectively, the first to third current transformers are used. First to third output circuits for outputting output voltages having values corresponding to the values of the first currents of the third transmission lines, respectively.
The first to third output circuits are respectively
A rectifier circuit for rectifying the second current;
A capacitor charged based on the second current rectified by the rectifier circuit;
A first output for outputting the output voltage within the input voltage range in the analog-to-digital converter for determining the value of the first current of each of the first to third transmission lines based on the voltage across the capacitor. A current detection circuit comprising: a resistor; The first to third output circuits are respectively
The current detection circuit according to claim 1, further comprising: a second resistor for setting a first time constant when the capacitor is charged. The first to third output circuits are respectively
The current detection circuit according to claim 2, further comprising a third resistor for setting a second time constant when the capacitor is discharged. The first and second time constants are set so that a value of the output voltage is a value corresponding to a difference between a maximum value of the first current and a minimum value of the first current. Item 4. The current detection circuit according to Item 3. The first to third output circuits are respectively
The current detection circuit according to claim 1, further comprising: a filter circuit for smoothing the output voltage. Based on the second currents in the first to third current transformers in which the second currents are generated in response to the first currents supplied to the three-phase first to third transmission lines, respectively, the first to third current transformers are used. First to third output circuits that each output an output voltage having a value corresponding to the value of the first current of the third power transmission line;
An analog-to-digital converter for obtaining the value of the first current of each of the first to third power transmission lines,
The first to third output circuits are respectively
A rectifier circuit for rectifying the second current;
A capacitor charged based on the second current rectified by the rectifier circuit;
A resistor for outputting the output voltage within the input voltage range in the analog-digital converter based on the voltage across the capacitor. First to third current transformers each generating a second current in response to a first current supplied to each of the three-phase first to third transmission lines;
First to third outputs for outputting output voltages having values corresponding to the values of the first currents of the first to third transmission lines based on the second currents of the first to third current transformers, respectively. Circuit,
An analog-to-digital converter for obtaining the value of the first current of each of the first to third power transmission lines,
The first to third output circuits are respectively
A rectifier circuit for rectifying the second current;
A capacitor charged based on the second current rectified by the rectifier circuit;
A resistor for outputting the output voltage within the input voltage range in the analog-digital converter based on the voltage across the capacitor.

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