JPH07244088A - Current detector - Google Patents

Abstract

PURPOSE:To provide a current detector which can easily transmit a detection signal of a main circuit current of a power circuit to a distant signal processor without using many wirings. CONSTITUTION:First and second main circuit current transformers CTu and CTv for respectively detecting main circuit currents of two or three phases are provided. The outputs of the transformers CTu and CTv are respectively rectified by first and second rectifiers 10u and 10v, then respectively divided by first and second voltage dividers 11u and 11v, outputs of which are combined via an OR circuit 12, and applied to a light emitting element LED. A peak value of the main circuit current is calculated according to a ripple included in an optical signal generated from the element LED and the peak value of the optical signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current detecting device suitable for detecting the current of a power circuit.

[0002]

2. Description of the Related Art In a power circuit, an abnormality determination, a life determination, etc. are performed by detecting a current flowing through the circuit and processing the detection signal. For example, in a gas-insulated switchgear, the breaking current is detected as a material for determining the life of the circuit breaker, the peak value of the breaking current is accumulated, and when the accumulated value reaches a predetermined value, maintenance inspection is performed. I try to exchange contacts and contacts.

A device used for this kind of purpose is composed of a current detection device for detecting a current flowing through a main circuit of a power circuit and a signal processing device for processing a detection signal obtained from the detection device. The current detection device of (1) was composed of a main circuit current transformer mounted in each phase circuit, and an insulated auxiliary current transformer (the primary coil and the secondary coil were insulated).

FIG. 10 shows the structure of a cumulative breaking current measuring device conventionally used for judging the life of a circuit breaker. In FIG. 10, 1u to 1w are gas insulated switchgear U, V, respectively. W3 phase main circuit conductor, CBu to CBw
Are circuit breakers inserted in the middle of the main circuit conductors 1u to 1w, respectively. CTu to CTw are main circuit conductors 1u, respectively
Main circuit current transformer that detects the main circuit current flowing through ~ 1w,
The outputs of these current transformers are the six wires Lu1, Lu2 to Lw1,
Power circuit through Lw2 (gas insulated switchgear in this example)
It is applied to the cumulative breaking current measuring device 2 provided at a place away from.

The cumulative breaking current detecting device 2 has a primary coil w1 and a secondary coil w2 which are insulated from each other.
Auxiliary current transformers CTu 'to CTw' with secondary and secondary insulation
Is provided, and the wiring Lu is provided between the input terminals of these auxiliary current transformers and the output terminals of the main circuit current transformers CTu to CTw.
1, Lu2 to Lw1 and Lw2 are connected. Outputs of the auxiliary current transformers CTu 'to CTw' are respectively amplifiers 2au to
It is input to the peak hold circuits 2bu to 2bw via 2aw, and the outputs of the peak hold circuits 2bu to 2bw are passed to the CPU 2d through the analog-digital converter (A / D converter) 2c.
Is given to. The CPU 2d is a central processing unit of the computer, which cumulatively calculates the output of the A / D converter 2c and stores the calculation result in the memory 2e.

In the cumulative breaking current measuring device shown in FIG. 10, the peak hold circuits 2bu to 2bw are supplied with breaker breaking commands and closing commands, and the breaking commands and current detection values when the closing commands are given. The peak value of is detected by the peak hold circuits 2bu to 2bw. The outputs of the peak value hold circuits 2bu to 2bw are converted into digital signals by the A / D converter and given to the CPU 2d. CPU2d
Accumulates the given peak values of the breaking current and the applied current and stores them in the memory 2e, determines whether or not the cumulative value has reached the judgment value, and when the cumulative value has reached the judgment value, It outputs a signal indicating that the contact of the breaker has reached the end of its life. The cumulative value calculated by the CPU may be transmitted to a control panel of a substation of a higher system as necessary.

In the example shown in FIG. 10, the main circuit current transformer CT
u to CTw and the auxiliary current transformers CTu 'to CTw' constitute a current detecting device, and the amplifiers 2au to 2aw and subsequent parts form a signal processing device (in the above example, the interrupting current value cumulative calculation and the life determining process are performed. Device) is configured. The auxiliary current transformers CTu ′ to CTw ′ are provided to insulate the main circuit side and the signal processing device side from each other and protect the measuring device from a ground fault accident, a short circuit accident, a surge caused by an inductive lightning, or the like. ing.

[0008]

In the conventional current detecting device, as shown in the above example, the main circuit current transformers CTu to Ctu.
Tw and auxiliary current transformers CTu 'to CTw', and since the main circuit current transformer and the auxiliary current transformer were provided at separate locations, a large number of wirings connecting the two current transformers Lu
1, Lu2 to Lw1, Lw2 had to be laid around for a long time, which was troublesome.

It is an object of the present invention to provide a current detecting device in which it is not necessary to extend the wiring connected to the output terminal of the main circuit current transformer for a long time.

[0010]

In the present invention, the main circuit current of the two phases of the three-phase power circuit (current to be detected)
And first and second main circuit current transformers for respectively detecting the current, and first and second rectifiers for full-wave rectifying the outputs of the first and second main circuit current transformers or outputs corresponding to the outputs, respectively. A circuit, first and second voltage dividing circuits for respectively dividing the outputs of the first and second rectifying circuits, and an OR circuit having inputs of the outputs of the first and second voltage dividing circuits, And a signal transmitting section for transmitting a signal corresponding to the output of the OR circuit.

In the present invention, "the output of the first and second main circuit current transformers or the output corresponding to the output" means that the outputs of the first and second main circuit current transformers are directly output. It may be supplied to the first and second rectifier circuits, and the outputs of the first and second main circuit current transformers may be supplied to the first and second rectifier circuits via other elements or circuits such as auxiliary current transformers. It means that it may be input to the rectifier circuit.

When the full-wave rectified waveform of the two-phase current of the three-phase AC current is input to the OR circuit, the output current of the OR circuit is the ripple component Δ produced when the two-phase full-wave rectified waveform is OR-added.
i will be included. This ripple component contains information about the main circuit current. That is, if the peak value of the output current of the OR circuit (corresponding to the peak value of the main circuit current) is i and the constant determined by the current waveform of each phase is K, then Δi = K
Since there is a relationship of × i, information of the peak value i of the output current of the OR circuit can be obtained by detecting the ripple component Δi. From the information of the output current of the OR circuit and the circuit constant of the voltage dividing circuit, Information on the main circuit current can be obtained. For example, if a sinusoidal three-phase symmetrical alternating current flows in three phases, the constant K becomes K = 1/2, and therefore the magnitude of the ripple Δi is the peak value i of the output current of the OR circuit. 1/2
Is equal to Therefore, by receiving the signal transmitted from the signal transmission unit through the signal transmission means and detecting the ripple component contained in the signal, it is possible to know the current information of each phase.

In the above construction, the main circuit currents of two of the three phases are detected, but the currents of the three phases are detected and the full-wave rectified outputs are combined through the OR circuit. Good. In this case, the first to third main circuit current transformers detecting the three-phase currents and the first to third full-wave rectification of the outputs of the first to third main circuit current transformers, respectively. Rectifying circuit, first to third voltage dividing circuits for dividing the outputs of the first to third full-wave rectifying circuits, respectively, and an OR circuit receiving the outputs of the first to third voltage dividing circuits as inputs. , A signal transmission unit for transmitting a signal corresponding to the output of the OR circuit, and signal transmission means for transmitting the output of the signal transmission unit. In this case, if the current waveforms of the three phases are symmetrical and the current waveform of each phase is a sine wave, the above constant K becomes approximately 0.134, and the magnitude of the ripple component Δi included in the output current of the OR circuit is large. Becomes approximately 0.134 times the peak value i of the output current of the voltage divider circuit of each phase.

The ripple component contained in the signal transmitted from the signal transmitting unit is easily detected by filtering the signal received from the signal transmitting unit through an appropriate signal transmission means and extracting only the AC component. can do.

The signal sending unit may send the output of the OR circuit in the form of an electric signal, but in order to facilitate the insulation between the power circuit and the signal processing unit, the output of the OR circuit is It is preferable that the light is transmitted in the form of an optical signal. In this case, the signal transmitting section is constituted by the light emitting element driven by the output of the OR circuit, and the signal transmitting means is constituted by the optical fiber for transmitting the light generated by the light emitting element. As the light emitting element, for example, a light emitting diode (LED)
Can be used. Also, an optical transformer using a Pockels element other than the light emitting element can be used.

The OR circuit is provided corresponding to each voltage dividing circuit, the anode is connected to the voltage dividing point of the corresponding voltage dividing circuit (the positive output terminal of the voltage dividing circuit), and the cathode is common. It can be composed of as many diodes (rectifying elements) as there are connected voltage dividing circuits. That is, in the case where the two-phase main circuit current is detected by the first and second main circuit current transformers, the anodes are respectively connected to the voltage dividing points of the first and second voltage dividing circuits. Also, an OR circuit can be configured by the first and second diodes whose cathodes are commonly connected. When the three-phase main circuit current is detected by the first to third main circuit current transformers, the anodes are connected to the voltage dividing points of the first to third voltage dividing circuits and the cathode is common. An OR circuit can be formed by the connected first to third diodes.

The common connection point of the cathodes of the diodes of the OR circuit is connected to the positive terminal of the light emitting element through the current limiting element. Here, the positive terminal of the light emitting element means
This is a terminal on the side to which a positive voltage is applied when the light emitting element emits light. When a light emitting diode is used as the light emitting element, the anode of the light emitting diode serves as a positive terminal.

In the signal sending section, the light emitting element has a constant value i.
It is preferable to provide a bias circuit in which a bias current in the forward direction of o (polarity for causing the light emitting element to emit light) is supplied.

The bias circuit can be composed of, for example, a bias current supply diode having a cathode coupled to the positive terminal of the light emitting element, and a power supply for supplying a bias current to the light emitting element through the bias current supply diode. .

On the output side of the optical fiber which constitutes the above-mentioned signal transmitting means, a light receiver for receiving an optical signal transmitted through the optical fiber and converting it into an electric signal, and an optical signal received by the light receiver are included. Ripple detection circuit for detecting ripple ΔP, ripple ΔP, and peak value Pm of optical signal
And a current value calculation means for calculating the peak value of the main circuit current using the bias current value io.

When a bias current io is passed through the light emitting element to constantly generate a constant light amount from the light emitting element, the peak value Pm of the optical signal output from the signal transmitting unit is the light emission amount Po due to the bias current io. Is added to the amount of light emission P corresponding to the peak value i of the current ior applied to the light emitting element from the OR circuit, and Pm = Po + P. I
Since there is a proportional relationship of / io = P / Po, the peak value i of the output current of the OR circuit is given by i = (P / Po) × io. Further, between the ripple component ΔP included in the optical signal output from the signal transmission unit and the light emission amount P corresponding to the peak value i of the current flowing through the light emitting element due to the output of the OR circuit, Δ
Since there is a relation of P = K × P (K is a constant), the peak value i of the current flowing through the light emitting element by the output of the voltage dividing circuit corresponding to the main circuit current is i = {ΔP / (KPm-ΔP)} × io
Given by. Therefore, the peak value i of the output current of the OR circuit can be known by detecting the peak value Pm and the ripple ΔP from the optical signal received through the optical fiber and the light receiver, and the peak value i can be determined. The peak value of the main circuit current can be obtained by correcting with the circuit constant of the voltage circuit.

As described above, the bias current i is applied to the light emitting element.
When o is flowed, the peak value i of the current corresponding to the main circuit current can be obtained from the received light amount with the emitted light amount Po due to the bias current as the reference light amount. In addition, in a region where the input current of the light emitting element is small, when the relationship between the input current and the light emission amount is non-linear, a bias current is passed through the light emitting element so that the relationship between the input current of the light emitting element and the output light amount is The linear region can be used for current detection to improve the detection accuracy.

Further, when the OR circuit is composed of a rectifying element, since the rectifying element has a threshold value with respect to the forward voltage, the OR circuit may generate an output when the level of the OR signal is low. Cannot be performed, and a dead zone occurs in a region where the OR signal is low. In order to prevent this, a bias current may be passed through the rectifying element forming the OR circuit to set the threshold value of the OR circuit to zero or a sufficiently low value. If a bias current is made to flow through the rectifying element that constitutes the OR circuit in this way, the output of the OR circuit can be obtained even when the level of the output signal of the voltage dividing circuit is low, so the detection sensitivity is increased and It becomes possible to detect a small current, and the detection accuracy is improved.

However, in the present invention, it is not always necessary to supply a bias current to the light emitting element or the rectifying element of the OR circuit, and a detection signal having a magnitude corresponding to the main circuit current is obtained without obtaining the current value of the main circuit current. When it is sufficient to obtain the output, the output of the OR circuit without the bias circuit may be supplied to the light emitting element without the bias circuit directly or through the current limiting element.

[0025]

As described above, when the full-wave rectified output of the detected value of the main circuit current is combined through the OR circuit and the combined output is sent from the signal sending section, the output signal of the signal sending section is sent to the main circuit. A ripple component having current information can be included, and information on the main circuit current can be obtained by detecting the ripple component and the peak value of the output signal. Therefore, when a signal is applied to a signal processing device located away from the power circuit, the output of the signal sending unit may be transmitted to the signal processing device via one signal transmitting means. There is no need to route many wirings to the signal processing device as in the case of using.

Particularly, when the signal transmitting section is composed of a light emitting element and an optical fiber is used as the signal transmitting means,
Since the signal processing device and the current detection device can be insulated from each other, it is possible to protect the signal processing device from a ground fault, a short circuit accident, a surge caused by induced lightning, and the like.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment in which the present invention is applied to a current detection device used in a device for measuring a breaking current value for judging the life of a circuit breaker. 1u-
Reference numeral 1w is a main circuit conductor of U, V, and W3 phases of the gas insulated switchgear, and CBu to CBw are three-phase circuit breakers respectively inserted in the middle of the main circuit conductors 1u to 1w.

In this embodiment, U, V, and W of the W3 phases are
First and second main circuit current transformers CTu and CTv are attached to the V2-phase main circuits 1u and 1v, respectively. As these current transformers, it is possible to use, for example, what is called a through type in which a secondary coil is wound around an annular iron core through which the main circuit conductor passes.

The outputs of the first main circuit current transformer CTu and the second main circuit current transformer CTv are input to the first and second auxiliary current transformers CTu 'and CTv', respectively. The output of the sink is a first rectifying circuit 10u and a second rectifying circuit 10v which are formed by connecting diodes D1 to D4 in a bridge connection
Has been entered in. The first voltage dividing circuit 11u is connected between the output terminals of the first rectifying circuit 10u. This voltage dividing circuit is composed of a series circuit of resistors R1 and R2 and a shunt resistor R3 connected in parallel to both ends of the series circuit of these resistors, and one end 11u1 on the side of the resistor R1 of the rectifier circuit 10u. Connected to the output terminal on the positive polarity side, the other end 11u2
Is connected to the output terminal on the negative side of the rectifier circuit 10u. In this voltage dividing circuit 11u, the current given from the rectifying circuit 10u is shunted to the resistor R3 and the series circuit of the resistors R1 and R2 to lower the current, and the voltage generated by this current is further divided by the resistors R1 and R2. Thus, the voltage for detecting the main circuit current is obtained.

Similarly, the second voltage divider circuit also includes resistors R1 and R1.
2 and a shunt resistor R3 connected in parallel to both ends of the series circuit of these resistors, one end 11v1 of the resistor R1 side is connected to the positive output terminal of the rectifier circuit 10v. The other end 11v2 is connected to the output terminal on the negative polarity side of the rectifier circuit 10v.

When the voltage dividing ratios of the first voltage dividing circuit and the second voltage dividing circuit are set equal, and when voltages having the same peak value are applied to both voltage dividing circuits, the peak value of the output voltage of both voltage dividing circuits is set. Be equal.

At the voltage dividing point (output terminal on the positive polarity side) 11u3 of the first voltage dividing circuit 11u and the voltage dividing point 11v3 of the second voltage dividing circuit 11v, the first and second diodes Du and Dv are respectively provided. The anodes are connected, and the cathodes of the diodes Du and Dv are commonly connected. In this example, the OR circuit 12 is composed of the first and second diodes Du and Dv. The common connection point of the diodes of the OR circuit 12 is connected to the anode of the light emitting diode LED as the light emitting element through the resistor R4 as the current limiting element, and the cathode of the light emitting diode LED is connected to the negative output terminal of the rectifying circuit 10u. . The cathode of the bias current supply diode Do is connected to the connection point between the anode of the light emitting diode LED and the resistor R4.
A positive terminal of a bias power source Eb composed of a battery or the like is connected to the anode of the. The negative terminal of the bias power source Eb is connected to the cathode of the light emitting diode LED through a resistor R5 as a current limiting element. A current ix corresponding to the sum of the output current ior of the OR circuit and the bias current io flows through the light emitting diode LED. The light emitting diode LED produces an optical signal Px proportional to this current ix.

In this embodiment, the resistor R2 of the voltage dividing circuit is used.
Is set to be sufficiently smaller than the resistance value of the current limiting resistor R4 of the signal transmitting section. With this setting, when the resistor R2 is seen from the signal sending side, the resistor R2
Can be regarded as a voltage source, and outputs of the first and second voltage dividing circuits can be OR-added by an OR circuit including diodes Du and Dv.

In this example, the bias current supply diode Do, the bias power supply Eb, and the resistor R5 constitute a bias circuit 13 for the light emitting element. The bias circuit 13, the resistor R4, and the light emitting diode LED The signal sending unit 14 is configured. In this example, the first and second auxiliary current transformers CTu ′ and CTv ′, and the first
And the second rectifier circuits 10u and 10v, and the OR circuit 12
And the signal sending section 14 constitute a detection signal synthesizing / sending circuit section 15, and the detection signal synthesizing / sending circuit section 15
And the first and second main circuit current transformers CTu and CTv constitute a main part of the current detection device according to the present invention.

In this current detecting device, the detection signal synthesizing / sending circuit portion 15 is arranged in the vicinity of the gas insulated switchgear, for example, in the operator box of the gas insulated switchgear, and is provided in the gas insulated switchgear main circuit. The current transformers CTu and CTv and the auxiliary current transformers CTu ′ and CTv ′ are connected via wiring. In this case, since the distance between the main circuit current transformer and the auxiliary current transformer can be shortened, wiring between them can be easily performed.

In this embodiment, the auxiliary current transformers CTu 'and CTv' are composed of primary coils w1 and w2 which are insulated from each other.
The following coil w2 is wound around an iron core. These auxiliary current transformers reduce the output current of the main circuit current transformer and
It is provided to insulate the main circuit current transformer side from the circuit side of the detection signal synthesizing / sending circuit section 15.

In the present invention, when the peak value of the main circuit current is calculated from the output of the signal sending unit, a signal processing unit for processing the signal of the signal sending unit is further provided. In this embodiment, one end of the optical fiber 16 constituting the signal transmitting means is coupled to the light emitting diode LED of the signal transmitting section 14,
The other end of the optical fiber 16 is coupled to a light receiver 18 of a signal processing device 17 installed at a remote place. Receiver 1
A light receiving element 8 such as a photodiode or a phototransistor 8 receives the optical signal Px transmitted through the optical fiber 16 and converts the received optical signal into an electric signal.

The signal processing device 17 of this embodiment further includes a ripple detection circuit 19, a current value calculation means 20, and a cumulative value calculation means 21. The ripple detection circuit 19 is composed of, for example, a circuit that detects the amplitude between peaks of the AC component detected through a capacitor, and detects the ripple component included in the output of the light receiver 18.

The current value calculating means 20 is realized by a computer, and the optical signal Px detected by the photodetector 18 is used.
The maximum value Pm of Rp and the ripple component ΔP included in the output,
The peak value i of the current ior flowing from the OR circuit 12 to the light emitting diode is calculated by using the light emission amount of the light emitting diode LED by the bias current, and the peak value i is corrected by a circuit constant such as a voltage dividing circuit. Calculate the peak value of current. Although not shown, the computer is provided with a breaker breaking command and a closing command, and the main circuit current when the breaking commands and closing commands are given to break the circuit breakers CBu to CBw. Accumulate the calculated values of (added to the current value calculated at the time of the previous interruption) to calculate the cumulative breaking current value (cumulative value of the breaking current from the start of using the circuit breaker) The cumulative value calculating means 21 is realized by the software of the computer that realizes this calculation. The computer also compares the cumulative peak value of the calculated breaking current with a predetermined judgment value, and when it detects that the cumulative breaking current value has reached the judgment value, the life of the contact of the circuit breaker When it is determined that the exhaustion has been exhausted, a predetermined signal is generated.

In the above embodiment, it is assumed that the waveform of the main circuit current of each phase is a sine wave and the waveforms of the three phases are symmetrical (a normal current flows in the three phases). When the output current of the first voltage dividing circuit is iu and the output current of the second voltage dividing circuit is iv, the waveforms of these currents are respectively shown in FIG.
2A and 2B, the waveform of the output current ior of the OR circuit 12 is iu and iv as shown in FIG. 2C.
The result is a waveform obtained by OR-adding and, and the light emitting diode LED is driven by either iu or iv, whichever is larger. In the waveform of FIG. 2C, the OR circuit 12
When the crest value of the output current ior is i and the ripple component is Δi, the ripple component Δi is given by the following equation.

Δi = K × i (1) When ORing the full-wave rectified waveforms of the two-phase currents as in the embodiment shown in FIG. 1, K = 1/2.

The above current ior is applied to the light emitting diode LED.
2D, the waveform of the current ix flowing through the light emitting diode is as shown in FIG. 2D, and the waveform of the optical signal Px generated by the light emitting diode by this current ix is as shown in FIG. As shown in (E). If the peak value of the current flowing through the light emitting diode is im, then
m is given by the following formula.

Im = io + i (2) Further, the light emission amount obtained by the peak value i of the output current ior of the OR circuit flowing through the light emitting diode LED is P, and the ripple component included in the light generated by the light emitting diode is ΔP. Then, ΔP is given by the following equation.

ΔP = K × P (3) Further, assuming that the light emission amount of the light emitting diode due to the bias current io is Po and the light emission amount obtained by flowing the current im through the light emitting diode is Pm, Pm is expressed by the following formula. Given.

Pm = Po + P (4) Since i, io and P, Po have a proportional relationship of i / io = P / Po, i = (P / Po) × io (5) ) When P is obtained from the equation (3), P = ΔP / K, and
When Po is obtained from the equation (4), Po = Pm-P = Pm-
Since it is (ΔP / K), the equation (5) becomes the following equation.

I = {ΔP / (KPm-ΔP)} × io (6) From the equation (6), the light receiving diode 18 is used by the light receiver 18.
The maximum value Pm of the optical signal Px generated by the
And the output current ior of the OR circuit 12 is detected.
It can be seen that the peak value i of can be obtained. Since this peak value i is proportional to the peak value of the main circuit current of each phase, the peak value of the main circuit current of each phase can be obtained from the peak value i. Further, if the peak value of the main circuit current of each phase is obtained, the average value or effective value of the main circuit current can be calculated as necessary.

When detecting a two-phase current as in the embodiment of FIG. 1, K = 1/2, so that the equation (6) is given by i = {ΔP / (0.5 Pm-ΔP)} × io ... (6) '.

In the above description, the normal current flows through the power circuit, but the peak value of the fault current can be detected even when the fault current occurs. For example, as indicated by an arrow a in FIG. 1, when a short-circuit accident between the U and W2 phases occurs, the U-phase main circuit current transformer CTu detects a fault current and the V-phase main circuit current transformation occurs. The device CTv does not detect fault current. Therefore, the output current i of the voltage dividing circuits 11u and 11v is
The waveforms of u and iv are as shown in FIGS. 3A and 3B, respectively, and the waveform of the optical signal generated by the light emitting diode is as shown in FIG. 3C. In this case, the V-phase voltage dividing circuit 11
The output current of v is sufficiently smaller than that of the U-phase voltage divider circuit 11u, and the output current waveform of the V-phase voltage divider circuit 11v is not included in the output ripple of the OR circuit. The ripple component ΔP itself contained in the optical signal Px to be obtained corresponds to the peak value of the fault current.

Further, as shown by the arrow b in FIG. 1, V, W2
When a short-circuit accident between phases occurs, only the V-phase main circuit current transformer CTv detects the fault current, so that ripples included in the optical signal are generated as in the case where a short-circuit accident between U and W phases occurs. This corresponds to the peak value of the breaking current (fault current).

On the other hand, when a short circuit accident occurs between the U and V2 phases or when a three phase short circuit accident occurs, as shown in FIG.
As indicated by an arrow c in FIG. 4, since currents flow in the U-phase main circuit and the V-phase main circuit, the output currents iu and iv of the voltage dividing circuits 11u and 11v are shown in FIGS. 4 (A) and 4 (B), respectively. As a result, the light emitting diode LED generates the optical signal Px having a waveform as shown in FIG. In this case, the peak value i of the output current of the voltage dividing circuit can be obtained by the above equation (6), and this peak value i corresponds to the peak value of the breaking current.

As an example, the waveform of the optical signal Px obtained from the light emitting diode when an accident occurs is shown in FIGS. 5 and 6. FIG. 5 shows the time t1 when the normal current is flowing.
2 phase short circuit of U, V or 3 phase short circuit occurs in U, V
The figure shows the waveform of the optical signal Px generated by the light emitting diode LED when a fault current flows in both phases and a break command is given at time t2 to break the breakers CBu to CBw. Further, FIG. 6 shows a waveform of an optical signal obtained from the light emitting diode when the breaker is turned on at time t3 after the breaker is cut off but the accident is not recovered.

As described above, according to the current detector of the present invention, the peak value of the breaking current can be known by detecting the peak value of the optical signal and the ripple component contained in the optical signal.

In the above embodiment, the main circuit current of two of the three phases is detected, but as shown in FIG.
You may make it detect three-phase main circuit current. In the example shown in FIG. 7, in addition to the configuration of FIG. 1, a third main circuit current transformer CTw for detecting the W-phase main circuit current is further provided, and the output of this current transformer is the third auxiliary current transformer. It is input to the third rectifying circuit 10w via the current transformer CTw ′. The output of the third rectifying circuit 10w is input to the third voltage dividing circuit 11w consisting of the resistors R1 to R3, and the output of the third voltage dividing circuit is passed through the third diode Dw and the resistor R4 to the light emitting diode LED.
Is being applied to. The cathode of the diode Dw is commonly connected to the cathodes of the diodes Du and Dv, and the OR circuit 12 is constituted by the first to third diodes Du to Dw. The other points are similar to those of the embodiment shown in FIG.

In the embodiment shown in FIG. 7, the currents iu to iw supplied to the light emitting diode LED from the first to third voltage dividing circuits 11u to 11w when a normal current is flowing in the three-phase main circuit. 8A to 8C, and the waveform of the current ior output from the OR circuit 12 is as shown in FIG. 8D. in this case,
K in the equation (1) is K = 0.134, and 1 / K = 7.463.
Therefore, between the ripple component Δi included in the current ior and the peak value i of the output current of the voltage dividing circuit, Δi = 0.134 ×
i or i = 7.463 × Δi.

Further, in the embodiment of FIG. 7, the OR circuit 12
The current ix (= ior + io) flowing through the light emitting diode LED when the current ior of FIG.
As shown in FIG. 8E, the waveform of the optical signal Px generated by this current ix is as shown in FIG. 8F.

In the case of the embodiment shown in FIG. 7, the output current i of the voltage dividing circuit when a three-phase symmetrical alternating current (normal current) flows in the power circuit can be obtained from the following equation.

I = {ΔP / (o.134 Pm −ΔP)} × io (6) ″ FIG. 9 shows still another embodiment of the present invention. In this embodiment, diodes D10 and D11 are used. And resistors R10 and R11
And a bias circuit for the OR circuit is added to allow a bias current to flow from the bias power source Eb to the diode Du of the OR circuit 12 through the diode D10 and the resistor R10, and the bias power source Eb to the diode D11 and the resistor R10.
A bias current is made to flow through the diode Dv of the OR circuit 12 through the line 11. In this embodiment, the bias circuit 1 for the light emitting element is used as the power source of the bias circuit for the OR circuit.
The bias power source Eb of 3 is also used. Other configurations are similar to those of the embodiment of FIG.

In the embodiment shown in FIG. 1, the dead band is generated in the region where the level of the OR signal is low due to the threshold value of the forward voltage of the diodes Du and Dv used in the OR circuit 12, but the embodiment shown in FIG. When the bias current is made to flow through the diodes Du and Dv forming the OR circuit as in the example, it is possible to prevent the above dead zone from occurring, so that the sensitivity of the OR circuit can be increased and the detection can be performed. The accuracy of can be improved.

In the embodiment of FIG. 9, the resistance values of the resistors R10 and R11 are set to values that make the forward bias voltage of the diodes Du and Dv zero (values that make the threshold value of the OR circuit zero). adjust. The resistance values of the resistors R10 and R11 are set sufficiently larger than the resistance value of the resistor R2.

In the above-described embodiment, the light emitting element is provided in the signal transmitting section so that the detection signal corresponding to the OR output of the plurality of rectifier circuits is transmitted as the optical signal. It may be transmitted in the form of an electric signal.

In the above embodiment, the signal transmitting section is provided with the bias circuit, but this bias circuit can be omitted.

As in the above embodiment, the voltage divider circuit has a resistor R.
If 3 is provided and the current given from the rectifier circuit is shunted, the output voltage of the voltage dividing circuit can be adjusted easily, but the resistor R3 can be omitted.

Although the auxiliary current transformers CTu 'to CTw' are provided in the preceding stage of the rectifier circuit in the above embodiment, these auxiliary current transformers may be omitted.

In the above embodiment, the current detecting device according to the present invention is used to obtain the cumulative breaking current value of the circuit breaker, but the use of the current detecting device of the present invention is not limited to this. It can be widely applied when it is necessary to obtain information about the current of a three-phase power circuit. The configuration of the signal processing device that processes the output signal of the signal transmission unit can be appropriately configured according to the purpose.

In the above embodiment, the light emitting circuit using the LED as the voltage / light converter is used, but a photovoltage transformer using the Pockels effect or the like may be used as the voltage / light converter.

The preferred embodiments of the present invention have been described above. The main aspects of the invention disclosed in this specification are listed below.

(1) Outputs of first and second main circuit current transformers CTu and CTv for detecting main circuit currents of two phases out of three phases, and outputs of the first and second main circuit current transformers Alternatively, first and second rectifying circuits 10u and 10v for full-wave rectifying the outputs corresponding to the outputs of both main circuit current transformers, respectively, and
The OR circuit includes first and second voltage dividing circuits 11u and 11v for dividing the outputs of the first and second rectifying circuits, respectively, and an OR circuit 12 having the outputs of the first and second voltage dividing circuits as inputs. And a signal transmitting section 14 for transmitting a signal corresponding to the output of the current detector.

(2) First to third main circuit current transformers CTu to CTw for respectively detecting three-phase main circuit currents,
First to third rectifying circuits 10u to 10w for full-wave rectifying the outputs of the first to third main circuit current transformers or the outputs corresponding to the outputs of the first to third main circuit current transformers, respectively.
And the first to third voltage dividing circuits 11u to 11w for dividing the outputs of the first to third rectifying circuits, respectively, and the OR circuit 12 receiving the outputs of the first to third voltage dividing circuits as inputs. And a signal sending unit 14 for sending a signal corresponding to the output of the OR circuit.

(3) The signal transmitting section 14 includes a light emitting element LED driven by the output of the OR circuit 12, and the signal transmitting means is an optical fiber for transmitting the light generated by the light emitting element. 3. The current detection device according to item 2 or item 2.

(4) The OR circuit 12 is provided corresponding to each voltage dividing circuit and has the same number of voltage dividing circuits as the anodes connected to the voltage dividing points of the corresponding voltage dividing circuits and the cathodes commonly connected. It is composed of diodes Du to Dw, and the common connection point of the cathodes of the diodes Du to Dw is the current limiting element R4.
4. The current detection device according to item 3, which is connected to the positive-side terminal of the light emitting element LED through.

(5) The current detecting device as described in the above item 4, further comprising an OR circuit bias circuit for supplying a bias current to each of the diodes forming the OR circuit.

(6) The signal transmitting section 14 includes the light emitting element L.
6. The current detecting device according to the above item 3, 4, or 5, further comprising a bias circuit 13 for a light emitting element which supplies a forward bias current having a constant value io to the ED.

(7) The bias circuit 13 comprises a circuit for supplying a bias current to the light emitting element LED through the bias voltage applying diode Do whose cathode is coupled to the positive terminal of the light emitting element. apparatus.

(8) The optical fiber 16 for transmitting the optical signal generated by the light emitting element of the signal transmitting section, the photodetector 18 for receiving the optical signal transmitted through the optical fiber and converting it into an electric signal, and The ripple detection circuit 19 for detecting the ripple component ΔP included in the output, and the ripple value ΔI, the peak value Pm of the output of the photodetector, and the bias current value io are used to calculate the peak value i = {ΔP / (of the main circuit current. KPm-Δ
P)} × io (where K is a constant), and the current value calculating means 20 is further included.

(9) The voltage dividing circuit is connected in parallel to the series circuit of the resistors R1 and R2 connected between the output terminals of the corresponding rectifying circuit and both ends of the series circuit of the resistors R1 and R2. 9. The current detecting device according to any one of items 1 to 8, which comprises a shunt resistor R3.

(10) The peak value of the breaking currents of the three-phase circuit breakers CBu to CBw inserted in the three-phase main circuit is detected, and the cumulative peak current value of the breaking currents is obtained as the cumulative breaking current value. A cutoff current measuring device, comprising: first and second main circuit current transformers CTu and CTv for detecting currents respectively flowing in two-phase main circuits of the three-phase main circuits;
And first and second rectifier circuits 10u and 10v for full-wave rectifying the outputs of the second and second main circuit current transformers or the outputs corresponding to the outputs of both main circuit current transformers, respectively. First and second voltage dividing circuits 11u and 11v for dividing the output of each circuit, an OR circuit 12 that receives the outputs of the first and second voltage dividing circuits, and light emission to which a driving current is given from the OR circuit. A signal sending section 14 for sending an optical signal Px corresponding to the sum of the output current ior of the OR circuit and the bias current io, comprising a device and a bias circuit for supplying a constant forward bias current io to the light emitting device; The signal transmitting means for transmitting the optical signal transmitted by the signal transmitting section, the photodetector 18 for receiving the optical signal Px transmitted through the signal transmitting means, and the ripple component Δ contained in the optical signal Px received by the photodetector 18.
Ripple detection circuit 19 for detecting P and ripple component ΔP
And a current value calculating means 20 for calculating a current value corresponding to the peak value of the main circuit current by using the peak value Pm of the optical signal Px and the bias current io, and a current when a break command is given to the circuit breaker. A cumulative breaking current measuring device comprising: a cumulative value computing means for cumulatively computing the current values computed by the value computing means 20 to compute the cumulative breaking current value.

(11) The peak value of the breaking currents of the three-phase circuit breakers CBu to CBw inserted in the three-phase main circuit is detected, and the cumulative peak value of the breaking currents is obtained as the cumulative breaking current value. A cutoff current measuring device, wherein first to third main circuit current transformers CTu to CTw for detecting currents respectively flowing in the three-phase main circuits and outputs of the first to third main circuit current transformers. Alternatively, the first to third rectifying circuits 10u to 10w for full-wave rectifying the outputs corresponding to the outputs of the first to third main circuit current transformers, and the outputs of the first to third rectifying circuits, respectively. First to third voltage dividing circuits 11u to 11w for voltage division, an OR circuit 12 to which outputs of the first to third voltage dividing circuits are input, a light emitting element to which a driving current is given from the OR circuit, and the light emitting element Constant forward bias voltage A signal sending section 14 for sending an optical signal Px corresponding to the sum of the output current ior of the OR circuit and the bias current io, and a light signal sent by the signal sending section 14. A signal transmitting means, a photodetector 18 for receiving the optical signal Px transmitted through the signal transmitting means, and an optical signal Px received by the photodetector 18.
Ripple detection circuit 19 for detecting the ripple ΔP included in the current value and a current value for calculating the current value corresponding to the peak value of the main circuit current using the ripple ΔP, the peak value Pm of the optical signal Px and the bias current io. Cumulative breaking current measurement provided with a computing means 20 and a cumulative value computing means 21 for computing a cumulative breaking current value by accumulating the current values calculated by the current value computing means 20 when a breaker command is given to the breaker. apparatus.

According to the cumulative breaking current measuring device of the above item (10) or (11), there is one connection between the power equipment such as the gas insulated switchgear provided with the circuit breaker and the signal processing device after the light receiver. Since they can be connected through a book optical fiber, it is possible to simplify the routing of the signal transmission means.

[0079]

As described above, according to the present invention, the full-wave rectified output of the detected value of the main circuit current is combined through the OR circuit, and the combined output is sent from the signal sending unit. The output signal of the signal transmission unit can include a ripple component having information on the main circuit current, and by detecting the ripple component and the peak value of the output signal, information on the main circuit current can be obtained. Therefore, when a signal is applied to a signal processing device located away from the power circuit, the output of the signal sending unit may be transmitted to the signal processing device via one signal transmitting means. There is an advantage that it is not necessary to route a large number of wirings to the signal processing device as in the case of using.

Particularly, in the case where a light emitting element is provided in the signal sending unit and the optical signal is sent from the signal sending unit, the signal sending unit and the signal processing device may be connected by an optical fiber. Therefore, it is possible to easily protect the signal processing device against a ground fault, a short circuit accident, an induced lightning surge, and the like.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a signal waveform diagram of each part of the embodiment of FIG.

FIG. 3 is a waveform diagram showing signal waveforms of respective portions when a short circuit accident of U and W2 phases occurs in the embodiment of FIG.

FIG. 4 is a waveform diagram showing signal waveforms of respective portions when a U-phase, V-phase short-circuit accident or a 3-phase short-circuit accident occurs in the embodiment of FIG.

5 is a waveform diagram showing an example of changes in the optical signal waveform when an accident occurs and the current is cut off in the embodiment of FIG.

FIG. 6 is a waveform diagram showing an example of changes in the optical signal when the circuit breaker is closed again before the accident is recovered in the embodiment of FIG.

FIG. 7 is a configuration diagram showing a configuration of another embodiment of the present invention.

FIG. 8 is a waveform diagram showing signal waveforms of various parts of the embodiment of FIG.

FIG. 9 is a configuration diagram showing a configuration of still another embodiment of the present invention. .

FIG. 10 is a configuration diagram showing a conventional current detection device.

[Explanation of symbols]

 1u to 1w Main circuit CTu to CTw Main circuit current transformer 10u to 10w Rectifier circuit 11u to 11w Voltage dividing circuit R1 to R3 Resistor configuring voltage dividing circuit 12 OR circuit Du to Dw Diode configuring bias circuit 13 Bias circuit Do Bias current supply diode Eb Bias power supply 14 Signal transmission unit 16 Optical fiber (signal transmission means) 18 Light receiver 19 Ripple detection circuit 20 Current calculation means 21 Cumulative value calculation means

Claims (7)

[Claims] 1. A first and a second main circuit current transformers for respectively detecting main circuit currents of two phases out of three phases, and outputs of the first and second main circuit current transformers or both main circuits. First and second rectifying circuits for full-wave rectifying the outputs corresponding to the outputs of the circuit current transformers, and first and second voltage dividing circuits for dividing the outputs of the first and second rectifying circuits, respectively. And a signal transmitting section for transmitting a signal corresponding to the output of the OR circuit by including an OR circuit that receives the outputs of the first and second voltage dividing circuits as an input. . 2. First to third main circuit current transformers for respectively detecting three-phase main circuit currents, and outputs of the first to third main circuit current transformers or the first to third main circuit current transformers. First full-wave rectification of each output corresponding to the output of the main circuit current transformer
To 3rd rectifier circuits, 1st to 3rd voltage divider circuits for dividing the outputs of the 1st to 3rd rectifier circuits, and outputs of the 1st to 3rd voltage divider circuits An electric current detection device comprising an OR circuit and a signal transmission unit for transmitting a signal corresponding to the output of the OR circuit. 3. The current detection device according to claim 1, wherein the signal transmission unit includes a light emitting element driven by the output of the OR circuit. 4. The OR circuit is provided corresponding to each voltage dividing circuit, the anode is connected to a voltage dividing point of the corresponding voltage dividing circuit, and the cathode is commonly connected to the voltage dividing circuit, and the same number of diodes are provided. The current detection device according to claim 3, wherein a common connection point of the cathodes of the diodes is connected to a positive side terminal of the light emitting element through a current limiting element. 5. The current detecting device according to claim 3, wherein the signal transmitting unit is provided with a bias circuit for supplying a forward bias current having a constant value io to the light emitting element. 6. The current detection device according to claim 5, wherein the bias circuit comprises a circuit for supplying a bias current to the light emitting element through a bias voltage applying diode having a cathode coupled to a positive side terminal of the light emitting element. apparatus. 7. An optical fiber for transmitting an optical signal generated by the light emitting element, a photodetector for receiving the optical signal transmitted through the optical fiber and converting the signal into an electric signal, and an output of the photodetector. A ripple detection circuit for detecting the ripple component ΔP, and a current value corresponding to the peak value of the main circuit current are calculated using the ripple component ΔP, the peak value Pm of the output of the photodetector and the bias current value io. 7. The current detecting device according to claim 5, further comprising: a current value calculating unit that operates.