JP3087155B2 - Leakage current detection sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a three-phase power receiving and transforming facility or a gas insulated electrical facility (GIS).
Leakage current due to deterioration of the overvoltage protection arrester and insulation material (for example, insulators, insulation spacers, etc.) connected between the system bus of each phase and the ground is detected, and the arrester or insulation is detected from the leakage current value. The present invention relates to a leakage current detection sensor for diagnosing the degree of deterioration of a material.

[0002]

BACKGROUND ART FIG. 1 3 shows an example of a conventional leakage current sensor used for detection of leakage current arrester. Although shown only 1 3, 1 phase diagram, the leakage current detection sensor in response to the arrester for three phases, respectively.

[0003] In Figures 1 to 3, 60 is the earth, 61 system bus of one phase in the incoming transfer facility, 62 arrester for overvoltage protection, 63 for leakage detection in which a primary winding arrester 62 in series Current transformer, 64 is an isolation amplifier, 6
Reference numeral 5 denotes an amplifier, and 66 denotes an electric signal for converting an electric signal into an optical signal.
An optical converter, 67 is an optical fiber, 68 is an optical-electrical converter for converting an optical signal into an electric signal, 69 is a signal determination circuit for determining the magnitude of the leakage current, and 70 is a predetermined threshold value for the leakage current. This is an alarm output terminal that generates an alarm output when it exceeds the limit.

The leakage current detection sensor having the above-described configuration supplies a current flowing from the system bus 61 to the ground 60 through the arrester 62, that is, a leakage current of the arrester 62, through a current transformer 63 to an insulation amplifier 64, and Amplifier 6
4 is converted into a voltage signal at the input of the amplifier 4 and amplified.
After the output signal (electric signal) of No. 4 is further amplified by the amplifier 65, it is converted into an optical signal by the electric-optical converter 66, and transmitted through the optical fiber 67 to, for example, a control room or the like remote from the power receiving and transforming equipment. The optical signal is converted into an optical-electrical
The signal is converted into an electric signal by the signal 8, and the signal level is compared with a predetermined threshold value in the signal judgment circuit 69 to judge pass / fail. The level of the electric signal, ie, the level of the leakage current exceeds the predetermined threshold value. In such a case, the arrester 62 is determined to be faulty and an alarm output is generated from the alarm output terminal 70. For example, an alarm buzzer or the like is sounded, or an alarm lamp is turned on or blinks, and the leakage current of the arrester 62 becomes excessive. That the arrester 62 has deteriorated and needs to be replaced.

Incidentally, as a conventional example in which it is not necessary to send the signal of the output of the amplifier 65 to a distant place, the output of the amplifier 65 is directly input to a signal determination circuit 69, and the level thereof is determined by a signal determination circuit 69 to a predetermined level. In some cases, an alarm output is generated from the alarm output terminal 70 when the level of the electric signal, that is, the level of the leakage current exceeds a predetermined threshold value.

[0006] Detecting deterioration of the arrester 62,
A leakage current detection sensor for detecting a leakage current flowing through the
The sensor generally needs to measure a current of the order of 10 μA.
Usually, the secondary side is about 2,000 to several thousand turns
The small current transformer 63 consisting of the wound winding and the core
The secondary current is supplied to the isolation amplifier 64 and the input amplifier 64 having a relatively large input resistance.
And an amplifier 65 and, if necessary, an electro-optical converter 6.
5 converts the signal to an optical signal, and receives and transforms the signal through an optical fiber 67.
Transmission to a control room, etc. away from the
The signal is converted into an electric signal by an optical-electrical converter 68.

In such a conventional leakage current detection sensor, the secondary current of the current transformer 63 is supplied to the insulation amplifier 64 having a relatively high input resistance, and the secondary current is generated at the input terminal of the insulation amplifier 64 by the secondary current. It is a configuration that amplifies the voltage, and it is necessary to reduce the magnetic flux density of the current transformer 63 at the time of measurement and reduce the exciting current for exciting the iron core in order to reduce the error in the microamp order. The current transformer 63 has a secondary winding of about 2,000 to several thousand turns, which makes the current transformer 63 difficult to manufacture, large in shape, and expensive. .

Further, in this leakage current detection sensor, the output of the current transformer 63 is amplified by the insulating amplifier 64 and the amplifier 65 in order to detect the leakage current. There is a problem that the size is increased as well as expensive as a whole in combination with the large size.

Further, although the isolation amplifier 64 is provided to prevent the surge from propagating to the circuits subsequent to the amplifier 65, when a surge voltage exceeding the capability of the isolation amplifier 64 is applied, the surge voltage is reduced. Amplifier 6 through
5, in particular, in the case where the output signal of the amplifier 65 is directly supplied to the signal determination circuit 69 without transmitting an optical signal, the surge voltage propagates to the signal determination circuit 69, and Alternatively, the signal determination circuit 6
9 has a high possibility of damaging the integrated circuit and the like constituting the semiconductor device 9.

[0010] Also, using an insulating amplifier 64 and an amplifier 65
Of a bipolar transistor or a field effect transistor.
There are many active elements such as transistors, and these components
Is easily destroyed by the application of such
There is a problem that the failure probability is high.

Therefore, it is necessary to solve such a problem.
Some of the things that can be done are listed below.
ing.

[First Proposed Example] FIG. 1 shows a circuit diagram of a leakage current detection sensor according to a first proposed example . As shown in FIG. 1, this leakage current detection sensor is for detecting the deterioration of an arrester 2 for overvoltage protection connected between a one-phase system bus 1 and the earth 4 in a three-phase power receiving and transforming facility, for example. And a current transformer 3 for detecting current.
Is provided in series with the arrester 2.

A light emitting diode (LED) is connected between both ends of the secondary winding of the current transformer 3 via a DC blocking capacitor 5.
A light emitting element 6 such as a laser diode is connected, and a DC power supply 8 such as a storage battery for supplying a bias current is connected between both ends of the light emitting element 6 via a current limiting resistor 7. Two protection diodes 9 and 10 for protecting the light emitting element 6 from a discharge surge voltage are connected in anti-parallel between both ends of the secondary winding of the current transformer 3.

The light emitting element 6 includes an optical fiber 1 for optical transmission.
The first end is optically coupled to the other end of the optical fiber 11 light - in mesh light forming the optical signal input portion of the electrical converter 12. This light-
An electric signal output unit of the electric converter 12 is provided with a first terminal 14 via a DC blocking capacitor 13, and a second terminal 14 via a low-pass filter including resistors 15 and 16 and capacitors 17 and 18. Terminal 19 is provided. The terminals 14 and 19 are connected to a high-precision signal determination circuit (not shown). A signal corresponding to the leakage current is output from the terminal 14, and a signal corresponding to the bias current is output from the terminal 19.

Next, the operation of the leakage current detection sensor will be described.

The light emitting element 6 has a threshold voltage of, for example, about 1.5 to 2 V, and emits light only when a voltage exceeding the threshold voltage is applied between both ends, so that a current flows to emit light. Even if the secondary winding of the current transformer 3 is simply connected, the light emitting element 6 does not emit light. Therefore, a predetermined bias current is applied to the light emitting element 6 from the DC power supply 8 having a voltage higher than the threshold voltage of the light emitting element 6 through the current limiting resistor 7 to emit light at a constant light amount (low level). At this time, the current flowing from the DC power supply 8 is cut off by the DC cutoff capacitor 5 and does not flow into the secondary winding of the current transformer 3.
The current transformer 3 does not saturate due to the flow of the bias current through the light emitting element 6.

[0017] In this state, when the leakage current of several μ to several hundreds μA to arrester 2 flows, current inversely proportional to the primary secondary turns ratio in the secondary winding of the current transformer 3 flows ,
This current passes through the DC blocking capacitor 5 and the light emitting element 6
Will flow into. As a result, the current i flowing through the light emitting element 6 is a constant bias current i ₀ flowing from the DC power supply 8 and a small leakage current Δi ₀ flowing from the secondary winding of the current transformer 3 (original This is the primary current, and for convenience, the secondary current of the current transformer 3 is referred to as leakage current). This minute leakage current Δi ₀ is the same frequency as the power supply frequency of the system bus 1, for example, 50/60.
Hz sine wave (when there is no distortion).

When the current i (= i ₀ + Δi ₀ ) flows into the light emitting element 6, the light emitting element 6 emits light according to the current i. The light emission amount I is the sum of a constant light amount I ₀ corresponding to the bias current i ₀ and a light amount ΔI ₀ that changes periodically according to the leakage current Δi ₀ . That is, the light emission amount I of the light emitting element 6 when the leakage current flows through the arrester 2 is as shown in FIG.
(A), the amount [Delta] I ₀ about the amount of light I ₀
Only in the form of a sine wave.

The light emitted from the light emitting element 6 is transmitted to the optical fiber 11.
Is transmitted to the optical-to-electrical converter 12 and is converted into an electric signal by the optical-to-electrical converter 12 to detect the variation width of the light emission amount, whereby the leakage current flowing through the arrester 2 can be detected. If the value of the leakage current is compared and determined by the signal determination circuit in the same manner as in the conventional example, the quality of the arrester 2 can be determined.

More specifically, the light emitted from the light emitting element 6 passes through the optical fiber 11 and is transmitted to the optical-electrical converter 12.
The electrical signal having a waveform similar to the waveform of FIG. 2A is output from the optical-electrical converter 12. The output signal of the optical-electrical converter 12 is sent to the first terminal 14 through the capacitor 13 and is connected to the resistors 15, 16 and the capacitor 1.
The signal is sent to the second terminal 19 via 7 and 18. As a result, the light amount ΔI ₀ from the first terminal 14, that is, the current Δi ₀
Output voltage signal .DELTA.j ₀ as shown in FIG. 2 (b) corresponding to. The second terminal 19 outputs a light amount I ₀ , that is, a voltage signal j ₀ corresponding to the current i ₀ as shown in FIG. 2C. Then, both voltage signals are sent to a signal determination circuit (not shown), and the level of the leakage current is determined. The determination of the level of the leakage current will be described later.

On the other hand, when the arrester 2 operates and an excessive discharge surge current flows, a discharge surge current also flows in the secondary winding of the current transformer 3 in accordance with the turns ratio. Then, a discharge surge current flows through the pair of overvoltage protection diodes 9 and 10, and a rise in voltage across the secondary winding of the current transformer 3 is suppressed by the pair of overvoltage protection diodes 9 and 10. In addition, the light emitting element 6 is protected, and the light emitting element 6 is not destroyed by an excessive discharge surge voltage.

Here, how to determine the level of the leakage current will be described.

The light emitting element 6 emits light with a bias current i ₀ and a small leakage current Δi ₀ , and light amounts I ₀ and ΔI ₀ are obtained correspondingly. This is converted into voltage signals j ₀ and Δj ₀ by the optical-electrical converter 12, and FIG.
The leakage current Δi ₀ can be measured by calculating the ratio j ₀ / Δj ₀ between the two as shown in FIG. Note that the actual leakage current is equal to the leakage current Δi ₀
Multiplied by the number of turns.

The reason why the leakage current Δi ₀ is determined from the ratio of the currents j ₀ and Δj ₀ is as follows. That is, the light emitting element 6
As shown in FIG. 3, the current i flowing through the light emitting device and the light emission amount I are proportional to each other at a certain current value or less, that is, Δi ₀ ∝ΔI ₀ , i _0.
There is a relationship of ∝I ₀ , and if it exceeds this, the light emission amount is reduced by heat, and eventually it is destroyed. 3, setting the bias current i ₀ so as to operate the light-emitting element 6 in a linear region by excluding the non-linear region as described above, since the bias current i ₀ is known, the leakage current .DELTA.i ₀ is Δi ₀ = (ΔI ₀ × i ₀ ) / I ₀ Here, the ratio ΔI ₀ / I ₀ of the light emission amounts in the above equation is
The ratio of the voltage signal can be replaced by Δj ₀ / j _0, and the leakage current Δi ₀ can be expressed as Δi ₀ = (Δj ₀ × i ₀ ) / j ₀ . Accordingly, in the signal determination circuit, the ratio of the voltage signal Δj ₀ / j ₀ is obtained and multiplied by the known bias current i ₀ to obtain the leakage current Δi ₀ , and the actual leakage current is further determined by the number of turns of the current transformer 3 Multiplied by Further, if the light emitting element 6 is broken, no light is emitted, so that it is possible to determine the failure.

Here, although the number of turns of the secondary winding of the current transformer 3 is reduced to increase the leakage current Δi ₀ flowing through the light emitting element 6, a DC bias current is supplied to the light emitting element 6 to perform the current transformation. Since the resistance of the light emitting element 6 viewed from the transformer 3 is reduced, the magnetic flux of the current transformer 3 at the time of measurement is reduced to about the same level as in the conventional example, and the excitation current for exciting the iron core of the current transformer 3 is reduced. The current detection accuracy in the current transformer 3 is equivalent to that of the conventional example. In the above description, the leakage current Δi ₀ accurately corresponds to the change in the light emission amount I of the light emitting element 6. However, if the conversion accuracy or the level detection accuracy of the photoelectric converter 12 and the subsequent circuit is low, the leakage current Δi ₀ is several μA or less. It is impossible to accurately measure the change in the light emission amount I due to the change in the current of the optical-electrical converter 1.
It is necessary to use a high-precision circuit for circuits subsequent to 2.

FIG. 4 shows a circuit in which one ends of arresters 2A, 2B, and 2C are connected to each of the three-phase system buses A, B, and C, and the other ends of the arresters 2A, 2B, and 2C are connected to ground. Is shown. The current transformer 3A is, for example, an A-phase arrester 2
A, the current flowing through A is detected, and the current transformer 3D detects A, B,
The configuration is such that the combined current of the leakage currents flowing through the three-phase arresters 2A, 2B, and 2C of C is detected.

FIG. 5 shows the waveform of the leakage current actually detected by the current transformer 3A when the current flowing through the A-phase arrester 2A is 300 μA, and FIG. 6 shows the leakage current of each phase of 20 μA. The waveform of the leakage current actually detected by the current transformer 3D is shown. Here, the number of turns and the detection error of the current transformer will be described.

The leakage current of several μA to several tens μA is insulated and converted into a signal by an n-turn wound current transformer.
The current is converted to n smaller currents (several tens nA to several hundreds nA).

In the case of such a small current transformer, the excitation current for exciting the iron core is reduced by lowering the magnetic flux density of the current transformer at the time of measurement, so that the current transformer is free from errors even with a small current. You can make vessels. Generally, the magnetic flux density of the current transformer can be reduced by increasing the cross-sectional area of the iron core, increasing the number of turns on the secondary side of the current transformer, or reducing the load on the current transformer. The reason is that when the magnetic flux density B is K as a constant, f is a frequency, i ₁ is a primary current, S _C is a core cross-sectional area, n is the number of turns on the secondary side, and R is a resistance, the following equation is used. Because it is done.

B = K × i ₁ × R / (n ² × f × S _c ) Of the above-mentioned methods, the method becomes large in size. A vessel is made. For example, if n = 2000 turns,
When the primary current is 10 μA, the secondary current is 10/2
000 = 5 nA, and the terminal voltage when a load of 1 kΩ is used is 10 × 10 ⁻⁶ / 2000 (A) × 1000 (Ω) = 5 μ.
V, which is the last value that can be amplified and detected by a general measuring instrument. As described above, usually, in order to obtain the input voltage of the amplifier, the voltage is obtained by increasing the number of turns to lower the magnetic flux density and increasing the load resistance to some extent.

In the present proposal , the magnetic flux density increased by reducing n is canceled out by reducing the resistance R, and the error is made approximately the same as that of the conventional example. That is, while the conventional method obtains a voltage output, the proposed example obtains a current output. Therefore, for example, the conventional method uses 2000 turns, 2
000Ω, to obtain the same magnetic flux density in 50 turns in the proposed example, B∝2000Ω / 2000 ² = xΩ /
Since 50 ^2, and x = 1.25Ω. That is, in order to realize the proposed example, the load resistance value needs to be set to, for example, about 1Ω. If the iron core cross-sectional area S _C is large, the resistance R can be increased by that amount.
Ohm. However, for example, a light emitting diode which is the light emitting element 6 has a threshold voltage (about 1 to 2 V) or less.
Since the resistance becomes as high as several hundred kΩ to several MΩ, the magnetic flux density increases as it is, and most of the current is consumed as the exciting current. In this proposal example, a DC bias current is applied to the light emitting diode, and the AC load of the light emitting diode is reduced to several Ω or less.
In addition, since there is a threshold voltage of the light emitting diode, a direct current flows into a current transformer side provided in parallel, and a DC blocking capacitor 5 is provided for the purpose of preventing the core of the current transformer 3 from being saturated. Provided.

According to the leakage current detection sensor of the first proposed example, the current flowing through the arrester 2 is detected by the current transformer 3 and supplied to the light emitting element 6 as a current signal via the DC blocking capacitor 5. At the same time, a predetermined bias current is supplied from the DC power supply 8 to the light emitting element 6, and the light output of the light emitting element 6 is changed in accordance with the current flowing through the arrester 2 centering on the light amount corresponding to the bias current. Since the load seen from the transformer 3 is reduced and the current flowing through the arrester 2 is detected from the change in the light output of the light emitting element 6, even if the number of turns of the secondary winding of the current transformer 3 is reduced. can be detected leakage current flowing to accurately arrester 2, the assembly time shorter production of current transformer 3 for detecting a leakage current flowing through the arrester 2 as easily, the current transformer 3 miniaturized It can be low-cost.

Further, the leakage current of the arrester 2 can be detected without the need for an insulating amplifier and an amplifier, the number of components can be reduced, and the size of the current transformer 3 can be reduced as a whole in conjunction with the size reduction. Cost can be reduced.

Further, since the light output of the light emitting element 6 is directly changed by the secondary output of the current transformer 3, the propagation of the surge can be reliably prevented, and the circuit element constituting the signal judgment circuit and the like can be obtained. Can be reliably protected.

Furthermore, since an insulating amplifier, an amplifier, and the like are not used, the number of active elements such as a bipolar transistor and a field effect transistor can be reduced, and the failure probability of the leakage current detection sensor can be reduced. Further, since the overvoltage protection diodes 9 and 10 are provided, the light emitting element 6 can be protected from a discharge surge voltage.

If the light emitting element 6 can sufficiently withstand the discharge surge, the overvoltage protection diodes 9, 1
0 can be omitted.

[Second Proposed Example] FIG. 7 shows a leakage current detection sensor according to a second proposed example. This leakage current detection sensor has a surge bypass capacitor 20 connected between both ends of a secondary winding of a current transformer 3 and a surge bypass capacitor in a path from the secondary winding of the current transformer 3 to the light emitting element 6. A current-limiting resistor 21 constituting a low-pass filter with the capacitor 20 is inserted and connected in series with the DC blocking capacitor 5. Other configurations are the same as those of the leakage current detection sensor of FIG.

In this leakage current detection sensor, when the arrester 2 operates and a large discharge surge current flows, an excessive discharge surge current flows in the secondary winding of the current transformer 3, but the discharge surge current is large. The portion flows through the surge bypass capacitor 20 connected between both ends of the secondary winding of the current transformer 3, preventing an excessive discharge surge current from flowing to the light emitting element 6, and protecting the light emitting element 6.

According to the leakage current detecting sensor of the second proposed example, the surge bypass capacitor 20 is connected between both ends of the secondary winding of the current transformer 3 and the secondary winding of the current transformer 3 is connected. Since a resistor 21 constituting a low-pass filter including a surge bypass capacitor 20 and a surge blocking capacitor 20 is inserted in series with the DC cutoff capacitor 5 in a path from the arrestor 2 to the light emitting element 6, the light emitting element is protected against a discharge surge current when the arrester 2 operates. 6 can be protected, and the reliability can be improved. Other effects are similar to those of the first proposed example.

[Third Proposed Example] FIG. 8 shows a leakage current detection sensor according to a third proposed example. This leakage current detection sensor has a surge bypass capacitor 20 connected between both ends of a secondary winding of a current transformer 3 and a surge bypass capacitor in a path from the secondary winding of the current transformer 3 to the light emitting element 6. A surge blocking coil 22 constituting a low-pass filter with the capacitor 20 is inserted and connected in series with the DC blocking capacitor 5. Other configurations are the same as those of the leakage current detection sensor of FIG.

In this leakage current detection sensor, when the arrester 2 operates and a large discharge surge current flows, an excessive discharge surge current flows in the secondary winding of the current transformer 3, but the discharge surge current is large. The portion flows through the surge bypass capacitor 20 connected between both ends of the secondary winding of the current transformer 3, preventing an excessive surge current from flowing to the light emitting element 6 and protecting the light emitting element 6.

According to the leakage current detecting sensor of the third proposed example, the surge bypass capacitor 20 is connected between both ends of the secondary winding of the current transformer 3, and the secondary winding of the current transformer 3 is connected. A surge suppression coil 22 that constitutes a low-pass filter with a surge bypass capacitor 20 is inserted in series with the DC blocking capacitor 5 in a path from the device to the light emitting element 6, so that a discharge surge current when the arrester 2 operates is formed. , The light emitting element 6 can be protected, and the reliability can be improved. Other effects are similar to those of the first proposed example.

[0043]

[Problems to be solved by the invention] However, the above
In each proposal example, the current transformer 63 was provided
Is configured to detect the current flowing through the
However, the number of discharge surges and several kA
Was unable to measure the discharge surge current.

Therefore, an object of the present invention is to provide a leakage current
Of the arrester and the number of discharge surges
To provide a leakage current detection sensor capable of measuring current
Is Rukoto.

[0045]

[Means for Solving the Problems] The leakage current according to claim 1.
The detection sensor detects the leakage current flowing through the arrestor or insulating material.
Both the current transformer to be detected and the secondary winding of this current transformer
Is connected through a DC blocking capacitor between
A light emitting element to which the current of the secondary winding of the generator is supplied, and
Connected to an optical element and supplies a predetermined bias current to the light emitting element
DC power supply and optical fiber
And the light that converts the light emitted from the optical fiber into an electrical signal.
-From the electrical converter and the secondary winding of the current transformer to the light-emitting element
A surge suppression coil inserted and connected in the path to
Current transformer on the current transformer side of the current blocking coil
Is connected between both ends of the secondary winding of
A rectifier that passes and rectifies and flows through this rectifier
Discharge surge current to appropriate value and flow to light emitting element
Flow means.

According to the second aspect of the present invention, there is provided a
Has an intermediate tap in the secondary winding and flows through arrestors and insulating materials
Current transformer for detecting leakage current
A DC blocking capacitor between one end of the secondary winding and the intermediate tap
Current through the secondary winding of the current transformer
A light emitting element to be supplied and a light emitting element connected to the light emitting element
A DC power supply for supplying a predetermined bias current to the
Optical fiber for transmitting the optical output of the
An optical-electrical converter for converting the emitted light into an electric signal;
Light emitting element from one end of the secondary winding of the generator and between the intermediate taps
A surge suppression coil inserted and connected in the path leading to
Current transformer across provided we are a discharge surge between the secondary winding
Rectifier that bypasses and rectifies
A current transformer that shunts the flowing discharge surge current to an appropriate value
The current between one end of the secondary winding of the
A flow dividing means for flowing the light into the light emitting element.

According to the third aspect of the present invention, there is provided a
Current transformation that detects leakage current flowing through a restor or insulating material
Transformer and the DC transformer between both ends of the secondary winding of this current transformer.
Of the secondary winding of the current transformer connected via a capacitor
A light-emitting element to which current is supplied, and a light-emitting element connected to the light-emitting element.
A DC power supply for supplying a predetermined bias current to the light emitting element,
An optical fiber for transmitting the light output of the light emitting element, and the optical fiber
An optical-electrical converter for converting the light emitted from the iva into an electric signal,
Inserted in the path from the secondary winding of the current transformer to the light emitting device
Connected surge suppression coil, arrester and insulating material
For discharge surge detection that can also detect discharge surge current flowing through
The current transformer and the secondary of this discharge surge detection current transformer
Connected between both ends of the winding to bypass discharge surges
Rectifier flowing and discharge surge flowing through this rectifier
Shunts the current to the appropriate value to obtain the current in the secondary winding of the current transformer.
And a flow dividing means for adding the current to the light emitting element.

[0048]

[Action] The following is mainly used to detect arrester leakage current.
The operation will be explained using an example.
The same.

According to the structure of the first aspect, the light emitting element
When a predetermined bias current is supplied from a DC power supply,
In addition, the current flowing through the arrester is
Since the light is supplied to the light emitting element, a predetermined bias voltage is applied to the light emitting element.
The current flowing through the arrester is divided by the turns ratio of the current transformer.
The superimposed current flows, and the current flows.
The light emission amount is centered on the light amount corresponding to the predetermined bias current.
Changes according to the periodic change of the current flowing through the arrester
Will be. The light emitted from this light emitting element passes through an optical fiber
To the optical-electrical converter, and the electrical
By converting it into a signal and detecting the change in the amount of light emission,
The leakage current flowing through the star can be detected. This leak
The current value is compared and judged by the signal judgment circuit as in the conventional example.
Lever, it is possible to perform quality determination of the arrester.

Here, the secondary winding of the current transformer and the light emitting element
Since a DC blocking capacitor is inserted between
DC current flows from the DC power supply to the secondary winding of the current transformer.
The current transformer does not saturate. In addition, the current transformer
Reduce the number of turns in the secondary winding to increase the current
Thus, the current flowing from the current transformer to the light emitting
Current signal corresponding to the current
When a DC bias current is applied to the optical element,
The resistance of the light-emitting element
The magnetic flux density of the current transformer
Reducing the exciting current that excites the core of the current transformer
The current detection accuracy of the current transformer
The equivalent of the example is obtained. However, the light emission
The change is accurate, but its value is small, so
The circuit at the subsequent stage of the converter is made highly accurate and
It is necessary to accurately convert the change into an electric signal.

Further , the rectifier is connected to the secondary winding of the current transformer.
Discharge surge current flowing through
To the light-emitting element,
It is also possible to measure the number of discharge surges, discharge surge current, etc.
It becomes possible. The arrester discharge surge current is
Flow directly into the light-emitting element by the coil
The light emitting element is protected.

According to the structure of the second aspect, the light emitting element
When a predetermined bias current is supplied from a DC power supply,
In addition, the current flowing through the arrester is
Since the light is supplied to the light emitting element, a predetermined bias voltage is applied to the light emitting element.
The current flowing through the arrester is divided by the turns ratio of the current transformer.
The superimposed current flows, and the current flows.
The light emission amount is centered on the light amount corresponding to the predetermined bias current.
Changes according to the periodic change of the current flowing through the arrester
Will be. The light emitted from this light emitting element passes through an optical fiber
To the optical-electrical converter, and the electrical
By converting it into a signal and detecting the change in the amount of light emission,
The leakage current flowing through the star can be detected. This leak
The current value is compared and judged by the signal judgment circuit as in the conventional example.
Lever, it is possible to perform quality determination of the arrester.

Here, the secondary winding of the current transformer and the light emitting element
Since a DC blocking capacitor is inserted between
DC current flows from the DC power supply to the secondary winding of the current transformer.
The current transformer does not saturate. In addition, the current transformer
Reduce the number of turns in the secondary winding to increase the current
Thus, the current flowing from the current transformer to the light emitting
Current signal corresponding to the current
When a DC bias current is applied to the optical element,
The resistance of the light-emitting element
The magnetic flux density of the current transformer
Reducing the exciting current that excites the core of the current transformer
The current detection accuracy of the current transformer
The equivalent of the example is obtained. However, the light emission
The change is accurate, but its value is small, so
The circuit at the subsequent stage of the converter is made highly accurate and
It is necessary to accurately convert the change into an electric signal.

Also, one end of the secondary winding of the current transformer and
When leakage current is supplied to the light emitting element from between the intermediate taps
The rectifier is passed from both ends of the secondary winding of the current transformer.
Of the surge current flowing through the
Flow to the light-emitting element, causing the arrester to discharge
It is also possible to measure the number of surges, discharge surge current, etc.
Becomes Also, the discharge surge current of the arrester is
The stop coil does not flow directly into the light-emitting element.
In addition, the light emitting element is protected.

According to the structure of the third aspect, the light emitting element
When a predetermined bias current is supplied from a DC power supply,
In addition, the current flowing through the arrester is
Since the light is supplied to the light emitting element, a predetermined bias voltage is applied to the light emitting element.
The current flowing through the arrester is divided by the turns ratio of the current transformer.
The superimposed current flows, and the current flows.
The light emission amount is centered on the light amount corresponding to the predetermined bias current.
Changes according to the periodic change of the current flowing through the arrester
Will be. The light emitted from this light emitting element passes through an optical fiber
To the optical-electrical converter, and the electrical
By converting it into a signal and detecting the change in the amount of light emission,
As possible out is possible to detect the leakage current flowing through the static. This leak
The current value is compared and judged by the signal judgment circuit as in the conventional example.
Then, the quality of the arrester can be determined.

Here, the secondary winding of the current transformer and the light emitting element
Since a DC blocking capacitor is inserted between
DC current flows from the DC power supply to the secondary winding of the current transformer.
The current transformer does not saturate. In addition, the current transformer
Reduce the number of turns in the secondary winding to increase the current
Thus, the current flowing from the current transformer to the light emitting
Current signal corresponding to the current
When a DC bias current is applied to the optical element,
The resistance of the light-emitting element
The magnetic flux density of the current transformer
Reducing the exciting current that excites the core of the current transformer
The current detection accuracy of the current transformer
The equivalent of the example is obtained. However, the light emission
The change is accurate, but its value is small, so
The circuit at the subsequent stage of the converter is made highly accurate and
It is necessary to accurately convert the change into an electric signal.

Further, the light emitting element is connected to the secondary winding of the current transformer.
Leakage current is supplied to the
Discharge circuit flowing from the secondary winding of the current transformer through the rectifier
The current is divided into appropriate values by the shunting means,
Arrestor discharge surge frequency and discharge
It is also possible to measure surge current and the like. Also,
The discharge surge current of the restor is controlled by the surge suppression coil.
Light does not flow directly into the light-emitting element, protecting the light-emitting element
Is done.

[0058]

【Example】 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Will be described.

First Embodiment FIG. 9 is a circuit diagram of a leakage current detecting sensor according to a first embodiment of the present invention. As shown in FIG. 9, this leakage current detection sensor detects deterioration of an arrester 2 for overvoltage protection connected between a one-phase system bus 1 and the ground 4 in a three-phase power receiving and transforming facility, for example. The primary winding of the current transformer 3 for detecting the current is provided in series with the arrester 2.

A light emitting element 6 such as a light emitting diode or a laser diode is provided between both ends of the secondary winding of the current transformer 3 via a surge blocking coil 23, a current limiting resistor 25 and a DC blocking capacitor 5. A DC power supply 8 for supplying a bias current is connected between both ends of the light emitting element 6 via a coil 26 and a current limiting resistor 7. A bridge type rectifier 24 for bypassing and rectifying the discharge surge voltage is connected between both ends of the secondary winding of the current transformer 3. Two protection diodes 9, 10 for protecting the light emitting element 6 from a discharge surge voltage are connected in anti-parallel between both ends of the series circuit. The output terminal of the rectifier 24 is connected to the light emitting element 6 through a current dividing means including resistors 27 to 30 so that a current obtained by shunting the discharge surge current to an appropriate value flows to the light emitting element 6. This shunt means also includes two overvoltage protection diodes 3 for protecting the light emitting element 6 from a discharge surge voltage in a series circuit of the resistor 30 and the light emitting element 6 therein.
1, 32 are connected in anti-parallel.

The light emitting element 6 includes an optical fiber 1 for optical transmission.
The first end is optically coupled to the other end of the optical fiber 11 light - in mesh light forming the optical signal input portion of the electrical converter 12. This light-
The first terminal 14 is connected to an electric signal output portion of the electric converter 12 through a DC cutoff capacitor 13 and a coil 33.
Is provided, a second terminal 19 is provided via a low-pass filter including a coil 34 and resistors 15 and 16 and capacitors 17 and 18, and a third terminal 36 is provided via a capacitor 13 and a capacitor 35. Is provided. The terminals 14, 19, and 36 are connected to a high-precision signal determination circuit (not shown). The terminal 14 outputs a signal corresponding to the leakage current, the terminal 19 outputs a signal corresponding to the bias current, and the terminal 36 outputs a signal corresponding to the discharge surge.

Next, the operation of the leakage current detection sensor will be described.

The light emitting element 6 has a threshold voltage of, for example, about 1.5 to 2 V, and emits light only when a voltage exceeding the threshold voltage is applied between both ends to emit light. Even if the secondary winding of the current transformer 3 is simply connected, the light emitting element 6 does not emit light. Therefore, a predetermined bias current is applied to the light emitting element 6 from the DC power supply 8 having a voltage higher than the threshold voltage of the light emitting element 6 through the current limiting resistor 7 and the coil 26 to emit light with a constant light amount (low level).
At this time, the current flowing out of the DC power supply 8 is cut off by the DC cut-off capacitor 5 and does not flow into the secondary winding of the current transformer 3. The transformer 3 does not saturate.

[0064] In this state, when the leakage current of several μ to several hundreds μA to arrester 2 flows, current inversely proportional to the primary secondary turns ratio in the secondary winding of the current transformer 3 flows ,
This current flows into the light emitting element 6 through the surge blocking coil 23, the resistor 25 and the DC blocking capacitor 5. As a result, the current i flowing through the light emitting element 6 includes a constant bias current i ₀ flowing from the DC power supply 8 and a small leakage current Δi flowing from the secondary winding of the current transformer 3.
₀ (Originally means the primary current of the current transformer 3,
(For convenience, the secondary current of the current transformer 3 is referred to as leakage current). The minute leakage current Δi ₀ is a sine wave of the same frequency as the power supply frequency of the system bus 1, for example, 50/60 Hz (when there is no distortion).

When the current i (= i ₀ + Δi ₀ ) flows into the light emitting element 6, the light emitting element 6 emits light according to the current i. The light emission amount I is the sum of a constant light amount I ₀ corresponding to the bias current i ₀ and a light amount ΔI ₀ that changes periodically according to the leakage current Δi ₀ . That is, the light emission amount I of the light emitting element 6 when the leakage current flows through the arrester 2 is as shown in FIG.
0 (a), the light amount ΔI around the light amount I ₀
It will change in a sinusoidal manner by ₀ .

The light emitted from the light emitting element 6 is
Is transmitted to the optical-to-electrical converter 12 and is converted into an electric signal by the optical-to-electrical converter 12 to detect the variation width of the light emission amount, whereby the leakage current flowing through the arrester 2 can be detected. If the value of the leakage current is compared and determined by the signal determination circuit in the same manner as in the conventional example, the quality of the arrester 2 can be determined.

More specifically, light emitted from the light emitting element 6 is transmitted through the optical fiber 11 to the optical-electrical converter 12.
The electrical signal having a waveform similar to the waveform of FIG. 10A is output from the optical-electrical converter 12. The output signal of the optical-to-electrical converter 12 includes a capacitor 13 and a coil 3
3 to the first terminal 14, and to the second terminal 19 via the coil 34 and the resistors 15 and 16 and the capacitors 17 and 18, and to the capacitor 13 and the capacitor 3.
5 to the third terminal 36. As a result, the first
The terminal 14 outputs a light quantity ΔI ₀ , that is, a voltage signal Δj ₀ corresponding to the current Δi ₀ as shown in FIG. Further, from the second terminal 19, the amount of light I _0, i.e. the voltage signal as shown in FIG. 10 (c) which corresponds to the current i ₀ j
₀ is output. The voltage signal j _{S at} the third terminal 36 is zero. Then, the three voltage signals are sent to a signal determination circuit (not shown), and the level of the leakage current is determined. The determination of the level of the leakage current will be described later.

On the other hand, when the arrester 2 operates and an excessive discharge surge current flows, the discharge surge current also flows in the secondary winding of the current transformer 3 in accordance with the turns ratio. Most of the rectifier 24
After flowing through the light emitting device 6, the light is rectified by the current flowing through the light emitting device 6, and further shunted by the shunting means including the resistors 27 to 30. This variation in light emission amount I is light intensity I _S by discharging the surge current shown in FIG. 10 (a), its frequency is very high compared to the light emission amount [Delta] I ₀ corresponding to the leakage current. Also at this time, the optical-electrical
An electric signal having a waveform similar to the waveform of (a) is output. The output signal of the optical-electrical converter 12 is sent to the first terminal 14 through the capacitor 13 and the coil 33 in the same manner as described above.
The signal is sent to the second terminal 19 via the switches 7 and 18 and supplied to the third terminal 36 through the capacitors 13 and 35. As a result, the first and second terminals 14, 19
Figure output is the same as above, from the third terminal 36 corresponding to the quantity I _S, i.e. discharge surge current i _S 10
A voltage signal j _S as shown in FIG. At this time, the overvoltage protection diodes 9, 10, 3
The light emitting element 6 is protected by the action of the arrester 2 due to the action of the arrester 2 and a discharge surge is generated, so that the light emitting element 6 is not destroyed by an excessive discharge surge voltage.

Here, the method of judging the level of the leakage current is the same as that described in the first proposal example, and the description is omitted. Also, the discharge surge current can be detected in the same manner as the leakage current by taking into account the shunt ratio and the like by the shunt means.

As described above, in this leakage current detection sensor, the discharge surge current flowing from the secondary winding of the current transformer 3 through the rectifier 24 is divided into an appropriate value by the current dividing means composed of the resistors 27 to 30. As a result, the number of discharge surges and the discharge surge current of the arrester 2 can be measured. Further, the discharge surge current of the arrester 2 does not flow directly into the light emitting element 6 by the surge blocking coil 23, and the light emitting element 6 is protected.

According to the leakage current detection sensor of this embodiment, the surge suppression coil 23 prevents the discharge surge current from flowing from the secondary winding of the current transformer 3 to the light emitting element 6, and also suppresses the surge suppression coil. A rectifier 24 for rectifying a discharge surge current is provided between both ends of the secondary winding of the current transformer 3 on the current transformer 3 side of the rectifier 23. The discharge surge current flowing through the rectifier 24 is connected to resistors 27 to 30.
The light-emitting element 6 is divided into appropriate values by a dividing means comprising
, The number of discharges and discharge current of the arrester 2 can be measured.
Can be protected from discharge surge. Other effects are similar to those of the first proposed example.

Second Embodiment FIG. 11 is a circuit diagram of a leakage current detection sensor according to a second embodiment of the present invention. As shown in FIG. 11, this leakage current detection sensor is provided between one end of a secondary winding of a current transformer 42 and an intermediate tap, and includes surge blocking coils 23 and 38, a current limiting resistor 25 and a DC blocking capacitor. A light-emitting element 6 such as a light-emitting diode or a laser diode is connected via a reference numeral 5, and a DC power supply 8 for supplying a bias current is connected between both ends of the light-emitting element 6 via a current-limiting resistor 7.

A bridge type rectifier 37 for bypassing and rectifying the discharge surge voltage is connected between both ends of the secondary winding of the current transformer 42. The output terminal of the rectifier 37 is connected to the light emitting element 6 via a current dividing means composed of resistors 39 to 41, so that a current obtained by shunting a discharge surge current to an appropriate value flows to the light emitting element 6.

The light emitting element 6 includes an optical fiber 1 for optical transmission.
The first end is optically coupled to the other end of the optical fiber 11 light - in mesh light forming the optical signal input portion of the electrical converter 12. This light-
A circuit similar to that of FIG. 9 is connected to an electric signal output unit of the electric converter 12.

In this embodiment, when detecting a discharge surge, the number of turns of the secondary winding of the current transformer 42 is increased as compared with the current transformer 3 of the first proposed example. The current is supplied to the light emitting element from one end of the transformer 42 and the intermediate tap (the same number of turns as the current transformer 3), and the discharge surge current is configured to supply the current from both ends of the current transformer 42. The transformation ratio of the surge current is increased to reduce the current on the secondary side, so that the shunt ratio by the shunt means including the resistors 39 to 41 can be made smaller than that in FIG. Other operations are the same as those in FIG.

According to the leakage current detection sensor of this embodiment, the surge surge coils 23 and 38 prevent the discharge surge current from flowing into the light emitting element 6 from one end of the secondary winding of the current transformer 42 and between the intermediate taps. While blocking
A rectifier 37 for rectifying a discharge surge current is provided between both ends of the secondary winding of the current transformer 42. The discharge surge current flowing through the rectifier 37 is divided into appropriate values by current dividing means including resistors 39 to 41 to emit light. Since the current is supplied to the element 6, the number of discharges and the discharge current of the arrester 2 can be measured, and the light emitting element 6 can be protected from a discharge surge.

[ Third Embodiment] FIG. 12 is a circuit diagram of a leakage current detection sensor according to a third embodiment of the present invention. As shown in FIG. 12, the leakage current detection sensor includes a light-emitting diode, a laser diode, and the like between both ends of a secondary winding of a current transformer 3 via a surge blocking coil 23 and a DC blocking capacitor 5. The light emitting element 6 is connected, and a DC power supply 8 for supplying a bias current is connected between both ends of the light emitting element 6 via a current limiting resistor 7 and a coil 26.

Further, a discharge surge voltage is bypassed between both ends of the secondary winding of another current transformer 43 (for a high frequency having a ferrite core or the like, preferably having a larger number of turns than the current transformer 3). And a bridge-type rectifier 44 for rectifying the power. The output terminal of the rectifier 44 is connected to the resistors 45 and 4.
6 is connected to the light emitting element 6 via a DC dividing means 47 and a DC blocking capacitor 47, so that a current obtained by shunting the discharge surge current to an appropriate value flows to the light emitting element 6. At this time, the bias current becomes
And the current transformer 43 does not saturate.

The light emitting element 6 includes an optical fiber 1 for optical transmission.
The first end is optically coupled to the other end of the optical fiber 11 light - in mesh light forming the optical signal input portion of the electrical converter 12. This light-
A circuit similar to that of FIG. 9 is connected to an electric signal output unit of the electric converter 12.

In this embodiment, in detecting a discharge surge, in addition to the current transformer 3 similar to the first proposed example,
In order to detect a discharge surge current, a current transformer 43 is added, and the discharge surge current is supplied from both ends of the current transformer 43. In this case, it is desirable to increase the number of secondary windings of the current transformer 43 to reduce the current on the secondary side, and to reduce the shunt ratio by the shunt means including the resistors 45 and 46 as compared with that of FIG. Other operations are the same as those in FIG.

According to the leakage current detecting sensor of this embodiment, the surge blocking coil 23 prevents the discharge surge current from flowing into the light emitting element 6 from between both ends of the secondary winding of the current transformer 3.
A rectifier 44 for rectifying the discharge surge current is provided between both ends of the secondary winding of the current transformer 43, and the discharge surge current flowing through the rectifier 44 is adjusted to an appropriate value by a shunting means including resistors 45 and 46. In this case, the number of discharges and the discharge current of the arrester 2 can be measured, and the light-emitting element 6 can be protected from a discharge surge.
Further, since the DC blocking capacitor 47 is provided, the current transformer 43 does not saturate. Other effects are the same as those in FIG.

Note that two overvoltage protection diodes may be provided in anti-parallel between both ends of the secondary winding of the current transformer 3 as in FIG. 1 to protect the light emitting element 6. .

[0083] In each of the above embodiments, the leakage of the arrester
The one that detects current has been described, but it is not limited to this.
Measure the leakage current of insulators, insulating spacers, etc.
Detecting the extent of these degradations can be done as well
You.

[0084]

According to the leakage current detection sensor of the present invention, the current flowing through the arrester is detected by the current transformer, and the detected current is supplied to the light emitting element as a current signal via the DC blocking capacitor. A predetermined bias current is supplied to the light emitting element from a DC power supply, and the light output from the current transformer is reduced by changing the light output of the light emitting element according to the current flowing through the arrester centering on the light amount corresponding to the bias current. Since the current flowing through the arrester is detected based on the change in the light output of the light emitting element, it is possible to accurately detect the leakage current flowing through the arrester even if the number of turns of the secondary winding of the current transformer is reduced. In addition, it is possible to easily manufacture a current transformer for detecting a leakage current flowing through the arrester, and to reduce the size and cost of the current transformer.

Further, the leakage current of the arrester can be detected without the need for an insulating amplifier and an amplifier, so that the number of parts can be reduced. In addition to the downsizing of the current transformer, the overall size can be reduced and the cost can be reduced. Can be

Further, since the light output of the light emitting element is directly changed by the secondary output of the current transformer, the propagation of the surge can be reliably prevented, and the protection of the circuit elements constituting the signal determination circuit and the like can be protected. Can be performed reliably.

Further, since an insulating amplifier, an amplifier and the like are not used, the number of active elements such as a bipolar transistor and a field effect transistor can be reduced, and the failure probability of the leakage current detection sensor can be reduced.

Further, the surge suppressor prevents the discharge surge current from flowing from the secondary winding of the current transformer to the light emitting element, and the secondary of the current transformer is located closer to the current transformer than the surge suppressor coil. A rectifier for rectifying the discharge surge current is provided between both ends of the winding, and the discharge surge current flowing through this rectifier is diverted to an appropriate value by the shunting means to flow to the light emitting element. Can be measured, and the light emitting element can be protected from a discharge surge.

According to the leakage current detecting sensor of the second aspect , the current flowing through the arrester is detected by the current transformer, and
The light emitting element as a current signal through the DC blocking capacitor
To the light-emitting element,
A constant bias current is supplied, and the light output of the light emitting
Current flowing through the arrestor centered on the amount of light corresponding to the
Negative from the viewpoint of the current transformer
A load is reduced, the arrester from the change in the output of the light emitting element
To detect the current flowing through the current transformer.
Even when the number of turns of the secondary winding is small, it flows into the arrestor accurately.
Leakage current can be detected and leakage current flowing through the arrester
Facilitates the manufacture of current transformers for the detection of
The device can be reduced in size and cost.

Also, if an insulating amplifier and an amplifier are required,
The leak current of the arrester can be detected without
And the overall size of the current transformer
And cost reduction
Can be.

Further, light is directly emitted from the secondary output of the current transformer.
Since the optical output of the element is changed, the propagation of surge
It can actually be blocked and constitutes a signal judgment circuit etc.
The circuit element can be reliably protected.

Further, an insulating amplifier and an amplifier are used.
Do not use bipolar transistors or field-effect transistors.
Active elements such as transistors can be reduced, and the leakage current detection
The failure probability of the sensor can be reduced.

Further, a surge blocking coil prevents a discharge surge current from flowing into the light emitting element from one end of the secondary winding of the current transformer and between the intermediate taps, and both ends of the secondary winding of the current transformer. A rectifier for rectifying the discharge surge current is provided between the rectifiers, and the discharge surge current flowing through the rectifier is divided into appropriate values by the shunting means to flow to the light emitting element. It is also possible to protect the light emitting element from a discharge surge.

According to the third aspect of the present invention , the current flowing through the arrester is detected by the current transformer, and
The light emitting element as a current signal through the DC blocking capacitor
To the light-emitting element,
A constant bias current is supplied, and the light output of the light emitting
Current flowing through the arrestor centered on the amount of light corresponding to the
Negative from the viewpoint of the current transformer
A load is reduced, the arrester from the change in the output of the light emitting element
To detect the current flowing through the current transformer.
Even when the number of turns of the secondary winding is small, it flows into the arrestor accurately.
Leakage current can be detected and leakage current flowing through the arrester
Facilitates the manufacture of current transformers for the detection of
The device can be reduced in size and cost.

Also, the need for an isolation amplifier and an amplifier
The leak current of the arrester can be detected without
And the overall size of the current transformer
And cost reduction
Can be.

Further, light is directly emitted from the secondary output of the current transformer.
Since the optical output of the element is changed, the propagation of surge
It can actually be blocked and constitutes a signal judgment circuit etc.
The circuit element can be reliably protected.

Further, an insulating amplifier and an amplifier are used.
Do not use bipolar transistors or field-effect transistors.
Active elements such as transistors can be reduced, and the leakage current detection
The failure probability of the sensor can be reduced.

Further, a surge surge prevention coil prevents a surge current from flowing from the secondary winding of the current transformer into the light emitting element, and a current transformer for detecting a surge discharge is provided. A rectifier is provided in the secondary winding of the rectifier to rectify the discharge surge current, and the discharge surge current flowing through this rectifier is diverted to an appropriate value by the shunting means to flow to the light emitting element. It is also possible to measure current etc.
In addition, the light emitting element can be protected from a discharge surge.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a leakage current detection sensor according to a first proposed example of the present invention.

FIG. 2 is a waveform diagram showing waveforms at various parts of the leakage current detection sensor of FIG.

FIG. 3 is a characteristic diagram of current-light emission amount of a light-emitting element.

FIG. 4 is a circuit diagram showing a state in which an arrester is connected to a system bus.

FIG. 5 is a waveform diagram showing a waveform of a leakage current (large current) of the arrester.

FIG. 6 is a waveform diagram showing a waveform of a leakage current (small current) of the arrester.

FIG. 7 is a circuit diagram showing a configuration of a leakage current detection sensor according to a second proposed example of the present invention.

FIG. 8 is a circuit diagram showing a configuration of a leakage current detection sensor according to a third proposed example of the present invention.

FIG. 9 is a circuit diagram showing a configuration of a leakage current detection sensor according to the first embodiment of the present invention.

FIG. 10 is a waveform chart showing waveforms at various parts of the leakage current detection sensor of FIG.

FIG. 11 is a circuit diagram showing a configuration of a leakage current detection sensor according to a second embodiment of the present invention.

FIG. 12 is a circuit diagram showing a configuration of a leakage current detection sensor according to a third embodiment of the present invention.

FIG. 13 is a block diagram illustrating a configuration of an example of a conventional leakage current detection sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 System bus 2 Arrester 3 Current transformer 4 Ground 5 DC cutoff capacitor 6 Light emitting element 7 Current limiting resistor 8 DC power supply 9,10 Overvoltage protection diode 11 Optical fiber 12 Optical-electrical converter 13 Capacitor 14 First terminal 15 , 16 resistor 17, 18 capacitor 19 second terminal 20 surge bypass capacitor 21 resistor 22 surge blocking coil 23 surge blocking coil 24 rectifier 25 resistor 26 coil 27-30 resistor 31, 32 overvoltage protection diode 33, 34 coil 35 Capacitor 36 Third Terminal 37 Rectifier 38 Coil 39-41 Resistance 42 Current Transformer 43 Current Transformer 44 Rectifier 45, 46 Resistance 47 Capacitor

Continuation of the front page (56) References JP-A-2-73165 (JP, A) JP-A-5-273285 (JP, A) JP-A-5-87866 (JP, A) JP-A-55-128161 (JP) JP-A-57-182178 (JP, A) JP-A-58-76248 (JP, U) JP-A-61-40668 (JP, U) JP-A-5-48189 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01R 31/12, 31/08 G01R 15/00-15/26

Claims (3)

(57) [Claims] A current transformer for detecting a leakage current flowing in an arrestor or an insulating material; and a current transformer connected between both ends of a secondary winding of the current transformer via a DC blocking capacitor. A light emitting element to which a current of the next winding is supplied, a DC power supply connected to the light emitting element and supplying a predetermined bias current to the light emitting element, an optical fiber for transmitting an optical output of the light emitting element, and the optical fiber -To-electrical converter for converting the output light of the current into an electric signal, and a secondary winding of the current transformer
A circuit inserted and connected in the path from the wire to the light emitting element
From the surge suppression coil and the surge suppression coil.
On both sides of the secondary winding of the current transformer on the side of the current transformer
To rectify by bypassing discharge surge current
Current surge and the surge current flowing through this rectifier.
A leakage current detection sensor comprising: a shunt means for shunting the light to a light value and flowing the light to the light emitting element . 2. An arrester having an intermediate tap in a secondary winding.
A current transformer that detects leakage current flowing in
Between one end of the secondary winding of this current transformer and the intermediate tap
Connected via a DC blocking capacitor to transform the current
Light-emitting element to which current is supplied to the secondary winding of the
A predetermined bias current is supplied to the light emitting element and connected to the light emitting element.
DC power supply and light for transmitting the light output of the light emitting element
Fiber and the output light of this optical fiber are converted into electrical signals
And a secondary winding of the current transformer.
In the path from the end and the intermediate tap to the light emitting element
A surge suppression coil inserted and connected to the current transformer;
Is installed between both ends of the secondary winding to bypass discharge surge
Rectifier and discharge flowing through the rectifier
Shunt current is shunted to an appropriate value and the secondary of the current transformer is
Add the current between one end of the winding and the intermediate tap to
A leakage current detection sensor comprising a shunt means for flowing an optical element . 3. A leakage current flowing through an arrestor or an insulating material.
Both the current transformer to be detected and the secondary winding of this current transformer
Connected between the terminals via a DC blocking capacitor.
A light-emitting element to which the current of the secondary winding of the current transformer is supplied;
Is connected to a predetermined light emitting element.
DC power supply to supply current and light output of the light emitting element
Optical fiber and the output light of this optical fiber
And a secondary winding of the current transformer
Surge block inserted in the path from the wire to the light emitting element
And a discharge coil that flows through the arrestor and the insulating material.
Discharge surge detection current transformer that can also detect surge current
And both ends of the secondary winding of the current transformer for discharge surge detection
Rectifier that is connected between and bypasses discharge surge and rectifies
And the discharge surge current flowing through this rectifier
And shunts the current to the secondary winding current of the current transformer.
And a shunt means for flowing the light to the light emitting element .