JP2002315180A - Current optical differential system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a current optical differential system that a transmission line and a signal processing section isolated each other are required. SOLUTION: The current optical differential system comprises a plurality of photocurrent sensors 113, a transmission line 112 connecting them in series, and a signal processing section 115 for inputting light from a light source section 111 to the transmission line 112 and detecting a failure of an objective conductor based on the quantity of light detected by each sensor wherein the sensors fixed to respective conductors separated into three-phases are connected entirely in series such that the incident light from the light source is outputted as a sample quantity Ik based on the following formula thus detecting any fault in three-phases. Ik =(Ka1 Ia1 +Kb1 Ib1 +Kc1 Ic1 +K01 I01 )+(Ka2 Ia2 +Kb2 Ib2 +Kc2 Ic2 +K02 I02 )+...(Kan Ian +Kbn Ibn +Kcn Icn +K0n I0n ), where Ia(square) , Ib(square) , Ic(square) , I0(square) : a, b, c three-phase current values and zero-phase current value of (square)-th photocurrent sensor. Ka(square) , Kb(square) , Kc(square) , K0(square) : coefficients for a, b, c three-phase current values and zero-phase current value of (square)-th photocurrent sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current-optical differential system for detecting a fault occurring in a conductor in a power distribution facility or the like.

[0002]

2. Description of the Related Art FIGS. 7, 8 and 9 show examples of a conventional current optical differential system. FIG. 7 shows an example in which each phase is configured, and the phase A will now be described. The other phases B and C make the same movement as the phase A. Linearly polarized light is emitted from the light source section 711 and passes through a sensor group 714 in which a plurality of sensor sections 713 having the same sensitivity as the transmission path section 712 are connected in series, and penetrates the sensor section 713 in the sensor group 714. The output light reflects the differential current of the output current.

The output light is input to a signal processing unit 715, and if the input light equivalent to the differential current has reached a predetermined sensitivity,
It is determined that the conductor surrounded by the sensor unit 713 has a failure, and a signal is output from the output unit 716 to the outside. FIG.
Is an example of a configuration in which the outputs of the signal processing units 715 of each phase in FIG. 7 are combined, and an output processing unit 717 that outputs a signal is added.

FIG. 9 shows an example of the sensor group 714 shown in FIG.
The conductor 920 separated into three phases of a phase, b phase, and c phase includes:
Each has several drawers, and the drawers
Each I _a1, I_a2, ..., I_an, I_b1, I_b2, ..., I_bn,
I_c1, I_c2, ..., I_cnIs flowing.

The same sensitivity sensor 921 whose polarization plane direction rotates in proportion to the current flowing therethrough due to the Faraday effect is provided at all the outlets of the conductor 920 to be protected.
And optical elements 923 that convert linearly polarized light into circularly polarized light or vice versa are attached to both ends of the sensor 921, and the optical transmission path 922 that maintains the polarization plane orientation between the optical elements 923 of each sensor 921. , Sensor 9 for each phase
The system is configured by combining the two.

Here, taking the example of the phase a as a representative of the three phases, the linearly polarized light incident from the optical transmission line 922 that maintains the polarization plane orientation, which is one end of the system, is the optical element 923 , Is converted from linearly polarized light into circularly polarized light, and is incident on a sensor 921 having a Faraday effect. The circularly polarized light that has entered the sensor 921 has a current I flowing through a conductor 920 to which the sensor 921 is attached.
_The polarization plane direction is rotated according to _{□ n,} and the light is converted from circularly polarized light into linearly polarized light by the optical element 923 and enters the optical transmission line 922.

Similarly, the light that has passed through the sensor 921 attached to the a-phase conductor 920 one after another is transmitted to the optical transmission line 92 that maintains the polarization plane orientation at the other end of the system.
By (2), a linearly polarized light reflecting the differential current Id based on the equation (1) is output.

[Number 2] _{Id = I a1 + I a2 +} ... + I an .................. (1) I a1 + I a2 + ... + I an = 0 .................. (2) I a1 + I a2 + ... + I an ≠ 0 (3) where I _{a □} : a-phase current value of the □ th photocurrent sensor.

For example, if an accident does not exist in the conductor in the protection section, equation (2) is obtained according to Kirchhoff's law, but if an accident exists in the a-phase conductor, equation (3) is obtained. . By using such a method for the b-phase and the c-phase, a fault in the conductor can be detected.

These are described, for example, in the Institute of Electrical Engineers of Japan, Protection Principles of Protection Relay Systems, PSR-99-8, "Basic Study on Current Differential Protection Systems Applying Optical CT Technology," and in the National Institute of Electrical Engineers of Japan, 6-295, "Lead. Glass fiber type light C
Optical phase detection method current differential protection operation system using T "
Etc., such as the loop type shown in, etc.
No. 1998, it can be realized in a reflection type such as "Development of an optical current transformer using a twisted double coated fiber".

[0010]

However, in this current-optical differential system, a photocurrent sensor is connected in series for each conductor separated into three phases, so that a transmission line and a signal processing section separated into three phases are connected. Needed. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. It is intended to provide a differential system.

[0011]

According to a first aspect of the present invention, there is provided a current optical differential system comprising: a plurality of photocurrent sensors arranged so as to detect a failure of a target conductor; A transmission line that connects sensors in series, and a signal processing unit that receives the input of light serving as a light source and the output of light changed by each sensor in this transmission line, and detects the failure of the target conductor from the received light amount in becomes the current optical differential system, the light incident from the light source by connecting the respective sensor attached to people conductor respectively separated in all three phases in series is output as the sample quantity I _k based on the following equation (4) By doing so, any faults in the three phases were detected. Record

I _k = (K _a1 I _a1 + K _b1 I _b1 + K _c1 I _c1 + K ₀₁ I ₀₁ ) + (K _a2 I _a2 + K _b2 I _b2 + K _c2 I _c2 + K ₀₂ I ₀₂ ) + ... (K _an I _an + K _bn I _bn + K _cn I _cn + K _0n I _0n ) (4) where I _{a □} , I _{b □} , I _{c □} , I _{0 □} : the □ th photocurrent A, b, c three-phase and zero-phase current values of the sensor. Ka _□ , _{Kb □} , _{Kc □} , K0 _□ : Coefficients for the three-phase and zero-phase current values of the □ th photocurrent sensor.

According to a second aspect of the present invention, there is provided a current optical differential system according to the first aspect, wherein the optical current sensor and the transmission line are connected so that a short-circuit fault and a ground fault can be individually determined. The signal processing part is separated for short-circuit detection and ground fault detection,
The specimen amount I _k to derive was to be separated by and for detecting short-circuited with a ground fault detecting.

According to a third aspect of the present invention, in the current optical differential system according to the first aspect, coefficients K _{a □} , K _{b □} , K _{c □} , and K _{0 □} are used for deriving the sample amount I _k. In order to change the sensitivity, the sensitivity of each photocurrent sensor is changed in proportion to the coefficient.

According to a fourth aspect of the present invention, in the current optical differential system according to the first aspect, coefficients K _{a □} , K _{b □} , K _{c □} , and K _{0 □} are used for deriving the sample amount I _k. In order to change the number of turns, the number of turns of a photocurrent sensor having the same sensitivity is changed in proportion to the coefficient.

In the current optical differential system according to claim 5 of the present invention, in claim 2, coefficients K _{a □} , K _{b □} , K _{c □} , K _{0 □} for deriving the sample amount I _k. In order to change the sensitivity, the sensitivity of each photocurrent sensor is changed in proportion to the coefficient.

In the current optical differential system according to claim 6 of the present invention, in claim 2, the coefficients K _{a □} , K _{b □} , K _{c □} , K _{0 □ in} deriving the sample amount I _k. In order to change the number of turns, the number of turns of a photocurrent sensor having the same sensitivity is changed in proportion to the coefficient.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The current-optical differential system according to the present invention has the same configuration as that of the conventional current-optical differential system. Therefore, referring to FIG. The overall configuration of the motion system will be described.

Linearly polarized light is emitted from the light source 111 to the transmission path 112, and the transmission path 112 outputs light to the next block while maintaining the polarization plane of the input light. Transmission line section 11
The sensor unit 113 receiving the light from 2 rotates the plane of polarization in proportion to the current flowing through the conductor passing through the sensor 113. Here, the output light whose polarization plane is rotated is transmitted to the transmission path unit 112.
Through to the next sensor unit 113.

Finally, a plurality of these sensors 113 are passed through a group of sensors 114 connected in series,
An output light reflecting a sample amount Ik calculated by each current passing through the sensor unit 113 in the sensor group 114 is output. The output light is input to the signal processing unit 115, and if the input light has reached a predetermined sensitivity, it is determined that the conductor surrounded by the sensor unit 113 has a failure, and the output unit 11
6 to output a signal to the outside.

(First Embodiment) (corresponding to [Claim 1]) FIG. 2 shows an example of the sensor group 114 in FIG. Each of the conductors 230 separated into each phase has several outlets, and the outlets respectively include I _a1 , I _a2 ,..., I _an ,
_{I b1, I b2, ...,} I bn, I c1, I c2, ..., and current is flowing that I _cn.

A sensor 231 whose polarization plane direction is rotated in proportion to the current flowing therethrough by the Faraday effect is wound around all the outlets of the conductor 230 to be the protection range. A system is configured by attaching an optical element 233 for converting to circularly polarized light or vice versa, and connecting all the sensors 231 by an optical transmission path 232 for maintaining the polarization plane orientation between the optical elements 233 of each sensor 231. I do.

The linearly polarized light incident from the optical transmission line 232 that maintains the polarization plane orientation, which is one end of the system, is converted from the linearly polarized light into a circularly polarized light by passing through the optical element 233, and the Faraday effect is obtained. Incident on the sensor 231. The circularly polarized light incident on the sensor 231 is a current I _{□ n} flowing through a conductor to which the sensor 231 is attached.
, The direction of the plane of polarization rotates according to a proportionality constant K _{□ n} previously determined so that various accidents can be detected.

Therefore, the light is converted from circularly polarized light into linearly polarized light by the optical element 233 and enters the optical transmission line 232.
Similarly, the light that has passed through all the sensors one after another passes through the optical transmission line 232 that maintains the polarization plane orientation at the other end of the system, and the sample amount I based on the above equation (3) (4) is obtained.
Outputs linearly polarized light of _k .

For example, the sensitivities of the sensors installed in each of the three phases a, b, and c are expressed as K _{a □} = 3, K _{b □} = 2, K _{c □} = 1,
Assuming that K _{0 □} = 0 (because there is no sensor corresponding to zero phase), if there is no accident in the conductor in the protection zone, Equation (5) is obtained according to Kirchhoff's law, (6) when there is an accident in the conductor, Ik = 0 when there is no accident in the conductor, and Ik ≠ 0 when there is an accident in the conductor, and a fault in the conductor can be detected. .

[0025]

I _a1 + I _a2 +... + I _an = 0 I _b1 + I _b2 +... + I _bn = 0 I _c1 + I _c2 +... + I _cn = 0... I _a1 + I _a2 +... + I _an 0 I _b1 + I _b2 +... + I _bn = 0 I _c1 + I _c2 +... + I _cn = 0 …………………… (6)

The currents of the phases a, b, and c at the respective outlets are expressed by the following equation (7). Here, since the sample amount I _k is given by the equation (9), it can be understood that any value can be taken depending on the state of the fault in the conductor. Therefore,
The magnitude of I _k makes it possible to determine a fault in the conductor.

[Expression 5] 3Ia _□ + 2Ib _□ + 1Ic _□ ………… (7) 2Ia _□ + _Ib + 3I0 _□ ............ (8) I _k = Ｉ2Ia _□ + _Ib + 3I0 _□ ............ (9)

According to this embodiment, all the sensors 23
1 can be connected in series, so that the transmission path, light source, and signal processing unit, which were conventionally separated for each phase, can be shared. Can be built.

(Second Embodiment) (corresponding to [Claim 2]) FIG. 3 is a configuration diagram showing a second embodiment. In FIG. 3, the same reference numerals denote the same functional parts as in FIG. And the description is omitted. In this embodiment, the portion from the light source section 111 to the output section 116 is separated for short-circuit detection and ground fault detection.

According to the present embodiment, the transmission line section, the light source section, and the signal processing section conventionally separated for each phase can be shared for short-circuit detection and ground fault detection. It is excellent in maintenance and can construct a simple but equivalent system. In addition, it is possible to detect with high sensitivity even in a system with a small ground fault current.

[0030] (Third Embodiment) ([Claim 3] corresponding) the third embodiment, coefficients in the derivation of the specimen amount _{I k K a □, K b} □, K c □, K 0 To change _□
The sensitivity of each photocurrent sensor is changed in proportion to the coefficient. For example, if the length of each optical current sensor the same, based on the sensitivity of _{K c □, K b □ =} 2K c □, K
Use a sensor with a sensitivity of _{a □} = 3K _{c □} .

According to the present embodiment, all the sensors 23
1 can be connected in series, so that the transmission path, light source, and signal processing unit, which were conventionally separated for each phase, can be shared. Can be built.

(Fourth Embodiment) (Claim 4)
A) In the fourth embodiment, the sample amount I_kIn the derivation of
Coefficient K_{a □} , K_{b □} , K_{c □} , K_{0 □} To change
Change the number of turns of a photocurrent sensor with the same sensitivity in proportion to the coefficient
It is like that. For example, the sensitivity of each photocurrent sensor
Are the same and K _{c □} The number of turns for a conductor_cif,
K_{b □} The number of turns for a conductor is 2T_c, K _{a □} Pair of conductors
3T turns_cUse a sensor that

According to this embodiment, all the sensors 23
1 can be connected in series, so that the transmission path, light source, and signal processing unit, which were conventionally separated for each phase, can be shared. Can be built.

(Fifth Embodiment) FIG. 4 is a block diagram showing a fifth embodiment. In FIG. 4, the same reference numerals are given to the same functional portions as in FIG. 3, and the description will be omitted. In the present embodiment, signal processing is performed with the outputs from the signal processing units separated for short-circuit detection and ground fault detection as inputs, and output through a common output processing unit 117. It is. According to the present embodiment, since the output processing unit can be shared, the configuration is simplified.

(Sixth Embodiment) FIG. 5 shows a sixth embodiment.
FIG. 5 is a configuration diagram showing an embodiment, and in this embodiment, FIG.
9 shows an example of a sensor group 114 in the middle. As shown in FIG.
Each of the separated conductors 540 has several outlets.
There are I_a1, I_a2, ..., I _an,
I_b1, I_b2, ..., I_bn, I_c1, I_c2, ..., I_cnCalled
Suppose the current is flowing. All conductors 540 to be protected
Flow through the Faraday effect
Phase sensor 5 whose polarization plane direction rotates in proportion to the applied current
41 and the zero-phase sensor 542 are wound.

Optical elements 543 for converting linearly polarized light into circularly polarized light or vice versa are attached to both ends of each phase sensor 541 and the zero-phase sensor 542. All the phase sensors 541 are controlled by the optical transmission line 544 that maintains the polarization plane orientation.
And a zero-phase sensor 54
The system is configured by a ground fault detection transmission path obtained by combining the two.

The linearly polarized light incident from the optical transmission line 544 that maintains the polarization plane orientation, which is the end of each of the short-circuit detection transmission line and the ground fault detection transmission line, passes through the optical element 543 to form a straight line. The polarized light is converted into circularly polarized light and is incident on a sensor 542 having a Faraday effect.

The circularly polarized light incident on the sensor 542 has a current I flowing through a conductor to which the sensor 542 is attached.
_{□ n} , the plane of rotation rotates according to the proportionality constant K _{□ n} determined in advance so that various accidents can be detected, and the optical element 543 converts the circularly polarized light into linearly polarized light to transmit the optical transmission path. 544. Similarly, the light that has passed through all the sensors one after another passes through the optical transmission line 544 that maintains the plane of polarization, which is the other end of the system.
(4) the linearly polarized light respectively outputted as the sample quantity I _k based on expression.

Sample amount I output from the short-circuit detection transmission line_kTo
Especially I_kS, sample amount I output from ground fault detection transmission line_kTo
Especially I_kDefined as G. Here, for example, each of a, b, and c
The sensitivity of sensors installed in three phases is the same for all phase sensors
Sensitivity, and a-phase and c-phase are connected in opposite polarities at each outlet.
By taking the a-phase sensitivity as 1 as a reference,
_{a □} = 1, K_{b □} = 0, K_{c □} = -1. Also, zero phase
If the sensitivity of the sensor is the same as that of each phase sensor,
The flow is equivalent to 3I0 at the time of one-line ground fault, so K_{0 □} 
= 3.

If there is no accident in the conductor in the protection zone, according to Kirchhoff's law, [Equation 4] (5)
[Equation 4] (6) when there is an accident in the a-phase conductor, so that I _k S = 0 and I _k G = 0 when there is no accident in the conductor. If there is a fault in the conductor, if a single-line ground fault occurs, I _k G ≠ 0, and if it is equivalent to a short-circuit fault, I _k S ≠ 0, so that fault detection in the conductor can be performed.

The currents of the phases a, b, and c at the respective outlets are expressed by the following equation (10). Since the sample amounts I _k S and I _k G are given by the equation (11), it can be understood that any value can be taken depending on the state of the failure in the conductor. Therefore, it is possible to determine a fault in the conductor based on the magnitudes of I _k S and I _k G.

[Equation 6] Short circuit detection: _{Ia □} -Ic _□ Ground fault detection: 3I0 _□ (= 3 ( _{Ia □} + _{Ib □} + Ic _□ )) ………………………………………………………… (10) I _k S = ΣI _{a □} −I _{c □} I _k G = Σ3I _{0 □} …………………… (11)

According to the present embodiment, the transmission path, the light source, and the signal processor, which have been conventionally separated for each phase, can be shared for short-circuit detection and ground fault detection. It is excellent in maintenance and can construct a simple but equivalent system. In addition, it is possible to detect with high sensitivity even in a system with a small ground fault current.

[0043] In the (Seventh Embodiment) ([Claim 5] corresponding) seventh embodiment, in which to determine the short-circuit failure and the ground fault separately, coefficient when deriving the sample quantity I _{k K a □, K b □,} K c □, to alter the K 0 _□, it is obtained by proportional to the coefficient to alter the sensitivity of each optical current sensors. According to the present embodiment, the transmission path unit, the light source unit, and the signal processing unit, which have conventionally been separated for each phase, can be shared for short-circuit detection and ground fault detection, so that operation and maintenance are superior Thus, it is possible to construct a system that is simple but equivalent to the conventional one. In addition, it is possible to detect with high sensitivity even in a system with a small ground fault current.

[0044] In (Eighth Embodiment) ([Claim 6] corresponding) eighth embodiment, in which to determine the short-circuit failure and the ground fault separately, coefficient when deriving the sample quantity I _{k K a □, K b □,} K c □, to alter the K 0 _□, it is obtained so as to vary the number of turns proportional to the photocurrent sensor of the same sensitivity coefficient. According to the present embodiment, the transmission path unit, the light source unit, and the signal processing unit, which have conventionally been separated for each phase, can be shared for short-circuit detection and ground fault detection, so that operation and maintenance are excellent. Thus, it is possible to construct a system that is simple but equivalent to the conventional one. Further, it is possible to detect with high sensitivity even in a system with a small ground fault current.

(Ninth Embodiment) FIG. 6 is a block diagram showing a ninth embodiment. FIG. 6 is a configuration diagram showing another embodiment of the sixth embodiment (FIG. 5) at the sensor mounting portion at each conductor end. 6, the same functional portions as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the GIS serving as a protection section
When there is a three-phase separated cable 540 connected to 551, a zero-phase sensor 541 that senses the cable by three phases at a time, and each phase sensor 542 is attached to any two of the three phases, and An optical differential system is configured by connecting the optical transmission line 544 for short-circuit detection and the ground fault detection.

According to the present embodiment, the transmission line section, the light source section, and the signal processing section conventionally separated for each phase can be shared for short-circuit detection and ground fault detection. It is excellent in maintenance and can construct a simple but equivalent system. In addition, it is possible to detect with high sensitivity even in a system with a small ground fault current.

[0048]

As described above, according to the present invention, the transmission path, the light source, and the signal processor, which have been conventionally separated for each phase, can be shared, so that operation and maintenance are excellent. A simple but equivalent system can be constructed.

[Brief description of the drawings]

FIG. 1 is an overall block diagram (three-phase batch sample amount applicable type) showing a first embodiment according to the present invention.

FIG. 2 is a configuration diagram of a sensor connection of FIG. 1 (three-phase batch sample amount applicable type).

FIG. 3 is a block diagram ((short circuit detection / ground fault detection individual output) showing a second embodiment according to the present invention.

FIG. 4 is a block diagram showing a fifth embodiment according to the present invention (short circuit detection, ground fault detection individual detection, collective output).

FIG. 5 is a configuration diagram showing a sixth embodiment according to the present invention (individual detection of short-circuit detection and ground fault detection).

FIG. 6 is a mounting diagram of the sensor shown in FIG. 5 (individual detection of short-circuit detection / ground fault detection).

FIG. 7 is a block diagram of a conventional current optical differential system (three-phase individual output).

FIG. 8 is a block diagram of a conventional current optical differential system (three-phase individual detection / batch output).

FIG. 9 is a configuration diagram of a sensor connection of a conventional device.

[Explanation of symbols]

 111 light source unit 112 transmission path unit 113 sensor unit 114 sensor group 115 signal processing unit 116 output 117 output processing unit 540 conductor 541 each phase sensor 542 zero phase sensor 543 optical element 544 optical transmission path

(72) Inventor Kiyoshi Kurosawa 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company (72) Inventor Kenji Okawara 1-3-1 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Stock Inside the company (72) Shogo Miura, 1-1-1, Shibaura, Minato-ku, Tokyo Inside the Toshiba head office (72) Inventor Masao Hori, 1-1-1, Shibaura, Minato-ku, Tokyo Inside the Toshiba head office (72) Inventor Kiyoto Terai 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Hamakawasaki Plant (72) Inventor Kinichi Sasaki 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Toshiba Corporation F-term in Hamakawasaki Plant (reference) 2G014 AA02 AA04 AB33 AC18 AC19 2G025 AA15 AB10 AC06 2G035 AA11 AA12 AB08 AC13 AC15 AD28 AD37 5G047 AA01 AA08 BA01 BB01 CB07

Claims (6)

[Claims] 1. A light source for a plurality of photocurrent sensors arranged to detect a failure in a predetermined conductor of a three-phase AC circuit, and a transmission line connecting each of the photocurrent sensors in series. A current consisting of a signal processing unit for receiving light output changed by each sensor by inputting light and detecting a failure of a conductor from the amount of received light, and an output unit for outputting a processing result in the signal processing unit in the optical differential system, each sensor attached to people each conductor respectively separated into three phases and all connected in series, the light incident from the light source is to be outputted as the sample quantity I _k based on the following formula A current optical differential system characterized by the following. Note that I _k = (K _a1 I _a1 + K _b1 I _b1 + K _c1 I _c1 + K ₀₁
I ₀₁ ) + (K _a2 I _a2 + K _b2 I _b2 + K _c2 I _c2 + K ₀₂ I ₀₂ )
+ ... In _{(K an I an + K bn} I bn + K cn I cn + K 0n I 0n) _{Here, I a □, I b □} , I c □, I 0 □: first □ optical current sensor a, b, c Three-phase and zero-phase current values. Ka _□ , _{Kb □} , _{Kc □} , K0 _□ : Coefficients for the three-phase and zero-phase current values of the □ th photocurrent sensor. 2. The current-optical differential system according to claim 1, wherein a short-circuit fault and a ground fault are individually determined.
Current light difference and separating the sensor and the transmission line portion and the signal processing unit separates at the detection shorted for ground fault detecting a specimen amount I _k and a ground fault detection for detecting a short circuit to derive Motion system. 3. A current-optical differential system of claim 1, wherein the coefficient upon derivation of sample quantity _{I k K a □, K b} □,
K c _□, current optical differential system wherein the changing to alter the K 0 _□, in proportion to the coefficient the sensitivity of each optical current sensors. 4. A current-optical differential system of claim 1, wherein the coefficient upon derivation of sample quantity _{I k K a □, K b} □,
K c _□, to alter the K 0 _□, current optical differential system characterized by varying the number of turns proportional to the photocurrent sensor of the same sensitivity coefficient. 5. A current-optical differential system of claim 2, wherein the coefficient upon derivation of sample quantity _{I k K a □, K b} □,
K c _□, current optical differential system wherein the changing to alter the K 0 _□, in proportion to the coefficient the sensitivity of each optical current sensors. 6. The method according to claim 2, wherein the current optical differential system, coefficients when deriving the sample quantity _{I k K a □, K b} □,
K c _□, to alter the K 0 _□, current optical differential system characterized by varying the number of turns proportional to the photocurrent sensor of the same sensitivity coefficient.