JP2004184425A - Optical CT with failure judgment function - Google Patents

Abstract

An object of the present invention is to reduce the size and weight of a system that is inexpensive and can simplify surge countermeasures.
An optical CT includes optical fiber sensors 10a and 10b, an optical fiber transmission line 120a, and an electronic circuit unit 14c. The sensors 10a and 10b are installed so as to go around the outer circumferences of a plurality of conductors 18 connected to the power equipment 16 to be protected. The sensors 10a and 10b measure the Faraday rotation angle to determine the current value I flowing through each conductor 18. The circuit unit 14c includes a light source 14a, a photoelectric converter 14b, a signal processing unit 14c, and a determination unit 14d. A depolarizer 50 is interposed in the transmission line 12a. The signal processing unit 14c receives the output signal of the photoelectric converter 14B and calculates the sum of the Faraday rotation angles measured by the sensors 10a and 10b. The failure determining unit 14d receives the output signal of the signal processing unit 14c and determines a failure of the power equipment 16.
[Selection diagram] FIG.

Description

  The present invention relates to an optical CT having a failure determination function, and more particularly, to an optical CT having a failure determination function applied to power equipment and power equipment.

  Power equipment such as transformers installed in substations and other power equipment or power equipment should be shut down in the event of an abnormality to protect them and prevent the spread of accidents. There is a protective relay system installed.

  FIG. 3 shows a typical example of this kind of protection relay system. The protection relay system shown in FIG. 1 is connected to a transformer 2 attached to the equipment main body of the power equipment 1, a converter 3 connected to an output side of the transformer 2, and an output side of the converter 3. And a protective relay 4.

  The transformer 2 measures the current and voltage of the power equipment to be protected. The converter 3 converts the level of the detection signal of the transformer 2 and outputs it to the protection relay 4. The protection relay 4 receives the output signal of the converter 3 and performs necessary arithmetic processing, and determines an abnormality of the power equipment 1 from the result.

  When the protection relay 4 determines that an abnormality has occurred in the power equipment 1, a trip signal is transmitted, a circuit breaker or the like is operated, and the operation of the power equipment 1 is stopped. However, such a conventional protection relay system for the power equipment 1 has the following problems.

  That is, the conventional protection relay system is very expensive because it uses a large number of electronic components for the operation circuit and the like of the protection relay 4. In the detection of the current and voltage of the transformer 2, the winding type is easily affected by disturbance such as an external magnetic field, and it is difficult to take measures against surge in the protective relay system.

  In addition, since the current and voltage of the power equipment 1 are large, the transformer 2 for detecting these becomes large and heavy, and there has been a demand for a reduction in the size and weight of the entire system.

  SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and is inexpensive and can simplify a surge countermeasure, and furthermore, has an optical failure determination function capable of achieving a small and lightweight system. It is to provide CT. Another object of the present invention is to provide an optical CT capable of determining a practical failure.

In order to achieve the above object, the present invention provides a plurality of optical fiber sensors which are installed around an outer periphery of a plurality of conductors connected to a power facility and individually measure input / output current of each conductor, a light source, and a photoelectric converter. , A signal processing unit and an electronic circuit unit having a failure determination unit, between the light source and the optical fiber sensor, between the optical fiber sensors, and between the optical fiber sensor and the photoelectric converter. An optical fiber transmission line connected in series is provided, and the sum of the current values measured by the optical fiber sensor is obtained by the signal processing unit, and the failure judging unit judges the abnormality of the power equipment from the sum of the current values. In an optical CT having a failure determination function, the optical fiber sensor is connected to the power equipment, and the input side and the input side installed around the pair of conductors through which the input and output currents of the power equipment flow. And the output side optical fiber sensor, while matching the direction of propagation of light in the input side optical fiber sensor and the direction of the magnetic field created by the input current, and the direction of propagation of light in the output side optical fiber sensor. The direction of the magnetic field generated by the output current is set to a direction opposite to the direction of the magnetic field generated by the output current.
According to the optical CT having the failure determination function configured as described above, the optical fiber sensor is installed around the outer periphery of the plurality of conductors connected to the power equipment, and the input / output current of each conductor is individually measured.
Current measurement by an optical fiber sensor measures the Faraday rotation angle at which the polarization of light propagating through the optical fiber sensor rotates according to the magnitude of the current magnetic field. Also, no output distortion due to magnetic saturation of the iron core occurs.
In addition, since the current measurement is performed by an optical fiber sensor, and the optical fiber transmission line connects in series between the light source and the optical fiber sensor, between the optical fiber sensors, and between the optical fiber sensor and the photoelectric converter, respectively. The size and weight of the entire system can be reduced, and the surge measures can be simplified.
Further, in the present invention, based on Kirchhoff's first law, the signal processing unit obtains the sum of the current values measured by the optical fiber sensors, and the failure determination unit determines the abnormality of the power equipment from the sum of the current values. Therefore, the arithmetic processing is also simplified.
In this case, in the present invention, since the Faraday rotation angles are all added and then converted into a change in light amount by the photoelectric converter, the calculation accuracy for a large current concentration can be ensured.
Further, the optical fiber sensor has an input side and an output side optical fiber sensor which are connected to the power equipment and are installed on the outer periphery of a pair of conductors through which the input and output currents of the power equipment flow. Since the propagation direction of the light and the direction of the magnetic field generated by the input current are made to coincide with each other, and the propagation direction of the light in the output side optical fiber sensor and the direction of the magnetic field generated by the output current are set in opposite directions, When two input and output conductors are connected to the power equipment, practical failure determination can be performed by using an existing optical fiber sensor or the like within a relatively small current value range.
The optical fiber transmission line may include a depolarizer that converts the polarization of the light emitted from the input-side optical fiber sensor into non-polarized light and causes the converted light to enter the output-side optical fiber sensor.
According to this configuration, since the depolarizer that converts the polarization of the light emitted from the input-side optical fiber sensor into non-polarized light and enters the output-side optical fiber sensor is provided in the optical fiber transmission line, the optical fiber transmission A decrease in measurement accuracy due to a change in polarization in the path can be prevented.

  According to the optical CT having the failure determination function according to the present invention, it is possible to simplify the countermeasures against the surge at low cost, and furthermore, it is possible to achieve the reduction in size and weight of the system.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an outline of a basic configuration of an optical CT having a failure determination function according to the present invention.

The optical CT having the failure determination function shown in FIG. ₁ includes a plurality of optical fiber sensors ₁₀₁ to ₄ , an optical fiber transmission line 12, and an electronic circuit unit 14. The optical fiber sensors _{101 to 4} are installed so as to orbit the outer circumferences of a plurality of conductors 18 connected to the power equipment 16 to be protected.

Each optical fiber sensor _{10 1-4} measures the output current value _{I 1 to 4} of the conductors 18, respectively. Measurement principle of the current values I _{1 to 4} of the optical fiber sensor 10 _1-4 when propagating light in the optical fiber sensor 10 _1-4 which is orbiting installed on the outer periphery of the conductor 18, the polarization of light propagating Rotate in accordance with the magnitude of the current magnetic field, the Faraday rotation angle is measured, and the current values I1 to _I4 flowing through the conductors 18 are obtained.

The electronic circuit unit 14 has a light source 14a, a photoelectric converter 14b, a signal processing unit 14c, and a failure determination unit 14d. Optical fiber transmission line 12 includes a light source 14a and between the first-th optical fiber sensor 10 _1, the second after the optical fiber sensor _{10 2-4} between each other and the end portion of the optical fiber sensor 10 ₄ and the photoelectric The converter 14b is provided so as to be connected in series.

The signal processing unit 14c receives the output signal of the photoelectric converter 14b and obtains the sum of the Faraday rotation angles for the current values I1 to _I4 measured by the optical fiber sensors ₁₀₁ to ₁₀₄ , respectively. The failure determination unit 14d receives the output signal of the signal processing unit 14c and determines a failure of the power equipment 16 based on Kirchhoff's first law. That is, according to Kirchhoff's first law, the sum S = k (I ₁ + I ₂ + I ₃ + I ₄ ) of the current values I ₁ to I ₄ flowing into and out of the power equipment 16 becomes zero if there is no abnormality.

Therefore, the failure determination section 14d, when the sum of the current value I _{1 to 4} has become non-zero, it is determined that there is an abnormality and sends a signal to that effect to the outside, based on the outgoing signal power The equipment 16 is stopped.

According to the optical CT having the failure determination function configured as described above, the polarization of the light propagating through the optical fiber sensors ₁₀₁ to ₄ determines the Faraday rotation angle that rotates according to the magnitude of the current magnetic field. Since the current values I1 to _I4 are obtained by measurement, even when a large current including a DC component flows at the time of an accident, output distortion due to magnetic saturation of the iron core does not occur.

Further, performs current measured by the optical fiber sensor _{10 1-4,} an optical fiber transmission path 12, the light source 14a and the first between the optical fiber sensor 10 _1, of the second subsequent optical fiber sensor _{10 2-4} between each other and since the series connection between the last optical fiber sensor 10 ₄ and the photoelectric converter 14b, consists of a portion of all the optical fibers to be laid in the power plant 16, the entire system compact, lightweight achievement In addition, surge measures can be simplified.

Further, based on Kirchhoff's first law, the signal processing unit 14c calculates the sum of the current values I1 to _I4 measured by the optical fiber sensors ₁₀₁ to ₄ , and determines the failure from the sum of the current values I1 to _I4. Since the abnormality of the power equipment 16 is determined by the unit 14d, the calculation process is also simplified.

  In this case, since the Faraday rotation angles are all added and then converted into a change in light amount by the photoelectric converter 14b, the calculation accuracy for a large current concentration can be ensured.

  FIG. 2 shows an embodiment of an optical CT having a failure determination function according to the present invention. The same reference numerals are given to the same or corresponding parts as those in the above basic configuration, and the description thereof will be omitted. Only the characteristic points will be described.

In the embodiment shown in the figure, the present invention is applied when _two input and output conductors 18 ₁ and 182 are connected to the power equipment 16 to be protected. The outer periphery of the input conductor 18 _1, the input current input side optical fiber sensor 10a for measuring the I ₁ is disposed on the outer periphery thereof, k is the propagation direction (FIG. 2 of the light in the optical fiber sensor 10a, 1 indicates the direction), and is provided so as to coincide with the direction of the magnetic field generated by energization.

The outer periphery of the output conductor 18 _2, the output side optical fiber sensor 10b for measuring the output current I2 is disposed on the outer periphery thereof, k is in the light propagation direction in the optical fiber sensor 10b (FIG. 2, l The direction of the magnetic field is provided opposite to the direction of the magnetic field generated by energization.

  A polarizer 22 is arranged on the incident side of each of the optical fiber sensors 10a and 10b, and a λ / 2 plate 23 and an analyzer 24 are arranged on the exit side. Between the light source 14a and the polarizer 22 provided on the input side of the input side optical fiber sensor 10a, between the light source 14a and the analyzer 24 provided on the output side of the input side optical fiber sensor 10a and on the input side of the output side optical fiber sensor 10b. The single-mode optical fiber or the polarization-maintaining fiber is connected between the polarizer 22 provided and the analyzer 24 provided on the emission side of the output-side optical fiber sensor 10b and the photoelectric converter 14b, respectively. Thus, these constitute the optical transmission line 120a.

  The depolarizer 50 is provided in the optical transmission line 120a. The depolarizer 50 is interposed between the analyzer 24 provided on the output side of the input-side optical fiber sensor 10a and the polarizer 22 provided on the input side of the output-side optical fiber sensor 10b. The polarization of light emitted from the fiber sensor 10a is converted into non-polarized light, and the converted light is incident on the output-side optical fiber sensor 10b.

  When such a depolarizer 50 is interposed, in the optical transmission between the optical fiber sensors 10a and 10b, which are current detectors, when the propagating light has a polarization characteristic, the incident light from the output side optical fiber sensor 10b is incident. It is conceivable that the amount of light incident by the polarizer 22 provided on the side is greatly reduced and the loss of the amount of light from the optical fiber sensor 10b is increased, so that the light emitted from the optical fiber sensor 10a is incident on the depolarizer 50. After being depolarized, the light is made to enter the optical transmission line 120a constituted by a single-mode fiber for transmission or a polarization-maintaining fiber.

Next, the operation principle of the optical CT having the above configuration will be described. In the optical CT shown in FIG. 2, the light P ₀ from the light source 14a is made into linearly polarized light by the polarizer 22 of the optical fiber sensor 10a, when incident linearly polarized light to lead glass fiber made of the optical fiber sensor 10a, While passing through the fiber, the incident light undergoes a rotation θ ₁ of the polarization plane due to the Faraday effect due to the magnetic field generated by the current I ₁ .

The relationship between the current I ₁ and the rotation θ ₁ of the plane of polarization is expressed by the following equation (4-1), where Verde's constant is ν.
θ ₁ = νI ₁ (4-1)
Outgoing light P ₁ of the optical fiber sensor 10a, from the analyzer 24 rotates the half-wave plate 23 of the polarization plane, if the measured current is alternating current, is intensity modulated pulsating DC component + AC components and becomes light, the outgoing light _{P 1} is expressed by the following equation (4-2).

_{P 1 = P 0/2 (} 1 + sin2θ 1) = P 0/2 {1 + sin (2νI 1 sinωt)} ......... (4-2)
Here, ω (= 2πf), f: frequency of the measured current, t: time The intensity-modulated light from the optical fiber sensor 10a is converted into non-polarized light by the depolarizer 50.

  Next, the intensity-modulated non-polarized light is guided to the optical fiber sensor 10b by an optical transmission line 120a formed of a single mode fiber or a polarization-maintaining fiber, and by a polarizer 22 disposed on the incident side thereof. The light becomes linearly-polarized intensity-modulated light.

By entering the light to lead glass fiber made of the optical fiber sensor 10b, similarly to the optical fiber sensor 10a, the incident light, while passing through the fiber, the polarization plane by the Faraday effect by the magnetic field generated by the applied current I ₂ subject to the rotation θ _2.

As a result, outgoing light P ₂ from the optical fiber sensor 10b, similarly to the optical fiber sensor 10a becomes intensity modulated light is represented by the following formula (4-3).
_{P 2 = P 1/2 (} 1 + sin2θ 2)
_{= P 0/4 {1 +} sin (2νI 1 sinωt)} {1 + sin (2νI 2 sinωt)}
_{= P 0/4 {1 +} sin (2νI 1 sinωt) + sin (2νI 2 sinωt) + sin (2νI 1 sinωt) sin (2νI 2 sinωt)} .................. (4-3)

Here, if the optical fiber sensor 10a, mounted so as to match the direction of light propagating in the magnetic field direction and lead glass fibers produced by the applied current I _1, the formula (4-3), electric current I ₂ of current direction is opposite the direction of the applied current I _1.
Outgoing light _{P 2} from the optical fiber sensor 10b thus becomes as shown in Equation (4-3.a).

_{P 2 = P 1/2 (} 1 + sin2θ 2)
_{= P 0/4 {1 +} sin (2νI 1 sinωt)} {1-sin (2νI 2 sinωt)}
_{= P 0/4 {1 +} sin (2νI 1 sinωt) -sin (2νI 2 sinωt) -sin (2νI 1 sinωt) sin (2νI 2 sinωt)} .................. (4-3.a)

If the currents I ₁ and I ₂ are not large currents, sin (2νI ₁ sinωt) sin (2νI ₂ sinωt) in the equation (4-3.a) becomes a very small value.
As a result, sin (2νI ₁ sinωt) sin (2νI ₂ sinωt) ≒ 0 can be set. Therefore, equation (4-3.a) can be expressed as equation (4-4).
_{P 2 = P 0/4 {} 1 + sin (2νI 1 sinωt) -sin (2νI 2 sinωt)} ......... (4-4)

_P 0/4 of the formula (4-4), the DC component of the intensity-modulated _{light, P 0/4 {sin (} 2νI 1 sinωt) -sin (2νI 2 sinωt)} is the AC intensity modulated light Can be represented by components.

Outgoing light _{P 2} of the formula (4-4) is converted into an electric signal by the photoelectric converter 14b in the figure, then, _P 0/4 by LPF (low pass filter) of the signal processing circuit 14c, HPF (high-pass _P by the filter) 0/4 {sin (2νI 1 sinωt) -sin (2νI 2 sinωt)} is taken, the output S obtained by dividing these by the equation (4-5) is obtained.

S = AC component / DC component _{= P 0/4 {sin (} 2νI 1 sinωt) -sin (2νI 2 sinωt)}
P _0/4
= Sin (2νI ₁ sinωt) −sin (2νI ₂ sinωt) (4-5)
Here, in the sine function, when the angle Φ is small, the approximation of Expression (4-6) holds.
sinΦ = Φ (4-6)

Equation (4-5) satisfies equation (4-6) when the conduction current is small. Therefore, the formula (4-5) equation, the formula (4-7), and the output S, contains the difference component of the input current _{I 1} and the output current _{I 2,} by calculating this, power The failure of the equipment 16 can be determined.

S = 2νI ₁ sinωt−2νI ₂ sinωt
= 2νsinωt (I ₁ −I ₂ ) (4-7)

In the embodiment shown in FIG. 2, an example is shown in which the depolarizer 50 is provided in the optical transmission line 120a to compensate for the polarization characteristics during transmission in the optical fiber sensors 10a and 10b. In this case, although the detection accuracy is slightly lowered, when the two input and output conductors 18 ₁ and 18 ₂ are connected to the power equipment 16, a relatively small current value can be obtained. Therefore, a practical and inexpensive failure determination can be performed by using an existing optical fiber sensor or the like.

  According to the optical CT having the failure determination function according to the present invention, it can be effectively used for failure determination of power equipment or power equipment.

FIG. 2 is an explanatory diagram of a basic concept of an optical CT having a failure determination function according to the present invention. 1 is an overall configuration diagram illustrating an embodiment of an optical CT having a failure determination function according to the present invention. It is explanatory drawing of the conventional protection relay system.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 10 Optical fiber sensor 12 Optical fiber transmission line 14 Electronic circuit part 14a Light source 14b Photoelectric converter 14c Signal processing part 14d Judgment part 16 Power equipment

Claims (2)

A plurality of optical fiber sensors installed around the outer periphery of a plurality of conductors connected to the power equipment and individually measuring input / output current of each conductor, and a light source, a photoelectric converter, a signal processing unit, and a failure determination unit An electronic circuit unit, and an optical fiber transmission line for serially connecting the light source and the optical fiber sensor, between the optical fiber sensors, and between the optical fiber sensor and the photoelectric converter, respectively. In the optical CT having a failure determination function of determining the sum of the current values measured by the optical fiber sensor in the signal processing unit and determining an abnormality of the power equipment in the failure determination unit from the sum of the current values,
The optical fiber sensor is connected to the power equipment, and has an input side and an output side optical fiber sensor installed on the outer periphery of a pair of conductors through which input and output currents of the power equipment flow,
While matching the direction of propagation of light in the input-side optical fiber sensor and the direction of the magnetic field created by the input current, the direction of propagation of light in the output-side optical fiber sensor and the direction of the magnetic field created by the output current are An optical CT having a failure determination function, which is set in opposite directions.   2. The optical fiber transmission line according to claim 1, further comprising a depolarizer that converts the polarization of the light emitted from the input-side optical fiber sensor into non-polarized light and causes the converted light to enter the output-side optical fiber sensor. An optical CT having a failure determination function.

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