CN211123023U

CN211123023U - Optical current transformer based on coupler network

Info

Publication number: CN211123023U
Application number: CN201921390587.6U
Authority: CN
Inventors: 刘军; 陈创佳; 李重阳; 李德华; 彭潜; 陆明; 王红星; 李毅; 俞家良; 窦博文; 余涛; 贺儒飞; 王耀; 阎嫦玲; 罗苏南; 王凯
Original assignee: Shenzhen Storage Generating Co ltd; China Southern Power Grid Co Ltd; NR Electric Co Ltd; NR Engineering Co Ltd; Electric Power Research Institute of Guangdong Power Grid Co Ltd; Peak and Frequency Regulation Power Generation Co of China Southern Power Grid Co Ltd
Current assignee: Shenzhen Storage Generating Co ltd; China Southern Power Grid Co Ltd; NR Electric Co Ltd; NR Engineering Co Ltd; Electric Power Research Institute of Guangdong Power Grid Co Ltd; Peak and Frequency Regulation Power Generation Co of China Southern Power Grid Co Ltd
Priority date: 2019-08-26
Filing date: 2019-08-26
Publication date: 2020-07-28
Anticipated expiration: 2029-08-26

Abstract

The utility model discloses an optics current transformer based on coupler network for realize a plurality of optic fibre current transformer's integration, reduce the mutual-inductor cost. The utility model comprises a light source, a coupler network, a plurality of polarization maintaining optical path systems and a plurality of signal acquisition and processing units, wherein the coupler network is formed by cascading and connecting a plurality of optical fiber couplers in parallel; the polarization-maintaining optical path system is formed by sequentially connecting main devices such as a polarizer, a modulator, an optical fiber sensing ring with a reflector and the like; the signal acquisition and processing unit mainly comprises a light detector and an AD sampling and signal processing circuit. The optical fiber coupler network can realize the integration of a plurality of current measuring points and a sensing ring, each measuring point shares a light source, the cost of the mutual inductor is reduced, the influence of the power of the light source on the mutual inductor system can be effectively inhibited, and a reliable solution is provided for zero sequence current measurement, differential current measurement and the measurement of the combined current of other types of a plurality of measuring points.

Description

Optical current transformer based on coupler network

Technical Field

The utility model relates to an optics current transformer field, concretely relates to optics current transformer based on coupler network.

Background

The current transformer is an important device for monitoring the running state of the power system, and current information required by measurement, metering and protection is obtained by measurement, monitoring and protection control in a transformer substation. The traditional current transformer is an electromagnetic transformer, and the electromagnetic transformer can not meet the development requirements of power system automation, digital networks and the like due to the reasons of heavy volume, complex insulation structure, easiness in magnetic saturation, easiness in ferromagnetic resonance, small dynamic measurement range, narrow response frequency band and the like. The optical current transformer has the advantages of simple insulating structure, small volume, light weight, good linearity, no magnetic saturation and ferromagnetic resonance problems and the like, can replace the traditional electromagnetic transformer, and has wide application prospect.

The optical current transformer adopts an all-fiber structure, realizes the induction of optical signals to current based on the Faraday magneto-optical effect principle, coils a sensing optical fiber outside a current-carrying conductor, converts the measured current into the phase difference of two homologous beams of polarized light, and detects the phase difference to realize the measurement of the current.

The optical current transformer has small volume, light weight and flexible installation mode, and can realize the installation of the sensing coil in an optical fiber winding mode; the optical current transformer has excellent anti-interference capability, can effectively avoid the influence of a magnetic field outside a sensing optical fiber ring, and has good transient characteristics, so the optical current transformer has wide application prospect in a power grid or a power plant.

The prior art optical current transformers have exposed a number of problems in practical applications: the cost is high, and the popularization of the mutual inductor is influenced; for some application requirements, such as differential current measurement or zero sequence current measurement requirements, no cost performance scheme exists; in the long-term operation process, the light source may produce the decay, influences the mutual-inductor error.

At present, in the application requirements of using an optical current transformer to perform differential current measurement or zero sequence current measurement, or in the similar application requirements of measuring the combined current of a plurality of measuring points, there are two main configuration schemes:

(1) each measuring point is respectively provided with an optical current transformer, the data of the transformers at each measuring point are respectively collected, and the protection device is used for synchronizing and calculating the differential and zero sequence combined current. The configuration scheme is not limited by the arrangement mode and the distance of the through-current conductors, and the installation mode is flexible; however, because characteristics of each transformer such as precision, temperature drift, interference resistance, stability and the like have certain differences, the finally calculated superposed current precision is difficult to guarantee, and large errors are easy to occur in long-term operation. And meanwhile, the cost is increased due to the configuration of a plurality of transformers.

(2) When the conditions permit, all the measuring points are simultaneously contained in a sensing optical fiber ring of an optical current transformer, so that the currents of all the measuring points are measured by the sensing ring under the combined action, and the output of the sensing ring is directly the superposed resultant current value. According to the configuration scheme, the combined current of each measuring point can be measured only by one optical current transformer, so that the influence caused by the performance difference of the current transformers independently configured at each measuring point is avoided; however, the scheme has strict requirements on the distance, the size, the polarity and the like of the through-flow conductor of each measuring point, for example, when measuring differential current, the distance between two measuring points is generally very long, the simultaneous measurement is unrealistic by using an optical fiber ring, when measuring zero sequence current, the unbalance of a magnetic field can be caused by the uneven arrangement of the conductors of each measuring point, the accuracy of the measurement result of the current transformer is greatly influenced, meanwhile, the size of the sensing ring of the current transformer is very large, and the manufacturing process is difficult to guarantee.

Based on above analysis, the utility model discloses a research one kind integrates, based on Faraday magneto-optical effect, can satisfy the optics current transformer who measures a plurality of measurement stations and close the current demand, the present case produces from this.

SUMMERY OF THE UTILITY MODEL

The utility model aims at researching an integrated, based on Faraday magneto-optical effect, can satisfy the optical current transformer who measures a plurality of measurement stations and close the current demand, realize closing the measured optical current transformer of electric current to differential current, zero sequence current etc..

In order to achieve the above purpose, the solution of the present invention is: an optical current transformer based on a coupler network comprises a light source, the coupler network, N polarization-maintaining optical path systems and N signal acquisition and processing units, wherein N is an integer greater than or equal to 2.

The coupler network comprises a primary coupler and N secondary couplers, wherein the primary coupler at least comprises N output ports, and first to Nth output ends of the primary coupler are respectively correspondingly connected with first input ends of the N secondary couplers.

The polarization-maintaining optical path system is formed by sequentially connecting a polarizer, a modulator and an optical fiber sensing ring with a reflector.

The signal acquisition and processing unit comprises: and the optical detector and the AD sampling and signal processing circuit are connected in sequence.

The light source is connected with a first input end of the primary coupler, the N signal acquisition and processing units, the N secondary couplers and the N polarization-maintaining optical path systems correspond to one another one by one, and the optical detector of each signal acquisition and processing unit is connected with a second input end of the corresponding secondary coupler; the first output port of the secondary coupler is connected to a polarizer of a corresponding polarization-maintaining optical path system; the signal processing circuit of each signal acquisition and processing unit is connected to the modulator of the corresponding polarization-maintaining optical path system to provide a control electric signal for the polarization-maintaining optical path system.

Preferably, the coupler network is formed by mating a plurality of couplers of the same type or of different types.

Preferably, the light source has a broad spectrum of light signal, weak coherence and light power exceeding 1 mw.

Preferably, the light source is a superluminescent light emitting diode.

Preferably, all devices of the polarization-maintaining optical path system are connected through polarization-maintaining optical fibers, wherein the optical fibers between the polarizer and the modulator are welded at an angle of 45 degrees, and the modulator and the optical fibers between the optical fiber sensing rings with the reflectors are welded at an angle of 0 degree; the sensing optical fiber ring with the reflecting mirror is composed of a lambda/4 wave plate, a sensing optical fiber and the reflecting mirror.

Preferably, the lambda/4 wave plate is formed by cutting a long beat length optical fiber, the sensing optical fiber adopts an HB round optical fiber, and the reflector is positioned at the tail end of the sensing optical fiber and is manufactured in a vacuum coating mode.

Preferably, in the signal acquisition and processing unit, the optical detector converts the optical signal into an analog electrical signal, outputs the analog electrical signal to an AD sample, and then converts the analog electrical signal into a digital signal through the AD sample; the signal processing circuit receives the AD sampling signal, calculates and outputs the measured current, and provides a control signal for the modulator. The signal processing circuit may employ a field programmable gate array.

The laser input by the coupler network is changed into linearly polarized light by the polarizer, the linearly polarized light generates polarization split light after passing through a welding point of 45 degrees, the polarization split light is decomposed into two orthogonal linearly polarized lights and is modulated by the modulator, the two orthogonal linearly polarized lights are changed into a left circularly polarized light (L HCP) and a right circularly polarized light (RHCP) through a lambda/4 wave plate and enter the sensing optical fiber ring, due to the Faraday magneto-optical effect, the two circularly polarized lights are influenced by a magnetic field generated by primary current to generate a phase difference proportional to the current, the two polarized lights are reflected at the reflecting mirror and then return to the two input ends of the secondary coupler and input into the optical detector, and the signal processing circuit demodulates the measured primary current information from the phase difference information contained in the electric signal output by the optical detector.

The utility model discloses better solution with an optical current transformer direct measurement differential current or zero sequence current wait close the difficult problem of electric current. In the existing transformer scheme, the devices of the transformers at each measuring point are completely independent, the current of a plurality of measuring points is received simultaneously through a protection device, the vector sum of the currents is calculated, and the resultant current such as the differential current or the zero-sequence current is calculated. During the actual operation, there is certain power attenuation because of the light source along with time, causes each mutual-inductor error to have the change of different amplitude, the utility model discloses a light source of each mutual-inductor sharing, the luminous power subsides the influence that causes each optical path system is completely unanimous, consequently can play certain offset when calculating the closed current to reduce the influence that the mutual-inductor subsides and consume and cause.

The optical current transformer of the utility model can be applied to the occasion that the combined current needs to be calculated, if the zero sequence current needs to be measured, a sensing optical fiber ring can be respectively configured at the corresponding position of A, B, C, the combined current is the zero sequence current, and the combined current is close to zero when the three-phase current is balanced; to measure the differential current on the line, two sensing fiber rings are respectively configured at two ends of the line, and the combined current is the differential current.

The utility model discloses available mutual-inductor realizes closing the detection demand of electric current to differential current, zero sequence current etc. can effectively reduce system cost and complexity, improves system reliability. Meanwhile, the light source is shared, so that the consistency of the light power attenuation characteristics of each measuring point can be effectively guaranteed, and the error of the current combination calculation is reduced.

Drawings

Fig. 1 is an overall structural diagram of an optical current transformer according to the present invention, in which a primary coupler is a2 × 2 optical fiber coupler;

in the figure, 1, a light source, 2, a coupler network, 3, a polarization-maintaining optical path system A,4, a signal acquisition and processing unit A, 5, a polarization-maintaining optical path system B,6, a signal acquisition and processing unit B, 7, a primary coupler (the type is a2 × 2 optical fiber coupler), 8, a secondary coupler A, 9, a polarizer A, 10, a modulator A, 11, a sensing optical fiber ring A with a reflector, 12, a light detector A, 13, an AD sampling A, 14, a signal processing circuit A, 15, a secondary coupler B, 16, a polarizer B, 17, a modulator B, 18, a sensing optical fiber ring B with a reflector, 19, a light detector B, 20, an AD sampling B, 21 and a signal processing circuit B are arranged.

Fig. 2 is an overall structural diagram of the optical current transformer according to the present invention, wherein the primary coupler is a3 × 3 optical fiber coupler;

in the figure, 7 is a primary coupler (the type is 3 × 3 optical fiber coupler), 22 is a polarization-maintaining optical path system C, 23 is a signal acquisition and processing unit C, 24 is a secondary coupler C.

Fig. 3 is a block diagram of a coupler network in which the primary coupler is a2 × 2 fiber coupler.

Fig. 4 is a block diagram of a coupler network in which the primary coupler is a3 × 3 fiber optic coupler.

Fig. 5 is a structural diagram of the polarization optical path system a.

Fig. 6 is a block diagram of a signal acquisition and processing unit.

Detailed Description

The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

The utility model provides an optical current transformer utilizes the primary current of the faraday magneto-optical effect response a plurality of measurement stations of coupler network and optic fibre: when each polarized light beam is transmitted through the sensor fiber, if it is affected by a magnetic field, the phase angle of the polarized light beam is shifted in proportion to the magnetic field intensity.

The embodiment of the invention discloses an optical current transformer based on a coupler network, which comprises a light source, the coupler network, N polarization-maintaining optical path systems and N signal acquisition and processing units, wherein N is an integer greater than or equal to 2.

The light source is connected with a first input end of the primary coupler, the N signal acquisition and processing units, the N secondary couplers and the N polarization-maintaining optical path systems correspond to one another one by one, and the optical detector of each signal acquisition and processing unit is connected with a second input end of the corresponding secondary coupler; the first output port of the secondary coupler is connected to a polarizer of a corresponding polarization-maintaining optical path system; the signal processing circuit of each signal acquisition and processing unit is connected to the modulator of the corresponding polarization-maintaining optical path system to provide a control electric signal for the polarization-maintaining optical path system. The coupler network is composed of a plurality of coupler arrangements of the same type or different types.

As shown in fig. 1, the optical current transformer of the present invention comprises 2 paths, including a light source 1, a coupler network 2, a plurality of polarization-maintaining

optical path systems

3 and 5, and a plurality of signal acquisition and

processing units

4 and 6.

The coupler network 2 includes a

primary coupler

7 and 2

secondary couplers

8 and 15, the primary coupler 7 includes 2 output ports, and the 1 st and 2 nd output ports of the primary coupler 7 are respectively connected to the first input ports of the 2

secondary couplers

8 and 15.

Wherein, the polarization-maintaining

optical path systems

3 and 5 are formed by sequentially connecting

polarizers

9 and 16,

modulators

10 and 17 and optical

fiber sensing rings

11 and 18 with reflectors.

Wherein, signal acquisition and

processing unit

4, 6 include:

photodetectors

12, 19,

AD samples

13, 20, and

signal processing circuits

14, 21 connected in series.

The light source 1 is connected with a first input end of the primary coupler 7, the 2 signal acquisition and processing units, the 2 secondary couplers and the 2 polarization-maintaining optical path systems are in one-to-one correspondence, and the optical detector of each signal acquisition and processing unit is connected with a second input end of the corresponding secondary coupler; the first output port of the secondary coupler is connected to a polarizer of a corresponding polarization-maintaining optical path system; the signal processing circuit of each signal acquisition and processing unit is connected to the modulator of the corresponding polarization-maintaining optical path system to provide a control electric signal for the polarization-maintaining optical path system.

The light source is used for providing light signals meeting requirements for the coupler network and a follow-up light path system, the frequency spectrum of the light signals is required to be wide, the coherence is weak, and the light power exceeds 1mw, a super-radiation light-emitting diode (S L D) is generally adopted, and the light source system is provided with a corresponding control circuit and a temperature control system and used for adjusting the driving current of the light source and the temperature of a tube core of the light source.

The coupler network is composed of a plurality of couplers of the same type or different types in a cascade connection, parallel connection and other modes, the couplers are divided into a primary coupler and a secondary coupler, the number of the primary couplers is only one, the input end of the primary coupler is connected with a light source, the output end of the primary coupler is simultaneously cascaded with 2, 3 or more secondary couplers, the primary coupler can be a2 × 2 coupler, a3 × 3 coupler or other types of couplers, the secondary coupler is generally a2 × 2 coupler, and other types of couplers can be selected.

The first and second embodiments using coupler networks are shown in fig. 3 or fig. 4, respectively.

The primary coupler 7 shown in fig. 3 uses a2 × 2 fiber coupler, and the secondary coupler a8 and the secondary coupler B15 both use a2 × 2 fiber coupler.

The input ports of the primary coupler 7 are respectively Z1 and Z2, one of the input ports can be optionally connected with an output optical fiber of the light source 1, the output ports are Z4 and Z5, wherein the port Z4 is connected with the input port A2 of the secondary coupler A8, the port Z5 is connected with the input port B1 of the secondary coupler B15, light emitted by the light source is divided into two beams through the 2 × 2 polarization-maintaining coupler, and the light splitting percentages of the ports Z4 and Z5 are 50% and 50%.

The input ports of the secondary coupler A8 are a1, a2, wherein a2 connects the primary coupler as described above; a1 is connected with a signal acquisition and processing unit A4; the output ports are A3 and A4, one of the output ports can be optionally connected with a polarization-maintaining optical path system A3, and the other output port is idle or used as a monitoring port; the light splitting percentages of the ports A3 and A4 are 25 percent to 25 percent.

The input ports of the secondary coupler B15 are B1, B2, wherein B1 connects the primary coupler as described above; b2 is connected with a signal acquisition and processing unit B6; the output ports are B3 and B4, one of the output ports can be optionally connected with a polarization-maintaining optical path system B5, and the other output port is idle or used as a monitoring port; the light splitting percentages of the ports B3 and B4 are 25 percent to 25 percent.

The primary coupler 7 shown in fig. 4 employs A3 × 3 fiber coupler, and the secondary coupler a8, the secondary coupler B15 and the secondary coupler C24 each employ a2 × 2 fiber coupler.

The input ports of the primary coupler 7 are respectively Z1, Z2 and Z3, an optional input port is connected with an output optical fiber of the light source 1, the output ports are Z4, Z5 and Z6, wherein a Z4 port is connected with the input port A2 of the secondary coupler A8, a Z5 port is connected with the input port B1 of the secondary coupler B15, a Z6 port is connected with the input port C1 of the secondary coupler C24, light emitted by the light source is divided into three beams through the 3 × 3 polarization-maintaining coupler, and the light splitting percentages of the Z4, the Z5 and the Z6 are 33.33%: 33.33%: 33.33%.

The input ports of the secondary coupler A8 are a1, a2, wherein a2 connects the primary coupler as described above; a1 is connected with a signal acquisition and processing unit A4; the output ports are A3 and A4, one of the output ports can be optionally connected with a polarization-maintaining optical path system A3, and the other output port is idle or used as a monitoring port; the light splitting percentages of the ports A3 and A4 are 16.17 percent to 16.17 percent.

The input ports of the secondary coupler B15 are B1, B2, wherein B1 connects the primary coupler as described above; b2 is connected with a signal acquisition and processing unit B6; the output ports are B3 and B4, one of the output ports can be optionally connected with a polarization-maintaining optical path system B5, and the other output port is idle or used as a monitoring port. The light splitting percentages of the ports B3 and B4 are 16.17 percent to 16.17 percent.

The input ports of the secondary coupler C24 are C1, C2, wherein C1 connects the primary coupler as described above; c2 is connected with signal collecting and processing unit C23; the output ports are C3 and C4, one of the output ports can be optionally connected with a polarization-maintaining optical path system C22, and the other output port is idle or used as a monitoring port. The light splitting percentage of the C3 and C4 ports is 16.17 percent to 16.17 percent.

In a preferred embodiment, all devices of the polarization-maintaining optical path system are connected through polarization-maintaining optical fibers, wherein the optical fibers between the polarizer and the modulator are welded at an angle of 45 degrees, and the modulator and the optical fiber between the optical fiber sensing rings with the reflectors are welded at an angle of 0 degree; the sensing optical fiber ring with the reflecting mirror is composed of a lambda/4 wave plate, a sensing optical fiber and the reflecting mirror.

A preferred embodiment of a polarization maintaining optical system is shown in fig. 5. Polarizer) input end is connected with the output end of the coupler network 2, and both are single-mode optical fibers which are connected in a fusion mode; the output end is connected to the input fiber of the modulator 10, both of which are polarization maintaining fibers, and are fused at 45 °. The output end of the modulator 10 is a polarization maintaining optical fiber, and is connected with a sensing optical fiber ring 11 of the reflecting mirror in a 0-degree welding mode; the modulator 10 receives the control signal of the signal receiving and processing circuit 6, generates corresponding optical phase modulation information, and applies the optical phase modulation information to the optical fiber loop. The sensing optical fiber ring 11 with the reflecting mirror is composed of a lambda/4 wave plate, a sensing optical fiber and the reflecting mirror, wherein the lambda/4 wave plate is usually formed by cutting a long beat length optical fiber, the sensing optical fiber generally adopts an HB round optical fiber, and the reflecting mirror is positioned at the tail end of the sensing optical fiber and is manufactured in a vacuum coating mode.

Broadband light output by the secondary coupler A8 passes through a polarizer A9 and becomes linearly polarized light, and the linearly polarized light is injected into the fast axis and the slow axis of the polarization maintaining optical fiber through 45-degree optical fiber fusion points to form orthogonal linearly polarized light; after being modulated by the modulator A10, the orthogonal linear polarized light is transmitted to a sensing optical fiber ring A11 with a reflector, is converted into levorotatory circular polarized light and dextrorotatory circular polarized light by a lambda/4 optical fiber wave plate respectively, and then enters the sensing optical fiber respectively; under the influence of a magnetic field generated by primary current around a current-carrying conductor, the propagation speeds of the two beams of circularly polarized light change based on Faraday magneto-optical effect, so that phase difference is caused; after being reflected by a reflector, two beams of circularly polarized light are returned along the original optical path after exchanging mode fields, the Faraday phase shift of the circularly polarized light in the sensing optical fiber is doubled, and the circularly polarized light is converted into two beams of orthogonal linearly polarized light with mutually exchanged modes by a lambda/4 optical fiber wave plate again, namely the linearly polarized light originally transmitted along the fast axis of the polarization maintaining optical fiber is transmitted along the slow axis at the time, and the linearly polarized light originally transmitted along the slow axis of the polarization maintaining optical fiber is transmitted along the fast axis at the time; two linearly polarized lights carrying phase difference information sequentially return to the modulator A10 and the polarizer A9 and interfere behind the polarizer, and the two interfered lights are sent to the signal acquisition and processing system A4 through the coupler network 2.

The structures and the realization principles of the polarization-maintaining optical path system B5 and the polarization-maintaining optical path system C22 are completely consistent with those of the polarization-maintaining optical path system A3.

In a preferred embodiment, in the signal acquisition and processing unit, the optical detector converts an optical signal into an analog electrical signal, outputs the analog electrical signal to an AD sample, and then converts the analog electrical signal into a digital signal through the AD sample; the signal processing circuit receives the AD sampling signal, calculates and outputs the measured current, and provides a control signal for the modulator. The signal processing circuit may employ a field programmable gate array.

The structure of a preferred embodiment of the signal acquisition and processing unit is shown in fig. 6. The optical detector 12 is connected to the coupler network 2 through a single-mode optical fiber, and converts the optical signal into an analog electrical signal for output. The AD sample 13 collects an analog signal output from the photodetector 12 and converts the analog signal into a digital signal. The signal analysis and control circuit 14 provides a control electric signal for the polarization-maintaining optical path system 3, modulates the optical path system, receives the digital quantity signal output by the AD sampling 13, analyzes the phase difference information contained in the optical signal by means of demodulation and the like, converts the phase difference information into a measured primary current, and outputs the measured primary current to a subsequent device. The signal analysis and control circuit 14 typically employs a field programmable gate array.

The optical current transformer based on the coupler network can be configured with different numbers of polarized light path systems according to field requirements, and selects a proper coupler network structure and coupler type according to the polarized light path systems. If the differential current is tested, at least the primary current of two test points is needed to be tested, at least 2 sets of polarized light path systems are needed to be configured, and a coupler network shown in figure 3 can be selected; if the zero sequence current is tested, primary currents of A, B, C test points need to be tested simultaneously, at least 3 sets of polarized light path systems need to be configured, and a coupler network as shown in fig. 4 can be selected.

Above embodiment only is for explaining the utility model discloses a technical thought can not be injectd with this the utility model discloses a protection scope, all according to the utility model provides a technical thought, any change of doing on technical scheme basis all falls into the utility model discloses within the protection scope.

Claims

1. An optical current transformer based on a coupler network, characterized in that: the current transformer comprises a light source, a coupler network, N polarization-maintaining optical path systems and N signal acquisition and processing units, wherein N is an integer greater than or equal to 2;

the coupler network comprises a primary coupler and N secondary couplers, wherein the primary coupler at least comprises N output ports, and first to Nth output ends of the primary coupler are respectively and correspondingly connected with first input ends of the N secondary couplers;

the polarization-maintaining optical path system is formed by sequentially connecting a polarizer, a modulator and an optical fiber sensing ring with a reflector;

the signal acquisition and processing unit comprises: the optical detector and the AD sampling and signal processing circuit are connected in sequence;

2. The optical current transformer based on a coupler network of claim 1, wherein: the coupler network is composed of a plurality of coupler arrangements of the same type or different types.

3. The optical current transformer based on a coupler network of claim 1, wherein: the optical signal spectrum of the light source is wide, the coherence is weak and the optical power exceeds 1 mw.

4. The optical current transformer based on a coupler network of claim 1, wherein: the light source adopts a super-radiation light emitting diode.

5. The optical current transformer based on a coupler network of claim 1, wherein: the devices of the polarization-maintaining optical path system are connected through polarization-maintaining optical fibers, wherein the optical fibers between the polarizer and the modulator are welded at an angle of 45 degrees, and the optical fibers between the modulator and the optical fiber sensing ring with the reflector are welded at an angle of 0 degree; the sensing optical fiber ring with the reflecting mirror is composed of a lambda/4 wave plate, a sensing optical fiber and the reflecting mirror.

6. The optical current transformer based on a coupler network of claim 5, wherein: the lambda/4 wave plate is formed by cutting a long beat length optical fiber, the sensing optical fiber adopts an HB round optical fiber, and the reflector is positioned at the tail end of the sensing optical fiber and is manufactured in a vacuum coating mode.

7. The optical current transformer based on a coupler network of claim 1, wherein: in the signal acquisition and processing unit, optical signals of the optical detector are converted into analog electric signals and output to an AD (analog-to-digital) sample, and then the analog electric signals are converted into digital signals through the AD sample; the signal processing circuit receives the AD sampling signal, calculates and outputs the measured current, and provides a control signal for the modulator.

8. The optical current transformer based on a coupler network of claim 1, wherein: the signal processing circuit adopts a field programmable gate array.