CN203164257U - Flexible optical current transformer - Google Patents

Abstract

The utility model relates to a flexible optical current transformer, which comprises an optical fiber current sensing ring, a transmission optical fiber and an acquisition unit. The sensing ring is connected to the acquisition unit at the other end. Compared with the prior art, the utility model has the advantages of flexible installation mode, strong anti-interference ability, no need for insulation, high stability, and satisfies the needs of intelligent substation construction better.

Description

Flexible Optical Current Transformer

technical field

The utility model relates to a transformer, in particular to a flexible optical current transformer.

Background technique

The flexible installation method is a unique installation method for optical transformers. It makes full use of the characteristics of soft and flexible sensing optical fibers. It has the advantages of flexible installation, easy maintenance, strong adaptability, and no need to consider insulation. The sensing optical fiber ring is convenient. Installed around any conductor, it is convenient to temporarily or permanently add measurement points in the system, and can be installed at any time when the substation is running, without power failure of the measured line, especially suitable for substation reconstruction and other projects.

However, according to the research, only Canada's Nxtphase company has developed related products and applied them in engineering. Similar products in China have not yet been developed, and there are no reports of engineering applications. In order to meet the needs of power system development, break the technology monopoly of foreign products, and ensure the safe and stable operation of my country's power grid system, it is of great significance to develop domestic flexible optical current transformers.

The most important factor that has always limited the optical current mutual inductance is that environmental factors such as temperature changes, vibration, and stress will have a greater impact on the sensing accuracy and stability of the sensing fiber, which is mainly due to:

1. The linear birefringence existing in the sensing fiber ring will interfere with the current detection information of the system;

2. The change of the phase delay of the λ/4 wave plate will cause the change of the scale factor of the transformer, which will affect the accuracy and stability of the transformer;

3. The fiber-wound frame will affect the fiber ring, and the vibration and thermal expansion and contraction of the frame will also affect the measurement of the transformer.

Utility model content

The purpose of this utility model is to provide a flexible optical current with flexible installation, strong anti-interference ability, no need for insulation, high stability, and better meet the needs of intelligent substation construction in order to overcome the above-mentioned defects in the prior art. Transformer.

The purpose of this utility model can be achieved through the following technical solutions:

A flexible optical current transformer, characterized in that it includes an optical fiber current sensing ring, a transmission fiber and an acquisition unit, the optical fiber current sensing ring is wound around the periphery of the primary conductor to be tested, and one end of the transmission optical fiber is connected to the optical fiber current The sensing ring is connected to the acquisition unit at the other end.

The acquisition unit includes a light source, a coupler, a polarizer, a polarization beam splitter, a phase modulator, a photodetector and a demodulation circuit, and the described light source, a coupler, a polarizer, a polarization beam splitter, and a phase modulator , a demodulation circuit, and a photodetector are connected in sequence, the photodetector is connected to a coupler, and the phase modulator is connected to a transmission fiber.

The transmission optical fiber is an armored optical cable.

The output port of the optical fiber current sensing loop is provided with a wave plate and a mirror.

The wave plate is wave plate.

The optical fiber current sensing loop uses the Faraday magneto-optic effect of polarized light in the optical fiber to induce the magnetic field generated by the primary current, and the output optical signal is connected to the acquisition unit through the transmission optical fiber.

The acquisition unit calculates the received optical signal to obtain the primary current.

The optical fiber current sensing ring is wound in the form of an optical cable, the optical cable is filled with oil, and the sensing optical fiber is soaked in the oil.

The sensing fiber adopts low birefringence fiber.

Compared with the prior art, the utility model has the following advantages:

1. The utility model adopts a flexible optical current transformer with a reflective Sagnac interferometer structure, and realizes a reciprocal structure through a mirror, which can make two beams of orthogonally polarized light reflect and return through the original path. It is a fully symmetrical optical path, which can reduce the The influence of temperature, vibration, stress, etc. on the optical path improves the stability of the optical path and is less affected by environmental changes, ensuring that the optical current transformer has good stability and temperature characteristics.

2. The utility model selects a low-birefringence fiber as the sensing fiber. The low-birefringence fiber itself has good consistency, small linear birefringence, and is less affected by temperature.

3. In the utility model, the sensing optical fiber ring is wound in the form of an optical cable, and the optical cable is filled with oil, and the sensing optical fiber is soaked in the oil, which can evenly disperse the stress, vibration, oil thermal expansion and contraction of the optical cable, etc. , It can also effectively eliminate the influence of stress and vibration caused by the winding frame in other installation methods, and improve the stability of the transformer.

Description of drawings

Fig. 1 is a structural block diagram of the utility model.

Detailed ways

The utility model will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Fig. 1, a kind of flexible optical current transformer comprises optical fiber current sensing ring 1, transmission fiber 4 and collection unit 5, and described optical fiber current sensing ring 1 is wound around the periphery of the primary conductor 6 to be tested, and described One end of the transmission optical fiber 4 is connected to the optical fiber current sensing ring 1, and the other end is connected to the acquisition unit 5.

The acquisition unit 5 includes a light source 51, a coupler 52, a polarizer 53, a polarization splitter prism 54, a phase modulator 55, a photodetector 57 and a demodulation circuit 56, and the light source 51, the coupler 52, the The polarizer 53, the polarization beam splitter prism 54, the phase modulator 55, the demodulation circuit 56, and the photodetector 57 are sequentially connected, the photodetector 57 is connected to the coupler 52, and the phase modulator 55 is connected to the transmission fiber 4 connect.

波片。The transmission optical fiber 4 is an armored optical cable. The output port of the optical fiber current sensing loop 1 is provided with a wave plate 3 and a mirror 2 . The wave plate 3 is

wave plate.

The working principle is that the optical fiber current sensing loop uses the Faraday magneto-optical effect of polarized light in the optical fiber to induce the magnetic field generated by the primary current; the output signal is connected to the acquisition unit through the transmission optical fiber, and the transmission optical fiber transmits the optical signal from the acquisition unit to the optical fiber current sensor. At the same time, the signal returned by the current sensing ring is sent to the acquisition unit for processing; the acquisition unit sends the optical signal generated by the light source to the sensor end, and at the same time receives the optical signal carrying the primary current information returned by the sensor, and the returned The optical signal is processed, the primary current value is calculated, and the primary current is sent to the merging unit for synchronization of each phase, and then output to protection, measurement, metering and other devices, and can also be directly interfaced with computerized measurement and protection devices.

The acquisition unit adopts reflective optical fiber Sagnac interferometry technology to realize the measurement of optical signals. Reflective optical fiber Sagnac interferometric technology reduces the influence of the sensor from environmental temperature, vibration and other factors, and improves the accuracy of the sensor.

After the light output from the light source 51 is depolarized by a depolarizer, 50% of the light energy is coupled into the polarizer by the coupler, and the other 50% of the light leaves the system at the other output end (non-reflection end) of the coupler. The linearly polarized light output by the polarizer is divided into two beams of linearly polarized light after passing through the 45° welding point, and the two beams of linearly polarized light vibrate along the X and Y axes of the polarization-maintaining pigtail of the phase modulator respectively. The output polarization-maintaining pigtail of the polarizer and the length of the polarization-maintaining pigtail of the phase modulator must meet certain conditions to realize the depolarization function. The phase of the transmitted light can be modulated after the modulation signal generated by the signal generator is added to the phase modulator.

The light from the phase modulator enters the polarization maintaining fiber delay line. The two main axes of the polarization-maintaining fiber delay line are consistent with the main axes of the phase modulator. It has two functions: 1. Transmit the light output from the light source and the phase modulator far away from the sensing fiber to the sensing fiber, and transmit The sensing fiber is separated from the light source, detector and signal processing electronics. 2. Sufficient length of high-birefringence optical fiber provides sufficient time delay. During the time when the light goes back and forth between the polarization-maintaining optical fiber delay line and the sensing optical fiber, the modulation waveform added to the phase modulator changes just half a cycle.

波片，波片和保偏光纤延迟线的主轴成45°，然后进入传感光纤。波片的作用是把保偏光纤延迟线两主轴出来的两束正交线偏光转换为圆偏光。

波片是一小截长拍长的保偏光纤，其长度是1/4拍长的奇数倍。The two beams of polarized light coming out of the polarization-maintaining fiber delay line vibrate along their two main axes respectively. After passing through a 45° welding point, the two beams enter into the

wave plate, The major axes of the wave plate and polarization-maintaining fiber delay line are aligned at 45°, and then enter the sensing fiber. The role of the wave plate is to convert the two orthogonal linearly polarized lights from the two main axes of the polarization maintaining fiber delay line into circularly polarized light.

A wave plate is a small length of long beat-length polarization-maintaining fiber whose length is an odd multiple of 1/4 beat length.

波片出来的是两旋向相反的圆偏光。振动方向沿保偏光纤延迟线X轴的光被

波片转换成右旋圆偏光，振动方向沿保偏光纤延迟线Y轴的光被波片转换成左旋圆偏光。由于传感光纤周围存在电磁场，这两束圆偏光以不同速度在传感光纤中传输，累积的相位差和施加到传感光纤的磁场成正比。传感光纤的末端连有一反射镜。低双折射传感光纤中传输的两束圆偏光在遇到反射镜后发生全反射，二者旋向改变。在反射后返回途中，原来的右旋圆偏光变成左旋圆偏光，原来的左旋圆偏光变成右旋圆偏光。由于返回时两圆偏光的旋向和传输方向均改变，二者的累积相对相移加倍。这样，总相移Δφ＝4VNI，其中V是传感光纤的Verdet常数，N是缠绕在电流导线周围的传感光纤的圈数，I是导线中的电流大小。from

What comes out of the wave plate are two circularly polarized lights with opposite rotations. The light whose vibration direction is along the X-axis of the polarization-maintaining fiber delay line is

The wave plate is converted into right-handed circularly polarized light, and the light whose vibration direction is along the Y-axis of the polarization-maintaining fiber delay line is The wave plate converts to left-handed circularly polarized light. Due to the presence of an electromagnetic field around the sensing fiber, the two beams of circularly polarized light travel in the sensing fiber at different speeds, and the accumulated phase difference is proportional to the magnetic field applied to the sensing fiber. The end of the sensing fiber is connected to a reflector. The two beams of circularly polarized light transmitted in the low-birefringence sensing fiber are totally reflected after encountering the mirror, and the direction of rotation of the two is changed. On the way back after reflection, the original right-handed circularly polarized light becomes left-handed circularly polarized light, and the original left-handed circularly polarized light becomes right-handed circularly polarized light. Since both the handedness and the transmission direction of the two circularly polarized lights change when they return, the cumulative relative phase shift of the two is doubled. In this way, the total phase shift Δφ=4VNI, where V is the Verdet constant of the sensing fiber, N is the number of turns of the sensing fiber wound around the current wire, and I is the magnitude of the current in the wire.

波片后，原来沿HiBi光纤延迟线X轴振动的线偏光在返回时变为沿HiBi光纤延迟线Y轴振动的线偏光，原来沿HiBi光纤延迟线Y轴振动的线偏光在返回时变为沿HiBi光纤延迟线X轴振动的线偏光，这两束线偏光再次通过相位调制器，经过45°焊接点后，在起偏器处干涉。干涉后的光被耦合器分出一部分到达PD探测器。Two beams of circularly polarized light are transmitted back and forth in the sensing fiber and passed through

After the wave plate, the linearly polarized light that originally vibrated along the X-axis of the HiBi fiber delay line becomes the linearly polarized light that vibrates along the Y-axis of the HiBi fiber delay line when it returns, and the linearly polarized light that originally vibrated along the Y-axis of the HiBi fiber delay line becomes The linearly polarized light vibrating along the X-axis of the HiBi fiber delay line, the two beams of linearly polarized light pass through the phase modulator again, pass through the 45° welding point, and interfere at the polarizer. Part of the interfered light is split by the coupler to reach the PD detector.

In the optical path, the two beams undergo the same polarization change in reverse order. The sensing fiber is located in the middle of the optical path of the two beams of light, and the only phase difference between the two beams of light is caused by the magnetic field existing in the sensing area.

What the PD detector detects is the light intensity after the interference of the two beams of light, which contains the phase difference information of the two beams, which also contains the information of the magnetic field and current.

波片是光纤电流传感器的主要部分，传输光纤从绝缘子中穿过，其它光学器件则基本集中在采集单元中。In the above optical devices, the optical fiber sensing ring and

The wave plate is the main part of the fiber optic current sensor, the transmission fiber passes through the insulator, and other optical devices are basically concentrated in the acquisition unit.

Claims (5)

1. A flexible optical current transformer, characterized in that it comprises an optical fiber current sensing ring, a transmission fiber and an acquisition unit, the optical fiber current sensing ring is wound around the periphery of the measured primary conductor, and one end of the transmission optical fiber is connected to The fiber optic current sensing loop is connected to the acquisition unit at the other end. 2. A kind of flexible optical current transformer according to claim 1, it is characterized in that, described collection unit comprises light source, coupler, polarizer, polarization beam splitter prism, phase modulator, light detector and demodulator Circuit, the described light source, coupler, polarizer, polarization splitter prism, phase modulator, demodulation circuit, photodetector are connected sequentially, and described photodetector is connected with coupler, and described phase modulator is connected with Transmission fiber optic connection. 3. A flexible optical current transformer according to claim 1, wherein the transmission optical fiber is an armored optical cable. 4. A flexible optical current transformer according to claim 1, characterized in that the output port of the optical fiber current sensing loop is provided with a wave plate and a mirror. 5. A kind of flexible optical current transformer according to claim 4, is characterized in that, described wave plate is

wave plate.

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