With the establishment of a strong smart grid by the State Grid Corporation, vigorously developing large-capacity, high-efficiency, long-distance advanced transmission technologies such as UHV and promoting the construction of smart grids have become the focus of the power industry. Among them, UHV grid, as the backbone network of smart grid construction, must have the ability of inter-area scheduling, long transmission distance and large carrying capacity. Because UHV communication lines are different from ordinary carrier communication lines, their route planning is generally remote, and it is necessary to avoid development areas and densely populated areas. If the communication relay station is set according to the normal distance (less than 100 kilometers), the location, construction and operation of the communication relay station that can provide power supply are very difficult. Therefore, reducing the number of relay stations will save a lot of construction cost and maintenance. The cost, at the same time, can effectively reduce the number of faulty nodes in the communication line and enhance the stability and security of the long-term operation of the communication network. Supporting ultra-long-span optical communication solutions is an urgent need for smart grid and UHV grid construction.
Huawei solution
Huawei Technology Co., Ltd. MSTP series optical transmission products are in the leading position in the field of ultra-long-distance transmission, and have been widely used in the construction of communication system projects for power grid customers. The MSTP series consists of OSN products, namely OSN1500/OSN2500/OSN3500/OSN7500/OSN9560. The series has a unified development platform and management platform. On-demand selection and integrated management from the access layer to the core layer can be achieved.
The core technologies of MSTP series products for improving the length of optical transmission without relay are mainly forward error correction technology (FEC, EnhancedFEC), erbium-doped fiber amplifier (EDFA-BA, EDFA-PA), distributed Raman amplifier (Raman). ) and remote pump technology. Because the remote pump technology has high requirements on the attenuation of the optical cable and the environment, and the need to place the bait box in the middle of the optical cable, the original optical cable needs to be interrupted. The construction period of the project is several months. Therefore, in the actual engineering of the power system, except for special circumstances, Try to avoid it. At present, in the design of the power communication system, according to the following technical selection order, an appropriate combination of schemes can be selected to satisfy the ultra-long-distance application of 2.5 Gbps (gigabits per second, bandwidth transmission speed) and 10 Gbps.
1. First consider configuring the power amplifier (EDFA-BA) at the transmitting end to increase the transmitted optical power, and configuring the preamplifier (EDFA-PA) at the receiving end to improve the receiving sensitivity index; the mainstream power amplifier product gain is 10 to 23 dB (power) Between the units of gain, the output power can reach 14~23dBm (the value of the absolute value of the power is verified). The preamplifier gain is typically greater than 10 dB. The solution provided by Huawei successfully solves the power threshold limitation problem of the power amplifier by using the nonlinear suppression technology at the transmitting end. The output power indicator is at the leading level among similar devices in the industry.
2. Increase the configuration of forward error correction (FEC, EFEC) technology. Currently, optical communication systems have adopted forward error correction (FEC) technology to improve the BER performance of the system and extend the transmission distance of optical signals. The standard FEC coding gain is about 6 to 7 dB. Huawei uses Enhanced Forward Error Correction (EFEC) to provide an additional 1 to 3 dB coding gain compared to standard FEC.
3. Adding the configuration of the forward and backward Raman amplifiers, the gain region of the Raman amplifier is distributed in the fiber itself, featuring flat gain and low noise, which is very suitable for long-distance fiber transmission system applications. In G.652 fiber (a widely used single mode fiber), the gain value is 8 to 12 dB, and the typical amplification value is 10 dB. Raman amplifiers are typically used with EFDA amplifiers, ie forward Raman with power amplifiers, and backward Raman with preamplifiers.
To solve the dispersion problem in fiber transmission systems. The traditional solution uses a dispersion-compensating fiber with a negative dispersion coefficient to compensate, but the dispersion-compensating fiber has a large loss, and the loss becomes larger with the increase of the compensation distance, which increases the complexity of the design of the ultra-long-distance transmission system; Huawei adopts The passive å•å•¾ fiber grating type dispersion compensation module has the characteristics of small volume and constant insertion loss; it can effectively solve the problem that the additional insertion loss introduced by the dispersion compensation fiber changes with the amount of dispersion.
In summary, through the combination of the above schemes, the Huawei solution can achieve single-span transmission over 300 kilometers without using the remote pump technology. In particular, the fiber amplifier, Raman amplifier, and dispersion compensation module used in the above solution can be rate-independent, and the communication network can be upgraded from 2.5 Gbps to 10 Gbps at zero cost.
Practice has proved that these ultra-long-distance optical fiber transmission technologies can well solve the long-distance transmission requirements of power systems, such as the application of Huawei products in the “West-to-East Power Transmission†project of China Southern Power Grid, achieving multiple single-span distances over 220 km. The maximum measured line attenuation exceeds 62dB for cross-segment transmission.
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