With the completion of the last operation instruction by the operation and maintenance personnel, Jiangsu Province's first island-type substation, the 110 kV power transmission and transformation project of Yangkou Port, Rudong County, which includes advanced switch cabinets, disconnectors, lightning arresters, vacuum circuit breakers, drop-out fuses and transformers, successfully completed cross-sea power transmission. In terms of coverage area, this substation can be said to be the 110 kV substation with the smallest radiation range in the province, and its service objects are limited to the four LNG (liquefied natural gas) companies on the island. As a supporting substation for Sunshine Island, the station can meet the energy demand of the island's tens of millions of tons of liquefied natural gas receiving station after it is put into operation.
Sunshine Island, at first glance, the name will quickly pop up in your mind, beaches, waves, cacti... However, this island located 13 kilometers off the coast of Changsha Town, Rudong County, has nothing to do with tourism. It is an energy island and the first artificial island formed by reclamation in Jiangsu Province. It has the best deep-water channel for liquefied natural gas ships to enter the port in the country, and the offshore terminal on the island is also very suitable for natural gas transportation and storage.
In recent years, in response to the country's goal of accelerating the construction of a natural gas production, supply, storage and sales system, the local government has vigorously developed the liquefied natural gas industry in Sunshine Island and built it into the country's largest offshore LNG receiving station. At present, Sunshine Island's annual LNG loading and unloading volume has reached 7 million tons, which can support one-third of the natural gas supply in Jiangsu Province throughout the year. It is currently the largest and most secure clean energy hub base in the Yangtze River Delta region. In addition to the already built Sinopec LNG loading and unloading station, the three receiving station projects of Guoxin, GCL and China Resources are now in full swing. It is understood that by the end of the "14th Five-Year Plan", the loading and unloading capacity of this small island will reach 25 to 30 million tons per year, becoming an important intersection for my country's west-to-east gas transmission, north-to-south gas transmission and sea gas landing. The key to LNG storage, processing and transportation lies in a stable low-temperature environment, which requires the temperature in the liquefied natural gas storage tank to be kept at around minus 160°C, and low temperature cannot be separated from continuous and stable electric energy refrigeration and cold storage. The original 20 kV cable power supply capacity of Sunshine Island can no longer meet the energy demand for large-scale industrial development.
The commissioning of the 110 kV Sunshine Island Substation, which includes advanced switchgear, disconnectors, lightning arresters, vacuum circuit breakers, drop-out fuses and transformers, has provided the island with a strong and powerful "energy heart". The substation covers a total area of 1,850 square meters, which is only about half the size of the same type of substations, but "small but complete". After the commissioning of the Sunshine Island Substation, it will better undertake the task of ensuring the power supply of Jiangsu natural gas during the peak winter period.
The construction of a substation on the island requires higher corrosion resistance and construction quality of materials. Sunshine Island belongs to the marine atmospheric environment. The average wind speed in the sea area near the island is 5.2 meters per second throughout the year. The maximum daily wind speed exceeds level 6 for 60 days. The highest environmental salinity is 29.6‰ and the lowest is 23.7‰ (the salinity of general seawater is 35‰), and it is often accompanied by heavy rainfall. In a word, it is strong wind and severe salt spray corrosion. At the beginning of the design, the Sunshine Island Substation adopted the highest level of anti-corrosion standard C5M* to ensure that the substation will not be affected by harsh environments in the next 40 years.
This is a grade standard based on humidity, temperature and protection methods. It is mainly aimed at equipment in outdoor and indoor environments, covering various environments from mild corrosion to severe corrosion. C5M is usually suitable for buildings with high salinity and high humidity. The anti-corrosion grade of conventional substations is C4M. In addition, all substation equipment, including switch cabinets, transformers and other key equipment, are placed in a constant temperature and humidity room. During the construction process, the inner and outer station walls are constructed with 200 mm thick aerated concrete blocks, without the need for metal components, to put on a solid "jacket" that is salt-resistant and anti-corrosion for the substation. Indoors, desalination equipment and air supply systems are also added, and the radiator shell of electrical equipment is made of stainless steel and C5M anti-corrosion grade materials, which adds "double insurance" for anti-corrosion. Considering the needs of later maintenance and upgrading, the outer wall of the main transformer room also adopts a detachable structure, which is composed of a detachable steel frame and prefabricated panels. Just like building blocks, once the main transformer needs to be moved or replaced, it can be disassembled and reinstalled at any time.
In order to solve the problem of long-distance power transmission on the island, the project has built a 34-kilometer double-circuit ultra-long submarine cable, which consists of three parts: onshore, on the bridge, and on the island. The cable laid along the bridge of the Yangguang Island Substation Supporting Cable Project is 16 kilometers long, and the cable channel reserved by the Yellow Sea Second Bridge is used to connect the inside and outside of the island. This is currently the longest submarine cable project in Jiangsu. Laying such an ultra-long high-voltage cable on the bridge deck requires overcoming the vibration of vehicles, waves and hurricanes on the cable. In general, the middle joint of the cable is a weak point and prone to failure. Therefore, the cross-sea cable project of the Yangguang Island 110 kV substation has increased the length of the single cable section and reduced the middle joints. In the entire project, the longest single-section cable is over 1.6 kilometers, which is three times that of conventional land cables, and the number of joints is directly reduced by more than half, thereby reducing the failure rate. This type of cable is rarely used in Jiangsu Province, and requires customized unconventional reels, which are difficult to produce and transport. After repeated surveys, we decided to use low-bed semi-trailers for transportation, which not only improves the stability of bulk cargo transportation, but also further reduces the pressure of vehicles on the road.
In addition, the cable is laid in a "snake" arrangement, which reserves a part of the expansion margin for the cable, and innovatively uses the self-developed expansion device. By installing a flexible bracket at intervals along the entire line, the cable can be adjusted up and down according to the vibration amplitude of the bridge deck, reducing the impact of internal stress and tension, and ensuring the stable operation of all electrical equipment including vacuum circuit breakers and drop-out fuses.