The World¡¯s First Dual Inner Water Cooled 300MVar Phase Modifier was Successfully Connected to the Power Grid

On 10th Jan, in the UHV ¡À800kV Shaoshan Convertor Station, Hunan Electric Power Company Maintenance Branch carried out pre-service tests of the first UHV DC power transmission receiving-end phase modifier that had been newly connected to the grid. This is the world¡¯s first dual inner water cooled 300MVar phase modifier.

As a device offering reactive compensation to power grids, phase modifier is of great significance to the safe and stable operation of UHV projects. The No.2 dual inner water cooled phase modifier that has been connected to the grid this time is more efficient than the existing air-cooling facilities. As a world-leading Chinese technology with patent, it could greatly improve the operation of phase modifiers. Hunan Electric Power Company Maintenance Branch has been actively promoting the production of phase modifiers for Shaoshan Convertor Station to ensure the success of the connection to the grid.

Strengthening the development of technology expertise

¡°The first receiving-end phase modifier was installed in Shaoshan Convertor Station, presenting both an opportunity and a challenge,¡±said the person in charge of the project in Hunan Electric Power Company Maintenance Branch on the meeting for the start of the early-stage preparation of the project. As early as June 2016, the company established the phase modifier production preparation work team and started the training, research, and follow-up of the project.

Hunan Electric Power Company Maintenance Branch hired experienced technical experts to be consultants, transferred two electric engineering experts from hydropower stations with the help of Hunan Electric Power Company and selected several internal employees with doctor or master degree to form a team. At the same time, it identified the duties and responsibilities for each position to ensure that people in different positions during project operation and maintenance could master related skills.

From July 2016 to April 2017, Hunan Electric Power Company Maintenance Branch attended four meetings discussing the designing plans of phase modifiers organized by State Grid, with more than 20 professional suggestions proposed. The company also organized visits to suppliers to learn about and study the structure, operation and maintenance of electric machinery and master the key steps of installation of phase modifiers and invited technical experts to give lectures and exchange ideas with the team. Besides, the company organized on-site surveys and trainings in power plants for 271 people altogether and more than 60 reports had been completed.

¡°The huge phase modifier system is like a large reactive power plant,¡± said Ding Zijian, Head of Shaoshan Converter Station, excitedly during his field research. The system injects water into the air-core winding of the stator and the rotor through the dual inner water cooled system to realize uniformed cooling of all windings, which is more efficient than air-cooling, thus reducing loss and protecting insulation. This technology is unimaginable in the past.

In May, 2017, Shaoshan Convertor Station proposed a training program that allows experienced experts to guide young workers. Trainers were asked to write summaries of their investigations,  prepare presentation and organize regular training for other operation and maintenance staff to ensure that related workers could get familiar with phase modifiers as soon as possible.

Keeping track of on-site acceptance inspection

In July 2017, Shaoshan Convertor Station phase modifier production preparation work team finished 10 professional reports and collected 161 final design drawings. The Convertor Station opened an ¡°evening class¡± on the examination and approval of drawings and organized technical exchanges and lectures. ¡°We will not leave out a single question or mistake in order to have a well-thought-out plan before moving on to making the drawings,¡± said Mao Zhiping, a member of the team.

With the in-factory production and tests of phase modifiers entering the final stage, Shaoshan Convertor Station organized 28 people in 4 batches to conduct system debugging in the factory. Related workers carried out entire supervision on the general assembly and debugging of individual phase modifier as well as the whole system debugging, reported all 21 problems to the suppliers and related authorities on time, kept track of closed-loop inspection and repair and implemented reviews and checks. ¡°It is amazing that in just one month, you could propose so many high-quality professional suggestions and advices that are precious for our future design and production,¡± said the people in charge of technical issues on the supplier¡¯s side.

In September, 2017, the on-site installation of the phase modifier was rolled out. With the implementation of the on-site acceptance inspection, Hunan Electric Power Company Maintenance Branch, based on the existing equipment responsibility system, invited experienced power plant workers to establish a work team for the on-site follow-up and inspection of the phase modifier project. The team was asked to formulate plans for the assignment of responsibilities according to each member¡¯s technical expertise to ensure all-round on-site follow-up and acceptance inspection.

During the on-site follow-up and acceptance inspection that lasted for more than 100 days, members of the team came to the site before the construction workers and left the site after the construction workers. The work environment was extremely challenging with dust and the smell of oil paint. Members of the team were therefore suffering from respiratory allergy and cold. However, they were not intimidated by the harsh environment or illness.

The Project was connected to the grid and put into operation successfully

On 29th December, 2017, the live test of the No.2 phase modifier of Shaoshan Convertor Station was officially launched after project delivery.

The phase modifier operation rules were released after approval; compilation of related documents and preparation of operation order were carried out as well as essential project drawings were made; a copy of work conditions and the compilation of supervision disk guidance were finished and the training for on-site operation and maintenance staff were completed. Besides, instruments and tools for safe operation were ready; marks for on-site equipment and safety signs were installed; the smart key system was implemented and put into operation; the fixed value calculation and reorganization were finished and the value was submitted for approval; and the revision of operation log and the sorting of equipment rotation trial project were finished. ¡°With the first-class equipment, our phase modifier could be put into operation successfully,¡± said Sun Peng, Vice Head of Shaoshan Convertor Station.

At 1:00 a.m. 30th December, 2017, Shaoshan Convertor Station finished all tests in advance. ¡°A new record has been set! Back in the power plant, the same work has to take at least 4 or 5 days, but in State Grid, it took only less than 2 days thanks to the efforts in the early stage,¡± said technical workers of the supplier.

After 50 hours of hard work without stop, more than 20 pre-connection tests have been completed, marking that the phase modifier has entered the stage of ¡°grid connection¡±. ¡°The synchronous switching in of the 500kV switch 5602 was a success; the No.2 main transformer is in normal operation; the No.2 static thyristor microcomputer excitation regulator is in good shape and the No.2 phase modifier is connected to the grid successfully!¡±It was the morning of 5th Jan. The installation and modulation of the No.1 phase modifier has been basically finished. It is planned that the grid connection would be launched in late January and the phase modifier project would be put into trial operation for 168 hours in the first half of February.

Source: State Grid News

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