PTC3: The transmission network is under great pressure because many solar power plants come into operation

According to Mr. Dinh Van Cuong, Deputy Director of Power Transmission Company No. 3 (PTC3), the transmission network in addition to receiving electricity from the 500kV system and from power plants in the region via the 220kV transmission line, currently has to receive a large output of excess renewable energy from the distribution networks (110kV or lower) through 220kV transformers connected to the national grid, causing full and overload of the 220kV transmission network.

In 2019 and 2020, the total solar power capacity connected to transmission networks (220-500kV) and the distribution networks in the South Central region and the Central Highlands amounted to nearly 8,500MW, accounting for 42% of the total regional installed generation capacity.

In 2020, nine power companies in the South Central region and the Central Highlands (Khanh Hoa, Phu Yen, Binh Dinh, Gia Lai, Dak Lak, Dak Nong, Ninh Thuan, Lam Dong, Binh Thuan) received a total of 13.48 billion kWh through transmission networks managed by PTC3, while the excess of renewable energy (RE) (in addition to that supplied to the nine power companies) was transmitted from 110kV distribution networks to the 220kV, 500kV transmission network through 220kV transformers was 2.22 billion kWh, accounting for about 16.5% of the total amount of commercial electricity mentioned above. It is estimated that the output of RE exported to the transmission networks in 2021 could reach 5.4 billion kWh.

Currently, the dispatching centers are applying different measures, such as changing conductor connection, splitting busbar, opening network mesh, etc., to force capacity, maximize power carrying capacity of under-load 220kV transmission lines in the area. However, after changing conductor connection, full-load of conductors, sometimes an inter-area overload of 220kV transmission lines remain. PTC3 has directed its power transmission units to increase the frequency of inspection and supervision of the equipment, transformers, right-of-ways, of measuring the temperature of jumper contacts, connections, etc., in order to promptly overcome and deal with unusual events. In addition, for some major repairs, regular repairs, maintenance and periodic tests which need to cut-off power, PTC3 must arrange to conduct them at night when solar power stops generating, so it is very difficult and unsafe in performing them, potentially many risks.

Due to the rapid growth of solar power in the region on the distribution grid, the completion of the 2021 power transmission plan is very difficult, Mr. Dinh Van Cuong added.

PTC3 workers cleaning hotline Thap Cham 220kV substation

In order to release capacity from RE resources in the region and handle full-load and overload operation of the power networks managed by PTC3, the National Power Transmission Corporation has directed its units to complete and put into operation in 2021 the AT2 transformer at Phan Ri 220kV substation (Binh Thuan province), the Nha Trang-Krong Buk 220kV transmission line Circuit 2, the Krong Buk-Pleiku 2 Circuit 2 to solve the full load, overload operation situation of the regional 220kV transmission lines in Phu Yen, Khanh Hoa areas.

In addition, the Corporation also required its units to research and deploy 220kV double-circuit projects of Da Nhim-Duc Trong-Di Linh to deal with full-load, overloading operation of 220kV transmission lines in the areas of Lam Dong and Ninh Thuan; to construct Nha Trang-Thap Cham 220kV transmission line circuit 2 project and the circuit 2 conductor suspension project of the  Nha Trang-Thap Cham 220kV transmission line circuit 2, solving the full-load and overload conditions in Khanh Hoa, Ninh Thuan areas in the next years.

Some information about solar power sources operating in the area:

- 500kV level: 1,050MW (two PV power plants).

- 220kV level: 2,336MW (23 PV power plants).

- 110kV level: 2,308MW (61 PV power plants).

- Farm and rooftop solar power projects that are connected at a voltage level below 22kV: 2,755MW.

  • 03/03/2021 02:54
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