EVNNPT: striving for a secure operation, faults limitation

EVNNPT: striving for a secure operation, faults limitation

With the task on management and operation of 98 substations, 4,848 km of 500kV transmission line and 11,313 km of 220 kV transmission line, the highest difficulties for EVNNPT are that the transmission grid often operates in full-load and overload making the security of transmission grid is always in danger.  
Transmission system is always in tense operation  
Typically, the transformers of Nho Quan, Thuong Tin substations often operate in full-load. The overload is upto 23% in Phu Ly, Hai Duong, Bac Giang, Ninh Binh, Thai Binh, Nam Dinh, ho Noi, Nghi Son and Ba Che substations. The 220kV transmission lines of Nho Quan –Ninh Bình (circuit 1), Hoa Binh – Ha Dong, Pha Lai – Pho Noi often in tense operation, in which the 220kV Nho Quan – Ninh Binh (circuit 1) was in overload for 59 times, with a total duration of over 32 hours.
In the Western Highland area, because of the high mobilization of the hydropower plants, the 500kV Pleiku, Dak Nong transformers and the 500kV Dak Nong – Phu Lam transmission line are often in full-load operation. In many time, the transmission capacity of the 500kV Dak Nong – Phu Lam transmission line exceeded the allowed one of capacitor.
In the South, the 500kV O Mon – Nha Be transmission line was put into operation contributing to the reduction of tense for the 220kV Cai Lay – Phu Lam, Cai Lay – Phu My transmission lines, strengthening the links between the Western South and Eastern South areas. However, because of high mobilization of hydropower plants in Western Highland area, the 500kV Phu Lam, Tan Dinh substations are often in full-load and overload operation. Especcially, the 220kV transmission lines of Phu Lam – Tan Dinh, Cat Lai – Thu Duc, Phu Lam – Binh Tan are frequenty overload. The 220 kV Cat Lai – Thu Duc overloaded for 77 times (Circuit 1) and 83 times (circuit 2), with a total duration of 170 hours each circuit.

 In 2012, there were totally 32, 154 and 20 faults occurred to the substations, transmission lines and right of way (ROW), respectively. 45 transmission lines and 59 transformers at 550kV/220kV voltage level were in overload operation, totally 573 times and 592 times of overload of transformers and transmission lines, respectively.
In 2012, the loss of 500kV and 220kV transmission grid was 22.33% compared with in 2011, reduced by 0.26% in compare with the rate of 2.65% assigned by Vietnam Electricity (EVN). In which, most of losses were the technical ones caused by the operational manner of power system and the regional transmission grid. In fact, due to the power generation shortage, the load comsumption is quick and uneven in different localities, regions, the operational manner of power system is changed continuously. Sometimes, the diagram of operation of substations must be changed, making the quality of operation affected.

Objectives: Security, loss reduction, faults limitation 

To overcome such difficulties, many solutions have been applied by EVNNPT for the substations and transmission lines in order to reduce losses and minimize the faults to transmission lines.
Concretely, the solutions applied in transmission lines include: “Reducing the ground resistance value by using chemicals, adding the activated carbon and humus; Repairing, improving the ground wires system: Increasing the number of ground wires, lengthening the ground wires to the area of low ground resistance, repairing and maintaining periodically the ground wires; Increasing the number of direct ground access of the light arresters in some pillars; Increasing the porcelain bowls of isolators in the high mountainous areas, adjusting the distance of light arresters for the transmission lines of high density and intensity of light; installing the surge arresters for transmission.
Checking, scrutilizing, settling strictly the violations or dangers of violations on safety distance; Clearing regularly the right of ways (ROW); Strengthening the relation with localities, polices, social unions, propagandizing on protection and safety of ROW of transmission grid, finding and preventing the dangers of faults; Coordinating with the load dispatch centres to set up an appropriate operational manner to avoid the transmission line overload; Strengthening the inspection of light-up of heating of equipment, join points to ensure the secure operation of equipment.
The sollutions applied in the substations include: Inspecting, testing periodically the equipment; Setting up the regional testing and repairing units for quick reaction to any faults occurred; Organizing the training courses on capacity building for testers; Monitoring and providing timely solutions for upgrading the capacity of the overloaded substations. For the new substations, the expansion improvement must follow strictly procedures to minimize the faults; Carrying out periodical tests and reinforced tests of substations’ equipment as planned and when faults occurred; Organizing training on power safety.
Mr. Dang Phan Tuong - EVNNPT’s Management Board Chairman:

At present, EVNNPT is carrying out the speciality-based allocation of works and decentralization to its subsidiaries; strengthening the application of information technologies in management and operation, technical management and management of equipment and devices of substations; Using the automation technology for simplifying the operation and controlling the operational procedures for the operators; Strengthening the inspection and monitoring in all aspects: operation management, inspection, repair, management of equipment and devices; Developing a Smart Grid; Using the new technologies for ensuring the safety, economy, reliability and improving the ecological environment.