Imperatively ensure the safety of high-voltage power network

 

However, the biggest challenge of EVNNPT now is the 500kV transmission network from North to South and the 220kV line which have not guaranteed the safety standards (n-1). Besides, the violations of the high voltage power network’s right – of – way (ROW) is currently increasing. Especially, the incident at Binh Duong, where a tree felt down from a crane and was partly stuck in  500kV North-South transmission line, caused a serious damage. In addition to efforts of the power sector, the active and comprehensive contributions of ministries, agencies and local authorities are also needed to ensure the safety of high voltage power network’s ROW.

In fact, 500 kV transmission line (circuit 1), after nearly 20 years and 500 kV transmission line (circuit 2), after nearly 10 years of operation, both ensure operation safety and effectiveness. They are now both transmitting 3,000MW/day of electricity from North to south, in order to compensate the power shortage in the south of the dry season. However, the power transmission system, especially in the southern areas often operates in full capacity, sometimes lead to the overload. Moreover, due to the shortage of generations, increase in consumption and also uneven across the local region, which make the operation schedule of the power system is constantly changing. There are many moments, the conductor’s connection between substations does not operate at basic diagram which can reduce the operation efficiency.

 

The transmission network is also very stressful because the violations of ROW always happen. Right after the completion of 500 kV construction line (circuit 1), the regulations to protect the safety of power lines, substations, ROW ... had been issued by the authorities. Even the sag from the line to the ground depending on the terrain is also comply with the safety distance. The  regulations on ROW are stipulated very specific in Decree no.106/2005/ND-CP of the Government which guide the implementation of the Electricity Law to protect the safety of the high-voltage power transmission projects ... However, the power network is always threatened mainly by the people's awareness and behavior. Particularly, in 2012, the 220 kV transmission network in the North had four faults caused the cut of underground cables or discharge on the power lines or caused by kites of local people. The power transmission system in Central area and Highlands had 31 faults also, mainly due to protected forest fire…There were 22 faults occurred in the South, in which faults caused by violations of ROW counted about 36.4%. In the section passed Thai Nguyen province of Son La – Hiep Hoa 220 kV transmission lines, there were nearly 10 major faults because kites stuck on the transmission line caused discharge and electricity cut in many hours for fixing ... Obviously, the causes related to violations of the ROW which lead to faults on power transmission network are serious and have largest economic and social damage.

 

In many places, there are still construction projects in the ROW. Even serious, there are cases of people built houses by surrounding four high-voltage towers’ legs. Although the power sector has implemented many solutions to protect the ROW but it is not adequate because of insufficient sanction for violations. Many local authorities are not so excited and consider this as responsibility of the power sector. When a violation is detected, the authorities can only propaganda. In more serious case, they must depend on the law and authorities. The act of making people pay for the damage is irresistible since damages caused by the violations of ROW are often very large, such as the case where a tree shut down the 500 kV line. When this faults occurs, the protection system of transmission lines and substations have been working very well. So after just over three hours, EVN and EVNNPT gathered forces, quickly diagnosed and fixed the problem in time, revive the power back to normal. However, to minimize the occurrence of similar faults, it is needed to implement many comprehensive solutions and the contribution of the society as a whole from the local level, departments and agencies and most importantly the people's awareness of the safety of high-voltage power network’s ROW. In addition, the strictness of the law with strong enough sanctions is needed to reduce risks of faults.

 

To have a safe and sustainable power system, it is needed to complete power generation and network projects. Especially projects in the South area according to the Master Plan VII, reduce the dependence on power transmission network through 500 kV transmission line as current way. EVNNPT has invested a lot to build many 500 kV  and 220 kV power lines as well as substations in many areas, including rushing to complete the 500 kV lines  Pleiku- My Phuoc- Cau Bong, Vinh Tan - Song May, Phu My - Song May ... in order to ensure stable power supply for the South. However, the construction of power transmission network are facing a lot of financial difficulties and especially difficulties in the stage of site clearance. This should have the supports and contributions of the local ministries and departments to speed up the progress of projects.

In order to improve the consistency and safety in operation of power transmission network, recently, EVNNPT has value and apply new technologies such as Corocam to record electrical corona on series of insulators to prevent problems caused by discharge; composite insulators are used instead of glass insulators fitted to the line in the contaminated and moss areas, taking advantage of the emergency backup tower technology (Kema) by the Dutch in order to transfer to be ready for troubleshooting; online monitoring oil and partial discharge of transformer technology in order to detect the risk of faults ... Many scientific subjects are recognized and effectively applied in operation of the 500 kV transmission line North - South, such as cleaning insulators while operation, compiled procedures for maintenance of 500 kV transformer, replacing 500 kV transformers in 500 kV substations,  upgrading  capacitor of the 500 kV transmission line from 1,000A to 2,000A ... In addition, the maintenance and reinforcement of foundations, conductors, optical cables, strengthening the grounding wire system, the protection of high voltage power network’s ROW have been effectively implemented by the power transmission companies.

 

Many technical solutions were made in order to reduce losses and faults on transmission lines such as handling grounding wires, increasing the number of direct grounding connection points of the lightning arresters in some locations, increasing porcelain bowls of insulators in the high mountain areas, installing the surge arresters for transmission lines, regularly clearing ROW, enhancing heat detector for equipment and joints. Transmission force also strengthened relations with the local authorities,  police, social unions; propagandized and canvassed people to socialize the protection of high voltage power network’s ROW; coordinated with load dispatch units for appropriate operation scheduling. EVNNPT also established local testing and repairing units for rapid response to any faults; kept track of and had timely solutions to increase capacity of overloaded substations; performed routine tests, tests to strengthen equipment of substations as planned and tests to early detect defects in equipment which are only discovered during the period of regular testing by tools and machines. Base on that, timely repair or rejections were planned to limit causes of faults.