Operational Problems and Chalenges in Power System of Vietnam (Part I of III)

Ngày cập nhật: 30/11/2011
Ngo Son Hai, Nguyen The Huu, National Load Dispatch Centre of Vietnam

Abstract
- The Vietnamese power system is growing rapidly both in terms of scale and complexity. The load growth rate averages to 14% for the last 10 years. The development of the Extra High Voltage network of 500kV and interconnections with neighboring grids are the main characteristic of such growths. However the fast growth rate also brings problems in operating the network, for instance the short-circuit current becomes too high or the difficulties in voltage regulation (Abstract).


Index Terms – 500kV, Interconnection, Power market, Power system, Operation, 500kV, Short-circuit, Stability, Voltage regulation   (keyword)

I. HISTORY OF VIETNAMESE POWER SYSTEM DEVELOPMENTS

A.Vietnames power system prior to 1994: before the construction of the 500kV North – South line.

Before 1994, the Vietnamese power system was composed of separate sub-systems managed by regional power companies. These sub-systems are operated by system operators from respective regional power companies. Due to historical reasons, these systems utilized different types of equipments with diverse origins. Some areas in the South used two transmission voltage levels, 110kV and 66kV, with interchanging roles. The lack of interconnections leads to different operating problems, some areas have an excess of energy while others experience a deficit.

The maximum national and regional demands at the end of 1994 are National 2820MW – Northern region 1463 MW – Central Region 270 MW – Southern region 1151MW, respectively [1].

B. Vietnamese power system from 1994 to 2004: the introduction of the first 500kVNorth - South line

In 1994, the first extra high voltage (EHV) 500kV North-South line went into operation and connected regional systems. Starting with an initial length of 1488km, the 500kV EHV North – South links regional systems of the North, Central and South areas through 5 substations (Hoa Binh, Ha Tinh, Da Nang, Pleiku, and Phu Lam). During the period of 1994 – 2000, the exchanged electricity among regions totaled to 40 billion kWh, equivalent to 13.8% of the national amount during this time.

By the end of 2004, the demand of the national system – North – Central – South regions were 8283MW – 3494MW – 853 MW – 4073MW respectively. The corresponding energy amounts were 46,790 – 17,603 – 4,435 – 24,407 billion kWh. The average load growth for this period is 13.89% [1].

C.    Vietnamese power system after 2004

After 10 years of operating 500kV lines, several projects constructing new lines and substations have been started from mid-2004. Among them, the most important one being the links of the second 500kV North – South line which went into operation in 2004 – 2005. The 500kV Phu Lam – Nha Be – Phu My connects Phu My power generation centre (installed capacity of 4000MW) to the 500kV network commenced operation in 2004.

To date, the 500kV system has grown to become the backbone of the whole system, connecting not only heavily loaded zones but also large generating power plants in Vietnam (hydro generators in Son La, Hoa Binh, coal generators in Quang Ninh, gas turbines centers in Phy My,  O Mon). Outline of 500kV network is shown in the Figure 1.


Fig. 1. Map of Vietnamese 500kV network – August, 2011
(Source: National Load Dispatch Centre of Vietnam)


The operation of the 500kV line not only facilitates transmissions and interconnections among regions but also helps unite regional sub-systems into a single national power network. Advanced technologies have been applied, such as: SCADA/EMS system, load shedding using F81 under frequency protection, special load shedding system, automatic reclosing system and other automation systems. The interconnection also enables a more economical load dispatching process, better utilization of hydro sources and more efficient consumptions of gas for electricity generation.

By the end of 2010, the 500kV system has a total length of 3890km and 18 substations (total capacity of 10650 MVA). The recorded load in 2010 is: national – 15,416MW; North – 6,547MW; Central 1,648MW; South – 7,566MW. The respective amount of energy generation are: national –  99,711 billion kWh; North – 38,499 billion kWh; Central 9,536 billion kWh; South – 50,073 billion kWh [1].

D.    Power trading with neighboring countries

Starting from 2004, Vietnam power system began buying power from China Southern Power Grid through 110kV lines. By the end of 2006, Vietnam purchased power from China through both 110kV and 220kV lines. By the end of 2010, the amount of energy purchased totaled to 16,939 billion kWh, the maximum power was 900 MW. In addition, from 2009, Vietnam began to operate the 220 kV line Chau Doc – Takeo selling power to Cambodia with maximum capacity of 120 MW. In the years of 2009 – 2010, 1,337 billion kWh was sold to Cambodia.

Power trading among neighboring countries is a new step in the international integration of Vietnam power industry. However it also carries problems for the operating process including: the difference in rules and procedures, in operating standards, the chain effects of faults from either sides, and difference in languages (to communicate during network operation). Currently, the section of the power grid of Vietnam that receives power from China is separated from the national grid to connect to the Chinese grid, hence causing various operating problems.

E.    Establishment and development of the National Load Dispatch Centre (NLDC)
Together with the event of the construction of the 500kV North – South line, the National Load Dispatch centre was established on April 11, 1994, and was responsible for the 500kV network operation, generation scheduling and generators dispatching. At the end of 1998, regional Load Dispatch Centres in the North, Central and South regions, previously under the supervision of Regional Power Companies, were merged into NLDC, forming a united system operator with two level of authority: national and regional, operating the transmission network at 110kV, 220kV and 500kV voltage levels; planning and dispatching generation orders.

In 2005, NLDC was given the responsibility of operating the internal pilot power market of Vietnam Electricity (EVN). This was an internal competitive generation market with 8 EVN power plants as participants: Ba Ria, Da Nhim – Ham Thuan – Da Mi, Ninh Binh, Pha Lai, Phu My, Thac Ba, Thac Mo, Uong Bi.

Beginning from July 1, 2011, NLDC takes a role of the market operator of the Vietnamese competitive generation market (VCGM) with 48 participating plants (61% of the system’s total installed capacity) [5]. This first phase of competitive generation market is to test the synchronism of the legal framework, the level of adaptation of the technical infrastructure and to familiarize participants as well as to assess the effects of the power market.

(to be continued...)

REFERENCES

[1]    National Load Dispatch Centre, Annual Operating Summary 2010 and appendices.
[2]    Decision No. 26/2006/QD-TTg dated January 26, 2006 issued by the Prime Minister of the Socialist Republic of Vietnam, approving the development phases and establishing requirements of a power market in Vietnam.
[3]    Decision No. 12/2010/TT-BCT dated April 15, 2010 issued by the Minister of Ministry of Industry and Trade, approving the Grid Code.
[4]    Decision No. 1208/2011/QD-TTg dated July 21, 2011 issued by the Prime Minister of Vietnam approving the Master plan of Vietnam power developments for the period of 2011 – 2020, taking into accounts year 2030.
[5]    Dantri Online, http://dantri.com/vn/c76/x76-494482/khoi-dong-thi-truong-phat-dien-canh-tranh.htm
[6]    Grid Investments from a Nordic Perspective – Nordic Energy Regulators recommendations, https://www.nordicenergyregulators.org/.../Nordic_grid_conclusions.pdf
[7]    ACCC (Australian Competition & Consumer Commission) - State of the Energy market 2009 – Chapter 5, Figure 5.2, Page 128.

BIOGRAPHIES



Ngo Son Hai was born in Quang Ninh, Vietnam, in 1968. He received the B.E. degree in power electrical engineering from Hanoi University of Technology, Hanoi, Vietnam, in 1991, and the MEngSc degree in power electrical engineering from University of New South Wales, Sydney, Australia, in 1999, and the EMBA degree from Asian Institute of Technology, Bangkok, Thailand, in 2008.
In 1991, he joined the Dispatching Department of Hanoi Power Company, as a dispatcher. Since 1994, he has been with the National Load Dispatch Centre (NLDC), Hanoi, Vietnam where he was an Power System Operator in 1994, became a Deputy Manager of Dispatching Department in 1997, and a Manager of Dispatching Department in 2001, a Manager of Economic Operation Department in 2005, became a Deputy Director of NLDC in 2006, and a Director of NLDC in 2011. His experiences include power transmission network operation, power system operation planning, power generation scheduling and dispatching in the large system, power market operation.



Nguyen The Huu was born in Vietnam, in 1979. He studied electrical engineering at Hanoi University of Technology in Vietnam, graduating with with a B.E. degree in 2001. He joined the National Load Dispatch Centre (NLDC), Hanoi, Vietnam in 2001 and working as power system analysis engineer. From May 2011, Huu became deputy manager of Power System Analysis and Planing Department, NLDC. His special field of interest include electric power systems operation and planing, power market operation.

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