Sumatera-Jawa HVDC transmission Project

Singal Sihombing

Perusahaan Listrik Negara (PLN)

State Electricity Company of Indonesia

Abstract

In 2006, State Electricity Company of Indonesia (PLN), planned to build HVDC long transmission lines and submarine cables interconnection of Sumatera and Jawa grid. The aim of this interconnection is to transfer energy of IPP mine mouth coal power plant of Musirawas and Bangko in Sumatera island, with capacity of 2x600 MW and 4x600 MW respectively, to Jawa grid as load center.

The long distance transmission system of about total 700 km and submarine cables of 50 km, named Sumatera-Jawa HVDC transmission project, transmit 3000 MW, from the Bangko substation in South Sumatera to the load center in Jawa. It would be expected in operation in the beginning of 2013. The system, with a transmission voltage of ±500 kV, HVDC bipole.

This interconnection, could provide significant benefits to the economics of Indonesia particularly PLN. Enhanced system reliability, improved security and diversity of supply, increased economic efficiency in system operation, reduced environmental impacts. This interconnection coud also help attract private sectors investment to the power sector specially Independent Power Plant.

Now, the design of this HVDC system still in progress, and it is expected to be finish in the end of December 2008, devided into several contract documents packages, and bidding process and contract sign will take place in the beginning up to end of 2009.

Introduction

The average energy growth in the Jawa system is 6% to 7% each year with 16,000 MW as peak load, 72% as load factor and 22,000 MW of installed capacity. Considering the maintenance schedule of the power plants, season variation, FOR (force outage rate) of the units, also the de-rating of the units, the Jawa system needs about 2,000-3,000 MW of additional power generation in total every year. In 2007, PLN started building a number of coal-fired steam power plants with total generation of approximately 6,900 MW, most of which are expected to commercially operate in 2009 and 2010.

Given that, the question underlying now is how the system will be supplied for 2011 and in the proceeding years Jawa as an island with a very density in terms of population has a long list of issues, especially those related with land and the environment. One of the closest related to the power system is the difficulty to acquire land in order to construct new transmission lines and or power plants. Furthermore, issues with high pollution rates and infrastructure insufficiency are also experienced in the Jawa Island.

Close to Jawa is the island of Sumatera, an island with a very huge coal deposit. and The coal deposit has attracted the eyes of the investors to obtain its mining concession. Later, these investors propose to PLN that they would build mine mouth power plants in the area for PLN. This then resulted in the birth of two independent power plants named Musirawas (2x600) MW and Bangko (4x600) MW. The two power plants are separated by 200 km and are located as far as 450 km in land. To reach Jawa, the power must be transmitted over the Sunda Strait, which is approximately 50 km wide, to the tip of the Jawa Island.

In response to the proposal from the investors, PLN decided to build a transmission lines to transmit the power from this mine mouth power plant to the load center in the Jawa system. This idea is foreseen to provide direct benefits for both systems as the transmission line will interconnect Sumatera and Jawa grid, enhance both systems’ reliability, improve both systems’ security, increase economic efficiency in both systems’ operation, as well as reduce environmental impacts.

Choosing the Transmission System

In choosing the transmission system, PLN decided to transport the electricity over a HVDC (high-voltage direct current) transmission thus creating a link between the Sumatera and Jawa systems. The decision is made based on studies done. One of the major justifying reasons put forward in the study is that HVDC is more economically efficient in investment cost to transport electricity over a very long distance transmission line compared to HVAC transmission. Also, based on the aforementioned study, it is concluded that it is cheaper to transport electricity directly to Jawa from far-away coal mines over a transmission line rather than transporting the coal to Jawa in order to fire steam power plants build in the Jawa Island.

The following list is a number of quotes taken from the study to justify the HVDC as the transportation method for transporting energy from Sumatera to Jawa:

1. Less investment

2. Long distance water crossing

3. Lower losses

4. Better Controllability

5. To limit short circuit currents

6. Less Environment impacts

In general, it is best to base the choosing of HVDC transmission in light of the HVAC transmission from the technical and economic point of view, such as the following:

1. Easier controllability

2. Less total investment

3. Less Environmental impacts

Easier Controllability

One of the fundamental advantages of HVDC transmission is that it is very easy to control the active power within the link. The active power being transmitted can easily be controlled from the receiving end to sending end. This easiness does not exist within the HVAC system. This also means that the operating conditions of the AC network can be improved with the converter/inverter stations of the HVDC transmission.

Furthermore, an HVDC link can never become overloaded unlike the HVAC transmission system.

Less total investment

An HVDC transmission line costs less than an HVAC transmission line for the same transmission capacity for long transmission lines. However, the terminal stations are more expensive in the HVDC case due to the fact that the stations must perform the conversion from AC to DC and vice versa. But above a certain distance, the so-called "break-even distance", the HVDC will always give the lowest cost.

InvestmentCost

Total DCCost

Distance

Total ACCost

DC Line Cost

DC Terminal Cost

AC Terminal Cost

AC Line Cost

Break even Distance

500-1000 km

Cost of HVDC and HVAC Links

Environmental benefits

One of the best things of an HVDC transmission line is that for the same voltage level and the same power capacity, the HVDC transmission line requires a smaller right-of-way compared to that of an HVAC transmission line. For short, a single HVDC line, which can transport the same power as a double HVAC circuit, definitely has less right-of-way compared to its HVAC equivalent –a double HVAC circuit.

Project Scheduling

The project schedule of the Sumatera-Jawa HVDC link is synchronized with the project schedule of the two power plants. The power plants are planned to have their first units COD in early 2013, one unit for each Bangko and Musirawas with similar capacities of 600 MW. Afterwards, each power plant shall have a subsequent unit COD every six months. The HVDC transmission lines are expected to fully operate prior to the COD of these subsequent units.

PLN has entrusted this mission to PLN Engineering as the consultant to develop the basic engineering design of the HVDC link and package it in a form of bidding documents. The bidding documents are expected to be finished in December 2008. Bids will take place in 2009, continued by construction of each package of the project.

Dec. 07

Sept. 08

Jan. 08

Jun. 2013

COD

Survey- Land Survey - Seabed Survey - Eng. Design

Contract sign with

PLN-E

Bidding Process-Transmissi on Lines- Substation&Conv. Inv.- Sub Marine Cable

Construction-Substation 7 Units-Trans. lines 780 km- Sub Mrn Cable 50 km

Project Shedule of HVDC Sumatera-Jawa Link and 500 kV & 275 kV AC TL/SS

Musirawas&Bangko

Oct. 08-Jul. 09Jan. 13

PLN E Progress

To ensure the well-running of the project, especially at the Consultant’s-end, PLN Enjiniring has engaged co operations with several parties namely TransGrid Solutions Inc. Canada, LAPI ITB (Institute of Technology Bandung), Airlangga University, etc. The following is a brief elaboration on the work distribution amongst partnering institutions:

TransGrid Solutions Inc. Canada:

1. Technical Training for engineers included in the basic design arrangement

2. Management Training for management officials that will be manage the entirety of the project

3. Engineering Design for the Converter-Inverter Substation

4. Detailed Studies related to the technical specifications in order to complete the existing Feasibility Study

Lembaga Afiliasi dan Penelitian Industri ITB (Bandung Institute of Technologies)

Survey on the Sunda Strait Seabed

Airlangga University

Environmental Impact Study of HVDC and HVAC RoW

Powergrid Corporation of India (negotiation in progress)

HVDC Transmission Lines Design

Meanwhile, at PLN Enjiniring’s end, the tasks to be done are as follows:

1. Land Survey for both HVdc and Hvac lines in both islands; Jawa and Sumatera

2. Soil Investigation for the selected Converter/Inverter sites as well as along the HVdc and HVac transmission lines

3. Basic Engineering Design for the Submarine Cable

4. Bidding Documents for the transmission lines, converter/inverter station, and submarine cable

5. Bid Evaluation

Summary

PLN, Perusahaan Listrik Negara, the state electricity company of Indonesia, has decided to build HVDC link of Sumatera to Jawa. This link is meant to transmit the power from mine mouth power plants located in South Sumatera to Jawa system. It is expected to be in commercial operation by 2013 in order to meet the energy consumption growth of the Jawa Island in the 2013.

This interconnection could provide significant benefits to the economics of Indonesia particularly PLN. Benefits to be harnessed include enhanced system reliability, improved security and diversity of supply, increased economic efficiency in system operation, and reduced environmental impacts. This interconnection could also help attract private sectors investment to the power sector specially Independent Power Plant.

References

1. Roberto Rudervall; J.P. Charpentier; Raghuveer Sharma; High Voltage Direct Current (HVDC)Transmission Systems,Technology Review Paper; ABB power Systems, Sweden, World Bank, United States and ABB Financial Services, Sweden

2. HVDC, Why does the cook strait cable system use DC (Direct Current) Transmission?

3. Siemens; Answer for Energy. HVDC – High Voltage Direct Current Power Transmission from Siemens, Unrivaled practical experience.