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The Sarawak-West Kalimantan 275kV Interconnection
Hot Martua
Bakara
PT PLN
(Persero)
Indonesia
Sahala Turnip
PT PLN
(Persero)
Indonesia
Leslie K.P. Chai
Sarawak
Energy Berhad
Malaysia
T.H. Lo
Sarawak
Energy Berhad
Malaysia
J.H. Kueh
Sarawak
Energy Berhad
Malaysia
SUMMARY
Sarawak-West Kalimantan 275kV Transmission Line Interconnection Project is an integral
part of the efforts by ASEAN utilities to interconnect their electricity grids in the region. It is
the first major interconnection project in the island of Borneo. This paper outlines the
motivation behind this project, evaluation of the design, project specifications,
implementation and provide updates of the current status. The project is expected to be
operational by the end of 2015.
KEYWORDS
Sarawak-West Kalimantan Interconnection, ASEAN Utilities, AC Transmission.
AORC-CIGRÉ CIGRÉ 2015, Malaysia 21, rue d’Artois, F-75008 PARIS http: //www.cigre.org
AORC-CIGRÉ Technical Meeting
Kota Kinabalu, Sabah, 16th – 21st September 2015
2
1. INTRODUCTION
The Sarawak-West Kalimantan interconnection is a cross-border High Voltage Alternating
Current (HVAC) connection between the power systems of Sarawak Energy Berhad (SEB)
and PT Perusahaan Listik Negara (PERSERO), located on the west side of Borneo Island (see
Fig. 1).
This project is part of the Association of South East Asian Nations (ASEAN) Interconnection
Master Plan (AIM) to establish an interconnected grid among ASEAN countries for system
security, flexibility and reliability. Besides these operational benefits, the project can also
generate significant international and geo-political interests in the context of regional
cooperation [1]. This could provide opportunities to facilitate economic collaboration and
technical protocols in aid of other future conceptually planned interconnections within the
ASEAN region.
Intrinsically, the interconnection is the pioneer project linking two power utilities in the island
of Borneo with power transfer of up to 230MW to PLN West Kalimantan from the Sarawak
Grid. Such power trading opportunities empower PLN West Kalimantan to plan for its
generation development using economical resources whereby avoid running existing
expensive diesel and fuel oil generation plants which over the time could be in the position to
supply back to Sarawak [2].
In this paper, a comprehensive background information and motivation drivers behind the
project will first be discussed followed by evaluation of the design parameters, technical
specifications and basic scopes of the interconnection systems. The paper then gives updates
on the project implementation progress, current status and expected conclusion of this project.
Fig. 1: Locality of the interconnection
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2. MOTIVATION / BACKGROUND FOR SARAWAK-WEST KALIMANTAN
INTERCONNECTION PROJECT
ASEAN Perspective – Developing an Integrated Trans-national Power System Network
The Heads of ASEAN Power Utilities/Authorities (HAPUA) was founded in 1981 as an
association of national electricity utilities. Since its formation, HAPUA has been striving to
link the power systems of ASEAN countries as a means toward mutual enhancement of
electric supply adequacy, economic cooperation and system security with optimization of the
development of electricity infrastructures and sharing of energy resources in the region.
Prior to the above, several proposed power system interconnection projects in the past on a
bilateral power trading basis were then amalgamated into a framework of an ASEAN Power
Grid (APG) to become a long term plan and vision which was recognized at the Second
ASEAN Informal Summit in the year 1997. HAPUA was then officially requested to establish
the APG prior to the follow up 17th ASEAN Ministers on Energy Meeting (AMEM) in the
year 1999 [1]. Consequently, it had led to the initiation of the ASEAN Interconnection Master
Plan (AIMS) studies in [3] and [4]. The studies proposed many interconnection projects
between power systems in the region. The Sarawak-West Kalimantan HVAC interconnection
is an essential component upon the realization of the ASEAN Power Grid.
Facilitating PLN West Kalimantan’s Generation Plan
The existing generation in PLN West Kalimantan consists mainly of small sized thermal
generators driven primarily using fossil fuel oil. A few larger units of coal fired generators are
also under construction. Despite the recent fall in oil prices, this generation structure
continues to incur high operational cost on PLN West Kalimantan and may create extensive
constraints to the system stability due to the relatively small sized generators connected to its
network.
The interconnection enables PLN West Kalimantan to develop its generation expansion plan
with substantial coal powered generation from local supplies to meet local demand and
conceivably for export in the longer term. According to [6], the generation expansions plan in
West Kalimantan comprises of 1,130MW coal-fired power plants, 200MW of gas
turbine/combined cycle and 113MW of hydro power which will be built over the next ten
years.
The interconnection link can supplement generation at West Kalimantan by providing
adequate support to its load demand growth and bring beneficial support in terms of system
stability and reliability. The interconnector also enhances the security of supply for both
power systems by allowing the sharing of capacity and spinning reserves which provides
flexibility in grid operations.
On 5th September 2012, PLN and SEB come to a mutual agreement with the official signing
of the “Power Exchange Agreement between Syarikat SESCO Berhad and PT Perusahaan
Listik Negara (PERSERO)” or PEA.
The PEA is designed to facilitate power exchange between the two power systems with
designated review periods to cater for changes in the development of both networks.
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During the initial phase of the PEA, PLN will be importing power from SEB with the
quantum of 50MW at base demand and 230MW at peak demand. It is believed that the
interconnector can serve as a catalyst for achieving the APG vision by encouraging other
inter-Borneo links while spurring the development of integrated trans-national connected
power systems.
3. TECHNICAL SPECIFICATIONS AND DESIGN PARAMETERS OF THE
PROJECT
Technical Specifications of the Interconnector’s Transmission Lines
The Sarawak-West Kalimantan interconnection is a HVAC link connecting two systems at the
Mambong 275kV substation in Sarawak to Bengkayang 275kV substation in West
Kalimantan through a double circuit 275kV transmission line at a system frequency of 50Hz.
This project required the extension of two feeder bays at the existing 275kV Mambong
Substation in Kuching. From there a new 275kV transmission line is being constructed to
connect to a new 275/150kV Bengkayang Substation in West Kalimantan. This cross border
transmission line has a total length of 128.2km of which 35.57% is in Sarawak and the
remaining 64.43% lies in West Kalimantan [5] (See Fig. 2). The tower design is a typical
design similar to the existing design used in the SEB power system (See Fig. 3). While the
basic line parameters are comparable between the two power systems, the differences are
tabulated in Table 1 below. Both Table 1 and Fig. 3 were taken from the Planning and
Development System Study Final Report in [5].
Table 1: Comparison on basic line design practices between PLN and Sarawak Energy
Berhad
Description PLN SEB
Line Conductor
Conductor type/name ACSR/AS Zebra ACSR Drake
No. and diameter of Al wire 54/3.18 26/4.44
No. and diameter of St wire 7/3.18 7/3.45
Overall diameter 28.62 mm 28.11 mm
Cross-section 428.9/55.6 mm² 402/65 mm²
Resistance (DC at 20°C) 0.065 Ω/km 0.072 Ω/km
Breaking load 137.8 kN 145 kN
Weight 1,621 kg/km 1,680 kg/km
Ground/Earth Wire
Ground wire type AS 95 ACSR Skunk
No. and diameter of Al wire – 12/2.6
No. and diameter of St wire 19/2.5 7/2.6
Overall diameter 12.5 mm 12.95 mm
Cross-section 93.27 mm² 63/37 mm²
Resistance (DC at 20°C) 0.925 Ω/km 0.567 Ω/km
Breaking load 121.39 kN 53 kN
Weight 626 kg/km 490 kg/km
Tower Design Parameters
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Description PLN SEB
Tower height 50.4 m 35 to 37 m
Clearance open country 10.5 m 7.5 m
Clearance over plantations 7 m 4 m
Clearance to highway, roads 11 m 9 m
Clearance to other lines 5 m 4 m
Basic span 400 m 350 m
Insulators Cap and pin Cap and pin
Communication link OPGW OPGW
Surge arresters Class 3 Class 3
Cross arm – Cross arm >7.4m >6.8m
Cross arm – tower body ~6.9m ~6m
Conductor to ground
Clearance ~15m ~10m
Right of way 15m on each side of tower 20m on each side of tower
Moreover, SEB also adopted differential insulation for its transmission line where circuit 1 is
low and circuit 2 is high as follows:-
i) Circuit 1 has 18 numbers of insulation discs with Basic Insulation Level (BIL) of
approximately 1200kV;
ii) Circuit 2 has 20 numbers of insulation discs with Basic Insulation Level (BIL) of
approximately 1600kV.
As PLN does not have such practice, the numbers of insulation discs remain at 18 numbers
for both circuits.
Fig. 2: The Sarawak-West Kalimantan Interconnection Plan
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Fig. 3: Typical 275kV lattice tower design used in existing SEB power systems
Technical Specification of the Interconnector’s Substations
The basic technical specifications and design parameters of the two interconnected
substations in SEB and PLN system are summarized and tabulated in Table 2. They are
extracted from [5].
Table 2: Basic scope and design of Mambong and Bengyakang 275kV substations
Basic Substation Design Parameters Mambong
Substation
Bengkayang
Substation
1. Number of bays required 2 (extension) 2
2. Bay type Line Line
3. Switchgear type Outdoor
Outdoor (1½
circuit-breaker
scheme)
4. Environment Heavy Pollution Heavy Pollution
5. Busbar configuration Double Double
6. Busbar rating, A 2000 1600
7. Circuit breaker rating, A 2500 2500*
8. Circuit breaker short-circuit rating, kA 25 (3 sec.) 25 (3 sec.)
9. Busbar short-circuit rating, kA 25 (3 sec.) 25 (3 sec.)
10.Maximum voltage for equipment, kV 300 300
11.Short-duration power frequency withstand, kV 460 460
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Basic Substation Design Parameters Mambong
Substation
Bengkayang
Substation
12.Basic SIL/LIL, kV 850/1050 850/1050
13.Minimum safety clearance, mm 4800 4800
14.Line reactor rating 3x5MVAr 3x5MVAr
15.Teaser reactor rating TBA –
In addition to Table 2, there is a plan to install 275kV shunt capacitor banks at Mambong
substation with capacity of 2×40MVAR and 2×80MVAR while another 3×20MVAR capacity
of shunt capacitor banks will being installed at 132kV.
On the PLN West Kalimantan side, shunt capacitor banks are planned to be installed at
various 150kV substations including Singkawang 150kV substation in the year 2016 and Sei
Raya 150kV substation in the year 2017 each with a capacity of 1×25MVAR to be switched
on during maximum load [5].
As for the interconnection protection and control scheme, it was mutually agreed for both
PLN West Kalimantan and SEB to employ one current differential and one distance
protection for each circuit as below:-
i) Main 1: Current Differential (with backup of distance protection);
ii) Main 2: Distance Protection.
4. CURRENT PROJECT STATUS AND UPDATES
Current Project Status
The interconnector is scheduled to be operational by the end of 2015 supplying 50MW of
power to PLN West Kalimantan from SEB initially.
In due course, SEB will be exporting 230MW power to PLN West Kalimantan during peak,
upon majority completion of SEB’s 500kV backbone transmission line projects sometime in
2016. The SEB 500kV transmission line backbone is a high voltage transmission system
extending over 500 kilometers from Similajau in Bintulu to Tondong in Kuching. It is a
system reinforcement project supporting the future development of its generation system and
to provide adequate security of supply to cater for its electricity demand growth. Due to the
rapid growth in demand and consumption in Sarawak, this added transmission capacity will
further strengthen the network especially towards Kuching.
Table 3 shows the work progress for Mambong substation extension and transmission line
works in Sarawak whereas Table 4 shows the work progress for Bengkayang substation and
transmission line works in PLN West Kalimantan.
Table 3: Sarawak-West Kalimantan Interconnector substation and line progress in Sarawak
updated as at June 2015
Sarawak Completion Expected Completion
Mambong 275/132kV Substation Extension 78%* Quarter 3, 2015
Transmission Line 98% Quarter 3, 2015 * Progress reported includes portions not specifically related to this Interconnection
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Table 4: Sarawak-West Kalimantan Interconnector substation and line progress in PLN West
Kalimantan updated as at May 2015
PLN West Kalimantan Completion Expected Completion
Bengkayang 275/150kV Substation 85.46% July 2015
Transmission Line 89.33% July 2015
Planning and Operational Studies
Two joint system studies are currently being undertaken by SEB and PLN West Kalimantan
to analyze the impact, stability and operational aspects of the interconnection link.
These studies evaluate the steady state performance, transient responses and frequency
response of both power systems after the interconnector has been commissioned.
5. CONCLUSION
This paper outlines the motivation behind this project, evaluation of the design, project
specifications, implementation and provide updates of the current status.
The interconnection is the pioneer project linking two power utilities in the island of Borneo
with power transfer of up to 230MW to PLN West Kalimantan from the Sarawak Grid during
the initial phase. With the link expected to be operational by end of 2015, both SEB and PLN
West Kalimantan are looking forward towards a mutually beneficial interconnection.
Technically the interconnection link will improve the security of supply for both SEB and
PLN West Kalimantan through sharing of capacity and spinning reserves especially in the
long term. The interconnection will also improve operational flexibility where one system can
support the other in case of emergencies such as generation outages.
Immediately, the interconnection will help PLN West Kalimantan to reduce the running of
expensive fossil fuel generation such as diesel plants, leading to reduced cost of supply. The
power export to West Kalimantan also enables PLN to save the capital investment cost for
additional new generation capacity in the immediate term to allow it to concentrate on least
cost medium to long term solutions. On the other hand, Sarawak can benefit from a
reasonable revenue income from the power export to PLN West Kalimantan while helping to
ensure the stability of the interconnected power grid.
Moreover, this project is part of the ASEAN Interconnection Master Plan (AIM) to establish
an interconnected grid among ASEAN countries for system security, flexibility and
reliability.
It is hoped that besides operational benefits, the project can serve as a catalyst for future
interconnections within the ASEAN region.
6. BIBLIOGRAPHY
[1] ASEAN Power Grid Project A Working Group of HAPUA, "ASEAN Interconnection
Master Plan Study I," 2003.
[2] L. P. Tan, "Planning and Development System Study for The Sarawak - West Kalimantan
9
Interconnection Project," Transmission System Planning, Sarawak Energy Berhad,
Kuching, 2013.
[3] D. H. A. Lee, S. K. Liu and L. P. Tan, "Planning Considerations for the Proposed East-
West Malaysia HVDC Transmission Link," EPRI 2013 HVDC & FACT Conference, pp.
1-2, 28-29 August 2013.
[4] J. Irving, Y. Inoue and K. Prakoso, "An Evaluation of the Prospects for Interconnections
Among the Borneo and Mindanao Power Systems," Asian Development Bank, 2014.
[5] ASEAN Power Grid Project A Working Group of HAPUA, "ASEAN Interconnection
Master Plan Study II," 2010.
[6] PT PLN (Persero), "RUPTL 2015 - 2024 (Ten Year PLN System Planning)".
7. ACKNOWLEDGEMENTS
The SEB authors would like to acknowledge the contribution of various people, instrumental
in guiding this project forward specifically, Mr. Nick James Arnett Wright, Mr. Danice
Endawie Ita and Dr. Denis Lee Hau Aik.
The PLN authors would like to acknowledge the contribution of various people, instrumental
in guiding this project forward specifically, Mr. Murtaqi Syamsudin, Mr. Moh. Iqbal Nur and
Mr. Budi Chaerudin.