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UNIVERSITI TUN HUSSEIN ONN MALAYSIA
I. COMPANY INFORMATION
ENAGA NASIONAL BERHAD (TNB) is the largest electricity
utility company in Malaysia. TNB’s core activities are in
the generation, transmission and distribution of electricity.
Currently, the TNB group has a complete power supply
system, including the National Grid which is energized at
132, 275 and 500 kV. The National Grid is linked via 132 kV
HVAC and 300 kV HVDC interconnection to Thailand and
230 kV cables to Singapore.
T
Fig 1 : Grid Nasional
TNBT role is to ensure the adequacy and reliability of
electricity supply that are fundamental needs of modern
society. It also provides the link between electricity suppliers
(TNB Generators and IPPs) and electricity consumers.
Besides that, the transmission connects regional systems via
interconnectors to encourage cooperation for mutual benefits.
Fig 2 : Activity chain in TNBT
For Asset Maintenance (AM), their job are :
• To manage the transmission assets to ensure high
availability.
• Conduct effective operation and maintenance of the
transmission network to ensure the reliability of the
equipment.
• To optimize the lifetime performance of network
assets in terms of reliability, availability and costefficiency.
• Implement the Conditioned Based Maintenance
approach.
II. OUTCOME OF INDUSTRIAL TRAINING
A. Substation
This unit is responsible for the commissioning, safe
operation, effective maintenance, and repair of primary
equipment and civil work in substation installed at
transmission facilities in Asset Maintenance Melaka.
There are two types of transmission substation designs
used TNBT which is Air Insulated Substation (AIS) and GasInsulated Substation (GIS). The AIS design consists of air-
insulated equipment installed in outdoor switchyard while the
GIS design utilizes SF6 gas insulated equipment installed
inside the building.
Fig 3 : AIS Fig 4 : GIS
There are three types of voltage rating under AM Melakacustody which is 275/132 kV, 132/33 kV and 132/11 kV. The
AIS is easier to maintain compare than the GIS. Table I
shows the main equipment in substation. The equipment in
the GIS has the same equipment as AIS equipment.TABLE I
MAIN EQUIPMENT IN SUBSTATION
Equipment Description
Transformer Step down voltage from generation
system to much lower level so power can
be transmitted to distribution system
Lighting Arrestor Protect transformer and electrical
equipment from being damaged by
lighting pulse or over-voltage operation
Current
Transformer
Reduces the primary current to much
lower, standardized levels that suitable
for operation of relays
Voltage
Transformer
Reduces the primary voltage to much
lower, standardized levels that suitable
for operation of relaysCircuit Breaker Complete, maintain and interrupt
currents flowing in a circuit under
normal or faulted condition
Busbar Intermediate device that connects a
variety of electrical equipment in
Industrial Training at Asset Maintenance, TNB Transmission Melaka
Mohd Ghazali B. Mohd Nor CE080082
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substation
Isolator Switch to open/close circuit without
loads
Capacitor Bank Improve quality of the electrical supply
and the efficient operation of power
system
B. Lines and Cable
This unit is responsible for the commissioning, safe
operation, effective maintenance, and repair overhead lines
and cable. Overhead lines are used to deliver power at high
voltage from generating plants. Transmission lines in the
TNBT system range from 66 kV to 500 kV. There are two
types of lines towers which is self supported (275 kV, 132
kV)and guy supported (< 66 kV).
Underground transmission cable are commonly used in
urban areas where the land constraint to build overhead lines.
There are two types underground cable that used in TNBT
system which is Oil-filled cable and XLPE insulated cable.
Fig 5 : Overhead Line Fig 6 : XLPE insulated cable
In TNBT lines towers, there seven types of self-supported
lattice tower (SSLT) are used. The types of tower are
distinguished by the angle of deviation respectively as shown
in Table II.TABLE II
TYPES OF 132 KV OVERHEAD LINES AND ANGLE OF DEVIATION
Types of Overhead Line Angle of DeviationL - Suspension (Wooden Cross Arms) 0-2
SL – Suspension (Steel Cross Arms) 0-2
S - Section 2-10
M – Medium 10-30
H – Heavy 30-60R – Right 60-90
T – Terminal 0-10 Nowadays in transmission lines conductor, copper has
been largely replaced by aluminium. There are four types of
conductor that been used which is :
• ACSR – Aluminium conductor steel reinforced
• AAC – All-aluminium conductor
•
AAAC – All-aluminium alloy conductor • ACAR – Aluminium conductor alloy-reinforced
C. Protection
Protection system is required to detect abnormal activities.
There three scheme protection that installed at transmission
facilities which is transformer protection, line feeder
protection and busbar protection. All scheme protection used
a protection relay as it main device. This scheme has two
types of protection which is main protection and backup
protection.
Fig 7 : Protection system in TNBT
Transformer protection scheme is focusing on transformer
from fault or any abnormal condition. This scheme protect
HV and LV transformer. If any fault/tripping been detected,
this scheme will operate on its condition. There are several
main relays that installed in the scheme such as overcurrent,
differential, restricted earth fault (REF), standby earth fault
(SBEF) and transformer guards.
Line feeder protection scheme is focusing on distance from
substation to another substation. There four types of distance
protection zones which is :• Zone 1 – 80% long length forward
• Zone 2 – 100% + 20 % long length forward
• Zone 3 – 200% long lengh forward
• Zone 3 Reverse – 20% short length reverse
Busbar protection scheme is focusing on busbar protection
and protection zone. For busbar protection, high impedance
and low impedance scheme been installed. This scheme
mean the protection from the CT ratio. For protection zone,
each zone has been categorized in four different zone which
is :
• Generator zone
• Transformer zone
•
Buses zone• Line zone
In this scheme, the CB is located at overlap region as shows
at fig 8.
Fig 8 : Zone of protection
For backup source for relays, the station battery has been
installed in substation. The battery used nickel cadmium
battery type that’s flows a DC supply.
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Fig 9 : Station Battery
D. Condition Monitoring Unit
CMU is responsible for support maintenance especially
for Mechanical and Electrical (M&E) installations of
substation in term of scanning, measuring and analysis.
Type of test and measurement used are :
• Tangen Delta
• Dissolve Gas Analysis
• Leakage Current Monitoring
• Thermovision• Ultrasound
17.0°C
46.9°C
20
30
40
Fig 10 : Thermovision measuring Fig 11 : Ultrasound measuring
E. Telecontrol
Telecontrol’s unit is responsible to ensure the SCADA
(Supervisory Control and Data Acquisition) ready status isavailable at any substation for the safe operation and reliable
performance. This system monitored
• Status and alarms
• Sequence of events
• Binary Code Decimals
• Analogue inputs
There are two types of SCADA system which is RTU
(Remote Terminal Unit) and SCS (Substation Control
System) as shows in Fig 12 and Fig 13.
Fig 12 : SCS equipment Fig 13 : RTU equipment
R EFERENCES
[1] Abdullah Hj. Abd Rahman, Noor Adnan Abd. Aziz (Ogos 2003), TNBTransmission Electrical Safety Rules First Edition
[2] Asset Maintenance Guidelines for TNB Transmission Division, (Sept2008)
[3] Nor Akmal Mohd Jamail, Siti Amely Jumaat, Roziah Aziz (Julai 2009),Electrical Power System
[4] D. F. Warne (2005), Newnes Electrical Power Engineer’s Handbook, Newnes
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