Electric power is normally generated at 11-25kV in a power
station. To transmit over long distances, it is then stepped-up to 400kV, 220kV
or 132kV as necessary. Power is carried through a transmission network of high
voltage lines. Usually, these lines run into hundreds of kilometres and deliver
the power into a common power pool called the grid. The grid is connected to
load centres (cities) through a sub-transmission network of normally 33kV (or
sometimes 66kV) lines. These lines terminate into a 33kV (or 66kV) substation,
where the voltage is stepped-down to 11kV for power distribution to load points
through a distribution network of lines at 11kV and lower.
1.
Transmission main intake ( pencawang masuk utama-PMU )
Transmission Main Intake is the interconnection
point of 132kV or 275kV to the distribution network. The standard transmission
capacity and voltage transformation provided at the PMU are as follows:-
- 132/33kV, 2 x 90 MVA
- 132 /22kV, 2 x 60 MVA
- 132 /11 kV, 2 x 30 MVA
- 132/33kV, 2 x 90 MVA
- 132 /22kV, 2 x 60 MVA
- 132 /11 kV, 2 x 30 MVA
2.
Main Distribution Substation (pencawang pembahagian
utama-PPU )
Main Distribution Sub-station is normally applicable
to 33kV for interconnecting 33kV networks with 11 kV networks. It provides
capacity injection into 11 kV network through a standardized transformation of
33/11 kV.
3.
Main Switching Station ( stesen suis utama-SSU )
SSU at 33kV, 22kV
and 11 kV are established to serve the following function:-
1. To supply a dedicated bulk consumer ( 33kV, 22kV, 11 kV)
2. To provide bulk capacity injection or transfer from a PMU/PPU to a load center for further localized distribution.
4.
Distribution Substation ( pencawang elektrik-PE )
Distribution
sub-stations are capacity injection points from 11 kV, 22kV and sometimes 33kV
systems to the low voltage network (415V, 240V). Typical capacity ratings are
1000kVA, 750kVA, 500kVA and 300kVA.
Conventional
substation designs are of indoor type (equipment housed in a permanent
building) and out-door type (ground-mounted or pole-mounted). Standardized M
& E design of 11/. 433kV sub-station is available at TNB offices. Compact
substation (11 /. 415kV) has limited application and is to be strictly applied
in selective situations under the following circumstances:-
§ System
reinforcement projects for highly built-up areas where substation land is
difficult to acquire.
§ Any request to use compact substation for dedicated supply to a single
or limited group of low voltage consumers is subject to TNB approval in
accordance to site constraints situation, and to be considered as ‘special
feature design schemes’.
SUBSTATION
In the electrical distribution network, a sub-station has many components such as circuit breaker, transformer, and switches, fuses which must be housed properly to ensure continuous and reliable service. According to construction of sub-station, several factors need to be taken for the construction such as location and load demand
There have 4 types of sub-stations in electrical distributions network
In the electrical distribution network, a sub-station has many components such as circuit breaker, transformer, and switches, fuses which must be housed properly to ensure continuous and reliable service. According to construction of sub-station, several factors need to be taken for the construction such as location and load demand
There have 4 types of sub-stations in electrical distributions network
1.
Indoor substation
2.
Outdoor substation
3.
Pole-mounted substation (H-pole)
4.
Compact substation
Components
in substation
1.
Switchgears – not available in H-pole.
2.
Ring Main Unit – located in PPU only.
3.
Transformers
Protections
·
Protection Relays and Vacuum Circuit breaker
(VCB) – located in PPU only.
·
Transformer Fuses
·
Isolating Switch – Located in H-Pole only
·
Pin Insulator – Located in H-Pole only
·
Low Voltage Fuses – Located in H-Pole only
·
Lightning Arresters – Located in H-Pole only
·
Earthling
Underground
Cables
·
PILC
·
XLPE
Distribution
Boards
·
Low Voltage Distribution board (LVDB)
·
Feeder Pillar
Substation work
I. Visual Inspection
Done once
per 3 months
Done by
seeing, hearing, smelling and feeling the substation and its equipment to see
if there is anything wrong with the particular substation
If there
were any defect, report to Authorized Person (AP) for corrective maintenance.
II. Routine Maintenance
Done once
every 6 months
Take
substation data, load reading
Work
including cleaning and repairing inside and outside substation such as cut
grass, throw rubbish repairing broken gate and take LV current Data reading
at LVDB.
III. Preventive Maintenance
Done once
every 18 months
Full
maintenance from top to bottom, involving all of the equipment inside and
outside the substation
Done by
either the Substation Team or an outside contractor
Among the
list of things to do include servicing the LV distribution board (LVDB),
servicing the switchgears and servicing the transformers
Preventive
Procedure
1. The monthly shutdown schedule was prepared and submit to RCC ( regional control center ) two month before.
2. Submit the actual shutdown schedule to RCC a month before.
3. After getting an approval from RCC, they will key in the data in online shutdown management system to print out the notices for consumer.
4. Sent the notice to consumer to let them know there will be no electricity supply during this time.
5.The authorized person (AP) will request a permission from controller for the shutdown process.
6.RCC will issue authorization to AP.
7. For safety , AP will issue a SKMK ( Sijil Kebenaran Melakukan Kerja ) or PTW ( Permit To Work ) to CP.
8. Started the preventive works.
9. CP ( competence person) will canceled the PTW and submitted to AP.
10. AP will canceled the Autorization that given by RCC.
11.Start switching again
12. After everything was back to normal ( electric supply was back again ) informed RCC.
1. The monthly shutdown schedule was prepared and submit to RCC ( regional control center ) two month before.
2. Submit the actual shutdown schedule to RCC a month before.
3. After getting an approval from RCC, they will key in the data in online shutdown management system to print out the notices for consumer.
4. Sent the notice to consumer to let them know there will be no electricity supply during this time.
5.The authorized person (AP) will request a permission from controller for the shutdown process.
6.RCC will issue authorization to AP.
7. For safety , AP will issue a SKMK ( Sijil Kebenaran Melakukan Kerja ) or PTW ( Permit To Work ) to CP.
8. Started the preventive works.
9. CP ( competence person) will canceled the PTW and submitted to AP.
10. AP will canceled the Autorization that given by RCC.
11.Start switching again
12. After everything was back to normal ( electric supply was back again ) informed RCC.
