Transmission & Distribution

Transmission & Distribution

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Transmission & Distribution

Causeway Bay Zone Substation situated next to the Island Eastern Corridor
Causeway Bay Zone
Substation situated next to
the Island Eastern Corridor
Causeway Bay Zone Substation situated next to the Island Eastern Corridor
Causeway Bay Zone
Substation situated next to
the Island Eastern Corridor

The process of transmitting electricity from the power station to the load centres is termed 'Transmission', whilst the process for distributing electricity from the load centres to customer buildings is termed 'Distribution'.

The Hongkong Electric Co., Ltd. (HEC) supplies electricity to Hong Kong Island and Lamma Island. Electricity is generated at Lamma Power Station and transmitted at very high voltage - 275kV and 132kV - to various load centres via the transmission system. The network mainly comprises 275kV and 132kV underground and submarine cables. At present, there are only a few 132kV overhead lines remaining in the system. In the major load centres where the transmission circuit ends, large capacity transformers are used to step down the voltage to 11kV or 22kV before distribution to customer substations.

The world's first gas insulated 275kV power transformer using SF6 as insulation in the Sheung Wan Zone Substation
The world's first gas
insulated 275kV power
transformer using SF6
as insulation in the
Sheung Wan Zone
Substation.
The world's first gas insulated 275kV power transformer using SF6 as insulation in the Sheung Wan Zone Substation
The world's first gas
insulated 275kV power
transformer using SF6
as insulation in the
Sheung Wan Zone
Substation.

Electricity is distributed at 11kV and 22kV to over 3,700 customer (distribution) substations on Hong Kong Island and Lamma Island. Voltage is further stepped down to 380V 3-phase or 220V single-phase and supplied via the low voltage underground cable system to customers. Distribution substations are equipped with remote control and monitoring facilities so that operation of switchgear and auxiliary equipment can be activated remotely from the System Control Centre located at Ap Lei Chau.

First cable tunnel in Hong Kong --- Wah Fu-Bowen Cable Tunnel
First cable tunnel in Hong Kong
---Wah Fu-Bowen Cable Tunnel
First cable tunnel in Hong Kong --- Wah Fu-Bowen Cable Tunnel
First cable tunnel in Hong Kong
---Wah Fu-Bowen Cable Tunnel

The use of underground cables in the transmission system ensures supply reliability even in inclement weather such as typhoon and is ideal for a densely loaded area like Hong Kong. In addition to burying the cables directly underground, six dedicated cable tunnels have been built to accommodate some of the 275kV fluid-filled cable circuits. The first cable tunnel, connecting Wah Fu and Bowen and measuring 3.1km, was commissioned in 1988. Inside this tunnel, there are four conventional fluid-filled cable circuits.   The second cable tunnel between Nam Fung Road and Mount Parker, which was commissioned in 1993, has a length of 5.7km. It carries one XLPE insulated and two fluid-filled 275kV cable circuits which have adopted Polypropylene Laminated Paper (PPLP) as insulation material so that smaller conductor size could be used for the same cable rating, in order to reduce the transportation size of the cable used inside the tunnel. The other four cable tunnels are the Tin Wan-Wah Fu Cable Tunnel and Cyberport-Wah Fu Cable Tunnel, both of about 0.8km, the 0.2 km Yung Shue Wan Cable Tunnel and 0.1 km Pak Kok Tsui Cable Tunnel.


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