c) Mainsc) Mains
B) Advantage of HV Ring Main Distribution system Advantage of HV Ring Main Distribution system
B) Advantage of HV Ring Main Distribution system
Even in the event of a cable fault on the ring, it is still possible to Even in the event of a cable fault on the ring, it is still possible to
maintain or restore supply to all points by opening the switches on maintain or restore supply to all points by opening the switches on both sides of the fault.
both sides of the fault.
Additional outlets to the ring may be easily installed without shutAdditional outlets to the ring may be easily installed without shut
Additional outlets to the ring may be easily installed without shut Additional outlets to the ring may be easily installed without shut
downs. downs.
Greater maintenance facilities are available both on the ring feeder Greater maintenance facilities are available both on the ring feeder
i it b k d th RMU i it b k d th RMU circuit breakers and the RMUs. circuit breakers and the RMUs.
In additional, if the main HV switchboard is sectionalized and fed In additional, if the main HV switchboard is sectionalized and fed
from more than one supplier
from more than one supplier’’s substations, a ring main may bes substations, a ring main may be
from more than one supplier
from more than one supplier s substations, a ring main may be s substations, a ring main may be supplied from two different sections, thus improving security. supplied from two different sections, thus improving security.
Apart from fault conditions, it is also possible to operate a ring main Apart from fault conditions, it is also possible to operate a ring main
in open mode as the preferred arrangement but for whatever in open mode as the preferred arrangement but for whatever in open mode as the preferred arrangement but, for whatever in open mode as the preferred arrangement but, for whatever
purpose it must be ensured that neither of the section is overload. purpose it must be ensured that neither of the section is overload.
3.2 Internal Power Distribution
3.2 Internal Power Distribution
System
System
c) Mains c) Mains -- 11
Consumer main switch shall be installed and Consumer main switch shall be installed and
Consumer main switch shall be installed and Consumer main switch shall be installed and
connected immediately before the supply co.
connected immediately before the supply co.’’s meter.s meter.
A i it h h ll b i t ll d t t l ll
A i it h h ll b i t ll d t t l ll
A common main switch shall be installed to control all A common main switch shall be installed to control all
the communal installation of the same consumer. the communal installation of the same consumer.
The consumer main switch should incorporate:The consumer main switch should incorporate:
Means of isolation and switchingMeans of isolation and switching
Means of protection against Means of protection against overcurrentovercurrent, and , and
3.2 Internal Power Distribution
3.2 Internal Power Distribution
System
System
c) Mains c) Mains -- 22
The main switch or circuit breaker shall have a short The main switch or circuit breaker shall have a short
The main switch or circuit breaker shall have a shortThe main switch or circuit breaker shall have a short--
circuit breaking capacity of 40kA at low voltage. circuit breaking capacity of 40kA at low voltage.
Th h t i ti f th i it h h ll di t
Th h t i ti f th i it h h ll di t
The characteristic of the main switch shall disconnect The characteristic of the main switch shall disconnect
within 5 seconds during an earth fault. within 5 seconds during an earth fault.
The switchboard shall incorporate The switchboard shall incorporate CastellCastell key key
interlock or other means to prevent the supply interlock or other means to prevent the supply
f d i ll l All i i
f d i ll l All i i
transformers operated in parallel. All interconnecting transformers operated in parallel. All interconnecting devices including the bus
devices including the bus--section switch shall be of 4section switch shall be of 4--
l t ith l t i l d h i l i t l k
l t ith l t i l d h i l i t l k
pole type with electrical and mechanical interlock. pole type with electrical and mechanical interlock.
3.2 Internal Power Distribution
3.2 Internal Power Distribution
System
System
c) Mains c) Mains -- 33
Where standby generator is installed mechanically Where standby generator is installed mechanically
Where standby generator is installed, mechanically Where standby generator is installed, mechanically
interlocked
interlocked 44--pole changeover device shall be used pole changeover device shall be used for interconnection between the normal and standby for interconnection between the normal and standby for interconnection between the normal and standby for interconnection between the normal and standby source. A local switch shall be installed after a
source. A local switch shall be installed after a changeover device
changeover device changeover device. changeover device.
Single phase consumer main switch shall be of double Single phase consumer main switch shall be of double
pole type pole type pole type. pole type.
A schematic wiring diagram showing the main A schematic wiring diagram showing the main
di t ib ti t h ld b di l d th i
di t ib ti t h ld b di l d th i
distribution system should be displayed near the main distribution system should be displayed near the main switch with rating
3.2 Internal Power Distribution
3.2 Internal Power Distribution
System
System
c) Mains c) Mains -- 44
Each consumer installation shall provided his ownEach consumer installation shall provided his own
Each consumer installation shall provided his own Each consumer installation shall provided his own
earthing
earthing systemsystem
For 3 phase installation with main switch rating ofFor 3 phase installation with main switch rating of
For 3 phase installation with main switch rating of For 3 phase installation with main switch rating of
160A and above, C.T. operated meter shall be 160A and above, C.T. operated meter shall be installed.
installed.
Warning Notice: Warning Notice: ‘‘DANGERDANGER--ELECTRICITY, ELECTRICITY,
UNAUTHORISED ENTRY PROHIBITED
UNAUTHORISED ENTRY PROHIBITED’’ with Chinese with Chinese
translation shall be painted or engraved on plastic translation shall be painted or engraved on plastic boards permanently fixed outside the door of
boards permanently fixed outside the door of switchrooms
switchrooms Each character shall not less thanEach character shall not less than switchrooms
switchrooms. Each character shall not less than . Each character shall not less than 50mm high.
3.2 Internal Power Distribution
3.2 Internal Power Distribution
System
System
c) Mains c) Mains -- 55