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RING MAIN hNIT intelligent
RING MAIN hNIT
In an electrical power distribuƟon age power distribuƟon, from 7200 volts
sLJstem, a ring main unit (RMh) is a to about ϯϲ000 volts.
factorLJ assembled, metal enclosed set The ring main unit was introduced in
of switchgear used at the load connec- the hnited <ingdom and is now widelLJ
Ɵon points of a ring-tLJpe distribuƟon used in other countries. In North Amer-
network. It includes in one unit two ican distribuƟon pracƟce, oŌen the
switches that can connect the load to equivalent of a ring main unit is built
either or both main conductors, and into a pad-mounted transformer which
a fusible switch or circuit breaker and integrates switches and transformer
switch that feed a distribuƟon, trans- into a single cabinet.
former. Ring main units can be characterized
The metal enclosed unit connects to bLJ their tLJpe of insulaƟon, air, oil or
the transformer either through a bus gas. The switch used to isolate the
throat of standardized dimensions, transformer can be a fusible switch, or
or else through cables and is usuallLJ maLJ be a circuit breaker using vacuum
installed outdoors. Ring main cables or gas-insulated interrupters. The unit
enter and leave the cabinet. This tLJpe maLJ also include protecƟve relaLJs to
of switchgear is used for medium-volt- operate the circuit breaker on a fault.
Madžimum number of
electrical knife с 4
TLJpe 12kv 24kv
/ŶƉƵƚ ŬŶŝĨĞ ;<>Ϳ ʹ ŽƵƚƉƵƚ ŬŶŝĨĞ ;<>Ϳ ʹ
ŚĂŶĚůĞƌ ŬŶŝĨĞ ;<>Ϳ ʹ ĨƵƐĞ ŬŶŝĨĞ ;<>&Ϳ͘ ,ĞŝŐŚƚ ůĞƐƐ ƚŚĂŶ Ϯŵ ,ĞŝŐŚƚ ŵŽƌĞ ƚŚĂŶ ϭϮŬǀ
ϭнϭ͗ ŝŶƉƵƚ Žƌ ŽƵƚƉƵƚ Žƌ ŚĂŶĚůĞƌ ŬŶŝĨĞ н The volume of electricity knife is small The volume of electricity knife bigger
fuse knife. than 12kv
ϭнϮ͗ ĂŶLJ ƚŽǁ ŬŶŝĨĞ ;ŝŶƉƵƚͲŽƵƚƉƵƚͲŚĂŶ- The volume of dŚĞ ǀŽůƵŵĞ ŽĨ ƐĞƉĂƌĂƟŽŶ ďŝŐŐĞƌ ƚŚĂŶ
ĚůĞƌͿ н ĨƵƐĞ ŬŶŝĨĞ͘ ƐĞƉĂƌĂƟŽŶ ŝƐ ƐŵĂůů 12kv
ϭнϯ͗ ŝŶƉƵƚ ĂŶĚ ŽƵƚƉƵƚ ĂŶĚ The distance between bars small maybe The distance between bars is big from
ŚĂŶĚůĞƌ ŬŶŝĨĞ н ĨƵƐĞ 11cm 24cm to 26cm
knife.
Heater
It inside the ring main unit, ϮϬϬt͘ dŚĞ ŚĞĂƚĞƌ ŝŶ ϮϰŬǀ
used in the case to be water ƌŝŶŐ ŵĂŝŶ ƵŶŝƚ͗ ƚĂŬĞ ϰϬ DW
vapor or wet on the sepa- ĂŶĚ ϰϬϬt͘
ƌĂƟŽŶ Žƌ ĂŶLJǁŚĞƌĞ ŝŶƐŝĚĞ There are ammeter and
the ring so the heater based voltmeter to measure the
on the vaporized and have voltage and the current and
rheostat to control in tem- ŚĂǀĞ ƐĐĂůĞ ĨƌŽŵ Ϭ͗ϱ͘
perature. DĞĂƐƵƌĞ ƚŚĞ ǀŽůƚĂŐĞ ďĞ-
The heater in 12kv ring tween phase and phase or
ŵĂŝŶ ƵŶŝƚ͗ ƚĂŬĞ Ϯϱ DW ĂŶĚ phase and fuse or other.
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