Download - Ring Main Unit Sample PowerPoint1_ELECGATE
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GENERAL DESCRIPTION OFTHE EQUIPMENT
SABRE
RING MAIN UNIT
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SABREGENERALFEATURES
Cable boxesDoor handle
Actuator housing
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Controls &semaphore forleft hand RingSwitch
SF 6 gas pressuregauge
Controls &semaphore for teeoff Circuit Breaker
CT fuse chamber
under cover
Controls &semaphore forright handRing Switch
Circuit test access
selectors andcontrols
Anti-Reflex handle inclips
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The tee offcircuitcomprises aCircuit Breaker
CBCLOSED
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The tee offcircuitcomprises aCircuit Breaker
CBOPEN
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CLOSED
And a three positionswitch-
disconnector/earthingswitch
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OPEN
And a three positionswitch-
disconnector/earthingswitch
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And a three positionswitch-
disconnector/earthingswitch
EARTH
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Note: thecircuit is notearthed untilthe CB is alsoclosed
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The vacuumCircuit Breaker is
not a POINT ofISOLATION; thedisconnector isthe POINT ofISOLATION
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The RingSwitchescomprise athree positionswitchdisconnector/earthingswitch
CLOSED
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OPEN
The RingSwitchescomprise athree positionswitchdisconnector/earthingswitch
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EARTH
The RingSwitchescomprise athree positionswitchdisconnector/earthingswitch
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By opening thesesockets and usingthe operatinghandle to removethe star bar(referred to asEARTH LINK)from the earthcontacts, test accessto the circuit may
be obtained afterthe lower panel isremoved
Note that the test access can only be operated when the associatedRing Switch is earthed
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Circuit breakershutter selector
Pull to trip button
Disconnector shutterselector
Circuit Breakerstatus semaphore
Circuit Breakeroperating spigot
& slot
Disconnector statussemaphore
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L H Circuitvoltage testsockets
L H Ring Switchstatus semaphore
L H Ring Switchaccess selector
L H RingSwitchoperating spigot& shutter
L H Earth positionselector
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R H Earth position selector
R H Ring Switchstatus semaphore
R H Ring Switchaccess selector
R H RingSwitchoperating spigot& shutter
R H Circuit test sockets
THE RIGHT HAND RING SWITCH IS A MIRROR IMAGE OF THE LEFT SELECTOR, HANDLE END AND HANDLE ROTATIONAL MOVEMENTS
ARE REVERSED!
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SABREGENERALFEATURES
Both Ring Switches are fittedwith voltage test sockets,which may be used withportable Neon test devices.These should be used in aconfirmatory manner and not
as a primary or sole means ofconfirming that a circuit isdead
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Selector forshutter over L Hearth star bar(link) operatingspigot
Spigot for RHearth star bar(link)
Cover over chambercontaining test contactsfor both ring circuits
Selector for
shutter over R Hearth star bar(link) operatingspigot
Spigot for LHearth star bar(link)
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The SF 6 gas pressuregauge is located aboveand to the left of the lefthand Ring Switch ensure that the needle isin the green arc beforeeach switching operation
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Ring Switches may befitted with an actuator to
provide a remoteOPEN/CLOSE, but notan OPEN/EARTHcapability. Operationallocks must be removed
before an actuator may be fitted
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This is a rear view of thesame actuator, whichlocates in position usingthe lower spigot and isretained by two threadedfasteners
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The length of lead to the plug iscontrolled, so that it may only be fittedinto the nearest (which is the correct)of two possible sockets located on thefront panel
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Two spring loaded push buttons are fitted on the base plate, which in conjunction
with holes in the RMUoperating face allow theactuator to determine the RingSwitch (left or right) to whichit is fitted. This controls therotational logic (clockwise to
CLOSE or clockwise toOPEN)
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The Circuit Breaker protection system
comprises dual ratio CTs,CT secondary side fusesand a trip device. The fusesare located under a boltedmetal cover at the top ofthe operating face
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The CT connections arecontained in a box with a
bolted cover, located on theupper left hand side of the
RMU. Providing that theCTs are de-energised, it is possible to remove the bolted cover and bychanging a link, alter theCT ratio. Do not attempt to
change the CT ratio underlive conditions!
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SABREGENERALFEATURES
If the CT ratio is changed,the label on the operating
face of the RMU must also be changed. The two possible ratios are markedon the front and reverse