Ring Main Unit Sample PowerPoint1_ELECGATE

8/11/2019 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




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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



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EARTH



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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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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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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

Ring Main Unit Sample PowerPoint1_ELECGATE

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