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Topic Title: Dependent Manual Operation
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Created On: 24 March 2014 08:53 AM
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 24 March 2014 08:53 AM
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Joined: 22 July 2009

How to identify an switchgear or RMU is depedent manual operation? Is there any standard which defines the switchgear is of DMO type.
Is Long & Crawford, Yorkshire are DMO type and how it can be physically verified?
 24 March 2014 11:16 AM
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Originally posted by: Badshah

how it can be physically verified?

Isolate and earth it. Issue a PTW, open the lid and have a look whist you operate the mech.

First thing to do is get a hold of the maintenance manuals (from the manufacturer and the network operator) for the switchgear - this will tell you; and also tell you how to operate and maintain the switchgear.

Note that the network operator's maintenance manuals may differ from the manufacturer's: the network operator will have devised their own maintenance plan for the switchgear.

The L&C ETV2 fuse-switch is independent, whilst the earth switch is dependent. If I remember rightly, there is a connecting rod between the open/close handle that when in the open position, allows the release of a 1" brass bolt so that the earth switch can only be operated dead. Over the years, this can mis-align (epsecially if someone has tampered with it or tried to defeat it), so double check this on your maintenance.

Western Power have all their switchgear instruction manuals on-line as pdfs...which is handy for you!

Edited: 24 March 2014 at 11:59 AM by Zuiko
 25 March 2014 09:51 PM
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I have to agree - unfortunately the only way to know for sure is to take the unit out of service. I was dealing with an old CB recently that I hadn't come across before. I took two very experienced fitters with me to the site to get their opinions - one said it was dependent manual, the other said it wasn't!
 26 March 2014 07:14 AM
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IIRC quite a few Dep Manual units were retrofitted with special handles which effectively changed them into spring closing. I remember a long handle with a leaf spring built in. The challenge was to ensure that the switch couldn't be opened quickly after closing to give upstream OCB time to clear any fault.
There was one type of gear (L&C or possibly S&C I think) where the handle was so long you had to be very careful not to bang your knuckles on the housing.

The point of all this is that its easy to get confused about whether gear is DM or not. Unless you are 100% sure I would treat as DM and operate dead only.

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