Removing Split Core CT's

[Mark.W]

Hi peeps,

I need to remove some split core CT's from a school's Main Tails. The installers never used a shorting block but did earth the secondaries in the meter. I have tried unclipping the CT's but the magnets aren't releasing.

Can one of you kind people please advise me as to how I can get them off. Turning the supply off is not an option at this time.

I must add that this is an unofficial export meter that was installed a solar panel company.

Regards
Mark

 

[Bobster]

To short the secondary both S1 and S2 need to be linked together preferably to earth.

At the moment they are linked within the meter they are wired to.

 

[Mark.W]

Thanks RoB2,

I have also switched the meter off for the time being but left the CT's connected, is this ok?

 

[Bobster]

I haven't seen the installation myself so I can't guarantee anything over the forum, but yes. Even when powered down the meter will still keep the secondary of the CT as a closed loop.

It's only when the secondary goes open circuit that high voltages can become present.

If the CT has been overheating badly as you have suggested, it could well be possible the plastic surrounding the CT could have warped, possibly causing them to be difficult to remove.

 

[Mark.W]

Thanks mate,

I had a look at them yesterday, they seem in tact and warm to the touch but not scoulding hot. I will power down this evening and remove them. Just to clarify once powered down I should just be able to unclip them immediately?

Thanks for your help, much appreciated.

 

[Bobster]

Yes once powered down, just unclip them.

 

[Marvo]

......If the CT has been overheating badly as you have suggested, it could well be possible the plastic surrounding the CT could have warped, possibly causing them to be difficult to remove.

This was also my thinking, unless there's a hidden fixing I couldn't see any other reason they'd be difficult even when under load.

I'm glad you arranged to power down Mark, it's far safer. Did you managed to get them off without a hitch?

 

[Mark.W]

Hey Marvo,

The school is only allowing me to power down on Friday evening now! We are however keeping an eye on the CT's.

Cheers
Mark

 

[Mark.W]

Thanks for all the support guys.

The school has now asked that I put correct size CT's on this meter and looking at the current setup it looks as if the main incomers are fused as follows:
Red - 300A
Yellow - 500A
Blue - 300A

Now my question is do I size them all at 500:5 or can I use different ratio's ie. Red - 300:5 Yellow 500:5 and Blue 300:5?

Thanks again.

 

[Bobster]

Depends on what the power meter can be set up to, some can accept different ratios, others can't.

Personally as this isn't a high accuracy situation I'd fit 3 500:5.

Did you find why they were difficult to remove?

 

[Mark.W]

Hi RoB2

I have no idea, as soon as I powered down I was able to split them with no hassle. I gave them a good once over and there is no warping ect. It was mentioned in an earlier post about an overload magnetic circuit.

These are what were on there they are made by HOBUT

Thanks for your help, I was thinking down the same lines of 500:5 and as you say it's not a high accuracy situation, so 500:5 it is.

Cheers
Mark

 

[Mark.W]

Guys I am trying to find a supplier for shorting blocks but cannot find any, has anyone got a contact? Also a wiring diagram would be much appreciated if possible please?

Regards
Mark

 

[shanky887614]

Guys I am trying to find a supplier for shorting blocks but cannot find any, has anyone got a contact? Also a wiring diagram would be much appreciated if possible please?

Regards
Mark

have a google for

split core ct's uk


there are loads, if you want to actually pick them up ask a wholsaler if they can order some in.

online would be your best bet

 

[Mark.W]

Thanks Shanky, but I am actually looking for the shorting block not the CT's.

Regards
Mark

 

[Stu1312]

All you need is a row of terminals that you can put a shorting strip across, this lot sell it complete: CT Operated Meter Installation Block - Test Terminal Blocks - Installation Equipment