ct clamps too close together?

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jouleflow

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• Jul 15, 2018

• #1

Hi,

I have a 16kW array fed to my cu via 3 - 5kW solis inverters. I have a 4kW export limit so each inverter has a ct clamp. The 3 clamps are together on my main incoming cable.

Is it ok to have these 3 clamps touching each other?
How is it decided which inverter to shut down?

We have a lot of tripping issues, the system was installed incorrectly & still doesn't work properly. Could there be interference between the clamps & would them constantly turning on and off randomly be causing the tripping.

Thanks in advance

Greg Webb

 

UKMeterman

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• Jul 15, 2018

• #2

Well,
Each one will be indepently deciding, I am pushing out too much, need to to turn down the wick. Depending on the control loop and the nature of the local load this could cause instablitlies. You might also want to check the local supply voltage to see if you are tripping on over voltage.

 

Last edited: Jul 15, 2018

Wilko

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• Jul 15, 2018

• #3

Hi - just trying to understand how the 3 invertors can be limited to achieve 4kW total system output. Are you saying that each of the 3 invertors has their own CT and is independently trying to limit to 4kW? (likely result today being 12kW ...). Or if not, how does each know what the other is doing? If you've a circuit diagram and pics it might help .

 

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jouleflow

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• Jul 15, 2018

• #4

Wilko said:

Hi - just trying to understand how the 3 invertors can be limited to achieve 4kW total system output. Are you saying that each of the 3 invertors has their own CT and is independently trying to limit to 4kW? (likely result today being 12kW ...). Or if not, how does each know what the other is doing? If you've a circuit diagram and pics it might help .

Click to expand...

Thanks for the reply, I'm not an electrician so I can't say how each one is set up. I strongly believe that each one is set to 4kW so once this is reached one of them will turn down or off, if it still is over 4kW then another will turn down or off. I am positive they are all set up the same.

 

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jouleflow

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• Jul 15, 2018

• #5

here is a pic of all 3 ct clamps in a row on the incoming main cable.

 

UKMeterman

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• Jul 15, 2018

• #6

Ok a picture paints 1000 words, they need to be clamped round 1 of the 4 cables going into the bottom of the electricty meter!

 

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jouleflow

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• Jul 15, 2018

• #7

UKMeterman said:

Ok a picture paints 1000 words, they need to be clamped round 1 of the 4 cables going into the bottom of the electricty meter!

Click to expand...

Thanks, I will try that, it just seems that the clamps will then simply be the other side of the main incoming fuse. Wouldn't they still be sensing the reverse flow to the grid in either position? I am thinking of using the brown cable from the bottom of the fuse to the meter. See pic attached.

 

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• #8

Yep, that would be the one, if you clamp round the black cable the magnetic field of the flow and return cancel each other out so there is no signal to measure.

 

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jouleflow

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• Jul 15, 2018

• #9

Of course!!, brilliant deduction. Thank you so much, things are never quite what they initially seem. If it is ok I will post again after a few days to let you know how it is working.

 

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sean_ork

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• Jul 15, 2018

• #10

Was this a DIY installation ?

 

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• #11

sean_ork said:

Was this a DIY installation ?

Click to expand...

No a local company put it in last September and I had loads of problems far too many to list here but included no drip loops - ct clamps on the wrong cable - meter frying - loads of "spare" holes in roof, new supply cable from grid - earthing problems etccccccc.

p.s just tripped again!

 

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• Jul 15, 2018

• #12

Is your supply single or three phase ?

 

UKMeterman

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• Jul 15, 2018

• #13

sean_ork said:

Is your supply single or three phase ?

Click to expand...

You can see the meter and supply fuse, count the fuses / cables

 

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jouleflow

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• Jul 15, 2018

• #14

single phase.

 

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• Jul 15, 2018

• #15

If it helps I have an Iboost clamp on the same cable that was removed for the earlier pics. This is the current set up, the Iboost has the white wire.