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Participant

Join Date: Feb 2017
Posts: 2

Replacing MR On Load Tap Changer.

03/10/2017 9:11 AM

Hi,

I have a situation with two 66Kv-22Kv Pauwels transformers. A 10Mva and 5Mva transformer with same tap changers type: C 3 250 Y Oil.

The 5Mva transformer winding is blown but has a healthy tap changer selector switch while the 10Mva transformer has a faulty tap change selector switch.

Can I replace the faulty selector switch?

Problem occured when the 10Mva transformer was in service but due to faulty circuit breaker the transformer was isolated for 8 months. After replacing CB the CB test pass and transformer test failed.TTR tests indicates rise and low on the A phase of the transformer. Transformer trips on differential current.

what could be the cause?

Thanks

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Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 2989
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#1

Re: Replacing MR On Load Tap Changer.

03/10/2017 9:38 AM

Two separate issues. If the tap changer has the same part number and passes all the required tests then swapping should be OK.

The transformer that tripped on differential failed the TTR most likely has failed, so you need to make sure that its tap changer was not contaminated by the now dirty oil.

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Participant

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Posts: 2
#2
In reply to #1

Re: Replacing MR On Load Tap Changer.

03/11/2017 6:33 AM

Thanks RAMConsult for your comment on the swapping of tap changer. For the transformer that tripped on differential here`s what I have done; 1. Selector switch removed from tap changer compartment. 2. Inspection OK and clean switch contacts. 3. Wash down with new oil, selector switch and tap changer compartment. 4. Replace new oil. The TTR test improve but not OK, transformer trips again on differential current.

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Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 2989
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#3
In reply to #2

Re: Replacing MR On Load Tap Changer.

03/12/2017 8:20 PM

The transformer has internal damage. Take an oil sample for DGA then empty tank and inspect for exact location of damage.

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Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

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Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
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#4

Re: Replacing MR On Load Tap Changer.

03/13/2017 5:12 PM

<...Can I replace the faulty selector switch?...> CR4 is not a permission-giving entity, nor does it assess competence. If in doubt, contact the equipment manufacturer directly for advice, initially over the telephone, as time is valuable. If necessary, arrange for a Service Technician to call and effect the remedies required.

<...what could be the cause?...> Failure to maintain the settings of the circuit protective device(s) and the quality of fluids used throughout the life of the equipment to date in accordance with the equipment manufacturer's instructions.

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PWSlack (1); RAMConsult (2); Tops (1)

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