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Participant

Join Date: Oct 2017
Posts: 3

AVR vs OLTC

10/18/2017 1:52 AM

Hi,

We are going to install 11kv substation having two nos of 500 KVA, 11/0.433 KV, DYN-11, Copper wound Transformer - 2 Nos for our new 100 bedded hospital.Along with the HVAC system we will have sophisticated equipment like CT SCAN, MRI, X RAY, ECG, UCG etc.Total estimated demand load is 753 KVA. We are thinking of OLTC along with the transformer.Will it be better to go for separate AVR or simply having OLTC is OK.

Thank You

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Guru

Join Date: Oct 2008
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#1

Re: AVR vs OLTC

10/18/2017 5:13 PM
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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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#2

Re: AVR vs OLTC

10/19/2017 9:37 AM

It would be best to ask the Electrical Engineer who is familiar with the design. The chances are that this particular individual is not on CR4 at the moment.

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Participant

Join Date: Oct 2017
Posts: 3
#4
In reply to #2

Re: AVR vs OLTC

10/20/2017 7:09 AM

PWSlack thank you.

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Participant

Join Date: Oct 2016
Posts: 1
#3

Re: AVR vs OLTC

10/19/2017 10:56 AM

Hi,

An OLTC is used with Power Transformers to provide automatic voltage adjustment with Plus & minus percentage voltage corrections.
An AVR (Active Voltage Regulator) is a Servo-Controlled Voltage Stabilizer (SCVS) comprising of a Variac, Buck-Boost Transformer & Electronic Circuitry for Voltage sensing correction. However, in case of 500KVA & above load capacity a Servo-Stabilizer can give a correction in the output voltage when there variation at input side, @ a speed of say 5Volts per second. So say if the phase voltage shoots upto 270V. from 230V. to correct 40 Volts it will take 8 seconds to bring it down to 230Volts output.

A better solution for protecting your sophisticated equipment like CT Scan M/c, MRI M/c., X-Ray M/c., UGC, Etc. can be obtained for Voltage Correction at the output with +/- 2 to 3% Plus the protection from Spikes/Surges Plus protection from SAGs will be an Ferro-Transformer & Or "AVC" (Active Voltage Conditioner). These two products from M/s.ONLINE SYSTEMS, MUMBAI the most safest for the Medical Electronics in your Hospital equipment.

You may kindly write to me if you need any further details...

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Regards,

Hoshang Homi Udwadia

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Participant

Join Date: Oct 2017
Posts: 3
#5
In reply to #3

Re: AVR vs OLTC

10/20/2017 7:12 AM

Hoshang Udwadia thank you. Kindly provide your email id so that I can reach you.

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Power-User

Join Date: Jul 2016
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#6

Re: AVR vs OLTC

10/21/2017 4:59 PM

The more components you introduce into your power delivery system, the lower your reliability will be, more things to maintain and more things to break.

Many of the critical components you are concerned about already have primary power conversion equipment that has significant voltage recovery capability, so you may need no regulation at all, the old Keep It Simple principle.

You may wish to examine the serving utility records that they keep of their power system. If they have scheduled brownouts but few total interruptions, it may make sense to add voltage regulation for the entire plant. Otherwise, it doesn't make much sense to complicate your equipment with equipment you don't need.

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Guru

Join Date: Dec 2010
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#7

Re: AVR vs OLTC

10/24/2017 6:34 AM

A normal power supply system achieves +/- 5% at the 230/400V level and +/- 0.5Hz.

How does this compare with the limits given for those sophisticated equipments and their frequency tolerance?

How fast does the power supply change voltage & frequency within its limits?

What will the load equipment tolerate?

Have you asked the suppliers of the load equipment if they have experience in your country? What do they recommend? Have you asked what problems they have experienced with mains supplies in your country? Were they serious or just occasional need to repeat scans?

When the facts are obtained about these events are obtained it is possible to consider if HV regulation of transformers through to individual 415/240V regulation for each equipment is required or most economic.

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Guru

Join Date: Oct 2009
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#8

Re: AVR vs OLTC

11/10/2017 2:26 AM

An OLTC controlled by an AVR shall be an option.

However, considering the criticality of the power supply to the life saving equipment, I would rather suggest a UPS or a Servo controlled stabiliser.

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Users who posted comments:

67model (1); BIKASH TALUKDAR (2); electricalexpert65 (1); hoshang udwadia (1); lyn (1); PWSlack (1); rwilliams (1)

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