ANSI MV Load Interrupter or Air Switch SWGR

[iamdiscovery]

Hello

I'm designing substation consisting of a MV disconnect and trnasformer.
I have been looking for KVA transformer ratings that ANSI MV Load Interrupter or Air Switch SWGR is designed to protect ? The only information I can get is voltage and current ampacity of this disconnect but nothing about load.

Would someone explain how this size correctly an ANSI MV Load Interrupter or Air Switch SWGR for given transformer ? What is the maximum KVA rating this SWGR can handle ?

The customer is insisting to use this instead of vacuum breaker since it's cheaper ?

AMZ - End User

 

[jghrist]

Load interrupters or air switches are not designed to protect, just isolate. Load interrupters have an interrupting current rating. Air switches do not, just a continuous rating. If you need to de-energize an unloaded transformer with an air switch, you need arcing horns which will have a magnetizing current interrupting rating.

Neither will do what a circuit breaker does, which is interrupt fault current.

Compare the current rating of the switch to the full load current of the transformer if there is no possibility of overloading the transformer for short periods.

Not to be overly critical, but if you can't calculate full load current of the transformer from the kVA rating, you shouldn't be designing a substation.

 

[sonic02]

Hi there,

There are certain considerations you will need before choosing the right switchgear or disconnect switch for your application. The primary function of the switchgear is to isolate faulty equipment, to reconfigure networks in order to restore power supplies, to divide large network into sections and to control other equipment etc.

Factors like interrupting capacity, rated continuous current, basic impulse level need to take into consideration. Information on the transformer feeding this switchgear is essential in determining these parameters.

On the other hand, a disconnect switch is a mechanical device that conducts electrical current and provides an open point in a circuit for isolation for the transformer and are designed for no load switching. The same factors as mentioned above, with exception of interrupting capacity, applies to a disconnect switch. The disconnect switch comes in several switch blades configuration. You will have to choose the one most closely suited to your application.

Hope that helps!

Sonic02

 

[iamdiscovery]

Thanks folks....you corrected my understanding of switch function but still no one answered my question.

I'm working on project following North America Standards. I've given 13.8KV transformers in range of 2 - 10 MVA and MV SWITCHES is placed primary. In USA, some manufactures use unit substations which consists of (MV SWITCH/BREAKER + MV/LV XFR + LV PANEL). I have looked at catalogs and found out that maximum XFR MVA rating in this configuration is 5. So, I wonder what is maximum XFR MVA an ANSI MV SWITCH can isolate if this configuration is not applied (i.e. units is segregated) ? I hope someone working in manufactures sector reply to this question. What maximum transformer MVA can be isolated by an ANSI MV SWITCH ? Why ?


AMZ - End User