Integral instant protection

[DivanIMC]

What is meant by "Integral instant protection" rating on a Schneider circuit breakers?

[Christian_Bach]

Hello,

Which range are you referring to ?

Christian

[DivanIMC]

I see the rating on various Schneider circuit breaker ranges, however I am mostly interested in the MTZ range at the moment.

[RHH]

Dear Divan,

I think we're talking about the protective relay inside the circuit breaker. This is an very important item as this is the componenten that makes sure the breaker ''trips'' when its supposed to.
If not the circuit breaker would fail trip or not trip at all.
I guess the rating is about how quick/fast the internal protection relay can react (instantly) according to the amount of kA.

Hope this has given you a bit more insight.

[DivanIMC]

The rating is given in Amps (kA). So cannot be related to time. 

Example: LV848343 - MTZ3 50H2 5000A 3P

Icu:

150kA @ 440V

130kA @ 500/525V

100kA @ 660/690V

Integral instant protection:

243...297kA

[RHH]

''kA rating is known as the short-circuit withstand capacity or ultimate breaking capacity of a circuit breaker.''

EDIT:

So if its above the kA and the amount for the operational voltage given, the breaker will likely not be able to protect the components that are behind this breaker.

Got me a bit confused on the ''So cannot be related to time'' part.
However if we are talking about kA it almost always has to do with a reaction or time span (short-circuit).
However luckily my answer wasn't fully wrong, I edited the whole as reaction.

I see Christian from Schneider found the correct answer beneath (thanks!)
The integral instant protection is what the max. capacity of the breaker can handle to instantly trip (so without time delay).

Thanks @Christian_Bach 

[Christian_Bach · Accepted solution]

Hi,

The integral instant protection treshold is the instantaneous current level at which the breaker will trip without time delay.

Christian

[Christian_Bach · Accepted solution]

Hi @RHH ,

Thanks for your answer. Few additional info below.

The breaking performance of the CB is selected by the installation designer from the max prospective short circuit current at the level of the CB, in kA RMS (ex : 150kA Ics). This circuit has a given inductance, defined by the standard, which results in an "overshoot" peak value during the first wave of current. this value is given in the IEC60947 standard as 2.2x the RMS for high SC values.

The aim of this instantaneous protection is to react to this peak value instantaneously in case of ultimate SC event (ex : "bolted" SC), in order to optimize breaking process and thus ensure the protection of the installation (downstream devices, busbars etc, limiting the pass-through energy).

Hope this clarifies, available for further questions.

Christian