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Surge protection in industrial enclosures

M. Joshi
What are the requirements for determining whether surge protection should be installed in industrial enclosures?  The enclosures will typically have motor drives, emergency stop systems and sensors/data acquisition.


Are Type 2 & 3 surge protection modules commonplace?
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    M. Joshi:

    What are the requirements for determining whether surge protection should be installed in industrial enclosures?  The enclosures will typically have motor drives, emergency stop systems and sensors/data acquisition.


    Are Type 2 & 3 surge protection modules commonplace?


    Chapter 44 of B.S. 7671. Protection Against Voltage Disturbances.


    443.4 Over Voltage Control.


    Protection against over Voltages shall be provided where the consequences caused by the over Voltage could:


    (i) result in serious injury to, or loss of human life, OR


    (ii) result in interruption of public services and/or damage to cultural heritage, OR


    (iii) result in interruption of commercial or industrial activity, OR


    (iv) affect large number of co-ordinated individuals.


    For all other cases a risk assessment according to Reg. 443.5 shall be performed........

    New surge protective devices (SPDs) - for all types of installation and all risk levels - YouTube


    Z.

     


  • 0
    More info....

    Type 1 and type 2 SPD : installation and rules - YouTube



    Z.
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    What are the requirements for determining whether surge protection should be installed in industrial enclosures? The enclosures will typically have motor drives, emergency stop systems and sensors/data acquisition.

    Usually SPDs are placed in (or next to) distribution boards - and often that provides sufficient protection for downstream equipment, so in those cases you wouldn't then need them in separate enclosures for drives etc. A lot depends on the circumstances though - whether protection is needed just from external sources (lightning) or switching surges from other equipment within the installation, the distance from the DB's SPDs and the level of protection the equipment needs (some especially sensitive equipment may need type 3 SPDs very locally).

       - Andy.
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    There's also the 10m guideline. Due to some sort of resonance effect that I don't profess to understand, a spike reduced to 1.5kV at a DB/SPD can double back up to 3kV at a point further than 10m downstream from the SPD. Which is one reason for having a type 2 SPD at each DB supplied by a submain from the main DB.
  • 0
    wallywombat:

    There's also the 10m guideline. Due to some sort of resonance effect that I don't profess to understand, a spike reduced to 1.5kV at a DB/SPD can double back up to 3kV at a point further than 10m downstream from the SPD. Which is one reason for having a type 2 SPD at each DB supplied by a submain from the main DB.


    WW, have you got a reference for that please? (I wouldn't even try to understand it all.)


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    Chris Pearson:

    WW, have you got a reference for that please? (I wouldn't even try to understand it all.)




    The BEAMA GUIDE TO SURGE PROTECTION DEVICES (SPDs) document, section 6.2.2


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    wallywombat:

    There's also the 10m guideline. Due to some sort of resonance effect that I don't profess to understand, a spike reduced to 1.5kV at a DB/SPD can double back up to 3kV at a point further than 10m downstream from the SPD. Which is one reason for having a type 2 SPD at each DB supplied by a submain from the main DB.


    It's yer actual oscillation wot does it. The bit I did glean was this: In addition to keeping connecting leads short, they should be tightly bound together over as much of their length as possible, using cable ties or spiral wrap. This is very effective in cancelling inductance and hence inductive voltage dropped onto the connecting leads.


    Z.


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    Zoomup:
    Chapter 44 of B.S. 7671. Protection Against Voltage Disturbances.



    Probably doesn't apply to these industrial premises.

    In addition, the cable bursting strengths for multicore and cleated single cores requires to be within the design. I remember in a Scottish steelworks on 24 hour shifts when sleeping in a howff - (in an unused distribution transformer bay). During the early hours of a Sunday morning when there was no production; an armoured cable to the crutch of an 11kV distribution transformer blew out, it was completely vapourised with copper splatter on the brick wall. The 5 of us sleeping on nightshift made a beeline for the door and in the darkness. I never loitered around live transformers after that. Voltage regulation in the silent hours was probably the cause.  

    Jaymack    


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    It's yer actual oscillation wot does it. The bit I did glean was this: In addition to keeping connecting leads short


    This is really a feature of when things change quickly compared to the length -  In normal electrical theory we assume that when something is at XX volts it has reached equilibrium and we neglect the time it takes for the electric effect of doing something to get from one end to the other.

    The speed limit for signals on a wire is a bit less than the speed of light (300m per microsecond for light, more like 200m per microsecond in typical cables)  (this is a law of physics, not the traffic cop kind of law...)

    Much as there is very little slope in the level on the surface of a slow moving canal, water finding its own levels and all that, but in a fast flowing river in flood or at the moment you lift a sluice gate there may be all sorts of gradients, eddies, swirls and ripples, when things speed up, the assumption that everything  has reached a steady state level is not really true.

    The one dimensional problem of electrons being passed from atom to atom along a wire has something in common with the newtons cradle suspended balls toy, in that shocks 'reverberate' along the transmission like for a few cycles and sometimes, if you are unlucky with your lengths your kickback may be out of phase with what you put in, and a double amplitude peak occurs.

    A surge arrestor firing is rather like sneaking a brick wall in next to the last ball in the chain between swings - it does not stop the current flow as such and so does not absorb the energy, it forces the voltage down, but the current is then very high so abruptly altering the current to voltage ratio on the line.

    Mike.

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