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my surge protection 'cpd', such as it is...

psychicwarrior
Good morning all


I have obtained the following [I feel as the] 'best we can do for now' information from the DNO. They were helpful in my test case request for info.


"...address 1:

LV underground - 362m

HV underground to primary-  2000m

No Surge protection devices


address 2:

LV underground to substation - 110 m

HV UG from substation to HV pole is 823m then 301m 11kV overhead then 190m HV UG to the primary substation.

Distance to cable termination with surge protection device from secondary substation is 1124m (823m 11kV UG + 301m 11kV Overhead).  The nearest cable

termination does not have surge protection installed. ..."


In relation to the risk assessment equation variables dealing with distribution cable lengths  ie. the Lpal Lpcl Lpah Lpch, how would one fit the given values into the variables ?


For addr1, ignore the HV (e.g. use zero for Lpah Lpch),  then take Lpcl as 362 and Lpal as 638 ?


For addr2, i'm not sure on this one ?


Thanks for your input.

Habs


Parents
  • 0
    <snip>

     


    (a) I'm not sure it's always the case that surge protection is installed in all NTE5 Master Sockets. I understand that when we moved from ADSL to VDSL, SPDs were removed as they were affecting data rate. (Whilst info on this is sketchy, it's verified by vendors of the sockets, e.g. this listing on a popular internet sales web-site clearly says "Latest Design. Does NOT Contain Voltage Surge Protector as this can reduce BroadBand speeds.")


    (b) Even if there is, or you have the older style master socket with the SPD in it, there's definitely no surge protection to Earth at your installation (i.e. your MET), only between the two conductors. (And as the web-page says, protection of your stuff after the master socket is your problem).


    </snip>

     



    Indeed, I have found that modern NTE's (later than say 2005), tend not even to have an Earth terminal present. With the initial design of NTE5, you could add a 3 terminal Gas Discharge Tube and connect a protective earth to the E terminal (also linked through to the extension wiring. This was not there fundamentally for protection, but as a signalling earth, and likely would do nothing whatsoever with a lightning surge.)



    I've installed GDT protection on my incoming VDSL only line, just after the master socket, back to an outside earth rod. There was no effect on the sync speed of the VDSL (still 79.9 Mbit/s). But I am probably not a typical case, as the fibre cabinet is less than 100 cable metres away.



    I can definitely confirm however that a nearby lightning strike can induce voltages on the lines, even (or maybe especially) with underground distribution, sufficient to execute a PABX. That was with early 90's tech. With modern network gear, the problem might be even worse


Reply
  • 0
    <snip>

     


    (a) I'm not sure it's always the case that surge protection is installed in all NTE5 Master Sockets. I understand that when we moved from ADSL to VDSL, SPDs were removed as they were affecting data rate. (Whilst info on this is sketchy, it's verified by vendors of the sockets, e.g. this listing on a popular internet sales web-site clearly says "Latest Design. Does NOT Contain Voltage Surge Protector as this can reduce BroadBand speeds.")


    (b) Even if there is, or you have the older style master socket with the SPD in it, there's definitely no surge protection to Earth at your installation (i.e. your MET), only between the two conductors. (And as the web-page says, protection of your stuff after the master socket is your problem).


    </snip>

     



    Indeed, I have found that modern NTE's (later than say 2005), tend not even to have an Earth terminal present. With the initial design of NTE5, you could add a 3 terminal Gas Discharge Tube and connect a protective earth to the E terminal (also linked through to the extension wiring. This was not there fundamentally for protection, but as a signalling earth, and likely would do nothing whatsoever with a lightning surge.)



    I've installed GDT protection on my incoming VDSL only line, just after the master socket, back to an outside earth rod. There was no effect on the sync speed of the VDSL (still 79.9 Mbit/s). But I am probably not a typical case, as the fibre cabinet is less than 100 cable metres away.



    I can definitely confirm however that a nearby lightning strike can induce voltages on the lines, even (or maybe especially) with underground distribution, sufficient to execute a PABX. That was with early 90's tech. With modern network gear, the problem might be even worse


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