Lightning & Surge protection

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    Please refer to Epcos website and download form there


    Fuse only functioned in steady state condition.But lightning & surge happened in transient condition.The different is times d/dt .

    Some other manufacture use the fuse is to protect the current and temperature.for normal supply current is below than 2-3A.That why manufacturer will used fuse rating 10-15A.Depend on rating MOV’s.


    Our company manufactured surge protector. any question you can direct to my email


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    As you can see below, coordination between SPD and MCB(F2 in the text) is given by the manufacturer’SPD instructions

    extract from IEC 60364-5-534:
    “534.2.4 Protection against overcurrent and consequences of an SPD failure
    Protection against SPD’s short-circuits is provided by the overcurrent protective devices F2
    (see figures in the annexes A to D) which are to be selected according to the maximum
    recommended rating for the overcurrent protective device given in the manufacturer’s SPD

    moreover the product standard IEC 61643-11 refers to disconnector (overcurrent protective devices) as you can show below:

    extract from IEC 61643-11/2005:
    ” 6.2.7 SPD disconnector
    The SPD may have SPD disconnectors (which can be either internal, external or both). Their
    operation shall be indicated.
    NOTE Installation requirements not related to the SPDs may require additional and/or lower rated overcurrent protective devices.
    SPD disconnectors shall be tested with the SPD during the sequence of type tests of 7.7 and
    7.8.3, except for RCDs, which are not tested during the operating duty test according to

    My advice is to contact manuifacturer’s SPDs and ask to them this coordination table


    i am studying short circuit calculation for power systems.pls send me the data for designing and selection of protective devices for sc


    This is a very interesting comment because you give me the opportunity to clarify the end of life mode of SPD (including MOVs and gas tube):
    Let me explain two cases.
    A surge arrester can happen at the end of life in the following cases:
    a) by thermal runaway due to an accumulation of excessive constraints of not exceeding its lightning
    attributes, leading to a slow destruction of its internal components.
    The disconnection of the SPD is provided by a thermal fuse associated with the electronic components (MOVs) inside the SPD
    b) by short-circuit due to exceeding the maximum flow capacity or due to a fault under 50hz from the electrical distribution network (neutral rupture ,…). The disconnection of the SPD is provided by an external or integrated short circuit protection device like fuse or circuit breaker.

    Considering the short circuit protection device(b), why choose circuit breaker instead of fuse?
    ● Choose the rating must consider both surge withstand and low short circuit breaking capability
    ● Compare to fuses, CBs have good compromise between surge withstand and low short circuit breaking capability
    *The same rating CB has better surge withstand capability than fuse
    *The lower rating CB has better short circuit breaking capability

    For instance, SPD with following characteristics : In=5kA, Up=1,3kV is coordinated with its short circuit protection device:
    * circuit breaker C curve 20A
    * or fuse 22×58 63A


    I suggest you could also download the document “Cahier Technique n°151”, which deals with overvoltages and insulation coordination for MV and could complement what you found in the LV guide, from the Schneider-Electric web site at the following address:

    Have a good reading,


    The information you include about SPD´s iwill mislead the opinion of

    because there´re manufacturers that had consider the problem and
    include a fuse in front
    of each MOV, designed to open the circuit in case of a failure or end of life of the varistor.

    but it´s not any fuse, because it goes in the protection module in front of each MOV. On the other hand a limiting fuse for protection will jeopardize the function of the SPD


    SEREYBOTH said:


    I am cambodia.I am not well in writing English,working at Siem Reap diesel power plant(10MW).Now my country has many lightnings during raining that kills people, damages eletrical overhead transmission line(22kv) and low voltage electric devices.

    could you help me, how protection,how to get a good skill in surge protection ! ! !


    Dear Cambodia,


    I,m dinesh kumar represting an XXXXXXX, we here provide Power Quality solutions to such a type of poor line i.e. surge solution.

    kindly send your problem in detail with Electrical Pannel size.

    We will surely provide u solution within time frame.






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    Nice article. I think to avoid the fire of a building we will use the “external” lightning protection system such as lightning conductor or meshed cage. Thanks for sharing all the useful information with me. Keep it up.


    Excellent topic.  I jus want to add something that I guess is important, maybe you already talked about. It is very important to have a good grounding system , otherwise the SPD is not going to do its work properly, and for those star systems it is important to make a reference at the entrance of the system (Neutral to earht conection) in order to minimaze the transients.


    Hello, tree-phase protection at the building entrance (using heavy discharge tubes made by TTI Puerto Rico) has solved most problems in Venezuela. However there is a ever growing problem present, probably world-wide. The problem is as follows:

    Most computer users buy “stabilyzers” using MOV type surge protectors. These are single-phase devices and see what the happens doring a lighning storm: when surge arrives, the sinle phase MOV will cut the overvoltage surge to a save level for the computer it is ment to protect. But now the catastrophic effect is because the power clippling at one phase rises very dangerously spikes at athe other two phases at the whole building. I have seen a chane of PC failures that did not have MOV protection.

    This effect should be communidated to all computer-users !

    The real solution is really a building-entrance protection, while the individual MOV protection at the consumer load is too danderous !

    Please comment your experience ! Rehards Hans Stauffer, Caracas Venezuela (



    i want to know the Contruction and Functioning principle of MOV,GDT.


    Iwould say you have to install a 3 phase protector at the service entrance to avoid this problem.

    I would like to ask if someone have made measurements of the shape of the wave at the service entrance in any distribution system of any electrical utility any city or country.
    I´m curious to learn if a SPD should include EMI/RFI noise filtering or if a SINE WAVE TRACKING WILL BE ENOUGH in order to supply a clean signal to the utility customers.

    thanks for your help,



    You can protekt with ”PREVECTRON” INDELEC France.I put this from 5 years on the buildings.

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