Smart SPD(Surge Protective Device)

Smart SPD(Surge Protective Device)

The name “Smart SPD” appeared in working groups of the IEC 37A SPD committee, for the first time in 2015. Since then everybody tries to find a good definition for these SPDs even if a few people think that the name itself is confusing and should be changed.

The original need for Smart SPDs appeared in China.The first intent to define what is a Smart SPD was as follows:“an SPD able to communicate with its surroundings (user,maintenance company etc.)”.

                                                                                                                               REPSUN Smart SPD made in China

But it raised immediately other questions: communicate for which purpose?The best way to answer to that question is to investigate what the user needs are:be informed on the state of the SPDs (fine, becoming faulty, partially faulty or already faulty and disconnected)what are the stresses the SPD, system and equipment to be protected have been submitted to, for a better selection of next SPD (if the SPD fails it may be because the stress has been underestimated and this need to be corrected).

Of course, all SPDs should communicate and not only the power SPDs (telecom, data, …). The place to receive information is also important. It could be local, when SPDs are installed in a single factory or a single building remote for a company having a group building located in many different places far away for a manufacturer, installer, insurance company who want to follow the state of many SPDs in many places.

There are also possible additional functions in addition to monitoring:surge counting (able for example to differentiate single pulses, multi pulses, continuous current associated with direct lightning strikes, partial lightning current or induces surges)power quality (not only surge but also harmonics, under or overvoltages …)estimated life expectancy based on cumulated energy and number of impulses the SPD experienced…

Based on what exist in the market, there are also possible limitations or drawbacks:many devices consider only AC SPDs with measurement of leakage current used as an indicator of the state of the SPD – mainly for MOV based SPDs– made through a coil when DC application becomes more and more important.

Communication facilities and protocol may be different from one manufacturer to another one: for user sake it should be good that all smart SPDs use the same principles for communicating but it is not realistic. An internet platform, could be used to deliver the SPD status to the user. Whatever the communicating protocol used by the SPD manufacturer, the user could get information by simply connecting to the internet. An app on mobile phone/computer could be used to reduce the cost and avoid the burden to purchase a specific received for each SPD brand used in a factory (even if very often SPDs are from the same brand when a facility is protected, it is a fact that the surge protection plan evolves with time and many brands exist in the same place. In addition, more and more devices have built-in SPDs and in this case the probability to have to manage many brands is high). A dedicated emitter need of course to be developed for each SPD that will allow connection to the internet Smart SPDs should justify their use based on a cost/benefit comparison (for example maintenance and inspection cost can be reduced by using smart SPDs). By using a minimum of equipment and if possible existing equipment (computer, mobile phone …) the price could be lowered.

Smart SPD functions should be adaptable to all SPDs of a manufacturer and if possible to SPDs from different manufacturers based on common rules, even if this is probably difficult to achieve.

Smart SPD concept should include coaxial SPDs and telecom SPDs based on GDTs and more generally all SPD (such as ISG) that are presently difficult to test onsite and have quite often no embedded fault indicator.

Smart SPD functions could probably be provided by“intelligent” surge counters in series with SPDs. Should this assembly (SPD + intelligent surge counter) be considered as smart SPD?As many products exist already in the market, it was considered by a few members that it was more than urgent to make a specific standard or technical specification for Smart SPDs.A preliminary advanced definition for Smart SPDs, based on an industry meeting with mainly Chinese manufacturers was at this time:“an SPD providing monitoring of its environment and communication capability (either locally or remotely) to provide status of the SPD as well as lifetime expectancy and possibly other functions such as surge counting, power quality etc.(Note: environment may include surge counting, surge energy and wave forms, system voltage, type of signal, system frequency, temperature etc.).

Of course, many people wonder why such SPDs would be called “smart”. It is reasonable to consider that a “simple” SPD is only providing protection that is its basic function. Many SPDs incorporate disconnector and thus local fault indicator. A few of them also incorporate a switch that can provide a remote information but this remote information remains generally inside the structure or the industrial site for maintenance purpose. These SPDs may be considered as “smart” even if smart implies probably two things: interaction with other devices based on faraway communication (internet of things)and when possible a type of analysis (to inform a user that is SPD has failed in nice, but why it has failed is smarter). Smart is usually associated to devices with monitoring, control and communication functions. Smart SPD usually includes three functions: surge protection, monitoring and communication.