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  1. marks1080

    Cable Glands Earth Tags Location

    Have you tried asking a certified engineer? You haven't given enough information for a better response. Depending on where you are you will have different codes to conform to. Also, depending on what these earth tags are and what they're used for will make a difference. If this is related to...
  2. marks1080

    Effectiveness of Grounding Cable Over Trench for Transient Voltage Protection

    Cuky2000 - i believe waross is actually using the reference of EMI interference correctly. Think about geo-magnetically induced currents from solar storms, really the only way to protect against those is to install in-line caps on ALL transformer neutrals. Not really a practical solution. You...
  3. marks1080

    Effectiveness of Grounding Cable Over Trench for Transient Voltage Protection

    Remember that this cable trench ground run is just one component of your transient suppression. The ground runs are entirely meaningless if the cable shield grounds are not properly applied. The single biggest factor (imho) in bad grounding, when all the proper materials were bought and all...
  4. marks1080

    Effectiveness of Grounding Cable Over Trench for Transient Voltage Protection

    It's very effective. Without out you'll blow up a lot of relays taking in feeds from CVTs during disconnect switch operations. I would even suggest that the grounding conductors should be located more centrally in the trench, as opposed to being strapped to the side. You want any cables in...
  5. marks1080

    Manhattan Partial Blackout

    Sounds like years of 'do more with less' cut maintenance and spend big on useless capital. These relay rooms probably flooded in the past and have never been properly recommissioned... Just a guess
  6. marks1080

    What is the single line to ground UTILITY fault current and X/R when only given the 3-phase info?

    It's also possible that utility didn't give you any SLG fault data because the utility transformer connection will prevent any zero sequence current passing into your system.
  7. marks1080

    What is the single line to ground UTILITY fault current and X/R when only given the 3-phase info?

    bdn2004, the values from the utility will have to take into account the system. You can't accurately guess the ground fault values based on three phase values. It should be fairly simple for the utility to provide this information - i'd suggest just asking for it.
  8. marks1080

    What is the single line to ground UTILITY fault current and X/R when only given the 3-phase info?

    You can't assume this for a variety of reasons. A lot of sources that contribute to a phase fault may not have a zero sequence path to contribute for a ground fault. There are 'rules of thumb,' but for an HV system you need to get the actual ground fault values if settings any ground/neutral...
  9. marks1080

    How to test GFCI plug?

    It's generally not safe for non-technical people to perform electrical testing.
  10. marks1080

    Overpressure device on SF6 equipment

    Ahhh yes... I wasn't thinking about GIS. Sounds like different functionality vs what is intended for these VTs. Have you ever seen a trip signal from an SF6 over pressure or just alarms?
  11. marks1080

    Overpressure device on SF6 equipment

    The device in question comes with duel stage low SF6. I'm using stage 1 to alarm, and stage 2 to trip the zone. The over pressure device, as far as I know, is being added after the fact at our request. So my assumption is a hole will be drilled through the tank of the VT and an over...
  12. marks1080

    Overpressure device on SF6 equipment

    crshears - I've been pondering all the same points. It's also concerning when you google "SF6 over pressure device" and find nothing... Pretty sure we are working in the same system, just FYI you may see folks trying to in service this gear without technical documentation to go along with it...
  13. marks1080

    Overpressure device on SF6 equipment

    Has anyone ever seen an over pressure device used on SF6 gear? Specifically, something like a high power SF6 VT (100kva per phase)? It's being suggested for a project I'm working on but I don't have experience doing this. The functional analogy that is wanted would be like a Bucholtz relay...
  14. marks1080

    Help Modeling a NGR in CYMTCC

    I'm trying to model the damage curve of a neutral grounding reactor in CYMTCC... I'm used to having all the libraries I need already in the CYMTCC database, and I'm not sure what the correct way to properly build the custom model for the reactor. Does anyone have any experience or advice with...
  15. marks1080

    SCADA-less system

    HH - I believe traces of Stuxnet were eventually found throughout internet connected devices all over the world. I've only ever read about activation of the virus in the Iran nuke program. It was specifically made to infect a very specific type of PLC controller, so i doubt it would be able to...
  16. marks1080

    SCADA-less system

    Stuxnet was delivered by dropping infected USB sticks in the parking lot of a Siemens manufacturing plant. Eventually one of these sticks was plugged into a computer on the Siemens network. Siemens was manufacturing PLC's to control very high speed and sensitive centrifuges that Iran was using...
  17. marks1080

    Venezuela´s general blackout

    Completely possible. But a power station of that magnitude is probably going down once the operator (govt?) stops paying attention for any one of a million reasons.
  18. marks1080

    Symmetrical Components - Fault Between Two Transmission Lines

    Great topic. I've asked similar questions before... I've tried drawing out simple examples to solve the network equations, using the voltage difference between the two line and general impedances (lines, transformers), but I can't say i feel comfortable with using it in a real world scenario...
  19. marks1080

    SCADA-less system

    mbrooke: Look up StuxNet - anyone claiming any credibility in the 'cyber security' space should be well aware of this. Surprisingly you mention it in a 'cyber security' meeting and the MBAs just stare at you with a dumb look on their face. davidbeach - an 'attack' by definition, cannot be...
  20. marks1080

    SCADA-less system

    mbrooke, Most cyber attacks in this industry will likely come from equipment that's been 'infected' at the manufacturing level, before it's even purchased. The industry, in general, is basically ignoring this right now, though it is the biggest threat. Just because you have networkable...

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