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  1. Viceng

    Substation Fence Grounding

    Thank you both for your responses. PowerfulStuff: when you say fence "was OK as is" did you not place ground conductors below the fence as well as no gravel? Really it seems to come down to the top layer soil resistivity. If it is not low enough to ensure a surface potential nearly equal to...
  2. Viceng

    Substation Fence Grounding

    Hi, I am looking for some recommendations: currently designing a substation which is enclosed by a fence (all standard),however, in this particular case a security fence (attached to one side of the substation fence) is extended in a large perimeter around the substation area (footprint enclosed...
  3. Viceng

    Exciter Time constant Calculation

    Hello, I was wondering if anyone knows of a formula available to calculate an exciter time constant. I am looking at a DECS200 voltage regulator and I have the T'do (generator time constant) but I am looking for the Texc (exciter time constant)of a brushless machine to properly set the AVR...
  4. Viceng

    Unusual stopping of the generator

    You could check to see if the deflector has come out of proper alignment. Perhaps, when it came into the stream it forced water to bounce off the turbine walls and back onto the unit...acting like a braking jet.
  5. Viceng

    IEEE C37.32 Table 5 Phase-to-phase spacing

    "The minimum metal-to-metal clearances should be maintained at all times with the switches in the open position, closed position, or anywhere between the open and closed positions." - the metal-to-metal clearance seems to apply to the scenario of disconnect switch positions which would make...
  6. Viceng

    Voltage Regulator: Replacement Question

    Thanks for the input catserveng, Basic question: Why is it that the DECS doesn't treat a low voltage condition as a time when field forcing is required? Is it simply that it requires a certain p.u. current in addition to voltage to differentiate a start up condition from a fault? Has anyone...
  7. Viceng

    Voltage Regulator: Replacement Question

    I am hoping to replace some old Basler voltage regulators (type SSR 63-12F) with some new DECS200 units. The DECS200 units have a start input unlike the previous SSR regulators. I was wondering if anyone had experience with such a replacement and if so if there is an issue with leaving the START...
  8. Viceng

    Closed Delta

    My apologies, yes, broken delta Thank you for the responses "Current can't flow in the primary unless it can flow in the secondary" - really clarifies it for me. "No such thing as an "ungrounded system", just lots of systems with that name that are actually high impedance capacitively...
  9. Viceng

    Closed Delta

    I am dealing with an ungrounded system which is utilizing a closed delta VT configuration to sense a SLG fault. My question: The HV side of the VT is Wye solidly grounded - Does this configuration not introduce a ground reference into an otherwise completely ungrounded system? I would imagine...
  10. Viceng

    Out of Step Protection

    Thanks, This could be a problem - Perhaps I could update setting groups based upon which generator(s) is running. Has anyone else out there commissioned such a OOS scheme with multiple units? I would appreciate any settings recommendations.
  11. Viceng

    Out of Step Protection

    Hello, I was hoping for some help in setting up an out of step protection element on an SEL 300G. The manual calls for - Generator transient reactance - Generator step-up transformer impedance - Impedance of line beyond the generator step-up xfmr My question is: what if you have more than one...
  12. Viceng

    IEEE STD 998

    Hello, Question regarding substation shielding: can I confirm that a metallic equipment support structure, or wooden for that matter, also double as a lightning Mast? I cannot find it specically noted in the IEEE standard. Thanks in advance.
  13. Viceng

    Transformer Grounding

    Again, thank you all for the replies. Waross and LionelHutz, I should have clarified that I was speaking of the physical impedance of the ground system (remote earth) not the impdeance of the neutral connection to ground as Jghrist has pointed out. jghirst, I appreciate the input. I was...
  14. Viceng

    Transformer Grounding

    Thanks for the reply. I am still unsure why a high ground impedance would impose a larger H0 bushing requirement. The potential difference between the H0 bushing and ground would be the current through the neutral multiplied by the resistance of the cable from the winding to ground (quite...
  15. Viceng

    Transformer Grounding

    Hello, I have a question regarding neutral bushing ratings that I was hoping someone could help me with. Scenario: 16MVA transformer 138kV solidly grounded Wye - 13.8kV delta. the HV phase bushings are 550kV BIL while the neutral is 15kV 400A, 95kV BIL. This neutral bushing seems quite...
  16. Viceng

    Diesel Generator Paralleling

    Thanks for the replies. Alehman, I was thinking one should be in isochronous mode too but the system apparently works just fine under a real loss of utility scenario. burnt2x, the gen's are identically sized. While I have seen the transfer everything has gone fine, frequency of both units was...
  17. Viceng

    Diesel Generator Paralleling

    Hi, I was hoping someone on the board may be able to shed some light on an issue that I am dealing with: Setup: Two emergency diesel generators, 600V, paralleled together on a common bus. ATS, Governors, regulators all included. Both are in droop mode. Situation: When a true utility failure...
  18. Viceng

    Hydro Generator Paralleling

    ScottyUK, Good point. I neglected to mention that the we are tying into a 69kV system...quite stiff near a very large generating facility. Our intention (if the Utility allows) is to run in PF mode at or near unity, but often times we are requested to assist with voltage support. From what I...
  19. Viceng

    Hydro Generator Paralleling

    I appreciate the input. Waross, sounds like once we are tied to a grid (especially since there are small units - 5MW each), there really aren't many concerns (different from a single generator facility) after ensuring the regurlators are set similarly. motoxplosion, as you mention there are...
  20. Viceng

    Hydro Generator Paralleling

    Thanks DPC, Basler definitely has some good documentation.

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