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  1. m3ntosan

    GSU Transformer

    @Power0020 IEC 60076-1 May you grow up to be righteous, may you grow up to be true...
  2. m3ntosan

    GSU Transformer

    Transformers intended to be connected directly to generators in such a way that they may be subjected to load rejection conditions shall be able to withstand 1,4 times rated voltage for 5 s at the transformer terminals to which the generator is to be connected. May you grow up to be righteous...
  3. m3ntosan

    WTG fault contribution calculations

    Based on the size and the current contribution,I'll take it this is a type 3 DFIG and the 9.5kA would be the initial symmetrical short circuit current for a fault applied on the HV side of the transformer. The DFIG behaviour depends very much on the converter, the control system will react...
  4. m3ntosan

    Maximum transformer rating/circuit breakers in parallel configuration

    Hi I got a bit confused with your example above and I thought you're talking about distribution, feeding demand. I looked at two offshore windfarms just now and one of them has 240 MVA transformer offshore 132/33 kV with 2 breakers in parallel, Siemens 8DA10 2500 A and the other one 150/33 kV...
  5. m3ntosan

    Maximum transformer rating/circuit breakers in parallel configuration

    200 MVA is a big beast for a distribution transformer, most of them are 100 MVA 400/33 kV, I've seen a few 150 MVA with 2500A breakers. Never heard of paralleling breakers, is it possible to get a transformer with two LV windings 200/100/100 MVA to get around the issue? Alternatively you should...
  6. m3ntosan

    Substation/Switchgear capacity

    What would you expect to happen for a bar fault on the LV side? With 1 and 1/2 arrangement is it OK to assume you won't lose any demand or infeed from 380 kV and post fault you'll continue feeding the same demand via the two transformers all selected to the remaining busbar? Is the...
  7. m3ntosan

    Costs of Reactive Power

    @cranky108 If you're talking about 275 or 400 kV cables, SIL is so high that it makes almost no difference if the cable is lightly or highly loaded, still generates roughly the same amount of MVArs. May you grow up to be righteous, may you grow up to be true...
  8. m3ntosan

    Costs of Reactive Power

    @NewGrid, Looks like you're talking about the UK, to get an idea, National Grid is paying power stations £3 per MVArh. In some other parts of ENTSO-E you don't have to pay for MVArs as it's part of the grid code connection agreement for power station to provide it for free, unless you're...
  9. m3ntosan

    Stuck breaker protection

    Agreed, smallgreek! There are several ways to end up with a stuck breaker, loss of operating mechanism could cause it, if nitrogen and oil for instance. For a mechanical problem you don't get any alarm and you don't know you have a stuck breaker until you have a breaker fail. For loss of...
  10. m3ntosan

    Stuck breaker protection

    ScottyUK, In the UK, i heard 'stuck breaker' term being used when you really have a stuck breaker, like 'trip circuit 1 and 2 faulty' and you know whatever happens that CB is not going to trip/open, with only options left to open the breaker locally from the trip coil (if it works) or take it...
  11. m3ntosan

    NERC asks unusual questions

    @cranky108 In India, they thought that you need a fault to operate a distance protection as well and it ended up in tears:) May you grow up to be righteous, may you grow up to be true...
  12. m3ntosan

    NERC asks unusual questions

    @cranky108 In the UK the electromechanical distance relays will trip the circuit for a blown fuse, instead of locking up. In some other European countries there's a different approach and the protection will lock up for blown VT fuse, hence relying on the protection ‘to know’ if it's a genuine...
  13. m3ntosan

    NERC asks unusual questions

    Maybe if you still have old distance protection in the system, that will trip on VT blown fuse, VT supervision might be considered to give a hint on the maloperation May you grow up to be righteous, may you grow up to be true...
  14. m3ntosan

    India - 370M INDIANS SWELTER IN HEAT AFTER POWER FAILS

    REPORT OF THE ENQUIRY COMMITTEE ON GRID DISTURBANCE IN NORTHERN REGION ON 30th July 2012 AND IN NORTHERN, EASTERN & NORTH-EASTERN REGION ON 31st JULY 2012 16th AUGUST 2012 NEW DELHI http://www.powermin.nic.in/pdf/GRID_ENQ_REP_16_8_12.pdf May you grow up to be righteous, may you grow up to be...
  15. m3ntosan

    Why does the frequency increase when generation exceeds load?

    @cranky108 It's safe to say that resistive load (non-motor load) doesn't depend on frequency deviation Without a control system the generator should trip, unless you want to see the rotor running around the power station if overspeeding or lose the blades on the turbine if running well below...
  16. m3ntosan

    sympathetic inrush

    From experience, one inconvenience for the system, when simpáthetic magnetic inrush occurs in GSUT of power station(CCGT with big GSUTs) connected to fairly weak 400 kV system, huge voltage step change affecting the distribution network in the area, even with decent SVC connected in the area 2x...
  17. m3ntosan

    Reducing Fault Level Issues

    run split prefault and put in place auto-switching scheme on couplers, sections etc to couple up site for transformer loss May you grow up to be righteous, may you grow up to be true...
  18. m3ntosan

    Surge arrester on neutral terminal of transformer

    @lume7006, the ones I've oprerated were similar sizes and voltage levels, the surge arresters were rated for 72 kV, for Y windings at 110 kV. It's the same path to earth, by operating an isolator and/or earth switch you're getting the surge arrester in/out the circuit. May you grow up to be...
  19. m3ntosan

    Surge arrester on neutral terminal of transformer

    @odlanor, In the British system is not permitted to operate with transformer neutral ungrounded, at least at the transmission level, needs to be switched out asap, even if you lose demand... @davidbeach Please refer to EPRI Copper book and EPRI fault level management, grounded through a surge...
  20. m3ntosan

    Surge arrester on neutral terminal of transformer

    @davidbeach Agreed, is likely to find power system nonsense management nowadays Have you ever seen any surge arrester in service, without a ground terminal? May you grow up to be righteous, may you grow up to be true...

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