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  1. Gauss2k

    Transformer inrush vs short-circuit current

    I was reading an interesting document made by S&C about the calculation of a transformer inrush current based on the impedance and the short-circuit available at the primary side of the transformer: http://www.sandc.com/webzine/2003/012003_1.asp We usually use a 8 to 12x nominal value for 0.1s...
  2. Gauss2k

    Harmonic filter

    I am currently reading a report talking about the test and sizing of an harmonic filter. I have a couple of questions about how they managed to get their results. Here we go. The filter is made of one 3-phase reactor, with a value on the plate of 115 uH. In series with this reactor are four...
  3. Gauss2k

    Current decrement data for a turbo-generator

    I am currently working on the coordination study of a factory's emergency network. They have 2 500kW generators and 1 MW turbo-generator. I was able to get all the information I need about the 2 generators as they are only a few years old. But unfortunately, the turbo-generator was made in the...
  4. Gauss2k

    T-T connected transformers

    I was looking for informations about T-T connected transformers because I saw a couple of them in the last months. I found this thread via google where it was briefly discussed: thread238-151261 Some manufacturers like "Marcus Transformers" (http://www.marcustransformer.com), also found with...
  5. Gauss2k

    Medium to high voltage measurements

    We would like to take measurements on a 25kV transmission line (voltage and current). Other than installing permanent current and voltage transformers, is there something else we can use to record those values over a short period of time? A few months ago, I remember receiving a publicity...
  6. Gauss2k

    Water content in oil

    We regularely take oil samples from our clients transformers in order to analyse their dissolved gas content and oil properties. Sometimes (and it happens a couple of times in the last few months), we see a sudden change in water content (for example from 10 ppm to about 50 ppm a year later)...
  7. Gauss2k

    Current transformer saturation

    I have a question about current transformers saturation. Here's the situation. The building has a medium voltage breaker with its protection relays, on the primary side of its main transformer. The current transformers used by the relay have a ratio of 50:5A. The maximum short-circuit current...
  8. Gauss2k

    PCB transformers standards

    Hello everyone, We just tested 2 PCB transformers: ratio, winding resistance, PCB dielectric breakdown and insulation test (megger @ 1kV). All the tests gave good results on both transformers, but the insulation tests we're pretty low on -both- transformers primary side (about 8 to 9 MegOhm...
  9. Gauss2k

    Oil analysis results

    I just received the results of the oil analysis we made on a 2.5 MVA transformer. I'm a little puzzled by the results and I would like to have your opinion. We have the results from the last 4 years. The DGA show stable gasses (low concentrations) and no problem have been observed on that...
  10. Gauss2k

    25 kV fuse and fuse holder

    Hello everyone! We have been asked by one of our client to change his main circuit fuse/fuse holder. They are having problems with it and since it's getting old, they simply want to install a brand new one. The caliber of those fuses is 25 kV / 400 amps. They are indoor. Now.. I called...
  11. Gauss2k

    Tuned capacitor bank/filter configuration

    I am designing a tuned capacitor bank (which will probably also be used to filter some of the harmonics of the network, mainly 5th) for a factory. It's low voltage, 600V. I modeled the plant under PSAF (made by Cyme) to simulate the network and determine the resonance and harmonic...
  12. Gauss2k

    Chiller power consumption

    Anyone is familiar with chillers power consumption? I see in a technical data sheet that a 155 tons air-cooled chiller made by Trane requires a 310 amps disconnect switch (@575V). But I saw elsewhere on the net that "One ton of cooling is the amount of heat absorbed by one ton of ice melting...
  13. Gauss2k

    Maximum TDCG

    Hello, I have a transformer with stable dissolved gasses but I was wondering.. What is the maximum acceptable value of total combustible dissolved gasses (ppm) before degassing or oil change is necessary? I saw in IEEE Std C57.104-1991 a couple of tables where they mainly talk about gas...
  14. Gauss2k

    Transformer differential protection

    I am programming a digital relay that will be used to protect a transformer from overcurrents (50-51-50N-51N) and internal faults (87T). The settings for the 50-51 were determined by a coordination study, but I am unsure of which values I should use for the differential protection. I have...
  15. Gauss2k

    Oil furan Level standards (test ASTM D5837)

    I just received an oil analysis result for a transformer. The report included the level of furan, according to the test "ASTM D5837". I was able to find several references for the standard values from the IEEE and other sources for the dissolved gases (for each gas and for the several ratios)...
  16. Gauss2k

    Level sensor for low density, under pressure

    Hello, I'm looking for a sensor that could measure the level of a tank containing polypropylene beads (solid). Those beads have a density of approximatly 1 pound per cubic foot and the tank is under pressure between 60 and 100 psi. The tank itself is made of metal (probably steel) and we...
  17. Gauss2k

    Ventilation of a factory's second floor

    Hello, I've been asked to add ventilation on the second floor (about 32k sqf) of a factory and I'd like to have your opinion. Since several machines (using steam) are used one the first floor, a lot of heat rises to the warehouse on the second floor. The finished products are brought from the...
  18. Gauss2k

    Static electricity grounding

    Hello! I have to ground several stocking silos made of 100% polypropylene fabric (the silos are filled with polystyrene beads). It doesn't contain any grounding wires included within the fabric. The silos are about 4x6x10 feets and their frame is made of metal pipes. I am not familiar with...
  19. Gauss2k

    Savings in compressed air systems

    Hello everyone, I've just started to look at our compressed air system because we'll increase the number of production machines and we wonder if we'll need an extra compressor or not. Of course, we'd prefer not ;) I've just read some very interesting posts about leaks detection and how costly...
  20. Gauss2k

    Cooling tower and VSD

    Hello, We are considering to install Variable Speed Drives on our 2 cooling towers to save energy and money. The towers's fan is 10 HP and the pump is a Monarch Industries BSEF-750 (Specs: http://www.monarchindustries.com/v4/media/pdf/POP/bsef.pdf) (7.5 HP). Basically, the hot water arrives...

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