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  • Users: npower0073
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  1. npower0073

    Steam turbine control issue

    On site , a CCPP with a steam turbine Franco Tossi Mechanica and Siemens ORSI IT control system we experience lateley the following event: WHile ST runs her start up sequence the speed is controlled by HP Stop (throttle) valve). After the spped of 2800 rpm the conmtrol of spped goes to HP...
  2. npower0073

    Exciter EX2100 code 53 alarm and transfer blocking

    On site we have one Ge generator 325MVA 4-pole hydrogen cooled with static excitation system EX2100. We experience alarm code 53 fault, and M1 controller reads different current magnitude than M2 so it goes to transer block and we loose redundancy. There is a product bulletin from GE that says...
  3. npower0073

    Tap changer oil samplig

    On site we have a three winding step up transformer 440MVA, 400kV/15.75kV/15kV. Lately we made maintenacne on the tap changer (MR), changed the oil and put back in service. After 10 days we made ne oil analysis and after 40 days we made a second oil analysis. The results of the first analysis...
  4. npower0073

    HP Drum level measurement

    Our HRSG is a triple pressure one with an HP Drum that works at pressure of 115 bar at base load of gast turbine. During recent overhaul we saw that the actual level of the drum (red marks on the inside of the level drum) is almost 100 mm higher than the designed one. THe level is measured with...
  5. npower0073

    Gearbox oil decreasing pressure during summer

    On site we have 10 cooling tower fans, driven through eelctric motors , long shaft and gear box. We have experienced two issues upt o now, after 3 years of operation: 1) Ringing on the gears of the gearboxes, the most probable cause is the direct on line start of the motors 2) During summer...
  6. npower0073

    Steam turbine trip signal when GCB opens

    Usually steam turbines control system implements trip signal from several reasons like HP steam temperature and steam, electrical protection of generator, generator slot temperatures, low condenser vacuum or level, lube oil pressure, control fluid temperature etc. The trip scenario is that when...
  7. npower0073

    ST Lube oil mist eliminator issue

    On site we have a steam turbine. The Lube oil skid is equiped with 2 mist eliminator fans. The OEM of ST states that there should be a 5mbar vacuum to ambient. in order to get the oil bak in the tank and not lose it. We usually worked with higher vacuum (20mbars). Also we experience the fact...
  8. npower0073

    GT 9FA increased proximity readings at TE of generator

    Dear all. On site we have a 9FA DLN +2 gas turbin coupled with a hydogen cooled 270MW generator. After the end of a combustion inspection outage we saw the following : When GT goes from 140 MW to base load 260MW then we see increase readings on the proximity of bearing 1 (TE) of generator. When...
  9. npower0073

    Sea water underground pipe leak detection

    On our power plant we take sea water through a 6 km underground line. This line has faced a lot of leaks from vents and flanges. We are thinking of a way to detect leaks using some intrumentation. One way could be to use flow sensors on the intkae line, one on the pwoer plant and one near the...
  10. npower0073

    Sea water underground pipe leak detection with flow meters

    On our power plant we take sea water through a 6 km underground line. This line has faced a lot of leaks from vents and flanges. We are thinking of a way to detect leaks using some intrumentation. One way could be to use flow sensors on the intkae line, one on the pwoer plant and one near the...
  11. npower0073

    Bearings of motors powered through VFD

    On site we have 3 400V motors 200kW , spupplied via ABB ACS 800 inverters. he motor bearings are nit special insulated bearings , for applications that use inverters, they are typical nearings. The frame of the motor and the driven fan are grounded, the motor cbles are special shielded power...
  12. npower0073

    CT and PT failute temporary repair

    lately on plant we faced aproblem with the secondary of one CT and one VT. CT was used for protection 8000/1 5P20 toroid, VT (or PT for US) was used for exciation control 15750/V3 / 120 V Cl.0.2s. In order to put the unit back in service i put in parallel the secoindar of the PT of another phase...
  13. npower0073

    Exchange of current transformers of defferent class

    I want to ask if I can exchange a current transformer of the same burden and ratio but with different class, meaning to use a 0,2s class to replace a 5P20 class. Is that feasible? I understand that 5P20 or 5P30 are used for protection purposes and have higher strength against short circuits in...
  14. npower0073

    Drop of hydrogen purity in GT generator

    On site we have a 324 GE generator hydrogen cooled. 8 months before GE made a MAGUC inspection when it removed the end shield and seal ring from collector end. During the last month we have experienced sudden drop of H2 purity while the unit starts up and mainly when it syncjronizes. From 98% we...
  15. npower0073

    Step up transfomer oil temperature control issue

    Dear all, on site we have a 460MVA step up transformer. It is equipped with 6 collers (air to oil, with fans and oil pump). The transformer is ODAF(oil draught, air forced). during thermography survey we found out that the part of the main oil tank that is on the part of the coolers out of...
  16. npower0073

    Diesel generator troubleshooting

    On site we make regular tests of a diesel generator set, 800kW 1500 rpm. What we experienced lately is that the generator suddenly decreased load (from 400kW to 117kW), increased frequency (from 50Hz to 60 Hz) adn tripped from overfrequency. Afterwards the opearation was OK. This is a stand by...
  17. npower0073

    Isolated phase busducts maintenance

    Dear all. On site, a CCPP 400MW nominal output and IPB manufactured by EGE. We are in the process of making maintenance contract with a contractor. I know tht somethings to be done is leak test with pressurized air, insulation test, inspection of bars, paint checks tightness of bolts, and so on...
  18. npower0073

    Vibration limits on motors

    On site we have a vertical motor 1090kW 6.3kV 593rpm that develops 7.2-7.7 mm/s velocity on the Non Drive End during our vibration measurements. The motor comply with EN 60034-14. Is it OK to run it? We also plan to clean the impeller of the motor from dust. Also the motor drives an axial flow...
  19. npower0073

    Vibrations on Generator Coupling end bearing

    On site we have a 324 hydrogen cooled generator 270MW of GE. Recently we started receiving proximity vibration alarms from displaycement sensors located on the bearing of coupling end. The increase is picked up by both of the sensors (each sensor is located in 90 degrees distance from the...
  20. npower0073

    Steam tubine output on Combined cycle

    Dear all. On site we have a combined cycle power plant with gas turbine and steam turbine, in multiple shaft. I try to find a way to assess the output of Steam Turbine in relation with ambient temperature and condenser opearting status. What physical values should i check and how can i assess...

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