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  1. S

    PMG Vs AREP+PMI Vs Auxiliary winding

    The specification requires an AVR of the solid-state type with PMG. One vendor offers AREP+PMI, while another lists only an auxiliary winding. What prevents them from simply providing a PMG? This is for a diesel engine generator, with capacities ranging from 1.5 MW to 5 MW. Why might PMG not be...
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    Zone A / Zone B - Frequency Variations

    The specification states: "The AVR should have sufficient protection against voltage surges, be free from voltage drift, remain unaffected by temperature changes, and maintain regulation accuracy within a frequency variation of +/- 10% of the rated value." The vendor responded that the...
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    Reactive power exchange through ULTC (Under load tap changer)

    If both the Generator AVR and Transformer ULTC (OLTC) AVR are in Auto Voltage control mode, they would compete against each other to maintain control; building on this, I had a question, If the Generator AVR is set to PF/Var control mode while the Transformer ULTC (OLTC) AVR is in Voltage...
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    Reactive power exchange through ULTC (Under load tap changer)

    When the grid voltage is significantly higher than the generator terminal voltage while the generator is operating in PF/Var mode, what could occur? When the grid voltage is significantly lower than the generator terminal voltage while the generator is operating in PF/Var mode, what could occur?
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    Reactive power exchange through ULTC (Under load tap changer)

    From the previous discussions in this forum, it is understood that the generator absorbs reactive power from the grid when the grid voltage is higher than generator voltage, and supplies reactive power to the grid when the grid voltage is lower than generator voltage. However, there is confusion...
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    UFLS (Under frequency load shedding) in Islanded generation

    What is the typical time delay used in an under-frequency load shedding scheme for an Islanded generation, and what criteria are used to determine this time delay? 1. Should the under-frequency load shedding (UFLS) scheme be combined with a rate of change of frequency (df/dt) along with a time...
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    Maximum Acceptable Step load - LM2500 GTG

    Received the reply from GE, "Higher the step load, higher will be the turbine speed oscillation (and consequently generator frequency) and longer will be the recovery time. 50% step loads will exceed +-10% frequency variation and the recovery time to reach +-2.5% frequency will exceed 5 seconds...
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    Maximum Acceptable Step load - LM2500 GTG

    Thank you for your reply, Some quick answers to your questions, 1) There is no time interval mentioned in the operational test procedure. I believe it is also 10 minutes 2) Actually it is a 12MW motor started across DOL 3) The facility receives no power from grid. (only GTG's generated power)...
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    Maximum Acceptable Step load - LM2500 GTG

    We have three Gas Turbine Generators (GTGs) of the GE (LM2500+G4) model in parallel, each with a site rating of approximately 27.5MW. Inquiring about the maximum acceptable step load for this type of GTG, I reached out to GE for guidance and yet to get a response. However, I'm seeking additional...
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    "Isochronous Load sharing" Vs Droop Mode

    Managed to get the functional description;
  11. S

    "Isochronous Load sharing" Vs Droop Mode

    The machine is LM2500+G4. If the controller is from GE (MarkVie), external controllers are not required? On further reading, confused about "Isochronous Load sharing"? Is it (1) or (2) 1) All the machines operated in Droop mode with PMS control (or) 2) All the machines operated in Isochronous...
  12. S

    "Isochronous Load sharing" Vs Droop Mode

    Say, there are 4 machines not connected to grid. The four machines all worked in "isochronous load sharing mode" with the PMS and other controllers. What stops the governor from fighting one another in this mode? It seems all the machines talk to each other as to who will respond to the system...
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    Why Generator is rated at 0.8 PF?

    Why Generator is rated at 0.8 PF? Is it because the generator set manufacturers assume that most overall loads are somewhat inductive and apply an arbitrary rating of 80% PF.
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    Generator Rating Vs Turbine rating

    Why Gas turbine drive Generators have higher output rating than the Gas turbines? is it the same for Steam/Diesel/hydraulic turbines?
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    Generator Load Sharing

    Thanks a lot!
  16. S

    Generator Load Sharing

    My confusion stems from the general view that isochronous machine acts as swing bus and the droop machines would supply only the fixed loads. All the droop machines would supply constant (fixed) load only if the bus frequency/grid frequency is constant. In case of one machine in Isochronous and...
  17. S

    Generator Load Sharing

    Yes, but the droop speed control would increase the load only if the fuel is raised manually/Machine speed reference is changed or through some type of frequency control. Am I correct?
  18. S

    Generator Load Sharing

    I’m confused now. Why should it increase the load? Isn’t the function of BASE LOAD is to maintain the load constant regardless of the frequency changes? If the grid frequency decreases, the fuel that was previously used to maintain the frequency (before it got decreased) will be used to maintain...
  19. S

    Generator Load Sharing

    Thank you for the detailed explanation! If I understand correctly, when the 3MW load drops, either from the grid or from the parallel droop generators, the speed(frequency) of the grid increases or the frequency of the parallel running droop generators increases, with the explanation being that...
  20. S

    Quadrature droop Vs Cross Current compensation - AVR Controls

    1. What is the difference between quadrature droop Vs cross current compensation? Is cross current compensation method for AVR control equivalent to "Isochronous control" of governor? 2. Is the term line droop compensation same as the term "Line drop compensation"? 3. Is it possible for multiple...
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