FGMO & RGMO TEAM-C&I • From Grid point of view – If frequency is less than 50 Hz Load Generation < Connected – If frequency is greater than 50 Hz Generation > Connected Load .Fundamentals • It is desired that the operating frequency is maintained in Grid at 50Hz. Various Frequency Influence Modes • We can have three different mode of Frequency Influence – Primary Frequency Influence – Free Governing Mode of operation (FGMO) – Restricted Governing Mode of operation (RGMO) . – If frequency is greater than 50 Hz then all generating units should drop load automatically as per the droop set for that machine. all Generating stations should have primary frequency influence On and do correction as below:– If frequency is less than 50 Hz then all generating units should pickup load automatically as per the droop set for that machine.Primary Frequency Influence • To maintain Grid frequency at 50 Hz. . Free Governing Mode of Operation (FGMO) FGMO . as specified by IEGC Scheduling & dispatch by RLDCs/SLDCs is based on day ahead demand & availability Frequency control by load-generation balance in every 15 mins time block and Wide frequency variation during Grid disturbance. Emergencies caused due to frequency control only through importing /cutting load by system operator FGMO . Change in demand.GRID CODES All generating units should have their speed governors in normal operation at all times to enable Grid frequency control by loading / unloading Droop characteristic for primary response should be within 3% to 6% Each unit shall be capable of instantaneously picking up at least 5% extra load for a minimum of 5 mins (up to 105%MCR).5 Hz. Unit outage. during fall in frequency No dead bands and/or time delays shall be deliberately introduced .BACKGROUND Unique frequency band of 49. etc.0 Hz to 50. 5 Hz band. depending upon previous stable frequency. .FGMO • Reference Center Frequency is floating in 49.0 to 50. hence it is possible to have load drop even at 49. • The load correction are based on this frequency set point.5 Hz if there is sudden frequency increase. Thus a machine of 250 MW size will drop load of 250 MW if frequency is 52. 2.5 Hz .5 Hz.5 Hz ~ 250 MW. For 250 MW unit 5% of 50 Hz = 2.Droop Calculation • 5% Droop means. 5% of rated frequency corresponds to full load of the machine. 0 49.0 0:00 26/1/04 2:24 4:48 26/1/03 7:12 9:36 12:00 TIME 14:24 16:48 19:12 21:36 0:00 Source:ERLDC Website .0 PRE ABT REGIME WITHOUT FGMO 51.5 POST ABT REGIME WITH FGMO 48.5 50.FGMO SMOOTHEN THE WIDE FREQUENCY FLUCTUATION FREQUENCY COMPARISION 52.0 48.0 50.5 FREQUENCY 51.5 49. Therefore suitable control logic would have to be developed to limit the governor response to situations when frequency is rising and grid frequency is below 50 Hz.relevant extracts of which are furnished here below. it is not desirable to have any frequency response from generators by reducing generation when frequency is rising towards 50 Hz from a lower level.CERC Order Hon’ble CERC. .vide order dated 20.09 has issued directions for implementing the RGMO. Such a situation could be called a restricted governor mode of operation and not total FGMO.In the present scenario of deficit. Quote: 39. How ever this does not exempt the generators from getting the free governor mode in to operational state for use when required. Reduction of generation would be necessary when frequency is already above 50 Hz and tends to rise further.08. 5% droop of the governor would be effective with load change limited to +5% of MCR for frequency below 49 Hz and -10% of MCR above 50.” . For frequency below 49 Hz and above 50.5 Hz and sustained for about 5 minutes before ramping back to original load automatically.5 Hz.0.03Hz are ignored for load corrections.5 Hz. Small changes up to +/.Salient features of the CERC Order Load change is proposed to be limited to +/-5% of MCR in the frequency range of 49 Hz & 50. FGMO . FGMO . RGMO • Try to maintain Grid frequency at 50 Hz in power deficit environment. . all Generating stations should have load correction based on frequency as follows:– If frequency is less than 50 Hz no correction to be applied. – If frequency is greater than 50 Hz generating units should drop load automatically as per the droop set for that machine. • So the primary frequency influence is normally kept OFF. • However for Tata Grid we have made special provision to have controlled frequency correction during ISLANDING. . it is not possible to maintain the grid frequency exactly at 50Hz.Frequency Influence • In the present power deficient scenario in India. . Whereas for any fall in grid frequency.RGMO GUIDELINES “Governor Action generating units shall be operated under restricted governor mode of operation : (a)Thermal generating units of 200 MW and above.2 Hz.4 Hz.3 to 49. generation from the unit should increase by 5% limited to 105 % of the MCR of the unit subject to machine capability. then there shall not be any reduction in generation). ( for example if grid frequency changes from 49. (b) Hydro units of 10 MW and above: The restricted governor mode of operation shall essentially have the following features: (a) There should not be any reduction in generation in case of improvement in grid frequency below 50. in order to prevent governor hunting.0. All governors shall have a droop setting of between 3% and 6%.(b) Ripple filter of +/. the RLDC shall be immediately advised about the reason and duration of such operation. shall be provided so that small changes in frequency are ignored for load correction.03 Hz. . (c) If any of these generating units is required to be operated without its governor in operation as specified above. (d) After stabilisation of frequency around 50 Hz. the CERC may review the above provision regarding the restricted governor mode of operation and free governor mode of operation may be introduced. EHTC Blocks . WRLDC RGMO Test Guidelines . WRLDC RGMO Test Guidelines . WRLDC RGMO Test Guidelines . WRLDC RGMO Test Guidelines . .RGMO test on 5th April 2010 • As per WRLDC Order Generators above 250 MW were to switch on the frequency influence in order to test the unloading of generators when the frequency goes above 50 Hz. Below 50 Hz there should be no load correction applied by frequency Influence circuit.