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TYPES OF LOADS IN AN INTEGRATED STEEL PLANT

DOUBLE CHANNEL ISLANDING P K Panigrahi DGM( Opn ) NSPCL,Rourkela. Category-I Loads (Essential Loads) * Failure causes safety hazards with risk to human life and damage to vital equipment. Category-II Loads (Production Loads) * Stable

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TYPES OF LOADS IN AN INTEGRATED STEEL PLANT

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  1. DOUBLE CHANNEL ISLANDING P K Panigrahi DGM(Opn) NSPCL,Rourkela

  2. Category-I Loads (Essential Loads) * Failure causes safety hazards with risk to human life and damage to vital equipment. Category-II Loads (Production Loads) * Stable * Fluctuating (Mills, induction/arc furnaces) Category-III Loads (Non Production Loads) TYPES OF LOADS IN AN INTEGRATED STEEL PLANT

  3. Captive power plant combined with blowing station(PP1/PP3) Supply power to load centers catering to essential loads (Category-1) mainly located in primary zones of the plant. Captive power plant (PP-2) Supply power to production loads Power import from Utility Supply power to production loads SOURCE OF POWER FOR INTEGRATED STEEL PLANT

  4. Double bus arrangement one fed from captive power plant with alternate source of grid supply to the other bus. • Primary zone area with concentration of category-1 loads is normally fed from PP-1/PP-3 and grid sources. • Production loads normally fed from PP-2 and grid sources. • Arrangement of supplying all emergency loads from PP-1. Basic Power Distribution Philosophy

  5. Synchronised mode • With provision of islanding along with matching essential loads. • Plant can exchange power with Grid • Grid faults get reflected to the plant system resulting in disturbances. • Isolated mode • Failure of power plant will cause power interruption to essential loads. • Plant remains unaffected by adverse frequency & voltage profiles of the grid. MODES OF OPERATION OF CAPTIVE POWER PLANTS

  6. MERITS:- • Reliability & redundancy of supply particularly for Category-1 loads. • Provides high fault level which, helps in good voltage regulation for fluctuating/ peaking loads of Rolling Mills and furnaces. • Better management of power factor and demand for the imported power. DEMERITS:- • Grid disturbances get reflected to the plant system resulting in disturbances. Why Synchronised Mode ?

  7. OBJECTIVE:- • Under any grid disturbance Islanding Scheme should be able to preempt a grid catastrophe and bailout at least all category-1 & essential loads alongwith the power plant (preferably the primary zone loads alongwith the PPs). The Secondary zone loads alongwith rolling mills & furnaces shall hang radially on the grid. CONSTRAINTS:- • Captive power plant generation and connected load may vary. • Grid disturbances i.e. Voltage dips, frequency variations, interruptions may happen anytime and can not be predicted. Basic Islanding Philosophy

  8. Islanding Scheme has to keep constant vigil on PP generation and loads connected. • Islanding initiation and isolation shall be as fast as possible. • Post islanding management through better governor control and load-shedding. • Governor control changeover from Pressure Controller to Speed Controller Basic Features of Islanding Scheme

  9. More Sensitive Frequent islanding, operational problems. Better reliability Less Sensitive Rare islanding May lead to failures, Catastrophic NATURE OF ISLANDING

  10. Separate Islanding of CPP-1,CPP-2 & CPP-3 • Hardwired & FOC System • SCADA system • CPP-2 Islands in three schemes 1. Double Unit 2. Single Unit 3. Double Channel BASIC FEATURE OF ISLANDING SCHEME AT RSP

  11. DOUBLE UNIT ISLANDING OF CPP-2 (Basic Flow Diagram) DU islanding Mode has been selected at MSDS-II Sensing of Islanding Relay (installed on HSL fdr 1 & 2 at MSDS-II) AND Both HSL feeders trip at MSDS-II CPP-2 CPP-1for Islanding MSDS-3 for Town fdr-5 trip RM-1 for HSM Roll Stop RM-2 for Township fdr 3 & 4 trip LBSS-1 for LHF-2 trip LHF-1 trip at MSDS-II If both units are running AND DU islanding is selected gives command to both units governor for changeover to Speed Controller Mode & Setting of Reference speed as per actual load.

  12. RELAY BASED ISLANDING • Islanding points are preset • In actual circumstances of islanding, there may be wide variation of load/ generation. • Status of loads to be shed may change. • These may result in jerks or instability after islanding. COMPUTERISED ISLANDING SCHEME(SCADA) • All parameters like generation, connected loads, sheddable loads are constantly monitored. Islanding selection can be optimally changed in real time basis. • Sheddable loads priority may be selected and altered. • In post islanding regime, situations arising out of any reduction in generation can be dynamically controlled by load shedding. Hardwired Vs Computerised Islanding

  13. SINGLE UNIT ISLANDING, ROURKELA G G MSDS-3 FDR-2 MSDS-2 FDR-2 HSL-3 HSL-1 & 2 MSDS-3 132KV MSDS-2 132KV CPP-2 132KV MSDS-2 FDR-1 MSDS-3 FDR-1 AUTO TRF AUTO TRF MSDS-3 33KKV MSDS-2 33KKV The lines from MSDS-3 to CPP-2 and to MSDS-2 can be selected to trip on Single Unit Islanding depending on configuration at MSDS-3. LHF-1 TOWN 5 RM-1 33KV NO NO SEC-3 RM-2 33KV SEC-1 SEC-2 LHF-2 LBSS-1 TOWN 3 & 4 R0 V0 R1 R2 F1-F6 HSM STOP NO CPP-1 SEC-1 33KV CPP-1 SEC-2 33KV CPP-1 SEC-3 33KV NO NO CPP-1 G G G G G

  14. SINGLE UNIT AFTER DOUBLE UNIT ISLANDING, ROURKELA G G MSDS-3 FDR-2 MSDS-2 FDR-2 HSL-3 HSL-1 & 2 MSDS-3 132KV MSDS-2 132KV CPP-2 132KV MSDS-2 FDR-1 MSDS-3 FDR-1 AUTO TRF AUTO TRF The lines from MSDS-3 to CPP-2 and to MSDS-2 can be selected to trip on Single Unit Islanding depending on configuration at MSDS-3. MSDS-2 33KKV MSDS-3 33KKV LHF-1 TOWN 5 RM-1 33KV NO NO SEC-3 RM-2 33KV SEC-1 SEC-2 LHF-2 LBSS-1 TOWN 3 & 4 R0 V0 R1 R2 F1-F6 HSM STOP NO CPP-1 SEC-1 33KV CPP-1 SEC-2 33KV CPP-1 SEC-3 33KV NO NO CPP-1 G G G G G

  15. Statistics of Double Unit Islanding Double Machine Islanding kept defeated since June-2011

  16. Statistics of SU islanding

  17. Double Channel Islanding scheme operates with the philosophy of Single machine islanding. • Both the machines islanded independently with own islanded load. • It was possible after addition of two number of 132Kv lines at our end. • Two number of substation (MSDS#5 & 6) were installed and all 132KV substations were interconnected. • Load arrangement for independent islanding was possible for two channel islanding. • Control Circuit Modification done for tripping of different breakers at various locations via hardware or through FOC. Double Channel Islanding

  18. Directional O/C ( E/F) combined with Under Voltage • Over Current • Directional Forward ( towards line) • Extreme Inverse, 180mA ( Each Feeder), TMS-100ms. • Simple inverse ,150mA, TMS-100ms. • CTR -1000/1 • Under Voltage • 51V ( 80%) Phase- Neutral • Instantaneous Islanding Conditions…

  19. Under Frequency • 47.6 Hz for 200mSec • Rate of change of Frequency • 1 Hz /sec ( +/-) • Inhibit band – 49.5 – 50.5 Hz • Vector shift -7degree. Islanding Conditions…

  20. CHECKS FOR ISLANDING SCHEME • Check the Position of SU Selector Switches of Both units at Islanding Panel of CPP-2 • Always ensure that One Generator, MSDS-3 Fdr-1,MSDS#5 Fdr-1 & Station Transformer be in one 132KV bus at 132KV switchyard of CPP-2 . • Be sure to select Bus Coupler Trip and MSDS#5 Fdr#1 Trip at Islanding Panel at CPP-2 whenever Single Unit Islanding is selected & Both Units are running. • Similarly be sure to Select MSDS-3 FDr-2 trip when Double Channel Islanding is in service. • Always defeat islanding before carrying out any changeover at 132KV switchyard, as there is probability of asynchronous closing of isolators if islanding takes place at the moment of changeover.

  21. DOUBLE CH. BUS ARRANGMENT 220KV Fdr-2 220KV Fdr-1 FDR-1 FDR-1 GEN-2 MSDS-4 FDR-2 FDR-2 AT MSDS-5 CPP-II MSDS-3 FDR-1 STN TX FDR-1 GEN-1 FDR-2 Trips in case of Islanding Channel-1 Islanding Bus Channel-2 Islanding Bus MSDS-6 MSDS-2

  22. LOAD ARRANGMENT FOR DOUBLE CH. ISLANDING Channel-1:- Blast Furnace-5 SMS-2 TOP-2 CCD & Coke Oven Township Feeder-5 CPP-2 Houseload Channel-2:- Hot Strip Mill Plate Mill Pipe Plant Tarkera Pump House SMS-1 BOO Unit

  23. Comparison of Double Unit Vs Double Channel Islanding

  24. 1. Once unit gets islanded signal appears in UCR. 2. Check speed controller is active or pressure controller is active. 3. If the turbine control does not switch over to speed controller then switch off pressure control and turbine control changes over to speed controller. 4. Check the frequency of the machine and boiler conditions like drum level, boiler outlet steam pressure. 5 . Start up vent starts opening with islanding signal if it is selected in remote mode. Open/ close the valve as per boiler conditions. 6. Care is to be taken to control drum level and steam pressure. Open/ close start up vent and if required adjust coal feeding and/ or take oil burner(s) in service to maintain steam pressure above 80 ksc UCR OPERATION DURING ISLANDING

  25. 7. But if after islanding the frequency has stabilized at less than 50 Hz due to load-generation mismatch then efforts should be made to gradually but slowly increase the frequency by increasing coal feeding or by taking oil burners within the capacity of the boiler. 8.PD of RSP to be contacted for clearance to synchronization with Grid. 9. The system frequency should be brought down very slowly and smoothly for matching with Grid frequency for synchronization. 10. After synchronization with the Grid the machine control is to be changed to pressure control again. 11. Adjust the fuel firing and normalize the generation. Put the machines in islanding mode after getting clearance from PD. OPERATION DURING ISLANDING - Contd.

  26. SYNCRONISATION PROCEDURE IN CASE OF DOUBLE CHANNEL ISLANDING

  27. SYNCRONISATION PROCEDURE IN CASE OF DOUBLE CHANNEL ISLANDING

  28. SYNCHRONISATION PROCEDURE AFTER ISLANDING 132KV BUS# 1 BUS# 2 Bus Coupler U-1 Synchronisation through Bus Coupler When Islanding occurs ST TR. MSDS-5 Fdr-2 MSDS-5 Fdr-1 MSDS-3 Fdr-2 MSDS-3 Fdr-1 U-2 Synchronisation through MSDS-3 Fdr-2 Closing of MSDS-5 Fdr-1 G#1 G#2

  29. Post islanding stability of CPP-2 units is not always satisfactory due to generation & load mismatch. • Constraints of Islanding Load • Fluctuating Loads have to be shed during islanded condition • Manual estimation of islanding loads. • Post islanding load management feature (SCADA) is not established. • Failure of islanding due to load-starvation • Severe jerk on the machine due to Generation & islanded load mismatch. Constraints….

  30. Thank You

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