SUBSTATION OVERVIEW -B. Prasad Chartered Engineer [email protected] TYPE OF SUBSTATION Classification based on voltage levels, e.g. : A.C. Substation : EHV, HV, MV, LV; HVDC Substation. Classification based on Outdoor or Indoor : Outdoor substation is under open sky. Indoor substation is inside a building. Classification based on configuration, e.g. : Conventional air insulated outdoor substation or SF6 Gas Insulated Substation (GIS) Composite substations having combination of the above two Classification based on application Step Up Substation : Associated with generating station as the generating voltage is low. Primary Grid Substation : Created at suitable load centre along Primary transmission lines. Secondary Substation : Along Secondary Transmission Line. Distribution Substation : Created where the transmission line voltage is Step Down to supply voltage. Bulk supply and industrial substation : Similar to distribution sub-station but created separately for each consumer. Mining Substation precaution for safety needed in the operation of electric supply. Mobile Substation: Temporary requirement PROMARY/SECONDARY/DISTRIBUTION SUBSTATION Primary Substations receive power from EHV lines at 400KV, 220KV, 132KV and transform the voltage to 66KV, 33KV or 22KV (22KV is uncommon) to suit the local requirements in respect of both load and distance of ultimate consumers. These are also referred to ‘EHV’ Substations. Secondary Substations receive power at 66/33KV which is stepped down usually to 11KV. Distribution Substations receive power at 11KV, 6.6 KV and step down to a volt suitable for LV distribution purposes, normally at 415 volts SUBSTATION PARTSAND EQUIPMENTS Outdoor Switchyard Incoming Lines Outgoing Lines Bus bar Transformers Bus post insulator & string insulators Substation Equipment such as Circuitbeakers, Isolators, Earthing Switches, Surge Arresters, CTs, VTs, Neutral Grounding equipment. SUBSTATION PARTS ….CONTD… Station Earthing system comprising ground mat, risers, auxiliary mat, earthing strips, earthing spikes & earth electrodes. Overhead earth wire shielding against lightening strokes. Galvanised steel structures for towers, gantries, equipment supports. PLCC equipment including line trap, tuning unit, coupling capacitor, etc. Power cables Control cables for protection and control Roads, Railway track, cable trenches Station illumination system SINGLE LINE DIAGRAM Transformer part Batteries for industrial or substation applications Vented / Flooded Lead Acid batteries Sealed maintenance free batteries/Valve Regulated Lead Acid Nickel Cadmium (Ni-cd) batteries Battery AH LOAD CURRENT 10A for 3 hrs. Cell voltage =12V DC CALCULATION , AH=10X3 CAPACITY =30/ (0.75X0.8)=50AH Discharge factor=0.7 Ageing factor =0.8 Drain capacity =C10 CHARGER Type of charger Input voltage output voltage Application Protection Metering Indication Alarms Auto operation Clearance around an Indoor electrical panel (NES 110.26) Description of Clearance Distance (min) Left to Right the minimum clearance 0.9 Meter (3 Ft) Distance between Panel and wall 1.0 Meter Distance between Panel and Ceiling 0.9 Meter Clear Height in front of Panel >480V 2.0 Meter Clear Height in front of Panel <480V 0.9 Meter (3 Ft) Clearance When Facing Other Electrical Panels <480V 0.9 Meter (3 Ft) The width of the working space in front of The width of Panel or 0.762 Meter which is the Panel Greater. Headroom of working spaces for panel boards (Up to 200Amp) Up to 2 Meter Clearance between Bare Metal Busbar in Panel (NES 408.5) Voltage Opposite Opposite Polarity Polarity Live Parts to Mounted on Where Held Ground Same Free in Air Surface Up to 125 V 19.1 mm 12.7 mm 12.7 mm 125 V to 250 V 31.8 mm 19.1 mm 12.7 mm 250 V to 600 V 50.8 mm 25.4 mm 25.4 mm Clearance of Outdoor electrical panel to Fence/Wall (NES 110.31) Voltage Distance (min) 600 V to 13.8 KV 3.05 Meter 13.8 KV to 230 KV 4.57 Meter Above 230 KV 5.49 Meter GROUND CLEARANCE VOLTAGE LEVEL MINIMUM GROUND CLEARANCE less than 66kV 6.1m 66kV - 110kV 6.4m 110kV - 165kV 6.7m greater than 165kV 7.0m Earth resistance value Major power station= 0.5 Ohm. Major Sub-stations= 1.0 Ohm Minor Sub-station = 2 Ohm Neutral Bushing. =2 Ohm Service connection = 4 Ohm Medium Voltage Network =2 Ohm L.T.Lightening Arrestor= 4 Ohm L.T.Pole= 5 Ohm Measurement of Earth Resistance (Three point method) Size of earth wire for motor Sr. Capacity Size of earth wire Size Of Earth Electrode Cu Cu GI GI 1 01- 10 HP 8 SWG 8 SWG 60cmX60cmX3.18 60cmX60c mm mX6.35mm 2 10 – 15 HP 8 SWG 6 SWG 60cmX60cmX3.18 60cmX60c mm mX6.35mm 3 15 – 30 HP 6 SWG 4SWG 60cmX60cmX3.18 90cmX90c mm mX6.35mm 4 30 – 50 HP 4SWG 25mmX3 mm 90cmX90cmX6.35 90cmX90c mm mX6.35mm IR Value of Submersible Motor IR Value of Submersible Motor Motor Out off Well (Without Cable) IR Value New Motor 20 MΩ A used motor which can be reinstalled 10 MΩ Motor Installed in Well (With Cable) New Motor 2 MΩ A used motor which can be reinstalled 0.5 MΩ IR Value of Transformers: Voltage Test Voltage (DC) LV side Test Voltage Min IR (DC) HV side Value 415V 500V 2.5KV 100MΩ Up to 6.6KV 500V 2.5KV 200MΩ 6.6KV to 11KV 500V 2.5KV 400MΩ 11KV to 33KV 1000V 5KV 500MΩ 33KV to 66KV 1000V 5KV 600MΩ 66KV to 132KV 1000V 5KV 600MΩ 132KV to 220KV 1000V 5KV 650MΩ Standard voltage Type Voltage EXTRA LOW VOLTAGE Up to 50V AC/DC LOW VOLTAGE 50-1000V AC/DC MEDIUM VOLTAGE ABOVE 1000V AC/DC UPTO 6.6KV AC HIGH VOLTAGE ABOVE 6.6KV AC TO 33 KV AC EXTRA HIGH VOLTAGE ABOVE 33KV AC TO 400 KV AC ULTRA HIGH VOLTAGE ABOVE 400 KV AC TO 765 KV AC Cable end termination Breaker ACB/VCB/SF6/OCB EARTHING The following steps, when put into practice, will ensure a re lia ble , s a fe and tro uble -fre e s ubs ta tio n g ro und ing s y s te m : Size conductors for anticipated faults Use the right connections Ground rod selection Soil preparation Grounding using building foundations Grounding the substation fence Special attention to operating points Surge arrestors must be grounded properly Grounding of cable trays Temporary grounding of normally energized parts Earthing .....contd Cabling Depth of the trench 7 5 0 m m fo r c a ble s up to 1 . 1 KV Depth of the trench 1 2 0 0 m m fo r c a ble s up to 1 . 1 KV Sa nd - covered with 150 mm Width of the trench 350 mm minimum Loop –approximate -3 Cable laying Laying direct in ground In pipes, Closed or Open ducts, Cable trays and On surface of wall BUILDING Administrative building Conference room etc. Battery Room Operator room Check and change room Adjacent maintenance room ECC room Switchgear and Control Panel Building Low voltage AC. Switchgear High voltage AC. Switchgear Control Panels, Protection Panels Capacitor panel room Mechanical, Electrical and Other Auxiliaries Fire fighting system D.G. Set Oil purification system ACT FAST AND INITIATE FIRST बड़ा सोचो तेजी से सोचो व सबसे पहले सोचो िवचारो पर िकसी का एकािधकार नही होता. ----धीरभाई अमबानी THANK YOU
