PLANNING & DESIGN

OF SWITCHYARD

PLANNING STRATEGIES & CONSIDERATIONSPLANNING IS ESSENTIAL FOR SUCCESSFUL DESIGN, CONSTRUCTION AND OPERATION OF A SUBSTATIONRELIABILITYFLEXIBILITYMAINTAINABILITYECONOMICAL

BASIC DESIGN PARAMETERSVOLTAGEMVAFAULT CURRENTNUMBER OF BAYSBUS CONFIGURATIONTYPE OF INSTALLATION INDOOR / OUTDOOR / UNDER-GROUNDSTEP-UP / STEP-DOWNAUTOMATION REQUIREMENTS

TYPE OF SWITCHYARDSAIR INSULATED (CONVENTIONAL) GAS INSULATED SWITCHGEAR (GIS)HIGH VOLTAGE POWER ELECTRONIC SUB-STATION (HVDC)FLEXIBLE AC TRANSMISSION SUB-STATION (FACT)

AIR INSULATED SWITCHYARD BUS / SWITCHING CONF. There are 6 types of substation bus / switching arrangements commonly used in AISSingle BusDouble bus single breakerDouble bus double breakerMain and transfer busRing busBreaker and a half

SINGLE BUS ARRANGEMENT

This arrangement involves one main bus with all circuits directly connected to BusReliability Low, Entire substation is lost in case of a fault on the bus-bar or any bus-bar isolator and also in case of maintenance thereofOne of the methods for reducing the number of circuits lost in case of a fault is to sectionalise the bus Additional by-pass isolators are provided to permit a circuit breaker to be taken out for maintenance without switching out the associated feeder.

MAIN BUS & TRANSFEREssentially a single bus-bar arrangement with the difference of by- passing a circuit breaker on-load. Each circuit is connected to the main bus-bar through a circuit breaker and through an isolator to the transfer bus-bar. As in the case of single bus arrangement, this scheme also suffers from the disadvantages that in the event of a fault on the main bus-bar or the associated isolator, there is a complete shutdown of the substation. Widely used in Step-down Sub-station

DOUBLE BUS-BAR SCHEMEDouble bus-bar is provided and each circuit can be connected to either one of these bus-bars through an isolator Bus coupler breaker is also provided so that the circuits can be switched on from one bus to the other on load. Double bus-bar system is very suitable for large generating stations as well as large grid substations

DOUBLE MAIN AND TRANSFER BUS-BAR In this arrangement, the circuit breaker which is to be maintained is transferred to the transfer bus without affecting the other circuits. This scheme has been widely used in 220 kV and 400 kV substations.

RING BUS ARRANGEMENTEach circuit is controlled by two circuit breakers, therefore, any one circuit breaker can be taken out for maintenance without affecting the security of supply.A circuit fault also is cleared by opening of two adjacent breakers.

BREAKER AND A HALF ARRANGEMENT In this arrangement three circuit breakers are used for controlling two circuits Normally, both the bus-bars are in service.A fault on any bus is cleared by the opening of the associated circuit breakers without affecting the continuity of supply. Similarly, any circuit breaker can be taken out for maintenance without causing any interruption. All load transfer is done by the breakers, therefore, the operation is simple.

Comparison of Configurations Configuration Reliability Cost Available AreaSingle bus Least reliable - single failure can cause complete outage Least cost (1.0) fewer components Least area fewer components

Main bus and transfer Least reliable same as single bus, but flexibility in operating and maintenance with transfer bus. Moderate cost (1.76) fewer components Low area requirement - fewer components

Double bus, single breaker Moderately reliable depends on arrangement of components and bus Moderate cost (1.78) more components. Moderate area - more componentsRing bus High reliability single failure isolates single component Moderate cost (1.56) more components. Moderate area increase with number of circuitsBreaker-and-a-half Highly reliable single circuit failure isolates single circuit, bus failures do not affect circuits. Moderate cost (1.57) breaker and a half for each circuit Greater area - more components per circuit

GAS INSULATED SWITCHGEARGIS uses superior dielectric gas SF6 for phase - phase & phase - ground insulationSF6 has 2-3 times the insulating ability of air at same pressureSF6 is 100 times better than air for interrupting arcsHV conductors, devices are inside grounded metal enclosure filled with SF6GIS can be smaller to AIS by a factor of 10

No deterioration of active parts from air, moisture, contamination, etcGIS is more reliable, less maintenance than AISSF6 is used in GIS at 4 to 6 Atm.

CONSTRUCTION GIS is assembly of standard equipment modules to match SLDModules are joined bolted flanges with O ring seals for enclosures and sliding plug -in contacts for conductor. Internal parts are supported by cast epoxy insulators.Up to 170kV, all 3 phases are often in one enclosure, above that 3-ph enclosure becomes very large, so 1-ph design is usedEstimated Service life 30 years

CONTROL & MONITORINGLocal control cabinet (LCC) is provided for each bay Insulating & Interrupting capability of SF6 gas depends on minimum design density, so Gas Monitoring System provided.Gas compartments and zonesMost GIS designs have double bus, single breaker arrangement giving good reliability , simple operation, easy protective relaying & excellent economy

INSTALLATION GIS is mostly installed on a monolithic concrete pad or floor of buildingRigidly attached by bolting/welding GIS support frames to embedded steel plates

ENVIRONMENTAL FACTORS IN USE OF SF6SF6 is a strong greenhouse gas which could contribute to global warmingHas long life in atmosphere (half life 3200 yrs), so effect of SF6 is cumulative & permanentStandard requires GIS leakage less than 1% per year

HVDC Sub-stationsHVDC converters convert AC power to DC power and vice versa.They terminate DC transmission lines or form back to back asynchronous AC system coupling

BASIC SWITCHYARD EQUIPMENTBAY COMPONENTSCONTROL ROOM EQUIPMENT STATION EQUIPMENT

SUB-STATION STANDARD VOLTAGES1.1kV, 3.3kV, 6.6kV, 11kV, 22kV, 33kV, 66kV, 132kV, 220kV, 400kV, 765Kv

BAY COMPONENTSTRANSFORMERSCIRCUIT BREAKERSISOLATORSINSTRUMENT TRANSFORMERS ( CT / PT )LIGHTNING ARRESTORSINSULATORSCONDUCTORSCARRIER COMPONENTS (WAVE TRAP, CVT)STRUCTURES

CONTROL ROOM EQUIPMENTINDOOR HV SWITCHGEARCONTROL & RELAY PANELS110V / 220V DC SUPPLY SYSTEM (BATTERIES, CHARGERS & DCDB)RTCC PANELSACDBPLCC EQUIPMENT

STATION EQUIPMENTSTATION TRANSFORMERSREACTIVE COMPENSATION EQUIPMENTCONTROL PANELS

IMPORTANT FACILITIES / SYSTEMSOIL HANDLING EQUIPMENT: FOR TREATMENT OF INSULATING OIL IN TRANSFORMERS, PORTABLE OIL FILTERATION SET, DIELECTRIC STRENGTHCOMPRESSED AIR SYSTEM: FOR OPERATION OF AIR BLAST CB, PNEUMATICALLY OPERATED CBS AND ISOLATORS

FIRE FIGHTING SYSTEMEVERY HAZARD HAS FOLLOWING ATTRIBUTESProbability that a fire will occur during a specified time intervalA magnitude of possible fireConsequences of the potential loss

FIRE PROTECTION MEASURESPASSIVE MEASURESPassive measures are measures that controls the spread of fireIt confines fire to limited areaFire separators, Equipment spacing, use of non-combustible construction material, provision of gravels around oil filled equipment

ACTIVE MEASURESAutomatic fire protection measures designed to extinguish or control fire at early stageAutomatic separation system consists of extinguishing agent supply, control valves, delivery system, fire detection and control equipmentMANUAL MEASURESManual measures include manually operated fire extinguisher, fire hydrant etc by staff

ILLUMINATION SYSTEM, Objective of Illumination System

Quality lighting is an important factor that ensures efficiency productivity and employees comfort at work place. All vision requires light and the quality, direction and diffusion of the light are all important in determining how well one sees.

Illumination design should be based on the achievement of desired illumination level concept with minimum glare. Also, the concept of aesthetics in lighting should also be taken into consideration. Illumination should be uniform and free from dark patches. Illumination design must be energy efficient and reasonably decorative.

SUBSTATION GROUNDINGThe Substation Grounding System is an Essential part of the overall Electrical System. Proper Grounding is Essential for following two reasonsIt provides a means for dissipating Electric Current into Earth without exceeding the operating limits of the Equipment.Provides a Safe Environment to protect personnel in the vicinity of grounded facilities from the danger Electric Shock under fault conditionIMPEDENCE TO GROUND SHOULD BE AS LOW AS POSSIBLEWITHIN 1 OHM FOR LARGE SUBSTATION & 5 OHM FOR SMALL SUBSTATIONS

CABLING : TRENCHES AND CABLE DUCTS POWER CABLES IN FIRST RACK, LOWER RACK CONTAIN CONTROL CABLES, UN-ARMOURED CABLES IN BOTTOM MOST RACK

CRANE FACILITY: LARGE S/S HAVE REPAIR BAY ALONGWITH CRANEPROVISION OF RAIL TRACK FOR MOVEMENT OF T/F TO REPAIR BAY

SAFETY CLEARANCES Highest System Voltage BIL Minimum Clearance Sectional Clearance Ph Earth Ph - Ph36 170 32 40 30072.5 325 63 75 350

SWITCHYARD AUTOMATION Sub-station integration & automation can be broken down into 3 levels or layers Level 1 Field Devices Level 2 Substation Data ConcentratorLevel 3 SCADA System

COMMUNITY CONCERNSNOISE: INDUSTRIAL ZONE