SUBSTATION & SWITCHYARD STRUCTURE’S

HOW HOW ELECTRICITY ELECTRICITY IS IS DELIVERED DELIVERED TO TO YOUR YOUR HOME HOME GENERATION

TRANSMISSION 230kV DELIVERY POINT SUBSTATION

SUB-TRANSMISSION DISTRIBUTION

DEFINATION’S SUBSTATION:AN ASSEMBLAGE OF EQUIPMENT THROUGH WHICH ELECTRICAL ENERGY IN BULK IS PASSED FOR THE PURPOSE OF SWITCHING OR MODIFYING ITS CHARACTERISTICS

SWITCHYARD:AN ASSEMBLAGE OF SWITCHES, POWER CIRCUIT BREAKERS, BUSES AND AUXILIARY EQUIPMENT THAT IS USED TO COLLECT POWER FROM THE GENERATORS OF A POWER PLANT AND DISTRIBUTE IT TO THE TRANSMISSION LINES AT A LOAD POINT. AS FAR AS STRUCTURES ARE CONCERNED, THE TERMS SUBSTAION AND SWITCHYARD WILL BE USED INTERCHANGEABLY.

Switchyard Type • Conventional Air Insulated Type. • Gas Insulated type. • Outdoor Gas Insulated type.

Switchyard Type AIR INSULATED SUBSTATION :• AN AIR INSULATED SUBSTATION OR SWITCHYARD HAS THE INSULATING MEDIUM OF AIR

GAS INSULATED SUBSTATION:• SULFUR HEXAFLUORIDE (SF6) GAS INSULATED SUBSTATION

SUBSTATION & SWITCHYARD STRUCTURE’S • TO SUPPORT ELECTRICAL EQUIPMENTS SUCH AS • CABLE BUS, • RIGID BUS, • STRAIN BUS CONDUCTORS; • SWITCHES; • SURGE ARRESTERS; • INSULATORS

SUBSTATION & SWITCHYARD STRUCTURE’S • COMMON MATERIALS USED ARE; » CONCRETE » STEEL » ALUMINUM » WOOD

SUBSTATION & SWITCHYARD STRUCTURE’S • • • • •

LATTICED ANGLES ( CHORDS & TRUSSES) WIDE FLANGES TUBES (ROUND, SQUARE & RECTANGULAR) PIPES POLYGONAL TUBES (STRAIGHT OR TAPERED)

GANTRY BEAM & TOWER

EQUIPMENT SUPPORTING BOX / TUBE TYPE STRUCTURE

BUSWORK SYSTEM • RIGID BUS SYSTEM :An Extruded Metallic Conductor. The conductor material is usually an aluminum alloy / also be Copper.

• STRAIN BUS SYSTEM:A stranded wire conductor installed under tension.

• CABLE BUS SYSTEM:Low-tension, stranded conductors supported on station post insulators.

ELECTRICAL CLEARANCE ELECTRICAL CLEARANCES PROVIDE THE PHYSICAL SEPRATION NEEDED FOR PHASE-TO-PHASE, PHASE-TO-STRUCTURE AND PHASE-TO-GROUND AIR GAPS TO PROVIDE SAFE WORKING AREAS AND TO PREVENT FLASHOVERS.

SHORT-CIRCUIT FORCE SHORT-CIRCUIT FORCES ARE STRUCTURE LOADS THAT ARE CAUSED BY SHORTCIRCUIT CURRENTS. SHORT-CIRCUIT CURRENTS ARE THE RESULT OF ELECTRICAL FAULTS CAUSED BY EQUIPMENT OR MATERIAL FAILURE, LIGHTNING OR OTHER WEATHER-RELATED CAUSES, AND ACCIDENTS

ELECTRICAL EQUIPMENT AND SUPPORTS POWER TRANSFORMER & AUTOTRANSFORMER – SUPPORT :- THE POWER TRANSFORMER AND AUTOTRANSFORMER ARE SUPPORTED DIRECTLY ON A FOUNDATION. SHUNT REACTOR – SUPPORT :- THE SHUNT REACTOR IS SUPPORTED DIRECTLY ON A FOUNDATION

GENERAL DEFINITION:

TRANSFORMER IS AN ELECTRICAL DEVICE THAT TRANSFERS ENERGY FROM ONE CIRCUIT TO ANOTHER BY MAGNETIC COUPLING WITH NO MOVING PARTS TRANSFORMERS ARE USED TO CONVERT BETWEEN HIGH AND LOW VOLTAGES, TO CHANGE IMPEDANCE, AND TO PROVIDE ELECTRICAL ISOLATION BETWEEN CIRCUITS

TRANSFORMER FOUNDATION

FIRE PROTECTION WALL

ELECTRICAL EQUIPMENT AND SUPPORTS CURRENT-LIMITING INDUCTOR OR AIR CORE REACTOR – SUPPORT :- THE SUPPORTING PEDESTALS ARE BOLTED DIRECTLY TO THE FOUNDATION. LINE TRAP / WAVE TRAP – SUPPORT :- THE LINE TRAP CAN BE MOUNTED VERTICALLY OR HORIZONTALLY ON EITHER A SINGLE OR MULTIPLE PEDESTAL SUPPORT STRUCTURE. THE LINE TRAP CAN ALSO BE SUSPENSION MOUNTED FROM A STRUCTURE.

ELECTRICAL EQUIPMENT AND SUPPORTS COUPLING CAPACITOR VOLTAGE TRANSFORMER – SUPPORT :- THE CCVT IS USUALLY SUPPORTED ON A SINGLE PEDESTAL. DISCONNECT SWITCH (VERTICAL BREAK, CENTER BREAK, SINGLE SIDE BREAK OR DOUBLE SIDE BREAK) – SUPPORT :- THE DISCONNECT SWITCH IS SUPPORTED ON A COMMON STRUCTURE FOR VOLTAGE LESS THAN 500kV.

DISCONNECTOR SUPPORTING STRUCTURE

ELECTRICAL EQUIPMENT AND SUPPORTS LOAD INTERRUPTER SWITCH / CIRCUIT SWITCHER / LINE CIRCUIT BREAKER – SUPPORT :- THE CIRCUIT SWITCHER SUPPORTED ON A COMMON STRUCTURE FOR VOLTAGE LESS THAN 500kV.(DYNAMIC LOAD ON OPENING OR CLOSING . CIRCUIT BREAKER – SUPPORT :- CIRCUIT BREAKERS, INCLUDING THEIR SUPPOTING FRAMES, ARE ANCHORED DIRECTLY ON THE FOUNDATION.

ELECTRICAL EQUIPMENT AND SUPPORTS POTENTIAL AND CURRENT TRANSFORMERS – SUPPORT :- PTs & CTs ARE USUALLY SUPPORTED ON A SINGLE PEDESTAL OR LATTICE STAND STRUCTURE. CAPACITOR BANK – SUPPORT :- USUALLY SUPPORTED ON A SINGLE PEDESTAL OR LATTICE STAND STRUCTURE.OUTER PERIPHERY OF THE BANK SHOULD BE ENCLOSED INSIDE A FENCE FOR PROTECTION OF PERSONNEL; IF ELECTRICAL CLEARANCE IS NOT PROVIDED.

EQUIPMENT SUPPORTING LATTICE TYPE STRUCTURE

ELECTRICAL EQUIPMENT AND SUPPORTS SHUNT CAPACITOR – SUPPORT :- THE SUPPORT IS PROVIDED BY A METAL PLATFORM.THE PLATFORM MUST BE MOUNTED ON INSULATORS THAT ARE BOLTED TO THE FOUNDATION. SURGE ARRESTER – SUPPORT :- SURGE ARRESTER CAN BE SUPPORTED ON A SINGLE PEDESTAL OR LATTICE STAND STRUCTURE OR DIRECTLY MOUNTED ON TRANSFORMER.

EQUIPMENT SUPPORTING LATTICE TYPE STRUCTURE

ELECTRICAL EQUIPMENT AND SUPPORTS NEUTRAL GROUNDING RESISTOR – SUPPORT :- RESISTORS ARE SOMETIMES MOUNTED ON SEPARATE STRUCTURES BUT ARE USUALLY MOUNTED ON THE TRANSFORMER TANK.

CABLE TERMINATOR / POTHEAD – SUPPORT :- SUPPORT STRUCTURES OF CABLES TERMINATORS OF INDIVIDUAL PHASES CAN BE COLUMNS RESTING ON A FOUNDATION. A STRUCTURE SUPPORTING THREE PHASES CAN ALSO BE USED.

ELECTRICAL EQUIPMENT AND SUPPORTS INSULATOR (PORCELAIN,GLASS & COMPOSITE MATERIALS ARE USED FOR SUSPENSION & POST INSULATORS) – SUPPORT :INSULATORS CAN BE SUPPORTED ON A SINGLE-PHASE OR THREE PHASE STRUCTURE.

LOADING CRITERIA FOR SUBSTATION STRUCTURES • DEAD LOADS • EQUIPMENT OPERATING LOADS • TERMINAL CONNECTION LOADS FOR ELECTRICAL EQUIPMENT • WIRE TENSION LOADS • WIND LOADS • COMBINED ICE AND WIND LOADS • EARTHQUAKE LOADS • SHORT CIRCUIT LOADS • CONSTRUCTION & MAINTENANCE LOADS

SAG DUE TO CONDUCTOR Lc T

fs

9,81.mi

fs = w.Lc2 8.T fs = maximum conductor sag (m) wi = weight of conductor (kg/m) Lc = conductor span length (m) T

= tension per conductor (kg)

Construction and commissioning of sub station Construction and commissioning of sub station is a subject describing the actual execution details.

• These sub station land is initially selected and the final level to be kept for construction of substation is decided on the basis of contour survey of the sub station land. So that the land development is carried out economically. • The land development is then carried out accordingly • The sub station equipments and gantry foundations are then cast. • The control room is also constructed as per drawing.

SITE WORK FOR EQUIPMENT FOUNDATION

PEDESTAL WITH ANCHOR BOLT

CONNECTION BETWEEN STRUCTURE & PEDESTAL

Construction and commissioning of sub station • The construction of sub station includes some of following activities. • The arrangement of 3 phase supply up to 200 KVA • Erection of sub station columns and beams. • Stringing of various buses in the sub station. • Erection of equipment structures and equipments • Erection of equipment in control room • The earthing mesh and earthing electrodes work • The equipments are connected to each other, to bus, etc. by carrying out jumpering work as specified in the lay out . • The clamps and connectors are used while jumpering

INDOOR CABLE TRENCH

INSIDE CABLE TRENCH WITH PERFORATED TRAYS

CABLE ENTRY TO INDOOR TRENCH

Construction and commissioning of sub station • Commissioning of breakers, isolator alignments are carried out. • Battery charging, charger commissioning making DC supply available for testing purposes. • Commissioning of C & R panels relays etc. • The transformer erection filtration and testing Lightening in control room and switch yard. • Metal spreading • Commissioning after proper testing is carried out.

OUTSIDE CABLE TRENCH

CABLE TRENCH WITH COVER

CHAIN LINK FENCE

COMPLETED SUBSTATION VIEW

-: Design Example :Design a Single Phase Bus Support for a Substation in Nagpur, given the following information, – – – – – – – – – – –

Height of Bus Centerline above foundation = 5.5 m Schedule 40 aluminum bus = 100 mm (mass = 5.51 kg/m) Maximum Short Circuit force = 550 N/m Short Circuit reduction factor = 0.66 Bus Support Spacing = 6.0 m Insulator Height (hi) = 2.0 m Insulator Diameter (Di) = 0.28 m Insulator Weight (Wi) = 140 kg Basic Wind Speed (Vb) = 33 m/sec (Zone = 1) Reliability level = 2 (Return period of design loads 150 yrs) Terrain Category = 2

LATTICE STRUCTURE DETAILS:Main Leg = ISA65x65x6 @ 5.8kg/m Bracing, Inclined = ISA45x45x5 @ 3.4kg/m Plan = ISA45x45x5 @ 3.4kg/m Part of Structure = 04 Each Part Length = 850 mm Inclined Length = 931 mm Back to Back of Str. = 380 mm

• Short-Circuit Loading:• • • •

Fsc = 6.0 m x 0.66 x 550 N/m Fsc = 2178 N Mom @ Base = 5.5 m x 2178 N Mom @ Base = 11979 N.m

Wind Loading :• • • • • • • • • • •

IS 802 (Part 1 / Sec 1) :1995, Basic wind speed Vb = 33 m/sec Metrological Reference wind speed VR is, VR = Vb / K0 , where K0 = 1.375 (cl. 8.2 pg 3) VR = 33 / 1.375 = 24 m/sec Design wind speed Vd = VR x K1 x K2, Where K1 = Risk Coeff. (cl. 8.3.1) K1 = 1.08 (Table 2) Where K2 = Terrain roughness coeff. (cl.8.3.2) K2 = 1.00 (Table 3) Design wind speed Vd = 24 x 1.08 x 1.0 = 25.92 m/sec

Wind Loading :Design wind pressure Pd = 0.6 Vd2 (cl. 8.4) Pd = 0.6 x 25.92 x 25.92 = 403.11 N/sq.m ============================================== Wind load on Conductor Fwc (cl 9.2) Fwc = Pd x Cdc x L x d x Gc, Where, Cdc = Drag coeff, taken as 1.0 for conductor L = wind span, being sum of half the span on either side of supporting point in meters d = diameter of cable / tube Gc = gust response factor (Table 7) = 1.83 Fwc = 403.11 x 1.0 x 6 x 0.1 x 1.83 Fwc = 442.615 N (737.7 N/sq.m)

Wind Loading :• • • • •

Wind load on Insulator Strings (Fwi) :- (cl 9.3) Fwi = Cdi x Pd x Ai x Gi Where, Cdi = drag coeff to be taken as 1.2 Ai = 50 % of the area of insulator string projected on a plane which is parallel to the longitudinal axis of the string • Gi = Gust response factor (Table 6) = 1.92 • Fwi = 1.2 x 403.11 x 0.5 x 2 x 0.28 x 1.92 • Fwi = 260.1 N (928.8 N/sq.m)

Wind Loading :• Wind on structure Fwt = Pd x Cdt x Ae x Gt • Where, • Cdt = Drag coeff for panel under consideration against which the wind is blowing . Values of Cdt for different solidity ratios are given in Table 5. • Solidity ratio (Φ) is equal to the effective area of a frame normal to the wind direction divided by the area enclosed by the boundary of the frame normal to the wind direction. • Solidity ratio (Φ) = Aeff / Agross • Ae = Total net surface area of the legs, bracing, cross arms and secondary members of the panel projected normal to the face in m2 • Gt = Gust response factor, Table 6

Member

Nos

Length (m)

Width (m)

Area (sq.m)

1

2

3.4

0.065

0.442

2,4,6 & 8

4

0.931

0.045

0.168

3,5,7 & 9

4

0.38

0.045

0.068

Total Net Surface Area Ae = Gross Surface Area Ag = 3.4 m x 0.38 m

Solidity Ratio (Φ) = Ae / Ag Φ = 0.678 / 1.292 = 0.525 Drag Coeff Cdt = 2.0 (Table 5) Gt = 1.92 (Table 6) Fwt = 403.11 x 2 x 0.678 x 1.92 Fwt = 1049.50 N (1547.92 N/sq.m)

0.678 1.292

Wind load summary :Description

Force (N)

Lever Arm (m)

Moment @ Base (N.m)

Wind on Bus (Fwc)

442.62

5.5

2434.41

Wind on Insulator (Fwi)

260.1

4.4

1144.44

Wind on Structure (Fwt)

1049.5

1.7

1784.15

Totals

1752.22

5363.00

Earthquake Loading:IS 1893 (Part 1) : 2002 Design Horizontal Acceleration Coeff (Ah), Ah = Z I / 2R * Sa/g Z = Zone factor = Zone II = 0.10 (Table 2) I = Importance factor = 1.5 (Table 6) R = Response reduction factor = 4 (Table 7) Sa/g = Avg. response acceleration coeff for rock or soil sites as given by fig 2 & Table 3 based on appropriate natural periods and damping of the structure. Fundamental Natural Period Ta = 0.085 h0.75 Ta = 0.085 x 3.40.75 = 0.213 sec Sa/g = 2.5 Hence, Ah = 0.10 x 1.5 x 2.5 / 2 x 4 = 0.047

Earthquake Loading:IS 1893 (Part 1) : 2002 Design Seismic Base Shear VB = Ah W W = Seismic weight of the structure Description EQ on Bus EQ on Insulator EQ on Structure

Totals

Force (N)

L.A (m)

6m x 5.51 kg/m x 9.81 5.5 x 0.047 = 15.24 140kg x 9.81 x 0.047 = 4.4 64.55 180kg x 9.81 x 0.047 = 1.7 82.99 162.78

Moment @ Base (N.m) 83.82 284.02 141.08 508.92

Results:• SCF + WL :Force = 2178 + 1752.22 = 3930.22 N Moment @ Base = 11979 + 5363 = 17342 N • SCF + EQ :Force = 2178 + 162.78 = 2340.78 N Moment @ Base = 11979 + 508.92 = 12487.92 N The combined loading of wind and short-circuit forces produce the greatest forces and moment at the base design for this condition. Therefore seismic forces are not critical for this structure.

Forces in the Member:Moment at the base causes tension and compression in the chord angles. C = Tensile or Compressive force C = 17342 N.m / [ 2(0.380 – 2 x 0.0181)] C = 25221.1 N per leg P = Applied load P + C = [140 x 9.81 + 6 x 54] / 4 + 25221.1 P + C = 25645.45 N per leg Forces in bracing member shall be 25 % of the leg member.

Thank you..