substation grounding

Download Substation Grounding

Post on 30-Aug-2014

126 views

Category:

Documents

8 download

Embed Size (px)

TRANSCRIPT

Substation Grounding- Sahadeo Latchmepersad, T&TEC 1 T&T SubsectionLocal IAS Chapter GROUNDING-DESIGN AND CONSTRUCTIONSaturday 12thNovember 2005 Presented by Eng. Sahadeo Latchmepersad, MIEEE, MAPETT, R. Eng.Substation Grounding- Sahadeo Latchmepersad, T&TEC 2ACKNOWLEDGEMENTThe Trinidad and Tobago Electricity Commission Substation Grounding- Sahadeo Latchmepersad, T&TEC 3Range of Large Industrial Customers Rate D3- 4-25 MVA at 33, 66 or 132 kV Rate E > 25 MVA at 66 or 132kV Substation Grounding- Sahadeo Latchmepersad, T&TEC 4Substation Grounding- Sahadeo Latchmepersad, T&TEC 5Transmission B.C/Union Estate SchematicSubstation Grounding- Sahadeo Latchmepersad, T&TEC 6Objectives of Grounding To provide means to carry electric currents to earth under normal and fault conductors without exceeding any operating and equipment limits or adversely affecting continuity of service.Substation Grounding- Sahadeo Latchmepersad, T&TEC 7Objectives of Grounding- To ensure that a person in the vicinity of grounded facilities is not exposed to the danger of critical electric shock.Substation Grounding- Sahadeo Latchmepersad, T&TEC 8Basic Shock SituationsSubstation Grounding- Sahadeo Latchmepersad, T&TEC 9BRIGHTON 66kV SUBSTATIONSubstation Grounding- Sahadeo Latchmepersad, T&TEC 10Ventricular Fibrillation The most dangerous consequence of electric current passing through the vital parts of a human body is a heart condition ventricular fibrillation immediate arrest of blood circulation.Substation Grounding- Sahadeo Latchmepersad, T&TEC 11Design AlgorithmSubstation Grounding- Sahadeo Latchmepersad, T&TEC 12Measuring Soil Resistivity Procedure depends on the instrumentSubstation Grounding- Sahadeo Latchmepersad, T&TEC 13Substation Grounding- Sahadeo Latchmepersad, T&TEC 14Soil Resistivity Calculation = 2 x Pi x a x RWhere R is Maximum measured ValueSubstation Grounding- Sahadeo Latchmepersad, T&TEC 15Tolerable Step Voltage Step Voltage Limit 50 kgE Step 50= (1000 + 6 Cs s) 0.116tsE Step 70= (1000 + 6 Cs s) 0.157tsSubstation Grounding- Sahadeo Latchmepersad, T&TEC 16Tolerable Touch Voltage Limit E touch50= (1000 + 1.5 Cs s) 0.116ts E touch70= (1000 + 1.5 Cs s) 0.157tsSubstation Grounding- Sahadeo Latchmepersad, T&TEC 17Constants Cs= 1 [0.09 (1 - / s)][2 hs+ 0.09] = soil resitivity s= surface layer resistivity Ts= duration of shock current in seconds including clearance time of circuit breaker plus relaySubstation Grounding- Sahadeo Latchmepersad, T&TEC 18Conductor Sizing I = Amm2 [TCAP.10-4] Ln Ko+ Tm[tc r r] Ko+ TaSubstation Grounding- Sahadeo Latchmepersad, T&TEC 19Grid Resistanceburial of depth the is h conductor of length total the is/ 20 111201 1TTgL y resistivit soil the is Where A h ALR ((

|.|

\|++ + =Substation Grounding- Sahadeo Latchmepersad, T&TEC 20Substation Grounding- Sahadeo Latchmepersad, T&TEC 21Calculated Step Voltage Es= Ks Ki IGLs Ls= 0.75Lc+ 0.85 LRSubstation Grounding- Sahadeo Latchmepersad, T&TEC 22Calculated Mesh Voltage Em= KmKiIGWhereLM Lm= Lc+ 1.55 +1.22 Lr LRLX2 + Ly2 LR= total length of ground rods Lc= length of conductor Substation Grounding- Sahadeo Latchmepersad, T&TEC 23Earthing Designs Nitrogen 2000 66kV SubstationSubstation Grounding- Sahadeo Latchmepersad, T&TEC 24Output file Nitrogen 2000 substationSubstation Grounding- Sahadeo Latchmepersad, T&TEC 25Exothermic Joints Step 1Position clean, dry cables in mold and close clamp. Substation Grounding- Sahadeo Latchmepersad, T&TEC 26Insert disk, insert pour weld metal and starter material into crucible, and ignite to form the weld.Substation Grounding- Sahadeo Latchmepersad, T&TEC 27Remove finished connection. Clean mold Substation Grounding- Sahadeo Latchmepersad, T&TEC 28FENCE EARTHING1. Inclusion of the fence within the ground grid area. Under this philosophy, the perimeter conductor of the grid will parallel the fence at a short distance of 1.0m outside. The crushed rock covering will also be required outside the fence.Substation Grounding- Sahadeo Latchmepersad, T&TEC 29FENCE EARTHING2. Placement of the fence outside the ground grid area with close electric coupling between fence and adjacent earth along its length, but with no electrical tie between the fence and the main station grid Substation Grounding- Sahadeo Latchmepersad, T&TEC 30ANSI STANDARD 80-2000 Date: November 11, 2005Date:Line-to-line Voltage V 66000 Volts Touch voltage limit E touch 70 1792 VoltsMaximum fault curent HV side 20000 Amps Step voltage limit E step 70 5678 VoltsMaximum Fault Current LV side 20000 AmpsSoil resistivity 15 m Touch voltage limit E touch 50 1324 VoltsSubstation Length L 34 metre Step voltage limit E step 50 4195 VoltsSubstation Width W 30 metreSpacing D 4 metre GPR = 4944 VoltsNumber of ground rods 28 Ea Em= 606 VoltsLength of ground rod 2.44 metres Es= 619 VoltsDepth of grid burial h 0.5 metresFault Duration tf0.1 s Length of 4/0 Copper Required 574 metresCurrent Division Factor Sf1 Size of Copper d = 0.01 metresX/R Ratio 7.20 No. of Copper Rods 28 EaCrushed Rock Resistivity s2500 mAmbient temp Ta40oCGrid Resistance 0.23 Thickness of crushed rock hs0.102 metresGrid shape (Square=S, Rect.=R, L- shaped=L) rSubstation L-shape Length l 0 metreSubstation L-shape width w 0 metre 50kg Design O.K70kg Design O.KINPUT DATA RESULTST&TEC Grounding ProgramSubstation Grounding- Sahadeo Latchmepersad, T&TEC 31Development ProgramSubstation Grounding- Sahadeo Latchmepersad, T&TEC 32AutoGrid ProSubstation Grounding- Sahadeo Latchmepersad, T&TEC 33Connection to Customers Substation Fence eathing Number of Tails Increased area-lower Rg Increased amount of copperSubstation Grounding- Sahadeo Latchmepersad, T&TEC 34The End Questions? Thank You

Recommended

View more >