Determination of Minimum Right-of- Way (ROW) Width for Overhead Power Transmission Lines

Transcription

1 TransCo Determination of Minimum Right-of- Way (ROW) Width for Overhead Power Transmission Lines Bienvenido D. Valeros John C. Placente May 2013

2 Objective Study aims to: 1. Provide the technical basis of transmission line right-of-way (ROW) width based on applicable electrical and safety codes. 2. Determine opportunities on cost-savings by paying only the ROW width that is needed by TransCo. 2

3 Luzon TRANSMISSION LINE LENGTH (in CKT-KM) As of CY2011 9,482 4,979 Visayas 5,361 PHILIPPINES 19,822 Mindanao Mindanao 3

4 Transmission Line Length As of December 31, 2011 Voltage (kv) Luzon (km) Visayas (km) Mindanao (km) Total (km) , , , , , & Below 2, , , ,

5 Right-of-Way (ROW) is to provide an access corridor for maintenance of transmission lines, with consideration to safety clearances and EMF exposure limits. ROW Width ROW Width 5

6 ROW Width Determination 230 kv Voltage Level (kv) FIXED Width (m) m 40 Meters

7 Proposed ROW Width Determination 230 kv 12 m ROW= Design, EMF 7

8 References for Determination 8

9 W Horizontal Clearance at Rest Formula Above 36 kv, Altitude 1000 m Philippine Electrical Code Rule (a) HCL V m R WREST 22 3 LL 0.01 W HCL-R W REST V LL m is the effective horizontal clearance (@ rest), meters is the horizontal clearance on PEC Table (a)(1) for open supply conductors, 2.3 meters is the line to line voltage, kv is the maximum voltage multiplier; 1.05 (69-345kV) and 1.10 (500kV and above) 9

10 Nominal Voltage Level, in kv Horizontal Clearance at Rest (Computed) Maximum Voltage Level, in kv Horizontal Clearance At Rest, Altitude 1000 m, in Meters (Based on PEC)

11 Horizontal Clearance, Conductor Displaced by Wind Formula for Above 36 kv, Altitude 1000m, Wind Philippine Electrical Code Rule W HCL V LL m 0.01 W WWIND 22 3 W HCL-W W WIND V LL m is the horizontal clearance requirement when displaced by wind is the minimum wind clearance requirement as listed in Table (a)(2); for overhead conductor, 1.4 meters. is the line to line voltage. is the maximum voltage multiplier; 1.05 (69-345kV) and 1.10 (500kV) 11

12 Horizontal Clearance When Conductor is Displaced by Wind (Computed) Nominal Voltage Level, in kv Maximum Voltage Level, in kv Horizontal Clearance With Wind Displacement, Altitude 1000 m, in Meters (Based on PEC)

13 Conductor Swing Angle Calculation C IEC 60826, Philippine Electrical Code tan 1 / 2 C C V G m g a C 2 R L D a W Ø C is the swing angle of the conductor blown by wind ρ is the air density ( , assumption: 1.16 kg/m 3 ) C C is the drag factor equal to 1.0 for stranded conductor V R is the wind speed/velocity (meters/second) G L is the span factor taking into account the effect of span length (Values are 1.0 to for 200 m to 600 m) D is the conductor diameter (meters) m C is the conductor mass per unit length (kg/m) g is the gravitational acceleration constant (9.8 m/s 2 ) a W is the wind span a is the conductor span length (assumption: a=a W ) 13

14 Span Factor, G L IEC Wind Span, a W (meters) Span Factor, G L

15 15 Example Condor (795 MCM), 270 KPH or 75 m/s a m g a D G V C C W L R C C / tan a s m m km km kg a m s m m kg W C tan Assumption: conductor span, a is assumed equal to wind span, a W ; therefore, C

16 Conductor Swing Angles Per KPH Philippine Electrical Code 2, 2009 Condor (795 Span = 250 m Wind Speed Zone Swing Angle 240 KPH 270 KPH 270 KPH 75 m/s Zone O 240 KPH 67 m/s Zone O 160 KPH 44.45m/s Zone O 160 KPH

17 Example The 230 kv double circuit overhead conductors are supported by two towers with dimensions as shown. The two towers are on same elevation and the span between them is 250 meters. Surveyed data from the field indicates that the total insulator length and conductor sag amounts to 6.0 meters. Conductor is in Zone 1 (270 KPH). TOWER A 250 m TOWER B Recommend a minimum rightof-way (ROW) based on clearances of conductors at rest and under wind displacement. 1.5 m 1.5 m 4.5 m NOT TO SCALE FOR ILLUSTRATION ONLY 17

18 3.5 m Clearance At Rest 2.6 m Clearance With Wind A. Compute for the Horizontal Clearance at Rest W HCL R W HCL R 3.47m3. 5m B. Compute for the Horizontal Clearance, with Wind W HCL W W HCL W 2.57m 2. 6m 5.92 m 1.5 m 4.5 m 80.5 o 18

19 Illustration # m 19

20 Illustration #2 HORIZONTAL CLEARANCE, WITH WIND DISPLACEMENT m HORIZONTAL CLEARANCE AT REST HORIZONTAL CLEARANCE, WITH WIND DISPLACEMENT 20

21 ROW WIDTH ESTIMATES Voltage Level (kv) CURRENT (Fixed) PROPOSED* (Design Dependent)

22 LATEST EMF EXPOSURE LIMITS General Public, 60 Hertz, 2010 ICNIRP* *International Commission on Non-Ionising Radiation Protection PARAMETER VALUE Electric Field 4.17 kv/m Magnetic Field 2000 milligauss* *1998 Value = 833 mg 22

23 Limits: Electric Field = 4.17 kv/m Magnetic Field = 2000 mg Calculated EMF Levels Information: 230 kv, Bundle of 4, 820 Amps Per Cond, Double Ckt Distance from Conductor Centerline (m) Electric Field (kv/m) Magnetic Field (mg) Measured EMF 5 m from Conductor Centerline Transmission Line Electric Field Magnetic Field Sucat-Araneta-Balintawak 230 kv

24 Benefits Reduction of area acquisition cost of 28-32%. 24

25 Way Forward 1. Status. Completed 10 Consultation meetings with distribution utilities and other power experts. Preparing for 2 more technical consultations and then legal consultations. 2. Board Approval. Seek final approval/recommendation from management team. 3. Program Development. Create a software and database system (tower design data, sag, span) which will compute for ROW acquisition. 25

26 FOR COMMENTS MR. BIENVENIDO D. VALEROS MR. JOHN C. PLACENTE MS. SHELYMAR F. AURIGE MS. DIVINA I. CUSTODIO 26