OVERHEAD TRANSMISSION LINES AND COMMUNICATION STRUCTURES

Complete design, supply, construction, testing and
commissioning of:

• Overhead transmission lines (OHL) from 11kV to 500kV voltage level
• Communication structures
  

DESIGN

• Sag and tension computation
• Computation of external loading
• Loading trees
• Clearance diagrams and structure geometry
• Analysis and design of:
• OHL and Communication steel latticed towers
• Tubular steel poles
• Tubular steel frames and multi-pole structures
• Wood poles
• Wood frames and multi-pole structures
• Concrete poles
• Concrete frames and multi-pole structures


• Foundation design for different structures and soil conditions
• Terrain modeling by intelligent totals station or GPS with terrain data transfer to personal computer and generation of plan and profile UTM co-ordinate system.
• Interactive and automatic tower spotting with optimization, obtaining the lowest cost design
• Generation of plan and profile drawings with line reports including material list, usage of conductors and structures, clearance check etc.

SUPPLY AND TESTING

• Steel latticed OHL and communication structures
• Tubular steel poles and frames
• Wood poles and frames
• Concrete poles and frames
• OHL hardware, fittings and accessories
• OHL insulators
• OHL bare conductors and earth wires
• Optical fiber earth wires with jointing and splicing equipment
• Earthing material
• Communication equipment
• OHL aircraft warning system

CONSTRUCTION

• Soil investigation
• Access roads
• Foundation works
• Ground assembly and erection of OHL and communication towers
• Insulator string hoisting
• Preparing stringing charts
• Conductor / OPGW stringing sagging and checking of sag by total station
• OPGW splicing

TESTING AT SITE AND COMMISSIONING

• Tower earthing resistance
• Measurement of actual line parameters:
  • Positive/negative and zero sequence impedance
  • Phase to phase impedance
  • Phase to earth impedance
• OPGW attenuation and back scatter splice tests for every joint
• OPGW TDR scan link tests for every section
• OPGW dispersion tests for every section
• OPGW end to end test from substation to substation
  

CALCULATION OF OHL PERFORMANCE

• Transmission line electric field lateral profile. Electric field calculation for different heights and distances from line center.
• Transmission line magnetic field for different line loading. Magnetic field lateral profile. Magnetic field calculation for different heights and distances from line center.
• Comparison of electric and magnetic field levels regarding international regulations and recommendations. Definition of different protection zones.
• Transmission lines parameters. Capacitance, inductance and resistance matrices for all conductors and for the cases when ground wire(s) influence is (are) eliminated. Positive and zero sequence parameters. Couplings between zero sequence networks (for multi circuit lines).
• Transmission line lightning performance. Shielding failure and back flashover rate. Line composite performance. Multi circuit outage rate for multi circuit lines
• For lines having nominal voltage 220 kV or higher line switching surge performance. Phase to ground and phase to phase risk of failure. Switching surges related to line closing, high speed reclosing and single line to ground faults. Reduction of switching surge over voltages.

SOFTWARE USED FOR OHL COMPUTATIONS

• TOWERS Version 7.61, PLS CADD Version 4.71 +, Design of transmission lines with Optimum Spotting Facilities
• SOKKIA & TOPCON Surveying Instruments, GPS, GPT 7002, SET 2030R, SET 2010, SET 5F, SET 2B, Electronic Total Station with Expert Card.
• SIGMA SLP, Software for Determination of Transmission Line Lightning Performance.