3　Routing

3.0.1　The routes should be selected using new technologies such as satellite and aerial photos，full digital photogrammetry system and infrared radiation measurement.In areas with complex geological conditions，when necessary，geological telemetry should be used.When selecting the transmission line route，such factors as the length of line，landscape，geological conditions，icing area，traffic condition，construction，operation，and local planning shall be considered and schemes shall be technically and economically compared to ensure that the chosen scheme is safe，reliable，environmentally friendly and cost effective.

3.0.2　Military facilities，large industrial/mining establishments and important facilities shall be avoided and urban planning requirements should be met in routing.

3.0.3　Areas with complex geological conditions and mining affected areas should be avoided in routing，if unavoidable，necessary measures shall be taken.Areas subject to heavy ice and where conductors are liable to gallop or other areas where the safe operation is affected，primitive forests，natural reserves，and landscape and historic sites should be avoided in routing.

3.0.4　Interaction with adjacent facilities such as radio stations，airports and telecommunication lines shall be taken into consideration.

3.0.5　Routes should be selected close to existing national，provincial，municipal trunk ways and township roads to facilitate construction and operation by making full use of the existing traffic conditions.

3.0.6　The incoming and outgoing lines for large-scale power plants and key substations，adjacent doublecircuit or multiple-circuit lines shall be uniformly planned，and should be erected on common towers where the narrow line corridor is narrow.

3.0.7　The lengths of tension sections should not exceed 10km，5km and 3km respectively in light，medium and heavy icing areas.The tension section length for single conductor lines should not exceed 5km.In the case of long tension section，measures shall be taken to prevent collapse of towers in series.The length of tension section shall be reduced appropriately in areas with poor operation conditions，such as heavy icing areas or mountain areas with significant altitude or span length differences.In areas where power lines cross over trunk railways or highways，independent tension sections shall be employed.

3.0.8　When routing and locating power lines in mountain areas，the span length and altitude differences shall be restricted to avoid significant difference in span length on the two sides of a tower.Where this cannot be avoided，necessary measures shall be taken to enhance safety.

3.0.9　The routing scheme for transmission lines with large crossings shall be determined through comprehensive tech-economic analysis in combination with the specific condition of large crossings.