CEC Transmission Lines, California

The CEC Transmission Lines geospatial data layer contains electric power lines of transmission and some distribution or sub-transmission voltages covering California. Transmission lines can carry alternating current or direct current with voltages typically ranging from 110 kV to 765 kV. Transmission lines can be overhead and underground; underground transmission lines are more often found in urban areas. Sub-transmission lines generally carry voltages ranging from 33 kV to 100kV. These sub-transmission lines transmit power from higher voltage lines or other bulk power sources to local distribution network substations. An overhead power line can be single or double circuit. A single-circuit transmission line carries conductors for only one circuit. For a three-phase system, this implies that each tower supports three conductors. A double-circuit transmission line has two circuits. For three-phase systems, each tower supports and insulates six conductors. Single phase AC-power lines as used for traction current have four conductors for two circuits. Usually both circuits operate at the same voltage. In HVDC systems typically two conductors are carried per line, but in rare cases only one pole of the system is carried on a set of towers.

The detailed descriptions on the structure type, material and circuit can be found at here . If you cannot access to the PDF, you may request us to send you a copy of the PDF.

The transmission line, substation and power plant mapping database were started in 1990 by the CEC GIS staffs. The final project was completed in October 2010. The enterprise GIS system on CEC's critical infrastructure database was leaded by GIS Unit in November 2014 and was implemented in May 2016.

The data was derived from utility companies and USGS topographic map. Some of the data was rectified from GE and Platts transmission line geospatial data. The sources for the transmission line digitizing are including sub-meter resolution of Digital Globe, Bing, Google, ESRI and NAIP aerial imageries, with scale at least 1:5,000. Occasionally, USGS Topographic map, Google Street View and Bing Bird's Eye are used to verify the precise location of a facility. The data was digitized from pole to pole for >= 200 kV transmission lines. For transmission lines < 200kV, the data was digitized on the pole gaps of approximately 1:5,000 or greater. All the data was digitized based on ground level of where a pole was planted.

The transmission line was not digitized with one line segment from substation to substation. GIS Unit will merge the multipart lines into one segment in the future, after consulting with the Strategic Transmission Planning and Corridor Designation Office in identifying electricity flow between substation to substation or power plant to substation. Not all transmission line spatial data ended or started with a substation or power plant point spatial data. However, GIS Unit is current developing power plant and substation boundary spatial data which will enclose most of the transmission lines at both ends.

Data and metadata can be downloaded at: https://cecgis-caenergy.opendata.arcgis.com/datasets/transmission-line?geometry=-152.797%2C31.102%2C-84.725%2C43.303