How Phase Markers are Used Individual Passes During Construction

For industrial uses, Phase markers are reusable PVC markers which snap to power lines during construction and maintenance in order to identify individual passes. They come in a simple snap-fit design as individual markers or in kits of red, white and blue markers. Phase markers have a unique “V” shape design for maximum visibility contrast at all angles. They weigh five ounces, and can withstand 100 miles per hour winds for sustained periods. They can also be customized with a construction company’s logo.

Overhead power lines consist of one or more uninsulated electrical cables, suspended by towers or poles. The cables are typically constructed in multiples of three for three-phase power. Phase markers are used to identify individual passes during construction or maintenance. A single-circuit transmission line carries conductors for one circuit, so a three-phase power system supports three conductors. A double-circuit transmission line carries conductors for two circuits. In order to construct a three-phase system, a double-circuit transmission tower must support six conductors. 

Most overhead high voltage transmission systems are constructed in a three-phase Delta alternating current configuration requiring only three cables. Phase markers are used during construction to identify the various differences in voltages of the cables and by what amount of voltage they are out of phase, typically 120 degrees.

Phase markers identify power system phases and make construction and maintenance safer. There are many wire and power line identification standards that rely on color codes. The standards used in a construction project depend on its location, voltage, and other factors. Various voltage systems are coded with colors depending on its voltage phase. Additional lines seen on power systems are usually lightning attractors used to keep lightning off conductors. 

Overhead power line designs must maintain adequate clearance between energized conductors and the ground in order to prevent contact with the line and support conductors. Damage can increase the danger posed by voltages exceeding 765,000 volts between conductors. 

During construction or maintenance of overhead power transmission lines, workers must exercise caution not to work close to live phase conductors. They must know the voltage levels of the different power lines and the related safe clearance. The voltage level of an overhead power line can be identified by the length of the insulator string and the number of insulator elements. Overhead power transmission lines are classified in the industry by the range of voltages:

• Low voltage (LV) - less than 1000 volts and used for connections between the utility and residential areas or small commercial customers.
  
• Medium voltage (MV) - between 1000 volts (1 kV) and 69 kV, and used for power distribution in urban and rural areas. 
• High voltage (HV) - subtransmission less than 100 kV; subtransmission or transmission at voltages such as 115 kV and 138 kV, and used for subtransmission and transmission of bulk quantities of electric power to large consumers.
• Extra high voltage (EHV) - more than 230 kV and up to 800 kV, and used for very high power long distance transmission.
• Ultra high voltage - (UHV) - more than 800 kV.