Marker balls are required to be provided in aviation zones in any span where the low point of the shield wire (OPGW/ OHGW) catenary is above 90 m AGL (Above Ground Level), which is equivalent to the low point of bottom conductor catenary at approximately 63 m AGL. Marker balls shall be placed on the top OHGW and OPGW, for aircraft warning.
1) Marker balls are required to be provided in aviation zones in any span where the low point of the shield wire (OPGW/ OHGW) catenary is above 90 m AGL (Above Ground Level), which is equivalent to the low point of bottom conductor catenary at approximately 63 m AGL. Marker balls shall be placed on the top OHGW and OPGW, for aircraft warning. 2) Marker Balls shall be evenly spaced along the OHGW/ OPGW, at a maximum of 60m intervals. 3) Unlighted Marker Balls shall alternate on OHGW and OPGW with aviation colors: Orange, White, and Red, with aviation Orange markers always positioned at each end. 4) If less than four (4) marker balls (lighted or unlighted) are on the OHGW/ OPGW, all marker balls shall be aviation Orange. 5) Crossings with multiple transmission lines require additional marker balls when the outside lines on the adjacent structure are more than 60 m from the center of the primary structure. 6) The Marker balls shall be EHV (Extra High Voltage) qualified, with a speci...