In OPGW (Optical Fiber Composite Overhead Ground Wire) lines, ground wires and jumper cables form a key accessory combination for "electrical continuity + mechanical protection of the optical cable + O&M accessibility."
Grounding wires and jumper cables at three critical points in the optical cable suspension system
Whether the discharge path for lightning and induced current is reliable
OPGW is essentially part of the overhead grounding wire system and carries lightning current and induced current. The installation quality of the ground wire directly affects whether the tower grounding loop is continuous and whether the contact resistance is controllable, thereby affecting the lightning protection level of the line and operational safety.
Whether the jumper section meets the minimum bending radius and long-term mechanical stability
The jumper cable area near tension sections or splice points is the region most prone to "over-bending, wear, and vibration fatigue." Proper sag control and downlead clamp arrangement ensure that the optical unit will not develop risks due to bending stress, wind-deflection collision, or long-term friction (e.g., micro-bending loss, sheath wear-through, or even cable breakage).
Whether maintainability in the splicing and maintenance area meets requirements
For towers equipped with a splice box or slack storage rack, the arrangement of jumper cables and downlead clamps directly affects the splice box opening/closing space, the slack cable winding radius, and whether subsequent maintenance operation paths are smooth. If installation is standardized at the construction stage, then during operation and maintenance there will be less dismantling, less disturbance, and less rework.
Relationship with Other OPGW Accessories
Ground wires and jumper cables do not exist independently; they have a strong correlation with the tension/suspension system and the splicing system.
Relationship with OPGW Tension Clamp and Suspension Clamps
Tension tower: The jumper cable is usually located in the transition area between the tension clamp on both sides. Tension clamp define the load-bearing boundary of the OPGW, while the jumper cable is responsible for route transition and functional connection outside the load-bearing boundary.
Suspension Clamps: The ground wire is fixed by using the bolt holes on the ground-wire peak bracket or accessory holes, ensuring that the grounding downlead path is clear and the stress distribution is reasonable, without interfering with the swing space of the suspension string.
Relationship with parallel groove clamps / connectors
One end of the ground wire is connected to the optical cable through a parallel groove clamp. The crimping or tightening quality of such connectors determines the reliability of contact. The objective of grounding connection is not "just clamping it," but forming a stable electrical contact surface and having the ability to resist loosening under vibration.
Relationship with downlead clamps
Downlead clamps are essentially control points for "route shaping, collision prevention, and abrasion prevention."
Straight-through jumper cable: The key is that it does not contact tower members under wind deflection; if necessary, use 1–2 downlead clamps as limit fixing points.
Splice-type jumper cable: Downlead clamps are arranged at intervals of 1.5–2.0 m to form a smooth transition curve and avoid local over-bending and "polyline-style routing."
Relationship with splice boxes and slack storage racks
Splice-type jumper cables serve the splice box area: the optical cable between two tension fittings needs to be led down to the splice box or slack storage rack system.
The sag, clamp spacing, and routing position of jumper cables will affect the slack winding radius and the mechanical loading condition of the splice box, and the following must be ensured:
The optical cable transitions smoothly, and the radius meets requirements;
The splice box position is not "pulled" by the jumper cable or subjected to eccentric load;
Sufficient space is reserved for the slack storage rack to facilitate later opening, re-splicing, and testing.
Installation of Ground Wires and Jumper Cables
① One end of the ground wire for the tension string is connected to the optical cable through a parallel groove clamp, and the other end is grounded to the steel tower through a bolt. Use holes to fix the ground wire to the tower body, keeping the ground wire in a natural state; it shall not be excessively bent or overly tightened. The ground wire for the tension string has two application cases: for a tension tower without a splice box, the OPGW passes through directly and a single ground wire is used for connection; for a tension tower with a splice box, two ground wires are used for connection.
Direct-Type OPGW Jumper Installation
② For the ground wire of the suspension string, use the bolt holes of the ground-wire peak bracket accessories, and fix the ground wire to the tower body with bolts. The ground wires of suspension strings and the ground wires of non-splice tension towers shall be installed uniformly on the large-number side of the steel tower.
③ OPGW jumper cables are divided into a straight-through type (non-downlead jumper cable) and a splice type (downlead jumper cable).
For the jumper sag of a straight-through tension tower OPGW jumper cable, the minimum bending radius requirements shall be satisfied during construction, and there is no special requirement for the magnitude of the jumper sag. In addition to meeting the minimum bending radius and construction process requirements, the jumper sag shall be based on the principle that it does not contact tower members under wind deflection. If, after completion, the jumper sag is close to the tower members, use 1–2 downlead clamps according to actual conditions to fix the jumper cable on the tower members, to prevent friction between the jumper cable and tower members that could damage the OPGW.
For the installation of a splice-type (non-downlead jumper cable), the optical cable between two tension fittings shall be fixed to the steel tower with downlead clamps (clamps). The optical cable shall transition smoothly, and the installation spacing of downlead clamps (clamps) shall be 1.5–2.0 m.
Continuous OPGW Jumper Installation
Maintenance and Inspection After Installation
To convert "installation acceptance" into "long-term reliability," it is recommended to establish inspection items from four aspects: external routing appearance, mechanical condition, electrical continuity, and optical performance trends.
Appearance inspection
Focus on whether displacement, friction, collision, or loosening has occurred:
Whether jumper sag changes abnormally: whether wind vibration/ice coating/temperature difference causes excessive or insufficient sag; whether it is closer to tower members.
Wind-deflection collision risk: whether the jumper cable may sweep tower members, bolts, or angle-steel edges in the wind-deflection direction.
Downlead clamp condition: whether there is displacement, loosening, or clamp skew; whether the sheath at the clamp location shows indentations, cracking, whitening due to rubbing, or scratches.
Ground wire routing: whether it remains naturally straight and smooth; whether there is over-tensioning, twisting, or local sharp bending.
Parallel groove clamp/bolt connection points: whether there is corrosion, loosening, blackening, or missing anti-loosening parts.
Periodic tightening and anti-corrosion
Recheck torque or anti-loosening condition of key fasteners according to the O&M cycle.
In coastal/heavy pollution/high-corrosion areas,Key inspection:
Whether the grounding connection points have corrosion; whether dissimilar metal contact causes electrochemical corrosion; and the damage condition of anti-corrosion coating and hot-dip galvanizing layers.
Electrical inspection
During maintenance windows when conditions permit, sample-check the grounding connection condition at key towers (e.g., grounding downlead points and clamp connection points), focusing on: whether contact is reliable; whether there are abnormal temperature-rise indications at connection points (experience shows it may be accompanied by discoloration/blackening/accelerated corrosion).
Optical performance trend monitoring
Although ground wires and jumper cables are external accessories, their problems often ultimately manifest as abnormal optical performance. Trend judgments can be made in combination with the following:
OTDR trace changes: changes in backscatter or loss near splice points may be related to jumper cable bending, micro-bending, or compression.
Alarms and bit errors: if intermittent attenuation fluctuations occur after extreme weather, prioritize checking whether friction has occurred in the jumper cable and clamp area or whether the bending radius is insufficient.
FAQ
Q: What jumper cable sag is appropriate for OPGW?
A: Meet the minimum bending radius first, then ensure wind swing clearance from the tower.
For a straight-through (non-downlead) jumper cable, there is typically no fixed sag value. The key is that the jumper forms a smooth, natural curve and nowhere violates the minimum bending radius specified by the project/installation requirements.
After installation, verify clearance under realistic conditions such as wind deflection, ice loading, and temperature variation. The jumper must not contact tower members, bolts, or sharp steel edges when it swings.
If the installed jumper sits too close to tower steel, add 1–2 downlead clamps as limiter points to secure the routing and prevent abrasion.
Q: How is the OPGW ground wire connected to the tower?
A: A standard approach is two-end connection + secure routing + "natural lay" (no over-bending or over-tensioning).
OPGW end: One end of the ground wire is connected to the OPGW using a parallel groove clamp, providing stable electrical contact and resistance to vibration loosening.
Tower end: The other end is bonded to the steel tower grounding point using bolts (or the designated grounding hole/grounding member per design).
Fixing/routing: Use tower holes to fix the ground wire along the tower body, keeping it in a natural state-avoid excessive bending, twisting, or pulling it too tight.
Typical configurations: On tension towers without a splice box, a single ground wire is commonly used; on tension towers with a splice box, two ground wires are commonly used .
Q: Why is downlead clamp spacing specified as 1.5–2.0 m?
A: This spacing is an engineering balance between controlling the cable route and avoiding excessive clamping/stress concentration. It is mainly intended to:
Maintain a smooth transition curve: If spacing is too large, the cable between clamps can sag unpredictably or form local "kinks," increasing micro-bending and abrasion risk.
Reduce wind-induced movement: Proper spacing helps "shape" the downlead route and limits swing that could cause tower contact.
Prevent over-clamping damage: If spacing is too small, more clamp points can increase localized compression, fretting, and long-term fatigue at clamp locations.
Therefore, 1.5–2.0 m is a widely used practical range, unless otherwise specified by the project design or applicable standards.
Q: Why must the jumper cable avoid contacting tower members under wind deflection?
A: Because repeated contact usually causes progressive, hidden damage that can be more serious than obvious external defects:
Abrasion wear: Repeated rubbing can wear through the outer sheath, expose metallic layers, and accelerate corrosion.
Micro-bending loss: Intermittent compression/impact can create micro-bends, leading to attenuation fluctuation and abnormal OTDR signatures.
Fatigue and strand damage risk: Long-term vibration combined with rubbing can drive structural fatigue, and in severe cases contribute to strand damage or cable failure.
In acceptance checks, the goal is not "more sag," but sufficient clearance under worst-case wind swing.