FDZ Series Stockbridge Vibration Damper
The FDZ Series Stockbridge vibration damper is a protective fitting designed to control wind-induced aeolian vibration in overhead conductors and earth wires. It is commonly installed near suspension clamps or other conductor support points where repeated high-frequency vibration may cause fatigue damage to conductor strands and line fittings.
The damper consists of a conductor clamp, a flexible galvanized steel messenger cable and two tuned counterweights. When the conductor vibrates, relative movement of the counterweights bends the messenger cable and dissipates vibration energy. Correct model selection and installation position are essential for effective vibration control.
Key Features
- Stockbridge-type design for controlling aeolian vibration
- Suitable for overhead conductors and earth wires
- Multiple models available for different conductor diameters
- Aluminium-alloy conductor clamp
- Flexible high-strength galvanized steel messenger cable
- Cast-iron counterweights with protective coating
- Bolted clamp design for field installation
- Designed to reduce vibration-related conductor fatigue
- Model and installation position can be selected according to line parameters
How the Vibration Damper Works
Wind flowing across an overhead conductor can create alternating aerodynamic forces and high-frequency, low-amplitude conductor movement known as aeolian vibration. Repeated bending near suspension clamps and support points can lead to strand fatigue and eventual conductor damage.
The FDZ damper converts part of this vibration energy into bending and frictional movement within its messenger cable. The counterweight mass, messenger-cable stiffness and installation position are coordinated to provide damping over the required frequency range.
A vibration damper does not eliminate every type of line movement. Galloping, sub-span oscillation and bundle-conductor movement may require different control devices or a combined vibration-protection design.
Typical Materials and Surface Treatment
| Component | Typical Material | Typical Surface Treatment |
|---|---|---|
| Conductor clamp | Aluminium alloy | Natural aluminium finish or project-specified treatment |
| Counterweights | Grey cast iron | Protective paint, coating or project-specified treatment |
| Messenger cable | High-strength steel strand | Zinc galvanized |
| Bolts, nuts and washers | Carbon steel | Hot-dip galvanized |
Exact material grades, coating system, messenger-cable construction and fastener specifications must be confirmed using the approved product drawing and bill of materials.
Typical FDZ Model Selection
| Model | Suitable Conductor Diameter | Dimension a | Dimension h | Dimension L1 | Overall Length L | Approx. Total Weight |
|---|---|---|---|---|---|---|
| FDZ-1 | 7.0–11.0 mm | 50 mm | 58 mm | 120 mm | 320 mm | 1.8 kg |
| FDZ-2 | 11.0–15.0 mm | 50 mm | 58 mm | 130 mm | 350 mm | 2.3 kg |
| FDZ-3 | 15.0–19.0 mm | 60 mm | 72 mm | 150 mm | 430 mm | 4.4 kg |
| FDZ-4 | 19.0–23.0 mm | 60 mm | 72 mm | 160 mm | 470 mm | 5.5 kg |
| FDZ-5 | 23.0–30.0 mm | 60 mm | 89 mm | 180 mm | 520 mm | 7.4 kg |
| FDZ-6 | 30.0–36.0 mm | 60 mm | 96 mm | 180 mm | 520 mm | 8.9 kg |
Technical-data notice: The values above are representative published catalogue data. Some manufacturers use slightly different conductor ranges, dimensions, counterweight masses or suffixes such as F and T. Final selection must be confirmed using the manufacturer’s approved drawing and the project vibration study.
Typical Applications
- Overhead transmission-line conductors
- Overhead distribution-line conductors
- ACSR, AAC, AAAC and compatible bare conductors
- Overhead galvanized steel earth wires
- Single conductors
- Bundle conductors where a damper is attached to each sub-conductor
- Long-span and wind-exposed overhead lines
- Line sections near suspension clamps and conductor support points
Conductor and Cable Compatibility
The standard FDZ series is normally selected for bare conductors or earth wires according to the conductor diameter and line-vibration design. Use on OPGW or ADSS cables must not be assumed from the FDZ designation alone.
For OPGW or ADSS applications, the clamp type, allowable radial pressure, armour rods, cable diameter and optical-cable vibration requirements must be separately confirmed. A purpose-designed preformed vibration damper may be required.
Selection Information
Selection should not be based only on system voltage. The following information should be reviewed:
- Conductor or earth-wire type
- Actual conductor outside diameter
- Conductor unit weight
- Rated tensile strength and everyday tension
- Span length and terrain
- Wind conditions and exposure category
- Suspension-clamp and armour-rod configuration
- Number of dampers required per span end
- Specified installation distance from the suspension point
- Required damping-performance test
Installation Recommendations
- Verify the damper model against the actual conductor diameter and approved vibration-control design.
- Inspect the conductor, clamp, messenger cable and counterweights before installation.
- Measure the specified installation distance from the suspension-clamp exit point or the reference point shown on the construction drawing.
- Position the clamp so that the messenger cable and counterweights are correctly oriented.
- Install armour rods where required by the approved design.
- Tighten the clamp bolt evenly to the specified installation torque.
- Do not strike, bend or modify the messenger cable during installation.
- Check that the clamp is secure and that the counterweights can respond without contacting nearby fittings.
- Record the installed model, position and quantity for inspection.
Inspection and Testing
Recommended inspection and testing items include:
- Material and dimensional verification
- Conductor clamp fit inspection
- Clamp mechanical-strength and slip testing
- Bolt-tightening and assembly inspection
- Messenger-cable fatigue testing
- Counterweight attachment testing
- Damper frequency-response and power-dissipation testing
- Corona and radio-interference testing where required
- Galvanized-coating and corrosion-resistance inspection
- Marking, packaging and acceptance inspection
Applicable Standards
The FDZ vibration damper may be manufactured and tested according to the approved drawing, utility specification and applicable requirements of:
- DL/T 1099-2021 – Technical requirements and test methods for vibration dampers
- IEC 61897:2020 – Overhead lines: Requirements and tests for aeolian vibration dampers
- GB/T 2314-2008 – General technical requirements for electric power fittings
- ISO 1461 – Hot-dip galvanized coatings on fabricated iron and steel articles, when specified
Compliance with a particular standard must be verified for the ordered model through the applicable type-test report, inspection documentation or approved project specification. Standards must not be presented as product certification without supporting evidence.
Information Required for Quotation
- Required FDZ model
- Conductor or earth-wire designation
- Conductor material and outside diameter
- Span length and line tension
- Suspension-clamp and armour-rod arrangement
- Required number of dampers per span end
- Installation distance or vibration-study requirements
- Applicable standard and test requirements
- Required surface treatment
- Quantity, marking and packaging requirements
Frequently Asked Questions
What type of vibration does the FDZ damper control?
It is principally designed to reduce aeolian vibration caused by steady wind flowing across an overhead conductor or earth wire.
Can the model be selected only by voltage?
No. Selection is mainly based on conductor diameter, mass, tension, span length, wind conditions and the required damping-performance range.
Can an FDZ damper be installed on OPGW?
Only when its clamp arrangement, radial pressure and damping performance have been approved for the specific OPGW cable. A preformed optical-cable damper may otherwise be required.
How many dampers are required?
The quantity depends on span length, conductor tension, terrain, wind exposure and the results of the vibration-control design. One or more dampers may be installed near each span support.
Can the installation distance be estimated from the photograph?
No. The installation distance must follow the project drawing, damper-performance calculation or supplier recommendation for the specific conductor system.
