Overhead line protection describes all preventive and accompanying measures that safely enable work in the vicinity of electrical overhead lines—such as contact lines in rail transport or overhead power lines in the energy supply. In construction, demolition and deconstruction, particular risks arise from approach, impact, flashover, or induced voltages. Especially in concrete demolition and special deconstruction, in rock excavation and tunnel construction, as well as in building gutting and cutting, practice-oriented protection concepts are essential. Darda GmbH has deep application expertise in these fields, particularly in the use of concrete crushers and rock and concrete splitters, which allow controlled, low-vibration methods and thus support overhead line protection in a technically sound manner.
Definition: What is meant by overhead line protection
Overhead line protection refers to the entirety of technical, organizational, and personal protective measures to be taken when working within the influence area of electrical overhead lines to protect people, equipment, and installations from electrical hazards and from physical contact with the line. This includes, in particular, observing approach zones and minimum clearances, de-energizing and grounding lines, installing shielding, selecting suitable work methods and tools, and defining clear procedures for authorization, supervision, and documentation of the work. The goal is reproducibly safe execution that avoids risks such as electrical flashovers, unintended contacts, electric arcs, flying sparks, or the unintended swinging of components toward the overhead line.
Hazards, approach zones, and minimum clearances
The hazard situation at overhead lines arises from electrical effects (direct contact, flashover, induced voltages) and mechanical effects (impact from components, swinging of booms, wind load). The higher the voltage level, the greater the required protective distances; weather and contamination also influence flashover distances. In practice, approach zones are defined on a project-specific basis, often in coordination with grid operators or rail infrastructure. For work planning this means: component geometry, equipment reach, and the possible movement radii of tools must be dimensioned in advance so that the approach zone to the overhead line is not violated at any time.
Planning and risk assessment on construction sites with overhead lines
Overhead line protection starts with a detailed risk assessment. This considers line type, voltage level, location, sag, energization status, and accessibility. Construction methods, construction phases, traffic routing, use of cranes and aerial work platforms, weather, and the electrical influence on metal parts are also assessed. In the next step, a protection concept is developed that combines technical, organizational, and personal measures and defines responsibilities on a role basis. In Darda GmbH’s typical application areas—ranging from concrete demolition and special deconstruction through building gutting and cutting to rock excavation and tunnel construction—robust work instructions and authorization processes are derived from this.
Technical protective measures: de-energizing, grounding, shielding
Technical measures form the backbone of effective overhead line protection. Where operationally feasible, the line in the work zone is de-energized and grounded. If shutdown is not possible, barriers and shielding can be used to define the permissible work space and reduce the risk of uncontrolled approach. Effective building blocks include:
- Switching and grounding schemes with clear marking of release status
- Insulating protective scaffolds or barriers that clearly delimit the work area
- Equipotential bonding for conductive parts on the structure, formwork, or auxiliary constructions, where technically required
- Work equipment with a defined, limited reach to maintain approach zones
- Low-vibration, controlled methods (e.g., hydraulic splitting with rock and concrete splitters or targeted biting with concrete crushers) to avoid oscillations and unpredictable component movements
Organizational measures and workflows
Organizational measures ensure that technical protective measures remain effective. These include:
- Appointing a responsible person for work within the influence area of overhead lines
- Authorization processes with visual inspection and documentation before work begins
- Briefing the team on approach zones, emergency routes, and communication rules
- Limiting the number of trades working simultaneously in the hazard area
- Weather-window rules (e.g., suspend work during heavy rain, fog, or thunderstorms)
- Ongoing monitoring of the reach of machines and tools, particularly booms, cylinders, and carrier machines
Tool selection and work methods in the context of overhead line protection
The choice of work method significantly influences the risk profile. Methods with controlled, localized energy input minimize unwanted movements and reduce flying sparks and dust clouds that could become electrically charged. In the vicinity of overhead lines, the use of Darda GmbH hydraulic tools has proven effective:
Concrete crushers
Concrete crushers enable targeted biting of concrete, including reinforced members. By proceeding sequentially, cross-sections can be reduced in a controlled way so that components do not fail abruptly. This reduces the risk of fragments swinging uncontrollably or pivoting toward the overhead line. The cold separation effect also avoids flying sparks, which is advantageous near live installations.
Rock and concrete splitters
Rock and concrete splitters generate high splitting forces in the borehole and enable precise crack steering. The method is very quiet and low in vibration and shock, making it suitable for not impairing the integrity of adjacent structures—including mast foundations or load-bearing cables. Especially in rock excavation and tunnel construction under overhead lines or near rail corridors, splitting helps maintain defined protection spaces.
Other hydraulic tools
Combination shears, steel shears, multi-cutters, and tank cutters are used when reinforcement, sections, tanks, or composite components must be cut. Where flying sparks or hot work are undesirable, hydraulic shearing and cutting methods are often a suitable option. In all cases, reaches and component weights must be planned with respect to the overhead line so that movement radii do not contact the approach zone.
Hydraulic power packs and distancing
Hydraulic power packs supply the tools and—depending on the setup—enable safe positioning of the operator outside critical areas. Hose routing must be laid so that no large loops are formed that could be influenced inductively and so that hoses cannot whip toward the overhead line.
Application areas with a particular focus on overhead line protection
Requirements vary depending on the task and environment. Some typical scenarios from Darda GmbH’s application areas:
- Concrete demolition and special deconstruction: Deconstruction of superstructures, bridge edge beams, or noise barrier walls near contact lines requires staged deconstruction concepts with concrete crushers and splitters to control fall directions and maintain protective distances.
- Building gutting and cutting: When removing beams, columns, and composite elements in industrial areas near overhead lines, swing movements must be limited. Hydraulic shears minimize flying sparks compared to thermal cutting methods.
- Rock excavation and tunnel construction: During portal or cutting widening under overhead lines, splitting rock supports controlled fracture patterns and prevents rock fragments from entering the protection space of the lines.
- Natural stone extraction: In quarries near corridors or corridor buffers, splitting cylinders can support extraction with predictable block dimensions, ensuring that transport and lifting movements do not encroach on approach zones.
- Special deployment: Emergency measures after impact, storms, or ice accretion require particularly strict organizational procedures, clear communication, and robust shielding before cutting or splitting begins.
Component handling, lifting devices, and fall-direction control
Effective overhead line protection always accounts for the behavior of components after cutting or splitting. Proven practices include:
- Providing retention systems and guys to prevent swinging
- Gradually reducing cross-sections with concrete crushers before the final separation cut
- Targeted crack steering using rock and concrete splitters to create defined fracture edges
- Coordination with crane and aerial work platform operations; defined exclusion zones beneath overhead lines
Electrical effects on equipment and components
Metallic components, reinforcement, scaffolds, and machines can pick up electrical influences. The protection concept should consider:
- Equipotential bonding for larger metallic auxiliary structures, where necessary in the specific case
- Avoidance of large, closed loops in hose and cable routing
- Reduction of unnecessary metal lengths that could project toward the overhead line
- Orderly storage of removed steel sections to prevent them from tipping up into approach zones
Legal and normative guidance
Protective distances, authorization processes, and qualification requirements are oriented in practice toward the relevant rules of accident insurers and electrical regulations and are defined on a project-specific basis. Binding are always the arrangements agreed for the specific project with infrastructure operators and clients. Those carrying out the work should align with the approach zones, authorization paths, markings, and communication channels defined there.
Qualification, instruction, and personal protective equipment
Employees working within the influence area of overhead lines require targeted instruction on hazards, protective measures, emergency procedures, and roles. Depending on the task, personal protective equipment includes a safety helmet, safety glasses, hand protection, cut protection, and, where provided, insulating elements. When working with hydraulic tools, additional measures against crushing, shearing, and hydraulic hazards must be taken into account.
Weather, ambient conditions, and schedule control
Rain, fog, contamination, wind, or high humidity influence flashover distances and component movements. Work windows must be planned to avoid unfavorable conditions. Strong wind can push components and booms toward the overhead line; during thunderstorms, work within the influence area of electrical overhead lines must be suspended as a matter of principle.
Documentation, marking, and communication
Effective overhead line protection is transparently documented. This includes:
- Plans with marked approach zones and protection areas
- Switching and grounding logs with responsible persons and timestamps
- Work and rescue instructions, visible at the access to the work area
- Authorization documents before work starts and at every change of construction phase
- Photo documentation of shielding, barriers, and tool positions
Practice-oriented checklist for execution
- Determine and document line location, voltage level, and energization status
- Define, mark, and communicate approach zones
- Implement technical measures: de-energize/ground or install shielding
- Select methods: controlled splitting with rock and concrete splitters or targeted biting with concrete crushers; avoid flying sparks
- Position hydraulic power packs so that operators work outside critical areas
- Lay hose and cable routes without loops and secure against whipping
- Plan component handling: define retention, guying, and lifting points
- Check weather conditions; postpone start of work under unfavorable conditions
- Document authorization; assign responsible persons; clarify emergency routes
- Ongoing monitoring and adjustment at every phase change
Relation to typical components and materials
In deconstruction, components with reinforcement, prestressing steel, composite beams, and tanks are common. Hydraulic steel shears and multi-cutters cut sections and reinforcement in a controlled manner. Tank cutters are used where hollow bodies must be safely segmented. Near overhead lines, the sequence of separation cuts is crucial to prevent uncontrolled load redistribution. Gentle reduction of cross-sections with concrete crushers and the controlled opening-up of concrete with splitters enable predictable load transfer.
Emergency and incident management
Despite careful planning, contingencies must be anticipated. These include immediate suspension of work upon violation of approach zones, clearly defined reporting lines, and safely clearing the hazard area. Work may only resume after renewed authorization. In the event of damage to overhead line installations, hazard mitigation has priority; independent approaches must be avoided until specialist units release the area.
Quality and efficiency aspects in overhead line protection
A robust overhead line protection approach pays off in quality and efficiency: fewer stoppages, predictable construction times, and consistent work progress. Methods with high process control—such as hydraulic splitting or stepwise biting—reduce the risk of rework due to unintended component movements. Thoughtful positioning of hydraulic power packs, short hose runs, and clear communication signals between machine operators and signalers increase productivity without compromising protection goals.