Compensation grounding is a central concept in electric power supply, primarily used in medium-voltage networks. For applications such as concrete demolition and deconstruction, and for contexts involving rock demolition and tunnel construction, as well as building gutting and cut operations, understanding this grounding method is relevant because construction and deconstruction processes increasingly take place close to power networks. Metallic tools and attachments — such as concrete demolition shear or hydraulic wedge splitter — form large conductive structures that can pick up potential differences during earth faults. This knowledge helps plan the construction power supply, equipotential bonding, and protective measures in a practical way and ensures the safe operation of the hydraulic power pack and cutting tools.
Definition: What is meant by compensation grounding
Compensation grounding (also neutral-point compensation or resonant grounding) refers to grounding a network via an inductive reactor, the so-called Petersen coil. It is connected to the transformer neutral point and tuned so that the capacitive earth-fault current flowing during a single-phase earth fault is largely compensated. The goal is to minimize the fault current, extinguish earth-fault arcs, reduce touch voltages, and maintain supply until the fault can be selectively located and cleared.
Operating principle and components
The medium-voltage network has distributed capacitances to earth. If a single-phase earth fault occurs, a capacitive current flows to the fault location. The Petersen coil produces an inductive current that counteracts this capacitive current with a phase shift. When properly tuned, the residual current is small, the earth-fault arc often self-extinguishes, and thermal as well as mechanical stress on the system decreases. Modern systems feature automatic tuning to adapt the coil to changing network capacitances. Protection devices, such as wattmetric earth-fault protection relays, detect the remaining active-power component and enable selective fault location.
Neutral-point treatment in comparison
Networks can be operated solidly grounded, high-resistance grounded via a resistor, isolated, or compensated. Solid grounding results in high fault currents that allow fast line protection but cause higher thermal effects. Isolated networks avoid high currents but carry the risk of transient overvoltages. Compensation grounding combines low fault currents with improved arc stability and allows short-term continued operation until measures are taken — an advantage for complex supplies in tunnel construction or deconstruction projects with time-critical workflows.
Relevance for construction sites, deconstruction, and extraction
In areas with compensated medium-voltage networks — for example, feeders to plant sites, tunnels, or larger quarry and deconstruction projects — neutral-point treatment influences the hazard assessment. Conductive machine frames, pipelines, reinforcement, and tools such as concrete demolition shear, hydraulic wedge splitter, rock wedge splitter, steel shear or cutting torch can assume potentials relative to earth in the event of a fault. A well-thought-out grounding and equipotential bonding concept reduces step and touch voltages and increases the availability of the construction power supply for hydraulic power packs and controls.
Step and touch voltages in the context of compensation grounding
Even with compensated grounding, a residual current remains. Dangerous potential gradients can occur around an earthing system. Relevant scenarios include temporary site power stations, transformer containers, mobile distribution boards, and long metallic structures. When concrete elements are separated with concrete demolition shear or split using hydraulic wedge splitter, new conductive connections arise (e.g., exposed reinforcing steel) that must be included in the equipotential bonding. Protective measures include adequate earthing resistances, bonding conductors, insulating standing surfaces, and avoiding uncontrolled ground loops.
Planning the construction power supply in compensated networks
Planning considers the network type, the site earthing resistance, protection selectivity, and cable routing. When supplied via compensated medium-voltage networks, coordinating earth-fault protection with downstream overcurrent protection is crucial so that temporary installations disconnect safely without unnecessarily impacting the upstream supply. For devices with high inrush currents, such as hydraulic power packs, appropriate starting concepts and protection must be provided to avoid nuisance tripping.
Practical focus points
- Determine the network type and coordinate with the utility regarding compensation and protection philosophy.
- Design the earthing system with a focus on low transition resistances and uniform potential distribution.
- Consistent equipotential bonding of all conductive parts of machines, tools, and temporary structures.
- Route power cables to minimize loops and ensure EMC-compliant installation.
- Documented verification of protective measures before commissioning and at intervals.
Metallic tools and hydraulics: grounding and equipotential bonding
Hydraulically driven tools such as hydraulic demolition shear, Multi Cutters, concrete demolition shear and steel shear are connected to the carrier machine via frame parts, hose systems, and couplings. They thus form large, partly moving conductors. Systematic integration into the equipotential bonding of the work area prevents potential differences when contacting soil, reinforcement, or pipelines. Hydraulic power packs must be connected with protective conductors; metallic protective enclosures, hose protection spirals, and superstructures must be included in the protective and functional equipotential bonding.
Specifics for concrete demolition shears and hydraulic wedge splitters
When cutting or splitting reinforced concrete, contact points form between the tool and the reinforcement. These contact points can be conductive to site power systems. Clear definition of grounding points on steel structures, the use of short bonding jumpers with sufficient cross-section, and insulating mats for operators reduce risks. For hydraulic wedge splitter, rock moisture and potentially conductive borehole water must also be considered, as they can promote local potential paths.
Measurement, testing, and documentation
Before commissioning, protective conductor resistances, loop impedances, insulation resistance values, and the effectiveness of disconnection conditions are tested. In compensated networks, earth-fault protection functions and selectivity with downstream protective devices must also be verified. Periodic tests document the condition of the earthing system — especially important on long-running projects in tunnel construction or during natural stone extraction with changing work areas.
Typical fault scenarios and protection technology
Single-phase earth faults due to damaged cables, moisture ingress in distribution boards, or mechanical impacts are among the most common faults. Compensation grounding limits the fault current; nevertheless, the fault must be detected. Wattmetric relays, directional elements, and insulation monitoring are used for this purpose. In the case of intermittent earth faults, for example from vibrating cable runs near heavy demolition equipment, fast, sensitive fault detection supports localization without unnecessarily interrupting the construction power supply.
EMC, controls, and radio
Large conductive areas and moving metal parts affect electromagnetic compatibility. A cleanly implemented grounding and shielding strategy protects controls of mobile hydraulic power units, radio remote controls of concrete demolition shear or Multi Cutters, and sensors. Symmetrical cable routing, star-shaped equipotential bonding, and avoiding closed loops reduce susceptibility to interference — particularly in compensated networks where transient phenomena can occur during earth-fault arc extinction.
Organizational measures and training
Technical measures work best when complemented by clear procedures: defined grounding points, releases after testing, regular visual inspections of bonding conductors, labeling of grounding terminals on mobile equipment, and staff instruction. Operators of concrete demolition shear, hydraulic wedge splitter as well as concrete demolition shear hydraulic power pack should understand the basics of step and touch voltages, recognize warning signs during earth-fault events, and apply safe behaviors.
Alignment with codes and standards
Planning, construction, and operation of earthing systems, protective measures, and equipotential bonding in areas with compensation grounding follow the applicable standards and recognized rules of technology. These include requirements for neutral-point treatment, earthing system design, selection of protective measures, and testing of electrical installations. The specific implementation must be coordinated for the project and overseen by competent persons.