Overhead lines

The planning and construction of complex overhead line systems requires specialist knowledge and experience, as well as the trust and cooperation of all parties involved. PFISTERER is a pioneer of innovative solutions in overhead line technology. Our products are reliably in use on all continents, sometimes under the most extreme conditions – from the intense heat of the tropics and deserts to ultra-low temperatures at northern latitudes.

Everything between tower and conductor

PFISTERER is a system partner with global experience in developing, designing and manufacturing complete insulator strings up to 1,100 kV. We design, produce and supply composite insulators, fittings and damping systems. Using modern simulation models for electrical field properties and mechanical loads, PFISTERER develops efficient, customer-specific solutions for complex challenges – with 100 years of experience included.


Key factors:

  • Lightweight, compact designs
  • Aesthetic solutions
  • Extremely high mechanical strength requirements
  • Extreme conditions (terrain, weather…)

The PFISTERER portfolio:

  • Complete overhead line insulator strings
  • Insulators
  • String fittings
  • Damping systems and vibration recorders
  • Fittings for fibre optic cables
  • Warning Spheres
  • Customised developments
  • Innovative solutions
  • Tests, calculations and measurements
  • Investigations, studies and condition assessments

Insulator strings

PFISTERER is a full-service partner for customised insulator strings and special solutions on all tower types, including compact lines. The insulator string design is based on the respective customer specifications, relevant standards and the latest findings from CIGRE working groups.

Our aim is to develop cost-efficient solutions, with high reliability that are easy to install. The quality and overall performance of the insulator strings are tested and confirmed in PFISTERER’s own high voltage laboratories in Altdorf (Switzerland) and Selb (Germany), and at various independent laboratories in Europe. PFISTERER insulator strings ensure reliable transmission system operation over decades.



Voltage level: up to 1,100 kV
Nominal strength: up to 1,500 kN
Creepage distance: up to 55 mm/kV
Short-circuit current: up to 63 kA/1s
Standards: IEC, DIN, ANSI, country-specific standards
Committees: CIGRE, IEEE, INMR

PFISTERER competencies:

Complete system from a single source

PFISTERER has been manufacturing fittings for over 60 years and composite insulators for more than 40. This knowledge and experience in development, production and application is what makes integrated solutions for insulator strings possible. Perfectly matched individual components increase operational reliability and reduce the risk of failure.

Defined processes guarantee a smooth project flow from consultation to installation on the tower, as well as a high degree of transparency and planning certainty.

Effective corona and arc protection

The distance between the corona rings and arcing horns is critical for the functionality of the corona and arcing protection. When dimensioned correctly, any flashover will jump in a controlled manner between the arcing horns. The other components of the insulator string remain protected. If the distance is too small, an uncontrolled flashover could occur from the arcing horn to the corona ring, and consequently damage the string components.


Control of radio interference voltage (RIV)

Corona discharges are prevented by the correct dimensioning of the corona protection, which is usually in the form of corona protection rings. This prevents damage to string components and the insulating jacket, and keeps the radio interference voltage (RIV) level within permissible limits. To calculate electrical field strengths, PFISTERER uses its own in-house simulation software. It shows the electrical field strength at every single point of an insulator string. Excessive field strengths in the protective fittings and insulators are therefore avoided during the design process.


Vibration damping

Wind generated aeolian vibrations and subspan oscillation lead to high loads on conductors. PFISTERER offers studies and components for effectively damping these conductor vibrations.

Use of the latest simulation programs to carry out vibration studies allows an exact calculation of conductor vibrations. As a result, the appropriate type of dampers and their precise position can be determined during the planning phase. Retrofitting dampers to existing overhead lines is also straightforward.

With PFISTERER vibrationrecorder Vibrec 500, conductor cable vibrations are measured and damping systems can be optimized by the data obtained.

Corrosion-resistant components

Corrosion-resistant individual components are crucial for the reliable operation of the whole insulator string. High quality materials and decades of manufacturing expertise ensure the quality and durability of PFISTERER composite insulators and fittings.

Steel fittings are hot dip galvanised. The thickness of the coating follows the recommendations of DIN EN ISO 1461. A thicker coating is available on request for highly corrosive environments or DC applications.


Simple installation

Throughout the development process, PFISTERER focuses on easy, safe and efficient handling and installation of the insulator string. Our lightweight, compact designs enable simple attachment to the tower. The consistent 3D modeling excludes assembly errors as far as possible.

Simulations and tests

PFISTERER is a scientific partner for overhead line topics. The company group has its own laboratories for high voltage , vibration damper and material testing. These facilities carry out design, type and sample testing in accordance with the relevant standards.


Compact lines

Compact transmission lines offer a range of advantages compared to conventional overhead lines, and can be implemented using standard lattice tower or innovative round pylons. Aesthetic designs can achieve higher public acceptance and make approval processes much shorter. But compact lines are also superior to conventional overhead lines in technical respects.


Reduced corridor width

In compact lines, the conductors are fixed to the pylons by means of insulated crossarms. This largely prevents the conductors swinging sideways. As a result, the right of way (ROW) corridor for a compact line can be up to 50% narrower than for conventional overhead lines.


Lower field stress

Compact lines reduce exposure to electromagnetic fields by up to 85% compared to conventional overhead lines. Because the conductor cables are much closer together, the electromagnetic fields of the different phases neutralize each other out. As a result, exposure to electromagnetic fields in the vicinity of the overhead line is significantly reduced.

More power

Due to the smaller distances between the conductor cables, the surge impedance in compact lines is much lower than in comparable standard lines. As a result, compact lines can achieve 15 to 20% higher transmission capacities.

Higher supply reliability

In compact lines, each conductor is fixed to the tower with two insulators. If one insulator breaks, the second insulator holds the conductor in place. As the conductor cable does not fall, total failure of the overhead line is prevented.

Overhead line Case Studies

PFISTERER is supplying French transmission system operator Réseau de Transport d’Électricité (RTE) with silicone composite insulators including protective fittings for suspension and strain strings with 225 kV and 400 kV and load classes from 150 kN to 600 kN.


To reduce vibrations caused by the wind, you don’t just need to know how, you also need to know where. That is because damping systems are only really effective if they are installed in the right place. A task for PFISTERER’s unique vibration recorder.


An aesthetic appearance: To meet this criterion for overhead lines in Denmark, PFISTERER developed four-meter-long composite insulators for truly beautiful energy.


A major compact line project in the Netherlands was looking for insulator crossarms that could meet the strict electromagnetic limits and withstand high mechanical loads. Not a problem for the experts at PFISTERER.