The electrical networks of modern megacities evolve in conditions of rapidly increasing density of transmitted power, decreasing controllability and observability of the network, aggravation of social and environmental problems.

Therefore, the technical re-equipment of electric networks should be carried out on the basis of new innovative technologies leading to the creation of an adequate electrical equipment in accordance with modern requirements.

The company together with PJSC “FGC UES” carried out R & D activities on the topic: “Creation of a complex of equipment to provide deep power inputs to megacities and powerful sealed transfers based on gas-filled transmission lines”, whose goal was to develop basic technologies for creating gas-insulated power lines at a nominal voltage of 330 – 500 kV for use as deep power inputs in megacities, and powerful sealed power transmissions for in-plant substations nnyh ties transmission of electricity across rivers and other obstacles with the help of conductors embedded in bridges and transport tunnels, the establishment of production of gas insulated transmission lines, and the organization of their delivery to the power companies.



In the course of the project implementation, the work was carried out in the following areas:

  • Development of a gas conductor for a rated voltage of 500 kV

(GIL-500), adapted for use in megacities and other areas where its application is technically and economically feasible;

  • Development of end devices for gas conductors for connection to power transmission lines and 500 kV substations;
  • Development of technologies for laying gas-insulated extended current conductors;
  • Implementation of the pilot project for installation of the prototype GIL-500.

As a result of JSC “NPO VEI Elektroizolyatsiya” project, the basic elements of a new type of equipment have been developed and being manufactured. On the basis of gas-insulated lines of class 330-500 kV a pilot project of a 500 kV gas current conductor was performed and a new generation of energy efficient power equipment was created including all modern developments and achievements in the fields of high-voltage technologies, monitoring systems, production and installation of electric power equipment – powerful sealed environmentally friendly transmission lines.

Joints and parts manufactured by the company in accordance with the developed technologies as a result of R & D within the framework of the project:


Bellows compensator

(Thermal expansion compensation system)


Sealed insulator
Swivel section Disconnector Module


Gas filling flange


 Linear GIL module Sliding multi-point bracelet

current conductor

A conductor with a supporting insulator
Current conductors Screen of electric field equalization
Linear module

with insulator





During the implementation of R & D, the company have developed technologies for the manufacture of GIL of the second-generation, which are characterized by the use of mixtures of SF6 with nitrogen, which reduces costs and facilitates the use of GIL at low temperatures. It is mandatory to use special particle traps inside sealed sections, which significantly reduces the likelihood of possible gas leaks due to the use of modern welding systems, ultrasonic quality control of welding. In addition, the usage of effective line condition monitoring systems and special pre-start test procedures is also mandatory.

The most common application of GIL in the world practice is the implementation of deep power supply to large cities. The total cost of GIL laying is several times higher than the cost of construction of overhead power lines, but considering the cost of land in major cities, the total cost of GIL will be lower than the cost of overhead lines of the same voltage class.

The usage of GIL for the implementation of deep power supply to cities will significantly reduce the area occupied by power lines. In this case, the liberated territories can be used for roads and communications. This is especially important from the point of view of the development of infrastructure and transport support for large cities.

Priority areas for the use of gas-filled lines are also intra-substation connections, vertical input / output of electric power, transmission of electricity through rivers and other obstacles by means of current conductors embedded in bridges or transport tunnels.

The dielectric losses are insignificantly small. In addition, due to the outer shell, the diameter of which is much larger than that of the cable, the heat dissipation is more efficient, and, therefore, in almost all applications of GIL, a cooling system can be dispensed with.

GIL is heat resistant and does not increase the load during a fire, which in itself is also a protection of people and the environment. This is especially important for hydroelectric power stations in which the connection between the overhead line and the high-voltage switchgear passes through tunnels and mines.

Due to a wide range of advantages, a zone of the preferred use of GILs as a powerful (1000-4000 MW) power transmission line is currently being formed, the laying conditions of which do not allow the use of overhead lines and traditional cables due to the impossibility of alienating large areas of land for overhead lines, the level of external electromagnetic fields, power losses, as well as in the presence of obstacles for laying power lines.

We note that the electromagnetic field outside the GIL is also negligible. In this regard, even in critical areas from the point of view of electromagnetic compatibility (for example, airports, computer centers), no special screening of GILs is required.


The GIL laying methods are:

  • Installation above ground – ground; the main element for installing a ground GIL is steel or reinforced concrete structures. Steel structures can be mounted directly above the ground on concrete foundations and can reach several meters in height, depending on local conditions for laying the GIL route.
  • Underground installation – underground;
  • Tunnel gasket – tunnel.

For GIL laying, the following can also be selected:

The trench (usually does not exceed a width of several meters (3-5 m) and lies below the surface of the earth, depending on the voltage class of the GIL);

Tunnel (usually made of concrete sections of round or square shape .The dimensions for the single-line GIL line are 3 m in width and 1 m in height.



Line type Rated voltage, kV
110 220 330 500
Overhead lines 0,1-0,15 0,2-0,3 0,3-0,4 0,8-1,0
Cable line with natural cooling 0,1 0,2 0,3 0,5
Cable line with forced cooling 0,2 0,5 0,6-0,7 1,0 – 1,3
GIL of underground laying 0,1 0,3 – 0,5 0,7 – 1,0 1,4-2,0
GIL of aboveground laying and in the tunnel 0,25 1,2 3,0 6,5



In general, the economic effect of the introduction of GIL is achieved through:

  • Decrease in energy losses by more than 3 times compared to overhead lines and 2 times as compared with the cable line;
  • Increase the throughput more than 2 times compared to the cable line;
  • Decrease of the area of ​​alienated land by 30-50 times in case of ground laying in comparison with overhead lines;
  • Reducing the cost of the gasket in comparison with cable lines by the value of the cost of excavation;
  • Improved environmental friendliness, fire and explosion safety.
  • Adaptability – the possibility of combining with the existing load-bearing structures, including vertical ones, without deteriorating the safety of the facilities, which additionally reduces the cost of the gasket.


At present, the company’s specialists have the necessary skills and resources to carry out calculations and work packages for the design and implementation of GIL.

To improve the quality and reliability of the products, the elements and materials of the world’s leading manufacturers are used in part:

  • contact connections;
  • elements of the monitoring system;
  • connections of the conductor elements and shell.

The presence of a test base allows us to monitor the quality of products.

Our production sites: Moscow, St. Petersburg.