This article examines the use of busbar trunking systems for power distribution up to 1,000 V at facilities using nuclear energy. It analyzes the structural and operational advantages of busbar trunking over conventional cable lines under conditions of high-density utility routes, limited installation space, and increased requirements for reliability, fire safety, and maintainability. The article provides a classification of busbar trunking by functional purpose, technical characteristics, and the specific features of design and installation at restricted-access nuclear-industry facilities. Recommendations are given for selecting and operating busbar trunking systems.
Introduction
A busbar trunking system is a complete assembly consisting of conductors (busbars) separated by gaps and supported by insulating material, enclosed inside a pipe, tray, or similar casing. In essence, it is a factory-made rigid current conductor supplied in complete sections and used to transmit and distribute electricity in production areas and on industrial sites.
At nuclear power facilities, where power-supply systems must ensure continuous and safe operation of equipment throughout a 60-year service life, the choice of the power-distribution method becomes critical. The traditional solution - laying power cables in trays, pipes, or cable ducts - faces several limitations in the saturated engineering routes of an NPP: large bending radii of multi-core cables, the need for bulky connecting sleeves, the difficulty of adding new consumers without shutting down production, and increased energy losses.
Busbar trunking systems offer a fundamentally different solution that optimizes the use of available space, improves power-supply reliability, and reduces operating costs.
Limitations of Cable Systems under High-Density Engineering Routes
Despite their widespread use, cable power-supply systems have a number of disadvantages that are especially noticeable at facilities with high-density engineering utilities.
When power cables are laid, standardized bending radii must be observed, especially when three or four large-cross-section cables per phase are used. Bulky connecting and termination couplings are also required. In the confined conditions of NPP turbine halls, switchgear rooms, and cable trestles, this creates serious difficulties. In addition, conventional cable lines have increased fire risk: unlike busbar trunking, cable systems have a higher probability of ignition and contribute to flame spread.
Cables are also characterized by high energy losses during transmission - up to 5-7% of transmitted power. At the scale of a large industrial facility such as a nuclear power plant, this difference translates into the loss of millions of kilowatt-hours annually. The reactive impedance of cable lines is higher, which reduces the power factor and increases the load on generating equipment.
A major limitation is low maintainability and the difficulty of modernization. Adding new consumers or changing the connection scheme in densely packed cable routes is practically impossible without production stoppage and significant financial costs.
Structural and Technical Advantages of Busbar Trunking
Busbar trunking systems provide a comprehensive solution to the problems listed above. Key advantages of busbar trunking over cable systems include:
Compactness and reduced footprint. The main advantage of busbar trunking is its compact design, achieved by arranging conductors inside an enclosure. A busbar trunking system does not require much installation space, which is critical in the limited-space conditions of an NPP.
Low losses and better cooling. Due to its design and insulation quality, modern busbar trunking reduces electrical losses to 1-3%. Better cooling is achieved by the high compression density of the busbars, which are located inside a metal enclosure that dissipates heat efficiently.
Improved fire safety. Busbar trunking systems do not propagate fire, do not burn, and do not release harmful chemical substances during a fire. In the event of ignition, the busbar trunking does not create a draft effect. Many modern busbar systems maintain three-hour integrity under fire conditions (1,000°C) and provide IP68 protection for critical sections.
Flexibility and scalability. At facilities with existing electrical installations, relocating individual consumers or adding new ones is a serious financial and technical challenge. The features and advantages of the modular busbar design allow these tasks to be solved simply, quickly, and economically, because all system components can be easily disassembled and reassembled.
Durability and ease of maintenance. Under normal operating conditions, busbar trunking requires almost no maintenance, and its service life reaches 25-30 years.
Reliability. The rigid structure provides a high degree of resistance to short-circuit currents. The inductive reactance is significantly lower due to the minimum distance between conductors.
Classification of Busbar Trunking
By functional purpose, busbar trunking systems are divided into several main types.
Feeder busbar trunking is intended for constructing main lines, connecting substations on the low-voltage side, supplying distribution busbar trunking systems, and feeding individual large power receivers. Feeder busbar trunking ratings range from 630 A to 6,300 A. Main lines are built with a minimum number of joints and transmit high power over considerable distances.
Distribution busbar trunking consists of special sections with installed tap-off units to which power consumers are connected directly. Its main advantage is the ability to connect additional equipment easily without de-energizing and rebuilding the main line. Distribution busbar trunking ratings range from 100 A to 6,300 A.
Lighting busbar trunking is used to create lighting networks and connect low-power lighting fixtures at currents from 25 to 40 A. Such modules are most often used to create branched lighting routes along production lines.
Trolley busbar trunking is used to supply mobile power receivers: cranes, overhead traveling cranes, monorails, floor trolleys, and other equipment. It is produced for currents from 35 A to 1,000 A.
The design of most busbar trunking systems consists of a package of busbars tightly pressed together, insulated with polyester film, and placed inside an enclosure. The busbars are made of rectangular copper or aluminum.
Regulatory Requirements and Specific Features of Use at NPPs
Busbar trunking systems used at facilities using nuclear energy must meet increased safety requirements.
Busbar trunking equipment must have certificates of conformity and approval for use at nuclear-industry facilities. The main regulatory documents are NP-001-15, General Provisions for Ensuring the Safety of Nuclear Power Plants, the 7th edition of the Electrical Installation Code (PUE), and industry standards governing electrical installations at facilities using nuclear energy.
Chemical resistance of materials in aggressive environments is a critical requirement. Nuclear power plants and fuel-cycle enterprises operate under possible exposure to saturated vapors of nitric acid and other aggressive substances. Busbar trunking installed in such zones must have a special material composition and design that guarantee safe operation.
In zones with increased cleanliness requirements and in the containment area of an NPP, cast-resin busbar trunking with a high degree of protection - at least IP55 - and a smooth enclosure that prevents dust accumulation and allows decontamination is preferable. Fire safety of busbar trunking is also crucial: systems that do not spread combustion and do not release halogens when heated are mandatory in rooms classified as A, B, or C for explosion and fire hazard.
The classification of NPP power receivers by power-supply reliability categories according to the PUE (special category 1, category 1, and category 2) imposes requirements for redundancy and accident-free operation. Owing to high mechanical strength, lower probability of damage, and the possibility of rapid switching of sections, busbar trunking systems are a preferred solution for ensuring uninterrupted power supply to safety and control-system equipment.
Design and Installation
Switching to busbar trunking systems reduces installation time compared with cable systems and lowers the cost of electrical-installation works.
Electrical installation of busbar trunking at nuclear facilities must be carried out according to a Work Execution Plan (WEP) and in strict compliance with the requirements of the Unified Installation Standards and the Electrical Installation Code. For busbar trunking in safety-system circuits of category 1, 100% quality control of joints is mandatory: checking the tightening of bolted joints with a torque wrench, measuring contact resistance at joints with a milliohmmeter, and thermal-imaging inspection under load.
For cast-resin busbar trunking, the integrity of the cast insulation is checked before installation using a high-voltage test. Linear expansion must be taken into account: expansion sections are installed for extended lines. For rooms with increased seismicity - NPPs are built in seismic zones of up to 9 points - busbar trunking is attached to building structures through anti-seismic penetrations that allow building movements without destroying the busbar assembly.
All measurement results and concealed-work certificates are recorded in the as-built documentation and submitted to construction control.
Operation and Maintenance
Busbar trunking requires virtually no maintenance throughout its service life. The main activities are periodic thermal-imaging inspection of connection points (annually for category 1) and tightening of bolted joints in accordance with the manufacturer’s regulations (every 5-7 years).
Copper or aluminum busbars may corrode when they come into contact with acids and alkalis at nuclear-cycle enterprises; therefore, in zones with aggressive media, busbar assemblies must have a sealed enclosure of at least IP54 and an additional protective layer, such as silver plating or tinning of contact surfaces.
Conclusions
Busbar trunking systems are a technologically and economically justified alternative to cable ducts for power supply at facilities with high-density engineering utilities, including nuclear power plants and fuel-industry enterprises.
The compact design, modularity, and scalability of busbar trunking systems make it possible to use the limited space of cable rooms and turbine halls efficiently and to add new consumers quickly without shutting down production. Low energy losses (up to 1-3% versus 5-7% for cables) and better cooling provide energy efficiency and reduce operating costs. High mechanical strength, vibration resistance, non-combustibility, and resistance to aggressive media make busbar trunking a preferred solution for zones with special safety requirements, including chemically active environments and explosion- and fire-hazardous rooms.
The service life of busbar trunking reaches 25-30 years with minimal maintenance, reducing the total cost of ownership compared with cable systems that require periodic replacement and repair.
To receive a commercial proposal for the design, supply, and installation of busbar trunking systems for your facility, send a technical specification indicating capacity, redundancy scheme, zone safety class, and architectural constraints to the commercial department of TechAtomStroy LLC via the feedback form on the website. A cost estimate, an electrical-installation schedule, and a list of the required measuring and control equipment will be prepared.
*This material was prepared on the basis of the requirements of NP-001-15, the 7th edition of the Electrical Installation Code (PUE), and industry technical recommendations for power-supply systems at facilities using nuclear energy and industrial enterprises.*
Introduction
A busbar trunking system is a complete assembly consisting of conductors (busbars) separated by gaps and supported by insulating material, enclosed inside a pipe, tray, or similar casing. In essence, it is a factory-made rigid current conductor supplied in complete sections and used to transmit and distribute electricity in production areas and on industrial sites.
At nuclear power facilities, where power-supply systems must ensure continuous and safe operation of equipment throughout a 60-year service life, the choice of the power-distribution method becomes critical. The traditional solution - laying power cables in trays, pipes, or cable ducts - faces several limitations in the saturated engineering routes of an NPP: large bending radii of multi-core cables, the need for bulky connecting sleeves, the difficulty of adding new consumers without shutting down production, and increased energy losses.
Busbar trunking systems offer a fundamentally different solution that optimizes the use of available space, improves power-supply reliability, and reduces operating costs.
Limitations of Cable Systems under High-Density Engineering Routes
Despite their widespread use, cable power-supply systems have a number of disadvantages that are especially noticeable at facilities with high-density engineering utilities.
When power cables are laid, standardized bending radii must be observed, especially when three or four large-cross-section cables per phase are used. Bulky connecting and termination couplings are also required. In the confined conditions of NPP turbine halls, switchgear rooms, and cable trestles, this creates serious difficulties. In addition, conventional cable lines have increased fire risk: unlike busbar trunking, cable systems have a higher probability of ignition and contribute to flame spread.
Cables are also characterized by high energy losses during transmission - up to 5-7% of transmitted power. At the scale of a large industrial facility such as a nuclear power plant, this difference translates into the loss of millions of kilowatt-hours annually. The reactive impedance of cable lines is higher, which reduces the power factor and increases the load on generating equipment.
A major limitation is low maintainability and the difficulty of modernization. Adding new consumers or changing the connection scheme in densely packed cable routes is practically impossible without production stoppage and significant financial costs.
Structural and Technical Advantages of Busbar Trunking
Busbar trunking systems provide a comprehensive solution to the problems listed above. Key advantages of busbar trunking over cable systems include:
Compactness and reduced footprint. The main advantage of busbar trunking is its compact design, achieved by arranging conductors inside an enclosure. A busbar trunking system does not require much installation space, which is critical in the limited-space conditions of an NPP.
Low losses and better cooling. Due to its design and insulation quality, modern busbar trunking reduces electrical losses to 1-3%. Better cooling is achieved by the high compression density of the busbars, which are located inside a metal enclosure that dissipates heat efficiently.
Improved fire safety. Busbar trunking systems do not propagate fire, do not burn, and do not release harmful chemical substances during a fire. In the event of ignition, the busbar trunking does not create a draft effect. Many modern busbar systems maintain three-hour integrity under fire conditions (1,000°C) and provide IP68 protection for critical sections.
Flexibility and scalability. At facilities with existing electrical installations, relocating individual consumers or adding new ones is a serious financial and technical challenge. The features and advantages of the modular busbar design allow these tasks to be solved simply, quickly, and economically, because all system components can be easily disassembled and reassembled.
Durability and ease of maintenance. Under normal operating conditions, busbar trunking requires almost no maintenance, and its service life reaches 25-30 years.
Reliability. The rigid structure provides a high degree of resistance to short-circuit currents. The inductive reactance is significantly lower due to the minimum distance between conductors.
Classification of Busbar Trunking
By functional purpose, busbar trunking systems are divided into several main types.
Feeder busbar trunking is intended for constructing main lines, connecting substations on the low-voltage side, supplying distribution busbar trunking systems, and feeding individual large power receivers. Feeder busbar trunking ratings range from 630 A to 6,300 A. Main lines are built with a minimum number of joints and transmit high power over considerable distances.
Distribution busbar trunking consists of special sections with installed tap-off units to which power consumers are connected directly. Its main advantage is the ability to connect additional equipment easily without de-energizing and rebuilding the main line. Distribution busbar trunking ratings range from 100 A to 6,300 A.
Lighting busbar trunking is used to create lighting networks and connect low-power lighting fixtures at currents from 25 to 40 A. Such modules are most often used to create branched lighting routes along production lines.
Trolley busbar trunking is used to supply mobile power receivers: cranes, overhead traveling cranes, monorails, floor trolleys, and other equipment. It is produced for currents from 35 A to 1,000 A.
The design of most busbar trunking systems consists of a package of busbars tightly pressed together, insulated with polyester film, and placed inside an enclosure. The busbars are made of rectangular copper or aluminum.
Regulatory Requirements and Specific Features of Use at NPPs
Busbar trunking systems used at facilities using nuclear energy must meet increased safety requirements.
Busbar trunking equipment must have certificates of conformity and approval for use at nuclear-industry facilities. The main regulatory documents are NP-001-15, General Provisions for Ensuring the Safety of Nuclear Power Plants, the 7th edition of the Electrical Installation Code (PUE), and industry standards governing electrical installations at facilities using nuclear energy.
Chemical resistance of materials in aggressive environments is a critical requirement. Nuclear power plants and fuel-cycle enterprises operate under possible exposure to saturated vapors of nitric acid and other aggressive substances. Busbar trunking installed in such zones must have a special material composition and design that guarantee safe operation.
In zones with increased cleanliness requirements and in the containment area of an NPP, cast-resin busbar trunking with a high degree of protection - at least IP55 - and a smooth enclosure that prevents dust accumulation and allows decontamination is preferable. Fire safety of busbar trunking is also crucial: systems that do not spread combustion and do not release halogens when heated are mandatory in rooms classified as A, B, or C for explosion and fire hazard.
The classification of NPP power receivers by power-supply reliability categories according to the PUE (special category 1, category 1, and category 2) imposes requirements for redundancy and accident-free operation. Owing to high mechanical strength, lower probability of damage, and the possibility of rapid switching of sections, busbar trunking systems are a preferred solution for ensuring uninterrupted power supply to safety and control-system equipment.
Design and Installation
Switching to busbar trunking systems reduces installation time compared with cable systems and lowers the cost of electrical-installation works.
Electrical installation of busbar trunking at nuclear facilities must be carried out according to a Work Execution Plan (WEP) and in strict compliance with the requirements of the Unified Installation Standards and the Electrical Installation Code. For busbar trunking in safety-system circuits of category 1, 100% quality control of joints is mandatory: checking the tightening of bolted joints with a torque wrench, measuring contact resistance at joints with a milliohmmeter, and thermal-imaging inspection under load.
For cast-resin busbar trunking, the integrity of the cast insulation is checked before installation using a high-voltage test. Linear expansion must be taken into account: expansion sections are installed for extended lines. For rooms with increased seismicity - NPPs are built in seismic zones of up to 9 points - busbar trunking is attached to building structures through anti-seismic penetrations that allow building movements without destroying the busbar assembly.
All measurement results and concealed-work certificates are recorded in the as-built documentation and submitted to construction control.
Operation and Maintenance
Busbar trunking requires virtually no maintenance throughout its service life. The main activities are periodic thermal-imaging inspection of connection points (annually for category 1) and tightening of bolted joints in accordance with the manufacturer’s regulations (every 5-7 years).
Copper or aluminum busbars may corrode when they come into contact with acids and alkalis at nuclear-cycle enterprises; therefore, in zones with aggressive media, busbar assemblies must have a sealed enclosure of at least IP54 and an additional protective layer, such as silver plating or tinning of contact surfaces.
Conclusions
Busbar trunking systems are a technologically and economically justified alternative to cable ducts for power supply at facilities with high-density engineering utilities, including nuclear power plants and fuel-industry enterprises.
The compact design, modularity, and scalability of busbar trunking systems make it possible to use the limited space of cable rooms and turbine halls efficiently and to add new consumers quickly without shutting down production. Low energy losses (up to 1-3% versus 5-7% for cables) and better cooling provide energy efficiency and reduce operating costs. High mechanical strength, vibration resistance, non-combustibility, and resistance to aggressive media make busbar trunking a preferred solution for zones with special safety requirements, including chemically active environments and explosion- and fire-hazardous rooms.
The service life of busbar trunking reaches 25-30 years with minimal maintenance, reducing the total cost of ownership compared with cable systems that require periodic replacement and repair.
To receive a commercial proposal for the design, supply, and installation of busbar trunking systems for your facility, send a technical specification indicating capacity, redundancy scheme, zone safety class, and architectural constraints to the commercial department of TechAtomStroy LLC via the feedback form on the website. A cost estimate, an electrical-installation schedule, and a list of the required measuring and control equipment will be prepared.
*This material was prepared on the basis of the requirements of NP-001-15, the 7th edition of the Electrical Installation Code (PUE), and industry technical recommendations for power-supply systems at facilities using nuclear energy and industrial enterprises.*