In the upgrading of modern urban power grid, the large-scale construction of new energy, the development of commercial real estate and the transformation of power distribution in industrial parks, pad-mounted transformers have become the core equipment of underground power distribution systems. Compared with the traditional pole-mounted transformer, the pad-mounted transformer adopts a floor-to-floor closed structure, which has higher safety, cleaner appearance and lower difficulty in operation and maintenance, and can perfectly adapt to the modern urban landscape construction and high-standard power supply needs. At present, whether it is the North American municipal power grid transformation, overseas industrial and commercial power distribution projects, or domestic new energy power station supporting projects, the penetration rate of pad-mounted transformers continues to rise.
As a professional power equipment exporter, we have been in contact with a large number of overseas EPC projects, power design institutes and complete sets of contractors, most of the projects in the scheme selection stage, will give priority to replace the traditional overhead equipment, the use of standardized, customizable pad-mounted transformers.
Definition and core advantages of pad mounted transformer
Pad-mounted transformer is a floor-mounted oil-immersed transformer suitable for underground cable power distribution project. It is mainly used for 2.4 kV-35kV medium voltage conversion to civil, industrial and commercial standard low-voltage power, and is suitable for residential, commercial, industrial and new energy multi-scene power supply. Compared with the traditional pole transformer, the fully enclosed grounding design of the equipment has no exposed live parts, and the safety is higher. The low-rise floor structure is beautiful and hidden, which can be integrated into urban greening and municipal landscape, and is suitable for modern underground power grid transformation. The product supports conventional mineral oil and environmentally friendly natural ester insulating oil, with a conventional capacity of 15-5000kVA, and can also customize super-capacity models to cover various distribution loads.
The equipment adopts fully sealed steel tank and independent high and low pressure isolation cabinet. The bottom line has strong protection ability and can withstand outdoor humidity, temperature difference and corrosive environment. The internal low-loss iron core winding is matched with natural oil cooling for heat dissipation, stable operation and low failure rate. It integrates pressure relief, temperature control, open circuit protection and pressure regulating components, perfect protection and convenient operation and maintenance. It supports two networking modes of radiation and ring network, with strong power supply reliability. The whole machine is anti-corrosion and weather-resistant, all maintenance can be completed on the ground, no high-altitude operation is required, and the service life is long. It is the mainstream power distribution choice for municipal, park and new energy projects.
Pad mounted transformer mainstream type
Single-phase pad-mounted transformer
Single-phase pad-mounted transformer is the basic model of civil power distribution, designed for single-phase AC load design, small structure, economic cost, convenient installation, widely used in overseas residential areas, street shops, road lighting, single-family houses and other decentralized small power supply scenarios, is one of the most commonly used power distribution equipment in North American civil power grid.
The conventional capacity is 10kVA to 167kVA, and the standard specifications include 15, 25, 50, 75, 100 and 167kVA. The primary side is adapted to 4.16kV to 34.5kV medium voltage, and the secondary side outputs 120/240V standard single-phase voltage. The model adopts low-profile landscape design. The mainstream is equipped with front insulation structure and live-operated elbow joint to support dual networking mode of radiation and ring network. Some models have built-in through bus to facilitate power grid expansion. Products strictly follow the IEEE C57.12.25 standard, mature technology, stable performance, is the world’s civil low-voltage power distribution projects in the largest amount of the most versatile models.
Three-phase pad-mounted transformer
Three-phase pad-mounted transformer is the core model of high-power distribution, for commercial, industrial, new energy and other large-scale balanced load, large power supply capacity, stable voltage, strong load capacity, power supply balance and harmonic performance is better than single-phase equipment, is the first choice of large and medium-sized power engineering projects.
Conventional capacity is 45kVA to 5000kVA, customized models can exceed 10000kVA, and 75kVA to 3000kVA is the most widely used in commercial projects. The primary side is adapted to 4.16kV to 46kV medium voltage, and the secondary side can output 208Y/120V, 480Y/277V, 600V and other standard voltages. The equipment adopts multi-column iron core optimization structure, strong impact load resistance, standard load switch, pop-up fuse and backup current limiting fuse double protection, optional no-load voltage regulating device. Divided into pre-insulation (safe and convenient, mainstream selection) and rear porcelain casing (affordable, old transformation) two structures, widely used in commercial complexes, office buildings, schools, hospitals, industrial plants, data centers and other scenarios, in line with IEEE C57.12.34 standards.
Conventional pad mounted transformer
Conventional pad-mounted transformers are the most versatile and cost-effective standardized basic models in the market, featuring mature structure, stable performance and low failure rate, which are suitable for most conventional civil, commercial and municipal power distribution scenarios, and are also the category with the largest stock of power grids in the world.
The equipment adopts standard sealed oil-immersed structure, the iron core and winding are soaked in mineral insulating oil, insulation and heat dissipation are stable, the cabinet body terminals and interfaces are all standardized design, strong versatility, low procurement and installation costs. The protection takes the basic fuse protection as the core, which can efficiently deal with general faults such as overload and short circuit, and some models can be easily equipped with load switches. The overall structure is mature and durable, simple operation and maintenance, low maintenance cost, strictly follow the IEEE, ANSI general specifications, widely used in ordinary residential areas, small commercial blocks, municipal roads, conventional parks and other scenarios, is the cost-effective choice of small and medium-sized power projects.
Compartment pad mounted transformer
Compartment pad-mounted transformer is a modern upgraded high-end model, and is also the main push equipment for large municipal, new energy, data center and high-end commercial projects. Its core advantages are complete physical isolation of high and low voltage electrical areas, comprehensive upgrade of safety level, convenience of operation and maintenance, and equipment stability.
The equipment adopts the independent layout of the tank body and the wiring cabinet body. The high-voltage cavity and the low-voltage cavity are completely separated by thickened metal partitions, so as to prevent hidden dangers such as high and low voltage crosstalk, arc diffusion, misoperation and electric shock from the structure. The bottom centralized incoming line has good sealing performance and can effectively prevent rainwater and dust from invading. The cabinet body is equipped with anti-theft locking structure, pentagonal anti-theft bolts and interlocking door body, with strong anti-tampering and anti-damage ability, in line with IEEE C57.12.28 shell protection standard. It is also divided into two structures: front insulation and rear porcelain casing. Operation and maintenance personnel do not need to expose the live structure on the other side when overhauling one side of the line, thus greatly reducing the operation risk. It is widely used in key projects such as smart grid, high-end commercial cluster, large-scale new energy power station and data center.
Core application scenario of pad-mounted transformer
Residential Community Distribution
Residential community is the core and most common application scenario of pad-mounted transformers. Modern new residential areas and overseas residential areas generally adopt underground cable power distribution mode, abandoning traditional telephone poles and overhead lines, and the community environment is cleaner and safer. The small-capacity single-phase model is mainly responsible for household electricity consumption, and a single model can cover multiple household loads; the large-capacity three-phase model serves public supporting loads such as elevators, water supply pumps, landscape lighting, charging piles, fire fighting equipment, etc. The equipment is installed on the ground in the green space or corner open space of the residential area. The fully enclosed anti-misoperation structure can prevent children from touching by mistake. The power supply structure of the ring network has line redundancy capability. Automatic isolation of single-section faults will not cause power failure of the whole piece. It is fully adapted to the construction standards of smart communities and green communities.
Commercial Building Power Distribution
Shopping malls, office buildings, hotels, campuses, hospitals, convention and exhibition centers and other commercial public buildings with complex electricity load, many types of equipment, high power supply continuity requirements, large flow of people, three-phase pad-mounted transformer is the best solution for such scenarios. The equipment provides continuous regulated power supply for central air conditioning, fresh air system, elevator escalator, global lighting, security monitoring, office equipment, fire protection system, etc., with capacity ranging from hundreds of kVA to thousands of kVA. The design of full enclosure without exposed live parts can avoid potential public safety hazards, and the low landing structure will not affect the passage of personnel and commercial landscape. Commercial projects give priority to the front insulation type of ring network, which supports operation and maintenance without power failure and rapid isolation of faults, ensures uninterrupted power supply to the greatest extent, and avoids problems such as business losses and medical accidents caused by power failure.
Power distribution in industrial plant
The load power of the industrial plant area is large, the equipment runs continuously, the environment is dusty and humid, and the working condition fluctuates greatly, which requires high overload resistance, stability and durability of the transformer. Pad-mounted transformers are suitable for scenes such as production plants, industrial parks, storage bases, sewage treatment plants, automated workshops, etc. Conventional selection starts from 750kVA, and 1000kVA to 5000kVA is the most widely used. It can stably reduce the voltage power grid to industrial standard 480V three-phase power supply, meeting the high-power requirements of large-scale production machinery, motor units, air compressors, automated production lines, etc. The whole machine adopts thickened anti-corrosion steel shell, which is resistant to dust and moisture, anti-vibration, and can adapt to harsh industrial conditions for a long time. Compared with the traditional indoor substation, there is no need to build a special power distribution room, which covers a smaller area, has a shorter installation period, is easier to operate and maintain, and effectively saves land resources and infrastructure costs.
New energy projects connected to the grid
With the rapid development of global photovoltaic, wind power and energy storage industries, pad-mounted transformers have become the core grid-connected equipment of distributed and centralized photovoltaic power stations, wind power stations and BESS energy storage power stations. The new energy special model supports two-way power conversion, which can not only boost the low-voltage power output by the inverter to the medium-voltage grid standard to complete the grid connection, but also use the medium-voltage step-down power supply station in the grid for its own use. In view of the characteristics of intermittent and strong volatility of new energy power generation, the model optimizes the electromagnetic structure and heat dissipation system, has stronger anti-load impact ability, and can effectively suppress harmonic interference; at the same time, environmentally friendly flame-retardant natural ester insulating oil can be selected, which has excellent fire resistance and biodegradability, and meets the green environmental protection requirements of new energy projects. Equipment weather resistance is strong, compact, flexible installation, no need for complex infrastructure, can quickly adapt to the suburban open space, mountains, slopes and other new energy power station construction scenarios.
Municipal Infrastructure and Public Works
In the upgrading and transformation of urban power grids, municipal public works and public infrastructure construction, pad-mounted transformers are the core equipment of the underground smart grid system, which are widely used in urban trunk road power distribution, public venues, transportation hubs, large data centers, and public charging piles. Key projects such as clusters and urban water projects. Municipal projects on compliance, safety, landscape, reliability requirements are very high, pad-mounted transformers fully enclosed, anti-vandal, low noise, clean and beautiful features fully fit the modern urban public infrastructure standards. The equipment supports flexible networking of radiation and ring networks, which can help urban power grids to complete line segmentation optimization, rapid fault isolation and power supply reliability upgrading, and promote the transformation of traditional power grids to smart grids. At the same time, it can adapt to key load scenarios such as hospitals, emergency command centers and data centers, ensure uninterrupted power supply for key public equipment, and provide solid power support for stable operation of urban public services and livelihood security.
Scientific Selection Guide for Pad-mounted Transformers
Accurately Approved Equipment Capacity
Capacity selection is the core key of pad transformer selection, which directly determines the stability of equipment operation, service life and project investment cost. If the capacity selection is too small, the equipment will be in an overload state for a long time, which is prone to heating and aging, frequent tripping and frequent faults. If the capacity selection is too large, it will lead to light load operation of the equipment, high energy consumption, waste of procurement cost and insufficient economy.
In the early stage of selection, it is necessary to accurately count the total load power of all electrical equipment of the project, and scientifically convert the power of the equipment in combination with the industry standard load simultaneous coefficient. The simultaneous coefficient of electricity consumption in civil communities is generally 0.6 to 0.7, and the operation concentration of industrial and commercial production equipment is high. At the same time, the coefficient needs to be adjusted appropriately to ensure that the selection fits the actual operating conditions. In order to meet the needs of later project expansion, equipment addition and format upgrade, 10% to 30% of the capacity margin should be reserved during selection to avoid overload of equipment caused by later load increase. After the active power is counted, the system power factor is converted to apparent power, matching the most suitable standard capacity model, taking into account practicality and economy.
Matching high and low voltage level
High and low voltage levels must strictly match the local power grid standards and terminal equipment power demand, voltage parameters do not match will lead to equipment can not be connected to the grid, electrical equipment burned, serious also can lead to short circuit, fire and other safety accidents, is the core parameters of the selection process can not be wrong.
Before selection, the medium voltage distribution grade specified by the local power company shall be confirmed in advance. Common specifications in the industry include 4.16kV, 7.2kV, 12.47kV, 13.8kV, 24.94kV, 34.5kV, etc. At the same time, the grounding mode of the power grid and the BIL insulation impact grade of the equipment shall be confirmed to ensure that the insulation performance of the equipment is suitable for the working conditions of the power grid.
The secondary side output voltage matches the power consumption type of the project as required. 120/240V single-phase output is preferred for civil residence, and 208Y/120V and 480Y/277V three-phase output are preferred for commercial, industrial and equipment room scenarios. For remote lines and large fluctuations in the power grid, no-load voltage regulation device can be selected to realize multi-gear voltage regulation of ± 2.5 and ± 5% to ensure the continuous stability of the output voltage.
Reasonable choice of single-phase/three-phase architecture
The choice of single-phase and three-phase architecture is mainly based on the project load type, equipment power size and grid access mode. Small civil buildings, single-family houses, block lighting, small shops and other scattered light loads mainly based on lighting and sockets, give priority to single-phase pad-mounted transformers, with lower equipment cost, easier installation and less operation and maintenance costs.
All projects involving three-phase high-power equipment such as central air conditioning, elevators, production motors, air compressors, charging pile clusters, and automated production lines must use three-phase padded transformers. Three-phase power supply system voltage balance, low harmonic content, with strong load capacity, long-term stability to carry high-power load, operation stability is far more than single-phase equipment.
Under the working conditions of limited special site and emergency construction period, three single-phase transformers can be temporarily used in parallel to form a three-phase power supply system, but the overall power supply balance, stability and economy are not as good as the integrated three-phase pad-mounted transformer, which can only be used as a special alternative and is not recommended for long-term use.
Comprehensive consideration of equipment energy efficiency and loss
In the whole life cycle operation of transformers, the cost of energy loss is much higher than the cost of equipment procurement, so the energy efficiency and loss parameters of equipment are important assessment indicators for large-scale project selection. Although the initial purchase price of low-loss energy-saving models is slightly higher, the long-term energy-saving benefits are considerable, and the comprehensive cost performance is far higher than that of ordinary models.
Selection of priority in line with the United States DOE 10 CFR Part 431 energy efficiency standards of products, the use of high magnetic low-loss silicon steel sheet, optimized winding structure of high-efficiency models, can greatly reduce the no-load loss and load loss, long-term operation more energy-saving. For long-term full-load projects such as industry and new energy, the energy-saving effect is particularly significant.
The standard temperature rise of conventional equipment is 65 ℃, the temperature rise of high-efficiency and energy-saving models is lower, the operating temperature is more stable, the aging speed of insulation materials is slower, and the service life of equipment is longer. Large-scale engineering projects are recommended to achieve long-term cost reduction and efficiency through full life cycle cost accounting, giving priority to low-loss, energy-efficient models.
Combined with field environment custom configuration
Different installation environments have different requirements on equipment protection capability and adaptation performance, and special configuration needs to be customized according to on-site working conditions. Conventional inland mild environment, the selection of standard anti-corrosion coating, conventional mineral oil models can meet the long-term use needs, the best cost performance. The salt spray in coastal areas is heavy and corrosive, so it is necessary to upgrade and thicken the anti-corrosion coating or stainless steel cabinet to meet the IEEE C57.12.29 coastal protection standard to prevent corrosion and aging of equipment.
Schools, hospitals, wetland parks, closed parks and other scenes with high requirements for fire prevention and environmental protection, natural ester environmentally friendly flame retardant insulating oil can be selected, which has the advantages of strong flame retardancy, high spontaneous ignition point, and biodegradability. Environmental pollution. High altitude, extreme cold, high temperature, earthquake-prone areas, can be targeted to choose wide temperature adaptation models, high altitude special models, seismic reinforcement structure, to ensure the stable operation of equipment in extreme conditions.
Strict verification of industry standards and territorial specifications
All pad-mounted transformers must comply with IEEE C57 series general industry standards, UL certification, CSA certification, NEC installation specifications, and DOE energy efficiency regulations to ensure compliance with equipment basic performance. At the same time, different countries and different power companies have exclusive technical specifications. Project selection needs to strictly check the territorial standards to ensure that the equipment parameters, structure and certification fully meet the local grid connection acceptance requirements, so as to avoid the equipment from being unable to be accepted and connected to the grid.
Customized solution for pad mounted transformer
Electrical parameters customization
Standardized models can not adapt to all special conditions, professional manufacturers can provide full-dimensional electrical parameter customization services, comprehensive coverage of non-standard project requirements. Can be customized non-standard special capacity, double temperature level, large capacity models, the maximum can be customized 25000kVA large capacity equipment, to meet the large industrial, centralized new energy power station high power load demand. At the same time, it supports special high and low voltage ratio, double secondary winding, composite winding structure customization, and adapts to special grid voltage standards. For industrial harmonic loads and new energy bidirectional power flow conditions, K-class anti-harmonic models and bidirectional power flow special models can be customized to effectively suppress harmonic interference and adapt to nonlinear load operation requirements.
High and low voltage wiring structure customization
According to the project wiring habits, power grid networking mode, on-site installation space, personalized customization of casing specifications, 200A/600A elbow joint, incoming and outgoing line position and angle, flexible adaptation of ring network, radiation two networking modes. The specifications of low-voltage terminals, busbar structure and opening positions can be adjusted as required. At the same time, special grounding structure and insulated neutral wire structure can be customized to accurately match the grounding specifications of different countries and power companies to ensure wiring compliance and convenient installation.
Protection and switching system customization
On top of the basic fuse protection configuration, a full set of high-end protection system can be upgraded according to the safety level requirements of the project, including multi-level fuse combination, vacuum fault circuit breaker, surge protector, pressure relay, visual fracture device, etc., to improve the equipment fault protection capability in all directions. The 2-gear and 4-gear load switches can be customized to support line segmentation, grid-connected switching and ring network contact functions, and adapt to the regulation and control requirements of smart grid.
For high reliability and unattended projects, mechanical interlocking, electrical interlocking and remote data monitoring interface can be installed, which can monitor equipment temperature, oil level, pressure and operating load in real time, realize intelligent operation and maintenance of equipment, and adapt to modern smart grid construction standards.
Voltage regulation scheme customization
In view of the problems of long-distance line voltage drop, new energy power generation voltage fluctuation, grid voltage instability, etc., a multi-gear no-load voltage regulation scheme can be customized to support 5-gear and 7-gear voltage regulation structures, covering a variety of voltage regulation intervals such as ± 2.5% and ± 5%. According to the actual voltage fluctuation range of the project, the voltage regulation gear can be accurately matched, the output voltage can be effectively stabilized, the power quality of back-end equipment can be guaranteed, and the complex power grid conditions can be adapted.
Environment adaptation customization
For all kinds of complex extreme working conditions, we can provide all-round environmental adaptation customization scheme. Coastal salt spray environment can be upgraded with multiple anti-corrosion and customized stainless steel cabinets. Low-temperature flame retardant oil and wide-temperature insulation materials can be upgraded in alpine areas. High temperature and high humidity areas can strengthen the heat dissipation system and moisture-proof sealing structure; In high altitude and earthquake areas, reinforced seismic models can be customized. At the same time, environmentally friendly flame-retardant insulating oil and forced heat dissipation system can be selected as required to improve the environmental adaptation ability of the equipment in all directions.
Project standard customization
According to the exclusive technical standards of different countries, regions and power companies, the equipment size, appearance, nameplate, testing standards and certification system can be customized to meet the requirements of regional projects in North America, Southeast Asia, the Middle East, Africa and other global regions. It can provide a full set of factory test reports, third-party witness tests, project-specific technical data, and technical documents in Chinese and English, fully meeting all the data requirements for overseas project bidding, acceptance and grid connection.
Core evaluation criteria for reliable transformer manufacturers
Professional Engineering Technical Capabilities
High-quality pad-mounted transformer manufacturers must have independent electromagnetic design, structural research and development, thermal simulation optimization capabilities, and be able to independently complete standard model production and complex non-standard project customization. The mature technical team can accurately optimize the core winding structure, reduce equipment loss, improve short-circuit tolerance, and adapt to various complex power grid conditions. We also offer end-to-end technical support for overseas EPC projects and power engineering, including project load verification, scheme optimization, parameter matching, and technical consultation.
Mass Production and Manufacturing Capabilities
Reliable manufacturers have a complete independent production industry chain, covering the whole process of iron core processing, winding winding, tank welding, vacuum oiling, complete machine assembly, finished product testing, etc. The production process is independently controllable, with stable quality and accurate delivery date. It has the capacity of mass production of large quantities of standardized orders, and can flexibly undertake small quantities, high difficulty and non-standard customized orders, and can quickly respond to the delivery needs of various engineering projects at home and abroad.
Stringent Quality Control and Testing System
Regular manufacturers strictly in accordance with IEEE international standards to carry out a full set of factory testing, including DC resistance test, ratio test, polarity test, loss test, insulation test, sealing test and other routine testing items to ensure that the basic parameters of each equipment meet the standards. At the same time, the temperature rise test, lightning impulse test, short circuit withstand test and other type tests can be completed, and the equipment performance is fully up to standard.
Support third-party organizations to witness the factory test, the whole quality traceability, each equipment can provide a complete test report, certificate, technical parameter documents, to meet the strict requirements of overseas project bidding, acceptance, grid connection.
Comprehensive International Compliance Certifications
High-quality manufacturers suitable for overseas export must have complete international authoritative certification, including ISO quality system certification, UL certification, CSA certification, DOE energy efficiency certification, FM fire protection certification, etc., which fully meet the global mainstream market access standards such as North America, Europe and Southeast Asia. The equipment can be smoothly cleared through customs and connected to the grid, and is suitable for various foreign trade export projects.
Mature project delivery and after-sales capabilities
Professional export manufacturers have rich experience in landing projects at home and abroad, familiar with different national power standards, project processes, acceptance specifications, can provide drawing review, parameter docking, on-site guidance, bilingual technical information and other full-service. Perfect quality assurance system, sufficient spare parts reserves, long-term after-sales mechanism, can ensure the long-term stable operation of equipment, for overseas projects landing, long-term operation and maintenance to provide a solid guarantee.
Summary
As the core equipment of modern underground power distribution system, pad-mounted transformer completely replaces the traditional old overhead power distribution equipment by virtue of its multiple advantages of safety, reliability, beauty and concealment, convenient operation and maintenance, and strong adaptability, and is widely used in all-scene power projects such as residential communities, commercial buildings, industrial plants, new energy grid connection, municipal infrastructure and so on. Different types of single-phase, three-phase, conventional, compartment-type pad-mounted transformers can accurately match different load levels, working conditions and power supply requirements, and adapt to various standardized and customized projects.
Scientific capacity selection, accurate voltage matching, reasonable structure selection, and environmental customization for working conditions are the keys to ensure efficient, stable and long-term operation of pad-mounted transformers. At the same time, the manufacturer’s technical research and development strength, large-scale production capacity, strict quality control system, international certification qualification and perfect after-sales guarantee directly determine the quality of equipment and the landing effect of engineering projects, which is the core consideration of overseas EPC, engineering procurement and power bidding.
