Engineered for demanding sub-transmission networks and high-capacity industrial applications, this 35kV cast-resin dry-type power transformer delivers reliable voltage transformation from 4000 to 20000 kVA. Built with an oil-free, fire-safe configuration and advanced vacuum-cast foil windings, it eliminates fire risks while ensuring exceptional structural resistance against electromagnetic forces during short-circuit events.
Modern power distribution networks serving data centers, heavy manufacturing facilities, and urban utilities face escalating challenges regarding fire safety, environmental protection, and footprint limitations. Traditional oil-immersed units require extensive containment infrastructure, whereas this dry-type architecture utilizes high-grade epoxy resin vacuum-cast insulation to provide superior moisture resistance, minimal partial discharge, and robust thermal performance. Operating with high-efficiency core materials and optimized foil winding geometries, the unit minimizes both no-load and load losses while maintaining low acoustic emissions suitable for indoor substations close to load centers.
Product Overview and Key Features
This 35kV cast-resin dry-type power transformer is classified as an advanced distribution and sub-transmission unit engineered for indoor installations or specialized weather-protected enclosures. It bridges the gap between high-capacity grid power and heavy industrial loads, accepting primary voltages across 35kV tiers while stepping down to standard secondary distribution levels. The absence of liquid dielectric fluids eliminates environmental contamination risks and complex fire suppression requirements.
The vacuum-cast epoxy resin insulation system encapsulates high-voltage conductors under deep vacuum, creating a void-free matrix that prevents internal electrical tracking, reduces partial discharge levels, and protects against ambient humidity, dust, and corrosive airborne agents. Foil winding technology in both high and low-voltage sections ensures even axial Ampere-turn distribution, which dramatically enhances mechanical stability and short-circuit withstand capability under severe fault conditions.
The core is constructed from high-permeability grain-oriented silicon steel sheets assembled with precision step-lap mitered joints to curb core losses and acoustic noise generation. Natural air cooling (AN) is standard, with optional forced air (AF) cooling controlled by intelligent temperature monitors to expand capacity by up to 40% during peak operational cycles. Integrated PT100 thermal sensors embedded directly within the low-voltage windings provide real-time thermal tracking and automated trip signaling.
Technical Specifications
Rated Capacity: 4000 - 20000 kVA @ 50 Hz / 60 Hz
High Voltage Rating: 35 / 36 / 37 / 38.5 kV @ No-Load
Low Voltage Rating: 6 / 6.3 / 10 / 10.5 kV @ No-Load
Connection Group: Dyn11 / Yd11 @ Standard Vector Configuration
Impedance Voltage: 8 / 10 / 11 % @ 75 °C Reference Temperature
HV Tapping Range: ± 2 x 2.5 % @ Off-Circuit Tap Changer
Insulation Level: LI 200 AC 85 kV @ High Voltage Terminal
Winding Material: Copper or Aluminum @ Foil Conductor Specification
Cooling Method: AN / AF @ Natural Air or Forced Air
Enclosure Protection: IP00 (Standard Open) / IP20 / IP23 @ Customized Enclosure
Partial Discharge Level: < 10 pC @ Rated Voltage Test
Temperature Rise: 100 K @ Class F Insulation System
Applications and Selection Guide
Targeted deployment environments encompass large industrial manufacturing plants, data centers, municipal utilities, and renewable energy integration substations where safety and reliability are critical. In data centers and commercial complexes, the low noise signature and fire-safe construction allow direct installation inside or adjacent to power distribution rooms, minimizing secondary low-voltage cable runs and associated copper losses. Heavy industrial sites benefit from the high short-circuit mechanical strength and robust thermal capacity required to handle frequent motor starting surges and variable dynamic loads.
The selection workflow begins by verifying the primary system voltage matching the available 35kV sub-transmission feed and determining the peak apparent power demand to select the correct capacity tier between 4000 and 20000 kVA. Engineers must evaluate the required secondary voltage level, vector group compatibility with upstream and downstream switchgear, and environmental parameters such as ambient temperature and particulate pollution levels. Standard impedance values of 8%, 10%, or 11% should be cross-referenced with fault-level studies of the electrical network to ensure adequate fault current limitation.
Optional customization parameters include specialized enclosure protection ratings up to IP23 for demanding environments, reinforced seismic mountings for active zones, and remote communication modules utilizing RS485 interfaces for integration into SCADA energy management systems. Beijing Zhongping Technology provides expert engineering consultation and technical support to assist design teams in matching transformer configurations with complex system requirements.
Installation and Compliance
Proper mechanical positioning requires a rigid, level concrete foundation capable of supporting the total structural weight of the transformer assembly. The unit can be maneuvered via bi-directional flat rollers or secured through designated base mounting channels, ensuring stable alignment with incoming high-voltage cables and outgoing low-voltage busbars. High-voltage connections are typically executed via enclosed bus ducts or shielded cable terminations, while low-voltage connections utilize flexible copper busbar links to isolate thermal expansion and mechanical vibration from the transformer terminals.
Off-circuit tap changers must be adjusted exclusively while the transformer is completely de-energized and grounded, verifying identical tap positioning across all three phases prior to re-energization. Grounding protocols mandate that the core, clamping frame, and enclosure must be tied to a low-impedance station earth grid in strict compliance with safety codes. Temperature control units must be wired using shielded twisted-pair cables separated from high-current power conductors to prevent electromagnetic interference on PT100 sensor signal loops.
Compliance standards governing design, manufacturing, and routine testing include relevant international electrotechnical and national frameworks covering dry-type power transformers. Routine testing regimens verify turn ratio, vector group identity, short-circuit impedance, load loss, no-load loss, dielectric strength, and partial discharge inception thresholds. Type test documentation is maintained to confirm thermal endurance and dynamic short-circuit mechanical stability under rated operating conditions.
Frequently Asked Questions
Q: 1. What are the delivery lead times and stock availability for this transformer series?
A: Standard configurations benefit from streamlined production scheduling, and Beijing Zhongping Technology maintains responsive supply chain coordination to ensure minimized project downtime and rapid delivery timelines.
Q: 2. What warranty coverage and after-sales support protocols apply upon delivery?
A: The unit is backed by a comprehensive manufacturer warranty covering structural and operational integrity, supported by technical service teams from Beijing Zhongping Technology for prompt diagnostic assistance and field resolution.
Q: 3. What are the operational differences and selection criteria between copper and aluminum windings?
A: Copper windings offer higher electrical conductivity and mechanical tensile strength, resulting in a more compact footprint and lower operational losses, whereas aluminum windings provide a lighter weight and cost-effective alternative for standard industrial loading profiles.
Q: 4. Can this cast-resin dry-type transformer be installed outdoors?
A: The core and coil assembly features an IP00 rating by default and requires a weatherproof protective enclosure rated to IP23 or higher to prevent moisture ingress and direct solar radiation if deployed in outdoor environments.
Q: 5. What is the allowable continuous and short-term overload capacity of the unit?
A: Continuous operation is bounded by the Class F insulation thermal limit with a 100 K rise, while short-term overloads up to 40% are permissible when equipped with activated forced air (AF) cooling fans controlled by the winding temperature monitor.
Q: 6. What routine maintenance is required for an oil-free cast-resin transformer?
A: Due to the solid epoxy insulation and oil-free construction, maintenance is minimal, requiring periodic visual inspection of dust accumulation on winding surfaces, functional checks of cooling fans, and verification of terminal torque connections.
Q: 7. How does the transformer manage acoustic noise levels in sensitive environments like hospitals?
A: The core employs step-lap mitered Silicon steel construction and anti-vibration damping pads under the base frame to suppress magnetostriction noise, maintaining sound pressure levels well within standard commercial building codes.
Q: 8. What does the Dyn11 vector group designation signify for system integration?
A: The Dyn11 configuration indicates a delta-connected high-voltage primary and star-connected low-voltage secondary with a 30-degree phase shift, effectively absorbing third harmonic currents and providing a neutral point for balanced single-phase loading.
FAQ
1.Who are We?
Beijing Zhongping Technology Co., LTD., is a global industrial electrical automation service provider, is a scientific research, design, marketing, technical services, industrial Internet, international import and export services as one of the science and technology companies.
2.What can you buy from us?
PLC, inverter, human-machine interface, hydraulic products, low-voltage power distribution, industrial robots and core components
3.Is the item in stock or need to be purchased from another supplier?
We have a large inventory of goods and have our own warehouse.
4.What advantages do we have over other suppliers?
Our company has a large amount of inventory and a number of warehouses, but also in the country's important industrial provinces and cities with offices and a number of overseas service points. To provide you with intelligent manufacturing one-stop comprehensive services, save efforts, labor and cost.
5.Can you provide 100% new original authentic products?
We only sell new original genuine, no renovation, no fake, only for the original factory original!
6.How long is the delivery time?
If there is a stock, it will take 2-3 working days to ship, if the quantity is large, it will take 5-7 working days after receiving the payment, if it is not a conventional model, it will take some time, we will inform you of the specific delivery time.
7.Is there technical support available?
Of course, we have a professional technical team that can help you solve technical problems.
8.How do we guarantee quality?
We have three processes to control the quality of goods.
1) Our engineers will inspect the production and quality control in the factory regularly.
2) Incoming materials shall be inspected by experienced purchasing engineers before they can be stored.
3) At least 2 people in the logistics department cross-check the goods to be sent before delivery.
9.Can you guarantee the safe and reliable delivery of your products?
Yes, we strictly adopt the international standard packing. We also use special packaging for dangerous goods, and refrigerated shipping for items with temperature requirements. Special item packaging and general cargo standard packaging requirements may incur additional costs.
10.How about the freight?
The cost depends on how you choose to get the goods. Express is usually the fastest but also the most expensive way. Sea freight is the best solution for large quantities of goods. The exact shipping cost depends on the purchase amount、quantity and weight of your order. Please feel free to contact us for more information.
+86 010-64225983
+8613811814778
Building 26, Liyuan Community, Chaoyang District, Beijing, China
