Ⅰ. Definition of Dry Type Isolation Transformer Overload
A dry type isolation transformer operates with a fixed rated capacity, rated primary and secondary voltage, and corresponding rated current. Once the actual operating current of the transformer exceeds the rated current, and the actual load power surpasses the fixed rated capacity, the equipment is in an overload state. This judgment standard applies to all specifications of dry-type transformers, including the widely used 500 kva dry type transformer. Whether it is a high-power industrial static transformer or a conventional distribution unit for commercial and residential distribution, overload is defined by exceeding the rated current and capacity threshold.
For example, a 10kV/400V 500 kva dry type transformer and other large-capacity dry-type units with a capacity of 1000KVA have a rated primary current of 58A and a rated secondary current of 1440A. When the secondary current exceeds 1440A, the primary current will also exceed the standard value synchronously, triggering an overload condition. Long-term overload operation will cause continuous temperature rise of the transformer winding, accelerate insulation aging, and greatly shorten the service life of the dry type isolation transformer.
Ⅱ. Core Causes of Dry-Type Transformer Overload
In actual power distribution operation, the overload failure of dry-type transformers is mainly caused by three core factors, which are common in both industrial high-power units and conventional medium-capacity distribution equipment scenarios:
1. Excessive Mechanical Load: The most common overload cause. The overloaded operation of supporting electrical equipment such as motors leads to increased overall load current, which is manifested as obvious heating of electrical equipment and continuous excess of real-time operating current of the transformer. Long-term heavy load operation is the main cause of frequent overload of small and medium-sized transformers represented by standard medium-capacity models.
2. Unbalanced Three-Phase Voltage: Unbalanced voltage of the three-phase power supply will cause excessive current in a single phase of the transformer. Different from uniform overload, this fault features unbalanced heating of the transformer winding. Some conventional monitoring devices only display single-phase current, making it difficult to detect hidden overload risks, which easily causes sudden overload tripping of the unit.
3. Equipment Detection Failure: The internal current detection component of supporting frequency converters and power distribution equipment fails, resulting in detected current data being higher than the actual value, triggering misjudgment and false overload tripping of the transformer protection system.
Ⅲ. Overload Capacity & Allowable Operation Time Standard
The overload resistance of dry-type transformers is flexible, not fixed. The overload capacity of a dry type isolation transformer is affected by ambient temperature, initial load state before overload, insulation heat dissipation performance, and thermal time constant of the equipment. For accurate data, users can refer to the official overload curve provided by the manufacturer.
According to IEC and national industry standards, dry-type transformers have standardized allowable overload duration under different load multiples, which is the core basis for on-site operation and maintenance monitoring: 1.1 times rated load can operate continuously for 12 hours a day; 1.2 times rated load is allowed for 2 hours a day; 1.3 times overload can only last 30 minutes for emergency use; overload exceeding 1.4 times needs immediate power regulation and shutdown protection to avoid insulation damage and equipment burnout.
On-site power distribution staff need to monitor the operating status of transformers in real time. Once continuous overload is found beyond the specified time, they must immediately notify the production and dispatching department to adjust the load to ensure the safe and stable operation of power distribution equipment and the entire power grid.
Ⅳ. Industry Development Status & Future Trend of Dry-Type Transformers
China has become one of the world's largest producers and sellers of resin-insulated dry-type transformers, with an annual output of 10000MVA. The popularization of SC(B)9 series transformers features low noise (noise below 50dB for transformers below 2500kVA) and high energy saving (no-load loss reduced by 25%), making China's dry-type transformer manufacturing technology reach the world's advanced level.
In the future, dry-type transformers will develop in six major directions: energy saving and low noise, high operational reliability, environmental protection certification, large capacity, multi-functional integration, and multi-scenario adaptation. They will expand from conventional civil distribution to new energy, rail transit, nuclear power, marine engineering and other special fields, and the product specifications will also expand from small and medium capacity mainstream units to 35kV large-capacity power transformers.
Ⅴ. Enterprise Strength & Product Introduction
JINSHANMEN TECHNOLOGY CO., LTD is a professional manufacturer focusing on R&D, production and sales of power transmission and distribution equipment. The company mainly produces oil immersed power transformers, dry-type power transformers, oil immersed three-dimensional coiled power transformers, dry-type three-dimensional coiled power transformers, mining explosion-proof dry-type transformers, mining explosion-proof mobile substations, amorphous alloy power transformers, on load capacity regulating power transformers, locomotive dry-type transformers, as well as prefabricated substations, modular substations, wind energy box type substations, high and low voltage switchgear and other transmission and distribution equipment.
Adhering to strict production standards and quality control systems, we provide high-performance dry type isolation transformer, 500 kva dry type transformer and customized transformer solutions for global industrial, commercial, new energy and power distribution projects, with reliable product quality and perfect after-sales service, winning wide recognition from overseas customers.