2026-04-27

Why Use Oil-Immersed Transformers in Solar Power Plants? Key Selection Points for PV Step-Up Substations

In the global wave of energy transition, photovoltaic (PV) power generation has become a backbone of renewable energy systems. From large-scale ground-mounted plants to commercial and industrial distributed projects, every PV plant faces the same technical challenge: how to efficiently and stably connect the low-voltage AC power produced by inverters to the medium- or high-voltage grid. The core device that solves this problem is the PV step-up transformer – a critical component of the step-up substation. Among the various transformer types, oil-immersed transformers have been widely adopted in PV plants due to their unique technical characteristics. This article discusses “why choose oil-immersed” and “how to select the right transformer” for EPC contractors, PV plant investors, and technical engineers. 1. Core Role of Oil-Immersed Transformers in a PV Plant Before understanding “why oil-immersed”, it is essential to understand the basic function of a PV step-up transformer. PV modules convert sunlight to DC power, and inverters convert DC to AC. Because PV plants are often located far from the grid connection point and the low-voltage AC output of the inverters (typically 400 V–800 V) is not suitable for long-distance transmission, the voltage must be stepped up to medium voltage (e.g., 10 kV, 35 kV or higher) to reduce...

2026-03-27

Hot Spot Temperature: How to Monitor and Control the Internal Temperature of a Transformer?

In the operation and management of transformers, temperature is a core indicator for measuring the “health status” of the equipment. Among all temperature parameters, hot spot temperature is particularly critical—it refers to the temperature at the hottest spot inside the transformer and directly determines the aging rate of insulating materials and the service life of the equipment. What is Hot Spot Temperature? Hot spot temperature is the temperature at the point with the highest temperature inside a transformer. Due to uneven current distribution, differences in heat dissipation conditions and other factors, the temperature of each part of the transformer is not uniform. Why is hot spot temperature so important? According to the classic 8-degree Rule—for every 8℃ increase in the operating temperature of insulating paper, its thermal aging rate doubles, and the service life is halved accordingly. Therefore, controlling the hot spot temperature is equivalent to controlling the service life of the transformer. Hot spots usually appear at the following positions: – Inside the winding: high current density and long heat dissipation path – At the winding ends: concentrated leakage flux and poor heat dissipation conditions – Local parts of the iron core: areas near the iron core joints or...

2026-03-27

No-Load Loss and Load Loss of Oil-Immersed Transformers: How to Calculate and Reduce Them?

In the whole life cycle of a transformer, loss is one of the core indicators for measuring its economic efficiency. An oil-immersed transformer usually operates for 20 to 30 years, and the electricity cost incurred by losses during this period is likely to exceed the purchase cost of the equipment itself. Therefore, understanding the essence of no-load loss and load loss and mastering the methods to reduce losses are crucial for optimizing equipment selection and saving operating costs. I. No-Load Loss: The Persistent “Fixed Cost” What is No-Load Loss? No-load loss refers to the loss generated when the secondary side of a transformer is open-circuited (with no load connected) and the rated voltage is applied to the primary side. As long as the transformer is connected to the power supply, this part of the loss persists continuously, even if it supplies no power to any equipment. No-load loss mainly stems from core loss (iron loss), including: Hysteresis loss: Heat generated by the friction of magnetic domains when the iron core is repeatedly magnetized in an alternating magnetic field Eddy current loss: Thermal loss produced when alternating magnetic flux induces circulating currents inside the iron core, which flow through the core...

2026-02-27

Why Use Transformer Oil? Analyzing Its Dual Role in Cooling and Insulation

In the world of oil-immersed transformers, there is a seemingly ordinary yet crucial substance—transformer oil. It fills most of the internal space of a transformer, submerging the iron core and windings, and is an indispensable “blood” for the stable operation of transformers. So why oil specifically? Why not water, air, or other liquids?   This article will delve into the two key dual roles of transformer oil in oil-immersed transformers: insulation and cooling, and explore why it has become an irreplaceable choice in power transmission.   I. Insulation: Building an Invisible “Electrical Barrier” The core function of a transformer is voltage conversion, which means an extremely high electric field intensity exists inside—huge voltage differences are borne between the high-voltage and low-voltage windings, and between the windings and the earthed iron core and oil tank. Without effective insulation measures, breakdown discharge will occur in an instant, leading to equipment damage and system failures.   1. Insulation Properties of Transformer Oil Transformer oil is an excellent insulating medium mainly due to the following properties: High dielectric strength: Pure transformer oil has a much higher dielectric strength (breakdown voltage) than air. Under standard conditions, the breakdown voltage of transformer oil can reach 40-60kV/2.5mm,...

2026-02-27

How Does an Oil-Immersed Transformer Work? The Synergy Between Electromagnetic Induction and Insulating Oil

In the power system, the oil-immersed transformer is an indispensable core device that undertakes the key tasks of voltage conversion, electrical energy transmission and distribution. For many non-professionals, a transformer may just be a bulky “iron box”, but its interior is actually a sophisticated “electromagnetic synergy performance”. This article will explain the working principle of oil-immersed transformers in a simple and in-depth way, focusing on how electromagnetic induction and insulating oil work together to ensure the stable operation of the equipment.   I. Electromagnetic Induction: The Core Principle of Transformer Operation The working principle of an oil-immersed transformer is based on the law of electromagnetic induction, a great physical phenomenon discovered by the British physicist Michael Faraday in the 19th century. 1. Basic Structure The core of a transformer consists of two main parts: the iron core and the windings. Iron core: It is made of laminated silicon steel sheets with high magnetic permeability to form a closed magnetic circuit. The use of silicon steel sheets can effectively reduce hysteresis loss and eddy current loss, improving the operating efficiency of the transformer. Windings: Also known as coils, they are divided into primary windings (input side) and secondary windings (output side)....

2026-01-21

Maintenance of Power Transformers

Power transformers are among the core components of electrical power systems. Their function is to step up or step down voltage levels to ensure the safety and suitability of electricity during transmission and usage. However, like all electrical equipment, power transformers also require systematic maintenance and care to ensure their long-term stable operation. This article discusses the key aspects of transformer maintenance to ensure sustained and reliable performance.   Regular Inspection and Testing   The foundation of maintenance lies in regular inspections. Professionals should conduct comprehensive visual and mechanical checks on transformers to promptly identify and address visible issues such as oil leaks, loose connections, and component corrosion. Additionally, insulation resistance tests and oil quality analyses must be performed to assess the equipment’s condition from an electrical performance perspective.   Insulating Oil Management and Monitoring   Insulating oil serves multiple roles in transformers, including insulation, cooling, and arc suppression. During operation, the oil level may drop due to leaks or evaporation, and it must be maintained within the specified range at all times. Furthermore, regular oil quality testing should be carried out to analyze indicators such as dissolved gas content, moisture, acid value, and impurities, enabling early detection of potential faults....