ELECTRIC, WITH AN EDGE

Temperature rise design for oil-immersed photovoltaic transformers up to 35kV

Oil-immersed photovoltaic transformer is one of the most important electrical equipment for photovoltaic power generation systems. In this paper the author proposes to develop an energy efficient design solution for oil-immersed photovoltaic transformers by studying the temperature rise characteristics of oil-immersed photovoltaic transformers so that the safe operation of oil-immersed photovoltaic transformers tends to be reasonable.

Oil-immersed photovoltaic transformer1

Traditional oil-immersed photovoltaic transformers are based on the load guidelines and design specifications for oil-immersed power transformers, which are far from the actual working conditions of photovoltaic power generation, and the temperature rise characteristics do not match the actual working conditions and cannot adapt to the general trend of PV grid parity. In actual operation, due to the huge daily load variation of photovoltaic power generation, the average daily 70% time is in a near-no-load state, and the annual average efficiency of photovoltaic cells decays year by year, with a cumulative efficiency decay of over 15% in 20 years, resulting in the temperature rise characteristics of traditional oil-immersed photovoltaic transformers not being used reasonably and efficiently, and the economy is poor.

According to the incomplete statistics of several PV power station projects over the years, the highest oil surface temperature of traditional oil-immersed PV transformers is low, the highest oil surface temperature of a PV power station’s S11-1100/37 oil-immersed PV transformer running for many years is 57℃; the highest oil surface temperature of a PV power station’s S11-1600/37 oil-immersed PV transformer running for many years is 59℃. The installed capacity of oil-immersed photovoltaic transformers is often determined in accordance with meeting instantaneous or short-time loads and taking into account certain overload multipliers and insulation life.

The working life of an oil-immersed photovoltaic transformer depends on its insulation system. When the polymerisation of the insulation material drops to around 300 to 500, the transformer will reach the end of its life due to excessive ageing of the insulation material.

The study of the temperature rise in each region of an oil-immersed photovoltaic transformer is key to determining the temperature rise characteristics of an oil-immersed photovoltaic transformer, based on the typical power characteristic curve of an oil-immersed photovoltaic transformer.

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Why Choose Daelim As Your Oil-immersed Photovoltaic Transformer Supplier

DAELIM BELEFIC is a leading manufacturer of high-quality transformers for oil-immersed photovoltaic power generation. With over 15 years of experience in the design, engineering, and production of electrical equipment, our team leverages the “DAELIM EDGE + ADVANTAGE” concept to provide custom solutions that meet the unique needs of our clients.

As a result of our commitment to this concept, DAELIM BELEFIC has established itself as a trusted partner in the power industry, serving customers on six continents with products that meet international standards such as IEEE, IEC, CSA, AS/NZ, and GOST.

Our transformers for oil-immersed photovoltaic power generation are designed to meet the demands of the modern energy landscape, ensuring reliable and efficient power generation for our clients. Our team of experts is dedicated to providing the best products and services, and our “DAELIM EDGE + ADVANTAGE” concept is the cornerstone of our success.

At DAELIM BELEFIC, we understand the importance of working with a manufacturer you can trust. That’s why we offer top-quality transformers for oil-immersed photovoltaic power generation that are engineered to meet the highest standards. Contact us today to learn more about our products and how we can help with your energy needs.

Table of Contents

What is the oil-immersed photovoltaic transformers?

Oil-immersed transformer2

Transformer for oil-immersed photovoltaic power generation is the future of sustainable energy production. With an increased focus on clean and renewable energy sources, this technology is becoming more and more important. The transformer for oil-immersed photovoltaic power generation works by using oil as a coolant to enhance the performance of photovoltaic cells, leading to increased efficiency and reliability. The use of oil-immersed transformers also helps to improve the overall safety of the photovoltaic power generation system.

This transformer technology has numerous benefits, including improved energy efficiency, better reliability, and greater safety. In addition, the oil-immersed design helps to reduce the overall cost of photovoltaic power generation by reducing the need for maintenance and repairs. With the rise of renewable energy and the need for clean and sustainable energy sources, the transformer for oil-immersed photovoltaic power generation is an essential component for future energy production.

So, if you are looking for a more efficient and sustainable way to produce energy, the transformer for oil-immersed photovoltaic power generation is the perfect solution. With its numerous benefits and cutting-edge technology, it is the perfect choice for anyone looking to invest in the future of energy production. Contact us today to learn more about this innovative and environmentally friendly technology.

Typical power curve of oil-immersed photovoltaic transformers

The daily power output curve of the oil-immersed PV transformer is closer to the positive half of a sine wave on a sunny day, basically within the zone of 7:00 to 19:00, with less than 80% of the maximum daily peak power and weakened PV output in other non-ideal weather conditions.

The harmonic content at higher power stages is at a lower level and the harmonic content has less influence on the temperature rise characteristics of the oil-immersed PV transformer. The temperature rise of oil-immersed PV transformers can be studied according to the time-power sine curve to meet the requirements of most working conditions and has typical practical value.

Combined with the design of a 35 kV photovoltaic power station S11-3125/37 oil-immersed photovoltaic transformer and production actual measurement data.

This step-up transformer for photovoltaics guarantees a transformer winding with class A insulation material, the hottest spot temperature is maintained below 98°C and the design life expectancy of 30 years is guaranteed, taking into account the principle of equivalent ageing of the transformer.

Keep on reading :2022 Ultimate Oil Immersed Transformer Guide

Temperature rise characteristics of oil-immersed photovoltaic transformers

photovoltaic transformer3

According to the oil surface temperature rise curve, the highest value of oil surface temperature rise is 51.5K when the input power of the oil-immersed photovoltaic transformer is reduced from the peak to about 88%, and the oil surface temperature rise meets the requirement of the national standard of no more than 60K limit. However, as the temperature rise test of the oil-immersed PV transformer could not be brought to a steady state according to this simulated time-power sine curve, the winding temperature rise of the oil-immersed PV transformer could not be measured to accurate data.

The oil-immersed PV transformer had a maximum oil top layer temperature rise of 59.1K, with the oil surface temperature rise still meeting the industry standard limit of no more than 60K; the high voltage winding temperature rise was 67.6K and the low voltage winding temperature rise was 69.1K.

This oil-immersed photovoltaic transformer if according to the conventional power transformer temperature rise calculation method, the high voltage winding temperature rise design value is 77K, low voltage winding temperature rise design value is 76K, the oil top layer temperature rise design value is 65K.

After adjusting the design method by applying the operating characteristics of the PV transformer, the measured temperature rise fully meets the industry standard requirements, and the temperature of the hottest point of the winding remains below 98°C. The operating efficiency and life span is not affected, and still meets the requirements of most users for long-term operation of the transformer with 1.1 times overload.

Read on What is the Function of Transformer Core?Everything You Should Know

Conclusion

According to several simulated temperature rise tests as well as operational data collection and comparison, the temperature rise limit of this oil-immersed photovoltaic transformer designed according to the typical power curve of photovoltaic power generation can be appropriately increased by about 8K compared to the conventional temperature rise design scheme, and the overall cost can be reduced by more than 13% compared to the conventional design scheme with S11-3125/37 as an example.

The temperature rise characteristics of oil-immersed PV transformers can be determined according to the characteristics of different PV power output curves, combined with the requirements of economy, energy saving and environmental protection, which can effectively solve the problems of poor economic operation and low capacity utilisation of oil-immersed PV transformers.

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