During the years of operation of the power grid, many old transformers that have been serving for a long time have gradually shows many problems. From the perspective of energy consumption, due to the limitations of technology and materials in the early manufacturing of transformers, no-load losses and load losses are much higher than current standards. For example, the no-load losses of some S7 series aging transformers are 40% - 60% higher than those of new energy-saving transformers. This not only causes a large amount of power waste but also increases the operation cost of the power grid. In terms of safety performance, problems such as insulation aging and winding deformation of aging transformers have become increasingly serious. Under the long-term action of electrical, thermal, and mechanical stresses, the performance of insulation materials has decreased significantly, leading to frequent faults such as partial discharge and short circuits, which seriously threaten the stable operation of the power grid and the power consumption safety of users. In addition, aging transformers have a low degree of intelligence and cannot meet the requirements of modern smart grids for real-time monitoring and remote control of equipment, making it difficult to achieve efficient operation and maintenance management. Therefore, it is imperative to retrofit and upgrade aging transformers.
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Replacement of Key Components
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Core Replacement: The core is the main component that causes no-load losses in transformers. The cores of aging transformers are mostly assembled with silicon steel sheets, which have low magnetic permeability and large hysteresis losses. They can be replaced with cores made of high-permeability amorphous alloys or new-oriented silicon steel sheets. The no-load losses of amorphous alloy cores are only 1/3 - 1/5 of those of traditional silicon steel sheet cores, which can significantly reduce the no-load energy consumption of transformers. During the replacement process, strict control should be exercised over the stacking process of the core to ensure the closure of the magnetic circuit of the core and reduce magnetic leakage.
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Winding Retrofit: For problems such as insulation aging and unreasonable wire diameter of the windings, new insulation materials and optimized winding structures are adopted. High-temperature-resistant and high-insulation-performance Nomex paper or composite insulation materials are selected to replace the old insulation, improving the insulation strength and service life of the windings. At the same time, according to the actual load conditions of the transformer, the wire diameter of the windings is reasonably adjusted to reduce the resistance losses of the windings. For transformers with a large capacity, the method of parallel winding with multiple strands of wires can be used to reduce the additional losses caused by the skin effect.
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Optimization of the Control System
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Installation of Intelligent Monitoring Devices: Install intelligent sensors on the transformer to monitor key parameters such as oil temperature, winding temperature, gas content in oil, and load current in real time. Through Internet of Things technology, the monitored data is transmitted to the power grid monitoring center to achieve remote real-time monitoring of the operation status of the transformer. Once abnormal parameters are detected, the system immediately issues an alarm, facilitating maintenance personnel to take timely measures and avoid the expansion of faults.
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Configuration of On-load Tap Changers: The voltage regulation method of aging transformers is mostly off-load voltage regulation, which is inconvenient to operate and cannot meet the real-time voltage regulation requirements of the power grid. After configuring on-load tap changers, the tap positions of the transformer can be automatically adjusted according to the voltage fluctuations of the power grid, maintaining the stability of the output voltage, improving the power supply quality, and reducing the losses caused by unstable voltage at the same time.
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Energy Conservation Benefits: Take a 1000kVA aging transformer as an example. Before the retrofit, its no-load loss was 3kW, the load loss was 10kW, and the annual average load rate was 40%. After the retrofit, by using an amorphous alloy core and optimized windings, the no-load loss was reduced to 1kW, and the load loss was reduced to 7kW. Calculated based on an annual operation of 8760 hours, the annual power savings after the retrofit are: [(3 - 1) + (10 - 7)×0.4]×8760 = 26,280 kWh, with remarkable energy conservation benefits. If a large number of aging transformers in the power grid undergo similar retrofits, the overall energy conservation effect will be extremely significant. This can not only reduce the operation cost of the power grid but also comply with the national policies on energy conservation and emission reduction.
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Safety Benefits: By replacing aging insulation components and optimizing the control system, the failure rate of transformers will be greatly reduced. According to statistics, the number of outages caused by insulation failures of transformers can be reduced by 70% - 80% after the retrofit, effectively improving the power supply reliability of the power grid. At the same time, the application of intelligent monitoring devices enables maintenance personnel to detect potential fault hazards in advance, changing passive maintenance to active maintenance, reducing the impact of transformer failures on the production and life of users, and enhancing user satisfaction with power consumption.
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Economic Benefits: Although the retrofit and upgrade of aging transformers require certain upfront investment, in the long run, the benefits of energy conservation and the losses reduced due to fewer failures will far exceed the retrofit costs. Take a 1000kVA transformer as an example. The retrofit cost is about 150,000 yuan, while the annual electricity cost savings (calculated at 0.6 yuan/kWh) are about 15,800 yuan. Coupled with the indirect economic losses reduced due to fewer failures, the investment payback period is generally 5 - 8 years. In addition, the service life of the retrofitted transformer can be extended by 10 - 15 years, further improving the return on investment of the equipment.
In conclusion, the retrofit and upgrade of aging transformers in the power grid is great practical significant, whether considered from the aspects of energy conservation and consumption reduction, safety performance improvement, or economic benefits. Through scientific and reasonable technical plans, the problems existing in aging transformers can be effectively solved, providing a strong guarantee for the efficient, stable, and sustainable development of the power grid.
