Generator brushes and excitation brushes have low resistivity and stable performance, but due to factors such as flow size, brush pressure, ambient temperature, humidity, cleanliness, wear of the brush and slip ring surface, and manufacturing process, during long-term operation, if hidden dangers are not identified early and decisive actions are not taken, it is inevitable that brush sparking, ring fire, or even generator shutdown may occur. There are many reasons for brush sparking, and detailed data and procedures have been described. However, in actual production, there are several common causes for brush sparking: 1. Excessive brush current density. In real operation, if one or two brushes become stuck due to mechanical issues, or if spring pressure is insufficient, the current through other brushes increases to maintain normal load. This can cause a single brush to deflect, reducing the contact area with the slip ring and increasing contact density. According to Q=I²R, heat is proportional to the square of the current. If the heat cannot be dissipated quickly, the temperature rises rapidly, causing sparks at the contact point between the brush and slip ring. Once sparks occur, the working environment worsens, creating a cycle that intensifies the problem, potentially leading to ring fire. 2. Uneven or insufficient brush pressure. During equipment maintenance, manufacturers typically adjust brush pressure to the minimum level that prevents sparking. Scientifically, this is usually around 200–300 g/cm² or 1.022–1.03 MPa. Each brush should have uniform pressure, with differences not exceeding 100 g. Over time, if a brush wears down or gets stuck, the pressure becomes uneven. Additionally, heat from the machine or spring fatigue can reduce pressure below the required level. Sometimes, operators rely on feel rather than experience, leading to large operational errors. 3. Brush surface contamination. This is often overlooked. Normally, generator brushes are enclosed in a sealed cabinet. A gear-shaped axial fan on the shaft helps remove graphite dust and dissipate heat. If the door isn’t properly closed or left open during inspection, dust can enter and settle on the brush, affecting cooling. When sparks occur, an unclean brush surface can lead to poor contact and increase the risk of ring fire. The slip ring also has spiral grooves to enhance heat dissipation and improve contact. If dust accumulates in these grooves, the consequences are severe. Excitation brushes, being exposed and operating at lower voltages, also require regular cleaning. In the past, many generator shutdowns were caused by minor issues like this, emphasizing the need for vigilance. 4. High bearing vibration. Large shafts equipped with exciters are prone to vibration due to their length and additional components. Long-term operation leads to fatigue and aging, increasing vibration. This can cause uneven brushing, loose wiring, and springs, leading to localized sparks that escalate into larger problems. Other factors such as poor brush manufacturing, incorrect positioning, high resistance, or short circuits may also contribute, but in recent years, the four main causes have been most frequently observed. Although brush sparking has been well-documented, specific procedures for handling it are still lacking. Recently, effective measures have been introduced, which I believe are necessary. Based on my experience over the years, I share this information here and welcome your feedback and corrections. Transformer For Renewable Energy Transformer For Renewable Energy, Solar Transformer,Wind Mill Transformer, Energy Station Hangzhou Qiantang River Electric Group Co., Ltd.(QRE) , https://www.qretransformer.com