Complete Analysis of the Core Causes of Copper Busbar Burning

Copper Busbar is a flat rectangular conductor made of copper, which can efficiently and reliably distribute electricity in electrical equipment. Its design can integrate multiple individual conductors into one component, reducing the complexity of wiring systems. With the rise of renewable energy and electrification transformation, the use of Busbar in various applications in the new energy industry is becoming increasingly widespread. This article will systematically summarize all potential causes of Bus Bar burnout, making it convenient for everyone to compare and quickly locate the root cause of similar faults in the future. Due to space limitations, this article only focuses on the causes of burnout, and the fault feature recognition techniques corresponding to different causes will be shared in detail in subsequent articles based on frontline practical experience. The content only represents a personal industry practical summary.

Poor contact is the primary and core cause of copper bar burnout, accounting for the highest proportion among various fault causes, and is also a key inspection item during on-site investigation. The causes of poor contact can be divided into two dimensions: direct contact problems and process matching problems. Bolt-tightening-related problems are the most common causes. Insufficient initial tightening torque of bolts can lead to bolt loosening during long-term equipment operation due to environmental thermal expansion and contraction, mechanical vibration, and other factors, directly resulting in contact gaps; Deterioration of surface contact performance, damage to Copper Busbar coating, corrosion from humid environments on site, salt spray corrosion, sulfide pollution, etc., can all cause oxidation of the Electrical Bus Bar overlap surface, resulting in a sharp increase in contact resistance. When current passes through, a large amount of Joule heat is generated, ultimately leading to high-temperature burning; The non-standard overlapping process, especially in high current operation scenarios, such as failure to apply conductive paste or incorrect application methods, can directly amplify the harm of poor contact and accelerate the occurrence of faults; Structural design issues that are easily overlooked, such as the arrangement of Power BusBar bolts, unreasonable bolt spacing, inadequate flatness of the BusBar Copper itself, and insufficient overlap area to meet regulatory requirements, can directly affect the overlap fit and become hidden causes of poor contact.

Insulation failure is a high-frequency cause of Tinned BusBar faults in the field of new energy, which can easily lead to short-circuit burning problems. The fault exhibits typical scene characteristics and needs to be investigated in conjunction with the equipment structure and operating environment.
 

Arc gap of busbar: This is a typical phenomenon of insulation failure in Industrial BusBar in new energy products. The core cause is the free gas, metal particles, smoke, and other pollutants generated by the spray arc of the plastic shell circuit breaker in the equipment circuit, which can damage the air insulation layer between the busbars, causing insulation failure and further leading to secondary short circuit faults. The notch of this type of fault basically appears at the end of the copper bar. Based on practical experience, this feature is related to the direction of arc movement - the arc usually extends in the direction away from the power source, and eventually forms a clear notch at the end. To address this issue, the Bus Electronics layout can be optimized by installing arc extinguishing covers, arc blocking plates, and keeping it away from the arc spraying channel of the circuit breaker. Double-segmented molded case circuit breakers can be used for protection.
 

Environmental and aging insulation issues: Improper control of temperature and humidity inside the cabinet can lead to high humidity and condensation, which can cause inter phase creepage of the Inverter Bus Bar; The on-site environment is highly polluted, and the accumulation of dust, oil, and other substances can form conductive channels, which can directly damage the insulation performance; In addition, the insulation protection components that come with Power in Contacts may experience aging, cracking, and detachment after long-term use, leading to a continuous decline in insulation performance and significantly increasing the probability of insulation failure.
 

External intrusion type short circuit: Occasionally, there may be phase to phase short circuits caused by foreign objects invading the site, such as mice, snakes, and other small animals crawling into the distribution cabinet to come into contact with the Copper Busbar, or after equipment maintenance, foreign objects such as metal tools, wire heads, and metal debris are left in the cabinet, causing direct conduction between Bussbar phases and causing instantaneous short circuit burning.

The burning of copper bars caused by overcurrent is often due to long-term overload accumulation or sudden faults leading to a sharp increase in current, while overvoltage can indirectly damage insulation and induce overcurrent faults, often forming a chain reaction between the two.

The core causes of overcurrent mainly include: equipment overload operation, exceeding the designed current-carrying capacity of Bus Bar Connectors, or failure of the distribution cabinet cooling system, poor ventilation, resulting in poor heat dissipation of copper bars, forming a long-term overload state, and continuous accumulation of heat leading to overheating of High Voltage Bus Bars. When the fault further expands, there will be a sharp increase in current, causing instantaneous high-temperature melting of PCB Bus Bars. The harmonic interference generated by nonlinear load operation will superimpose harmonic currents on the power frequency current, causing the actual operating current to exceed the rated value, resulting in hidden overcurrent. Long-term operation will accelerate Tmgb heating, ultimately leading to burnout faults. Although overvoltage does not directly cause the busbar to burn out, it can penetrate the insulation layer of the busbar, causing a phase-to-phase short circuit and generating a huge short-circuit current, resulting in the instantaneous melting of the busbar, which is an important indirect cause of overcurrent burning out.