Study on optimization of sampling inspection strategy for distribution transformer

In recent years, the manufacturing industry of distribution transformer (DT) in China has developed rapidly with high competition. Since the pass rates of National Surveillance Sampling in China (NSSC) for DTs keep a low level, the quality is worried. During the 13th Five-Year Plan period, the investment of distribution network construction will reach 1.7 trillion RMB, which makes a big market for DTs. It is significant to study on optimization of sampling inspection mode and strategy, which can improve the efficiency, quality level, and the reliability of power supply. The research status and theory of sampling inspection are analyzed. The sampling action mechanism is analyzed based on game theory, where the quality cost theory is put forward. The quality cost model with zero-defect is analyzed. The key factors of the sampling inspection for DT are analyzed, including the risk, maneuverability, and economics of the test item. The optimization method of sampling inspection mode is proposed, where three sampling inspection modes are given out. The strategy with dynamic adjustment is put forward. The index system of sampling inspection is designed, which can reflect the efficiency objectively. Finally, the method is verified by the real examples.