Influence of oil–paper configuration on electric field distribution of main insulation structure on valve‐side winding of UHV‐DC converter transformer

Abstract

The main insulation structure of the valve‐side winding of converter transformer bears the effect of AC and DC superimposed voltage during operation. The electric field intensity in the pressboard is much higher than that in the pressboard in the AC transformer. This condition increases the probability of failure of insulation structure. Therefore, the design and optimization of the main insulation structure of the valve‐side winding are keys to ensure the stable operation of converter transformer. This study establishes a model of the main insulation structure of the valve‐side winding of the ±1100 kV converter transformer. The influence of the insulating oil–paper configuration on the electric field distribution of the main insulation structure of the valve‐side winding is analysed, and then, an optimization idea is proposed. The oil–paper configuration includes two aspects: oil–paper insulation structural design and combination selection, that is, the influence of typical oil–paper structural design parameters and the aging state of different oil–paper combinations on the electric field distribution. Finally, the optimization idea of the oil–paper configuration for valve‐side winding of converter transformer is obtained, and the established model is optimized.

Effect of Electric-Field Components on the Flashover Characteristics of Oil-Paper Insulation Under Combined AC-DC Voltage

“…Ultra high voltage direct current (UHVDC) transmission is the preferred long-distance DC transmission method in China owing to its advantages of low line loss, low cost, reliable system operation, and stability [1]. As the core equipment of the DC transmission system, with the rapid increase in power load, the capacity of a converter transformer needs to be increased, which implies that the transmission voltage level should be increased from ± 800 kV to ± 1100 kV [2]. Compared with conventional AC transformers, converter trans-The associate editor coordinating the review of this manuscript and approving it for publication was Guillaume Parent .…”

“…formers have a specific insulating structure and operating condition: the valve-side winding is subjected to AC, DC, impulse, and combined AC-DC voltage (CADV) during operation, which makes their operating conditions more complex and changeable [2], [3].…”

Power transformer oil–paper insulation degradation modelling and prediction method based on functional principal component analysis

“…Good oil-paper insulation is a prerequisite for maintaining reliable operation of power transformers [1,2]. However, in the operation of transformers, the oil-paper insulation gradually degrades and fails [3,4]. The objective of transformer oilpaper insulation degradation modelling is to predict its future degradation trend, degree of degradation, and failure time range by establishing a degradation model, and thereby provide a reference for the formulation of a power transformer insulation maintenance plan [5,6].…”