油浸式电力变压器一般都装设有机械式瓦斯继电器作主保护使用.但是,由于存在可靠性差、速动性低以及阈值整定困难等问题,目前广泛应用的瓦斯保护不正确动作时有发生.伴随着变压器内部故障的发生,故障电能将转换为热能、动能等其他形式能量,而油箱内部压强骤升是电气网络故障显著、快速的非电量表征.为此,建立变压器油箱内、外部故障压力特征模型,根据故障与非故障状态下油箱内部压力特征差异构造基于压力特征的变压器数字式保护.以63 MVA/220 kV变压器为例,仿真验证不同运行情况下的保护动作特性,结果表明:新原理正确可行,动作速度较传统瓦斯保护显著提高,能够灵敏甄别绕组小匝数短路故障,且本质上不受励磁涌流影响.
For a long time, power transformers are usually equipped with gas relay protections, which work with current differential protection as the transformer main protection. However, due to the lack of theoretical innovation and performance improvement, the deficiencies of reliability and speed remain in the existing gas relay protections. Therefore, this paper presented a theoretical model and its simulation method for the research on the relationship between the electrical faults and non-electric characteristics inside transformer tank. According to the huge differences among the internal faults, external faults and other running status, a novel transformer digital non-electric protection principle based on the pressure characteristics has been proposed. Simulation test results verify that this protection principle is able to reliably and quickly clear the internal faults, even a weak fault, without inrush current influence.