继电保护原理与应用(第三版)3.1-3.5(19)

在继电器和其他设备的三相连接中，了解现有相序非常重要；因此，应在图纸和信息文件中明确说明。如果不是a、b、c，尤其如此。从a、b、c到a、c、b或相反的连接通常可以通过完全互换设备和连接的b和c相来实现。
3.5 Polarity极性
Polarity is important in transformers and in protection equipment. A clear understanding of polarity is useful and essential for the chapters that follow.
极性在变压器和保护设备中非常重要。对极性的清楚理解对于后面的章节是非常有用和必要的。
3.5.1 Transformer Polarity变压器极性
The polarity indications for transformers are well established by standards that apply to all types of transformers. There are two varieties of polarity: subtractive and additive. Both follow the same rules. Power and instrument transformers are subtractive, whereas some distribution transformers are additive. The polarity marking can be a dot, a square, or an X, or it can be indicated by the standardized transformer terminal markings, the practices varying over the years. Polarity designated by an X in this book.
变压器的极性指示由适用于所有类型变压器的标准确定。极性有两种：减极性和加极性。两者遵循相同的规则。电力变压器和仪表变压器是减法的，而有些配电变压器是加法的。极性标记可以是一个点、一个正方形或一个X，也可以通过标准化的变压器端子标记来表示，这些做法多年来有所不同。在这本书中，极性是由X表示的。