软件翻译不评分！！！

近期翻译的都是关于电缆的发展史，国内相关的资料比较少，在此分享给大家。

读英文吃力的朋友，可以等翻译出来后，再读！！

另外，大家翻译时，最好校验一下，便于朋友们理解。

1.6 UNDERGROUND RESIDENTIAL DISTRIBUTION SYSTEMS
The development of modern underground residential distribution (URD) systems may be viewed as the result of drastically lowering first costs through technology. Post-war URD systems were basically the same as the earlier systems except that there were two directions of feed (the loop system.) System voltages rose from 2,400/4,160 to 7,620/13,200 volts. The pre-1950 systems were very expensive because they utilized items such as paper insulated cables, vaults, switches, and submersible transformers. Those systems had an installation cost of $1,000 to $1,500. Expressed in terms of buying power at that time, you could buy a luxury car for the same price! Underground service was, therefore, limited to the most exclusive housing developments.
But for three developments in the 1960s, the underground distribution systems that exist today might not be in place. First, in 1958–1959, a large Midwestern utility inspired the development of the pad-mounted transformer; the vault was no longer necessary, nor was the submersible transformer. Second, the polyethylene cable with its bare concentric neutral did not require cable splicers, and the cable could be directly buried. While possibly not as revolutionary, the load-break elbow (separable connector) allowed the transformer to be built with a lower, more pleasing appearance.
The booming American economy and the environmental concerns of the nation made underground utility systems for new residential subdivisions the watchword of the Great Society. In a decade, URD had changed from a luxury to a necessity. The goal for the utility engineer was to design a URD system at about the same cost as the equivalent overhead system. There was little or no concern about costs over the system’s life because the polyethylene cable was expected to last 100 years!

1.6地下住宅配电系统

通过技术开发，极大地降低了地下住宅配电系统（URD）的初装成本，促进了地下住宅配电系统的发展。战后，地下住宅配电系统和以前的系统没有本质的区别，只从两个方向供电（环形系统）不太一样。系统电压从2400/4160V升到7620/1320V。在1950年前的系统，由于 使用的纸绝缘，以及开关和深潜式变压器都非常昂贵。这些系统的安装成本达到$1000到$1500之间。用当时的话表示就是，用同样的价格可以买一个昂贵的汽车。受到成本的影响，地下电缆不适用于住宅电力系统。

如果没有20世纪60年代的三项重大发明，可能就不会有今天的地下配电系统。第一，在1958年至1959年，美国中西部的一个机构，发明了基座安装式变压器，因此就不再需要深潜式变压器了，也就不在需要建立地下室了。第二，同心式的聚乙烯绝缘电缆，不再需要连接件了，并可以直埋地下。还有一项可能不算是革命性的发明，过载开关可以让变压器工作在更加友好的、低负荷的情况。

美国经济的爆发式发展和对环境的关注，使得地下住宅配电系统成为了伟大社会的新标志。地下配电系统从奢侈品变成了必需品。公共事业的工程师们，致力于设计出和架空电缆一样成本的地下配电系统。由于取乙烯电缆被期望能够使用100年以上，当时很少关注电缆的寿命问题。