Investigation of the Reason for Low - voltage Circuit Overload Protection Formulas in IEC Standard

Wang Houyu（China Aviation Planning and Construction Development Co.，Ltd.，Beijing 100011，China）

 

作者信息

王厚余，男，中国航空规划建设发展有限公司，研究员，电话：010 - 62039071（宅）。

 

 

Abstract The low - voltage circuit overload protection in building electricity is a safety requirement that is familiar to us，but the overload protection formula （2）I2 ≤ 1. 45 IZ in IEC standard is considered to be very difficult to understand. The author investigated the reason for IEC to formulate this formula in foreign countries when he participated in the formulation of Code for Design of Low Voltage Electrical Installations 20 years ago. In combination with own understanding，the author reviewes the information acquired from the investigation and writes out this paper for readers’ reference.

Key words　Overload protection　 Short - circuit protection　Electrical fire　Conventional current　Conventional time

 

 

摘　要　建筑电气中的低压线路过载保护是大家非常熟悉的安全要求，但 IEC 标准过载保护公式（2）I2 ≤ 1. 45 IZ 却被认为是个令人难以理解的公式。作者 20 年前参编《低压配电设计规范》时曾在国外对 IEC 制订该公式的来由进行过调查。作者回顾当年调查所得信息结合本人的理解，书成此文供读者参考。

关键词　过载保护　短路保护　电气火灾　约定电流　约定时间