Jiangsu Xinya Shows You How to Identify a Transmission Line's Voltage at a Glance

Have you ever been on a high-speed train, seen the huge transmission towers outside, and known only that their voltage level is high without knowing exactly how high? Xinya can show you “how to identify a transmission line’s voltage at a glance.” Here’s a summary for anyone with the same question.

The “Three Things to Look At”

Method 1: Look at the height.

The higher the voltage level, the greater the clearance from the ground!

Overhead lines usually require greater actual ground clearance to account for conductor sag and insulator length. Generally, 110 kV, 220 kV, and 330 kV lines are a little over 10 meters above the ground; 500 kV lines are more than 20 meters above the ground; 750 kV lines are higher than 25 meters; and 1000 kV lines are higher than 35 meters.

Method 2: Count the insulators.

Overhead transmission-line standards provide a formula for calculating the number of insulators: n=λυ/Ls, where n is the number of insulator units; λ is the creepage-distance ratio; υ is the system nominal voltage; and Ls is the effective creepage distance of a single insulator. Remember: each insulator unit withstands approximately 15～20 kV.

One important point to remember: the number of insulators increases in high-altitude and heavily polluted areas.

Method 3: Estimate the transmission-line voltage level from the number of conductor sub-conductors in a bundle.

The conductor for each of the three phases is divided into several sub-conductors. For example, the line below is divided into eight sub-conductors and is called an eight-bundle conductor. (A phase conductor is divided into eight sub-conductors to increase its “equivalent diameter,” arranged in an approximate circle; together, these sub-conductors form one conductor.)

Jiangsu Xinya High Voltage Test Equipment Co., Ltd. is a high-tech enterprise specializing in the R&D, production, and sales of high-voltage testing and test equipment. It has been recognized as a “National High-Tech Enterprise” and obtained ISO9001:2000 quality management system certification. It is a member of the Testing Committee of the Chinese Society for Electrical Engineering and the only manufacturing enterprise to have participated in drafting the national electric power industry standard “Partial Discharge Detector” (DL/T846.4 - 2004). It holds 23 utility model patents, has 7 provincial high-tech products and 4 software copyrights, holds 2 authorized invention patents, and was approved for the 2017 “Yangzhou Lvyang Jinfeng” talent program.