Traditionally, the moisture level in SF6 gas - insulated equipments was checked by periodically collecting gas samples. However, in recent years, condition monitoring systems equipped with online instrumentation for measuring the dew point of SF6 have become increasingly prevalent.
Nowadays, it is quite common to install dew point sensors in the same sensor block as pressure relays or density sensors. Additionally, these sensor blocks are often not directly attached to the main gas tank. Instead, they are connected to the tank using either polymeric or metal tubing.
To ensure the most accurate online dew point measurement in an SF6 - insulated system, the sensor should be installed as close as possible to the main gas volume. Ideally, it should be directly mounted onto the tank wall. Minimizing the number of connection points and avoiding the use of plastic or rubber materials in the vicinity of the measurement cell are also highly advantageous.
The quality and long - term stability of the sensor being used are also crucial factors.
In the picture, we can see the installation of a dew point - pressure - temperature sensor for ABB GIS equipment. This sensor is directly connected to the main gas tank.
