The ETF (Energy Separation Filter) 3 kV was specially developed for the fault location on symmetrical communi-cation and pilot cables. The combination of burn unit, ETF 3 and a Telefl ex permits a fast fault prelocation on high resistive and humid cable faults. Where many other measuring technologies fail, the ETF 3 allows a safe prelocation of the fault especially for humid faults.

The ETF 3 provides a solution for such applications, where the permitted voltage due to the cable type and their allowed test voltage level is limited to a level which prevents the use of the standard burn and fault location technologies.

The burn procedure can be directly observed on the display of the connected Telefl ex. In the moment, when the fault breaks down, the fault distance is visible. This permits a “cable preserving” limitation of the burn time to the minimal required duration.

For safety reasons the input of the ETF 3 voltage is auto-matically limited to 3 kV by an internal arc gap due to the

fact, that the ETF 3 as well as the connected communication and pilot cables are limited in respect to their permittable voltage levels.

Exceeding these permitted values will have far reaching negative consequences. The use of the ETF 3 requires highest caution and observation of these values