Earthing Switch (SPT)

Is equipment that allows earthing, allowing improve time for action in emergencies, facilitating the involvement of different services, with the guarantee of the grounding provided and supervision.

Based on a request realize from Remote Control Center of Energy or CCO, the equipment verifies whether the conditions for carrying out the grounding and if the self-monitoring that is carried out is correct.

The earthing switch performs the connection of rail to the catenary and thereafter to ground or to guard wire by means of an auxiliary contact.

Proper connection can be monitored with measurement of insulation from the power substation. This system is specially designed for areas most critical to security such as workshops, tunnels, washing etc.

The reestablishment can be effected in the same way, ensuring its position although the replenishment of energy is monitored.

The main functions are:

  • Monitoring of the union between the rail and the disconnector by means double connection.
  • Communications with the ControlCenter for monitoring and control.
  • Measuring the voltage of catenary by means double connection
  • Monitoring switch position through an angular optical fiber sensor.

The system as such is NOT a substitute to existing operating procedures regarding grounding of power lines, is only intended as a support system for implementing this function, in order to minimize the time for action, not constituting therefore sufficient reason to think about the cancellation of the above procedures, but on the contrary, the support in the same is needed to ensure the same safety in operations.


The system consists of the following elements:

Motor Drive System

To maneuver the disconnector, transmitting the movement through the rigging, also delivered through the limit switch their position to the controller.

It incorporates mechanical locking articulated arm.

Motor controller and voltage comparator

Performs the control of the entire system, on the one hand obtains all the information from the equipment delivering it to the PLO for monitoring, on the other hand manages and evaluates the manoeuvres from the PLO.

It incorporates all the logic of protection, self-monitoring and blocking.

Analog inputs. Angle gauge connection. Recording data. Standard protocol for communication. Simple addressing and unique identification by means of serial number unique.

Transceiver power and Entrances

Provides the power to the Transceiver of the angular sensor and to the digital inputs of the controller.

Voltage sensor

Realize the measure of the catenary voltage and sends it via 4-20 mA current loop to the controller-comparator voltage for evaluation.

Earthing switch

SAC disconnector normalized standard of 3,150 A at 3.3 kVDC.

Additionally provides:

  • Kit blade for grounding.
  • Optical sensor angle in the blade (Isolator break monitoring).
Angular Sensor by F.O.

This sensor detects the position of the mobile paddle of the disconnector, is based on optical fiber technology to give a level of reflected power as a function of angular movement of the disconnector.