A Dual-powered Protection Relay for Overcurrent and Earth Fault Protection

December 08, 2022 by Shawn Dietrich

Siemens introduces a new addition to the Reyrolle protection product line that is capable of being installed in remote locations with the ability of dual-power sources.

In just about any electrical circuit you can find protection relays. These are special relays that open contacts and break circuits when abnormal conditions are detected. Sometimes these relays have internal processing capabilities and sometimes they are driven by external controllers. 

When power is produced at a power plant, the electricity goes through transformer stations to step down the voltage to a level that can be used by equipment and devices. Within these stations, devices need to monitor circuits for overcurrent, or earth faults, and when detected, the system needs to be shut down.

Siemens currently has a line of protection devices called the Reyrolle product line and recently Siemens has expanded this product line to include the new 7SR46. 


Siemens Reyrolle 7SR46 dual-powered protection relay

Siemens' Reyrolle 7SR46 dual-powered protection relay. Image used courtesy of Siemens


Dual-powered Protection Relay

The 7SR46 protection relay is a new addition to the Reyrolle protection device family for medium-voltage distribution transformer stations. The 7SR46 is an overcurrent and earth fault protection device designed to work in remote locations where there are distribution transformers. 

An overcurrent device monitors the amount of current the system is requesting and will open the circuit if the current draw is too high. This is an essential device because if devices are requesting too much current, there could be a problem with the device or with the wiring connecting the device to the electrical supply. 

A ground fault is when current is detected on grounded conductors. This can happen when insulators begin to degrade and leak small amounts of current to ground or chassis ground. When dealing with thousands of volts and hundreds of amps the importance of a device that detects overcurrent and ground faults is clearly visible. 


Siemens Reyrolle 7SR46 protection relay

The 7SR46 protection relay is made up of compact housing. Image used courtesy of Siemens


The Reyrolle 7SR46

Siemens Reyrolle 7SR46 protection device is made up of a compact housing with a 16-character, 2-line backlit LCD display that can display fault codes and system status and facilitate programming. The front panel is equipped with push buttons, LED indicators, and a USB interface that can double as a power source when system power is not available. The unit has two binary inputs, two binary outputs, and one pulsed output for trip coil activation. 

For communication, there is an RS-485 serial interface and a USB port. The USB port can be used to configure and set up the relay using the Evolution software. The 7SR46 can be powered with 24-240 VDC or 60-240 VAC. With transformer stations typically in remote locations, there is not always battery power to supply electronics such as protection devices. The 7SR46 was designed to be powered by current transformers or from batteries. 


Protection relay applications

The 7SR46 relay ensures that distribution transformer stations are protected from overcurrent or from earth faults. Image used courtesy of Iqram-O-dowla Shawon


Protection Relay Applications

Electrical circuits need to be monitored for overcurrent and earth faults. These scenarios are even more dangerous when dealing with thousands of volts. The 7SR46 provides monitoring of these transformer stations and will log faults as they are detected. The device can be programmed to make use of the internal binary outputs and is able to be powered by existing current transformers or by battery. By using an advanced protection device such as the 7SR46, users can ensure that their distribution transformer stations will be protected from overcurrent or from earth faults.