Complementing an extensive portfolio of protection relays for distribution and industrial grids, the primary application for the Reyrolle 7SR46 is to provide overcurrent and earth fault protection in medium-voltage distribution transformer stations. Mounted in a ring main unit, the protection device detects cable faults on the network and operates quickly to disconnect the fault. 

Due to their often remote locations, secondary substations do not always have a battery to provide power to electronic equipment, such as protection relays. With this in mind, the 7SR46 has been designed to operate using power from current transformers (CTs) when the line is live. Addressing scenarios whereby the line is switched off and there is already a fault on the line, or the earth connection has been mistakenly left connected, the 7SR46 has been specifically designed to power up quickly to provide protection in such circumstances. 

Providing additional flexibility and security, the 7SR46 is dual powered to allow a connection to an auxiliary battery supply. With power available from the CTs and an auxiliary power supply, this feature provides redundancy in case the battery fails. 

The 7SR46 device has a compact, molded enclosure. The front of the device includes an easy-to-use display and push buttons that can be used to program the relay and view fault records and instrumentation. Four LEDs provide information on the relay’s status, and a mechanical trip flag is also available. The front of the device features a USB communication port for connecting to a PC and can power the relay when no other power source is available. The USB port also allows plug-and-play connection to Reydisp to program the device and download fault and event information. The integrated battery allows users to program the device and download event and fault records without a connected power supply. The rear of the device features user-friendly detachable terminals for RS485 communication interface (Modbus RTU and IEC 60870-103), auxiliary power supply, binary inputs, binary outputs, external trip initiation input, external flag output, and a pulse output. The CTs (of type 5P80) are connected with a secure ring crimp. A clear connection diagram is also located on the rear of the relay to aid the user.

Adhering to stringent product testing standards, the 7SR46 is suited for use in distribution transformer stations where there is not a circuit breaker trip supply. The device features a pulse output that can activate a low-power trip coil to trip the circuit breaker.