Pilot wire current differential feeder protection

Pilot wire current differential feeder protection – Reyrolle 7PG21

Reyrolle 7PG21

The 7PG21 is a three-phase unit differential protection used to detect in zone phase and earth faults. The relay is applied to the overhead line and underground cable circuits as well as shorter circuits such as interconnectors.

Industry Mall

Select and buy

Features & functions

Pilot wire current differential feeder protection Reyrolle 7PG21


Relays (and associated CTs) are installed at each end of the protected circuit and connected together with dedicated metallic pilot wires.


This established protection system provides simple, robust protection of proven performance facilitating straightforward installation, commissioning and maintenance.


Relays have 3 current inputs and are housed in E6 cases.


Additional relays and components can be added to the basic protection to provide:

  • Increased insulation level

  • Pilot wire supervision to monitor the integrity of the pilot circuit.


Protection functions

  • Current differential protection over a single pair of pilot wires

Supervision functions

  • Optional pilot wire supervision

  • Optional overcurrent guard (check)

Control functions

  • Optional unstabilising / intertripping


Downloads and services

Retrofit and enhancement services

Retrofit and enhancement services

Extend the lifespans of your energy system and thereby significantly reduce your costs of ownership with our retrofits and enhancement services for energy automation.

Power Academy training services

Power Academy training services

Our goal is to prepare you for new professional challenges in power transmission and distribution. We offer professional training courses with different training methods like Virtual Classroom Training, Classroom Training, WBTs, Webinars and Blended Learning. You can choose between open enrollment training courses, customized training courses, workshops or long-term trainings (curricula).

Energy Automation and Digital Grid Newsletter


Receive news about the Digital Grid and Energy Automation portfolio and offerings!

Energy Automation Webinars

Energy automation webinars

Learn more in one of our energy automation webinars for protection and substation automation engineers and experts.