Type: Pilot Wire Current Differential Feeder Protection Relay
Brand: Siemens Reyrolle
Model: 7PG21
Applications: Overhead lines, underground cables, interconnector circuits
Features:
Relays and CTs installed at both ends of the circuit, connected via dedicated pilot wires
Simple and robust design ensuring reliable operation
Three current inputs per relay, housed in E6 enclosures
High transient stability and fast fault detection
Adjustable phase and earth fault settings
Minimal variation of performance with pilot wire length
Optional 15 kV pilot isolation and supervision schemes
Test points available on relay fascia
Optional remote intertripping via pilot cores
Functions:
Protection: Three-phase differential protection via pilot wires
Supervision: Optional pilot wire supervision and overcurrent check
Control: Optional intertripping/unstabilising control
Compliance: IEC standards, Reyrolle Solkor R & Solkor Rf compatible
Mounting: Panel-mounted design
Maintenance: Easy installation, commissioning, and servicing
Type: Interposing, Trip Circuit & Supply Supervision Relays
Brand: Siemens Reyrolle
Model Range: 7PG17 (XR105–XR351 series)
Applications: Control interfaces, DC voltage monitoring, trip circuit supervision, ferroresonance alarms
Features:
Remote control operation over pilot wires (up to 200 Ω resistance)
Designed to resist induced AC voltages
DC voltage monitoring with delayed drop-off and visual indicators
Trip circuit integrity monitoring and remote alarm capability
Configurable operation/reset modes with mechanical flags
Variants:
7PG173 – Interposing Relays (XR105, XR106, XR107, XR205, XR206)
7PG174 – DC Supply Supervision Relays (XR152, XR153)
7PG175 – Trip Circuit Supervision (XR151, XR250, XR251, XR350, XR351)
Compliance: CEGB, BEBS S15 Scheme H7, IEC Standards
Voltage: DC 24V–240V (model dependent)
Mounting: Panel-mounted
