SEL-751

Complete Feeder Protection
Maximize control scheme flexibility using time- and instantaneous-overcurrent, overvoltage, undervoltage, directional power, and frequency elements, with breaker failure protection for one three-pole breaker. Second- and fifth-harmonic blocking improves protection security during magnetizing inrush conditions caused by line re-energization, or by voltage recovery after an out-of-zone fault.

Optional Directional Control
Use overcurrent elements with directional control, and optimize radial and looped network protection for lines and equipment. Best Choice Ground Directional Element logic optimizes directional element performance and eliminates the need for many directional settings. The relay also supports high-impedance grounded, ungrounded, and Petersen coil-grounded systems in relays with the 200 mA neutral current transformer option. The 200 mA CT option can also be used for nondirectional SEF protection.

Optional Protection Features
Use the SEL-751 with the voltage input and arc-flash detection options to provide synchronism check, dc station battery monitoring, and arc-flash detection. The SEL-751 supports option cards with either 4 or 8 arc-flash detection inputs. An option for LEA voltage inputs (8 Vrms for phase and synch voltage) supports voltage sensors in pad-mounted and other compact gear.

Thermal Element
Protect cables and cable insulation against thermal damage using the IEC line/cable thermal (49) element.

Optional Vector Shift
Detect islanding conditions and prevent damage to local generation by detecting voltage angle shifts upon loss of bulk generation.

Optional High-Impedance Fault Detection
Apply the SEL-751 with AST to detect many high-impedance faults, a common result of a downed conductor. Alarm or trip for faults that produce low fault current and are undetectable with conventional relays.

Optional Touchscreen Display
The easy-to-use touchscreen interface provides a one-line mimic display for bay control and monitoring. View metered quantities, phasor diagrams, relay settings, event summaries, target statuses, Sequential Events Recorder (SER) data, and more. Extensive testing shows that the robust capacitive touchscreen display meets or exceeds industry standards as well as SEL quality and reliability requirements.

Convenient Controls
Use the programmable pushbuttons with tricolor LEDs on the front panel for quick, personalized control.

Easy Communications
Choose from Ethernet or serial communications and several protocols, including IEC 60870-5-103, Mirrored Bits communications, and IEC 61850. Pick multiple sessions of Modbus TCP, Modbus serial, DNP3 LAN/WAN, or DNP3 Serial for custom configuration of your applications. When dual-Ethernet ports are selected, the relay also supports the IEC 62439 PRP and Fast Failover Switching.

IEC 61850 Edition 2 Communications Protocol
Combine IEC 61850, an Ethernet network, and the SEL-751 for the fastest overall performance for substation automation and control. Streamline configuration of IEC 61850-enabled relays with acSELerator Architect SEL-5032 Software. Improve security using the password authentication and session time-out features. Transfer event files in COMTRADE and CEV formats as well as CID files, settings, and reports.

Simple Network Time Protocol (SNTP)
Simplify wiring and installation by receiving a time signal over existing Ethernet networks. SNTP makes a good backup to more accurate IRIG-B time synchronization. The 5 ms accuracy is ideal for basic time synchronization throughout a substation.

Built-In IEEE C37.118 Synchrophasors
Monitor distribution networks to detect a potential cascading voltage collapse before it happens. IEEE C37.118 synchrophasors, at up to 60 messages per second, allow access to system values for wide-area monitoring and control. The IEEE C37.118 standard simplifies communication and data coordination between synchrophasor measurement units.

Expanded SELogic Control Equations
Use math and logic combinations of analog and digital values for customized applications. Adapt system control based on prefault conditions. Scale analog values and latch momentary inputs for SCADA retrieval.

Enhanced Security on Heavily Loaded Feeders
Employ load-encroachment logic to set phase overcurrent elements independently of load levels.

Rugged Design
Rely on the industry’s widest ambient temperature operating range, –40° to +85°C (–40° to +185°F).

Easy Installation
Easily install the SEL-751 into existing locations using available retrofit kits and mounting adapters, with no cutting or drilling.

Flexible Design
Choose from many installation and integration options given the relay's small form factor and slide-in expansion card options.