The SEL-751 Feeder Protection Relay is ideal for directional overcurrent, fault location, arc-flash detection, and high-impedance fault detection applications. Flexible I/O options, easy mounting, and fast settings make the SEL-751 the right solution for industrial and utility feeder protection. The SEL-751 provides complete feeder protection, with overcurrent, overvoltage, undervoltage, directional power, IEC cable/line thermal, vector shift, sensitive earth fault (SEF), load encroachment, and frequency elements. Select the 5-inch, 800 × 480 color touchscreen display option to directly set, monitor, and control your system. Easily upgrade protection without cutting or drilling existing cutouts, given the relay’s small form factor and multiple mounting adapters. Quickly integrate the SEL-751 into serial- or Ethernet-based communications with IEC 61850 Edition 2, IEC 60870-5-103, the IEC 62439 Parallel Redundancy Protocol (PRP), Mirrored Bits communications, Modbus, DNP3, and other protocols.
Feeder Protection—Protect radial and looped distribution circuits with comprehensive protection capabilities, including time-overcurrent, directional overcurrent, autoreclosing, over-/undervoltage, frequency, second- and fifth-harmonic blocking, optional low-energy analog (LEA) voltage inputs, IEC cable/line thermal element, islanding detection, and much more.
Sensitive Neutral Input—Using the directional control capability, protect high-impedance grounded, ungrounded, and Petersen coil-grounded systems in relays with the 200 mA neutral current input option. The 200 mA neutral input option is also used for nondirectional SEF protection.
Arc-Flash Mitigation—Improve safety for personnel with optional arc-flash detection capabilities. The SEL-751 offers combined light and high-speed overcurrent detection for arc-flash events. This combination provides the ideal solution for speed and security.
High-Impedance Fault Detection—Detect downed conductors, even on poorly conducting surfaces, with Arc Sense technology (AST). AST algorithms detect arcing produced by some high-impedance faults and will alarm or trip the breaker. This technology provides an added level of protection over conventional feeder protection methods.
Automation and Control—Apply the SEL-751 on feeders and provide protection, automation, and control capabilities all in one package.
Event Analysis—Conduct postevent analysis more efficiently with the detailed event records that are available in the SEL-751. Combine oscillographic and digital information to find root cause. Add a satellite-synchronized time source, like the SEL-2401, SEL-2407, or SEL-2488 Satellite-Synchronized Clocks, for convenient alignment of event information from multiple devices.
Situational Awareness—Improve situational awareness and asset utilization with IEEE C37.118 synchrophasor measurements.
Reliable in Harsh Environments—Rely on the SEL-751 for protection and control applications, even in harsh and hazardous environments. The SEL-751 is designed and tested to meet and exceed utility and industrial requirements. An operating temperature range of –40° to +85°C (–40° to +185°F), Class 1, Zone 2 approval, and optional conformal coating mean this relay will provide years of reliable service.
Fault Location—Find faults faster and restore service more quickly with fault location algorithms. Communicate fault location information automatically to a control center by using serial or Ethernet communications and SCADA protocols.
With a simple tap, quickly access bay screens, metering and monitoring data, reports, settings, and more.
Select from predefined bay screens, or configure your own. Control a single breaker, monitor as many as five disconnect switches, and view analog and digital data in a contextual display.
Verify breaker and disconnect changes using the secure control interface.
Use the on-screen keyboard to quickly and easily enter passwords, search for Relay Word bits, and enter settings.
View the real, reactive, and apparent power of each phase, and monitor the power factor.
View a graphical and textual representation of the real-time voltages and currents in a power system. Analyze the phasors to determine power system conditions.
Display the real, reactive, and apparent energy metering quantities imported and exported in a system. Easily reset the values via the display, and record the time and date of reset.
Easily review the time-stamped Sequential Events Recorder (SER) data, including whether or not the Relay Word bit asserted or deasserted, during root cause analysis of an event.
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.
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.
Use the programmable pushbuttons with tricolor LEDs on the front panel for quick, personalized control.
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.
Rely on the industry’s widest ambient temperature operating range, –40° to +85°C (–40° to +185°F).
Easily install the SEL-751 into existing locations using available retrofit kits and mounting adapters, with no cutting or drilling.
Choose from many installation and integration options given the relay's small form factor and slide-in expansion card options.