Protection Applications
Apply the SEL-T400L to a variety of line and system configurations, including:

• POTT and direct transfer tripping (DTT) protection schemes for two-, three-, and four-terminal lines over a digital channel (select SEL Mirrored Bits encoding or IEEE C37.94 encoding), analog channel (use SEL-2500 series I/O modules), or direct-fiber channel (use wavelength division multiplexing to share fibers).
• TW87 protection scheme for two-terminal lines with a provision for unmeasured taps, over a direct-fiber channel. (Use wavelength division multiplexing to share fibers.)
• Underreaching directly tripping distance element.
• Single-pole tripping.
• Series-compensated lines.
• Lines with line-side and bus-side reactors.
• Hybrid lines with overhead and underground cable sections.
• In-line CTs and breaker CTs in dual-breaker applications with per-breaker current measurement.
• High-speed trip-rated outputs for two breakers and single-pole tripping.

Hassle-Free Installation
Use the SEL-T400L with standard control cables and wiring to connect to conventional current and voltage transformers, including coupling capacitor voltage transformers (CCVTs), and directly to breaker trip-coil circuits. The relay uses current traveling waves that are adequately measured with standard CTs and cabling. The relay uses the very first voltage traveling wave in the optional TW32 directional element, and this wave is reproduced correctly by many CCVTs, allowing good TW32 dependability. You can select either SEL MB8 encoding for signaling local SEL relays and SEL I/O devices for breaker failure protection and autoreclose control applications or IEEE C37.94 encoding for signaling a remote SEL-T400L over a compliant multiplexer for POTT, DTT, double-ended traveling-wave fault locating (DE-TWFL), autoreclose cancel logic, and line monitoring applications. The SEL-T400L provides a simple communications means to access relay metering data and records. These protocols include SEL protocols for ease of integrations with SEL systems, DNP3 over Ethernet for interconnecting with DNP-based SCADA systems, and generic Ethernet file transfer methods for ease of integration with Ethernet-based substation automation systems.

Relay Configuration and Settings
Designed with simplicity in mind, the SEL-T400L uses simple multiple-choice user preferences to accommodate a wide array of applications without the need to write custom logic equations. The protection elements and schemes have very few or no settings at all in addition to the customary enable and overcurrent supervision settings. The majority of protection settings involve nameplate data, such as current and voltage transformer ratios, line parameters, nominal voltage, or system frequency and phase rotation. These settings are easy to set and do not need to be reevaluated as the power system evolves and the short-circuit levels change.

Fault-Locating Applications
Trigger fault locating for line faults from the SEL-T400L protection or from external relays in redundant protection applications or in standalone fault-locating applications. SEL-T400L fault-locating highlights include:

• Fault locating for two-terminal lines that is accurate to a single tower span based on traveling waves from one or both ends of the line
• Double-ended traveling-wave fault locating for nonhomogeneous hybrid lines with overhead and underground cable sections
• Double-ended fault-locating result that is available in milliseconds, allowing the SEL-T400L to control autoreclosing based on the location of the fault
• Built-in fallback to single- and double-ended impedance-based fault-locating methods for dependability of fault locating during faults at the voltage zero crossing
• Support for off-line traveling-wave fault locating for multiterminal lines

Line Monitoring
Monitor the line for incipient faults, recurring faults, or incipient cable faults. Obtain a location-tabulated event count to detect low-energy activity and faults along the line. Prevent faults by selectively cleaning or replacing insulators, trimming vegetation, improving antigalloping solutions, applying line spacers, or improving lightning protection. Line monitoring works over a direct fiber-optic channel or a 64 kbps IEEE C37.94-encoded multiplexed channel.

Digital Fault-Recording Applications
SEL-T400L recording highlights include:

• High-fidelity (1 MHz, 18-bit) time-stamped sampling with the frequency response up to about 400 kHz
• Programmable trigger for standalone recorder applications
• Recording duration of up to 1.2 seconds per record
• Storage for up to 50 1.2-second events
• Back-to-back recording capability for the total length of up to 3.6 seconds
• Local voltages and individual breaker currents
• Time-aligned remote voltages and line currents if the dedicated point-to-point fiber channel is used
• Ultra-high-resolution records (1 MHz analogs) for analysis of power system events and of traveling-wave protection and fault-locating functions
• High-resolution records (10 kHz analogs and digitals) for analysis of protection functions
• IEEE COMTRADE (2013 version) file format
• TCP/IP File Transfer Protocol (FTP) over a Gigabit Ethernet port for fast access to the large record files
• Streaming FTDV over a Gigabit Ethernet port for wide-area high-fidelity event recording and continuous monitoring