ASPEN OneLiner™ is a PC-based short circuit and relay coordination program for relay engineers. OneLiner is a productivity tool. It relieves the engineer from the tedious and time-consuming tasks of leafing through stacks of printouts and plotting and re-plotting relay curves and one-line diagrams. OneLiner works very quickly under the control of the engineer. The engineer can change the relay settings and network configuration and see the results of the change immediately. The software also includes a built-in API engine that lets users create applications in Python and other programming platforms for custom studies.

ASPEN OneLiner is the leading short circuit and relay coordination program with a 46% market share, according to an independent survey of 87 utilities in 24 countries (55 in the US, 12 in Europe, 3 in Latin America, 7 in Asia Pacific, 5 in the Middle East and Africa, and 5 in Canada) by Newton-Evans Research Co., Inc. in 2009.

The following are some highlights of OneLiner:

• Native Microsoft Windows desktop program with easy-to-use interactive graphics interface.
• Accurate modeling of 2- and 3-winding transformers, phase shifters, lines, switches, series capacitors (with and without nonlinear MOV elements), series reactors, dc lines (including VSC converters), generators, wind turbines, converter interfaced resources, loads, shunts and zero-sequence mutual coupling.
• Detailed modeling of fuses, reclosers, and overcurrent relays. Comes with an extensive relay library that can be edited by the user.
• Detailed modeling of distance relays using make- and model-specific parameters and operating logic. User-defined distance-relay methods using DLLs written in C++.
• Modeling of line differential relays, voltage relays, and protection logic schemes and reclosing of lines.
• Simulation of the following fault types: bus faults, line-end, line-out, intermediate faults, bus-to-bus fault, and phase-open faults.
• Unlimited system size with modest memory requirement.
• Lightning fast solution speed.  Parallel processing on multi-core CPU.
• Graphical display of post-fault solution and relay operating time on the one-line diagram and the phasor diagram.
• Advanced analysis tools: stepped-event analysis, bus fault summary, boundary equivalence, voltage sag analysis, fault location, arc flash analysis, and more.
• Automatic checking of overcurrent and distance relay coordination, plus automatic checking of overcurrent relays' pickup and instantaneous settings.
• Automatic plotting of overcurrent and distance relay characteristics on the screen, as well as fault-based time-distance diagrams for all relay types.
• Tools for PRC compliance: PRC-023-3, PRC-025-1, PRC-026, and PRC-027.
• High-quality printed outputs on a large variety of printers and plotters.
• Generates relay end-to-end test files in Doble, COMTRADE and other formats.
• Built-in model data management with 2-way and 3-way file comparison and case builder tools.
• Data exporting in CIM, PTI PSS/E, ANAFAS, ANAREDE and GE data formats.
• Data exporting in CIM, PTI PSS/E raw and sequence data format, GE PSLF and Short Circuit formats, ANAFAS data format, and AREADE data format.
• Two-way data exchange with ASPEN Relay Database.  Ability to download relay settings from Doble/ENOSERV PowerBase.
• CIM-compatible model data management.
• Built-in scripting engine using the BASIC programming language.
• Application Programming Interface module supports Python, C++, and other programming languages.