Create a new project, explore the demo, or open an existing one to begin.
Optional — maximum load current per device, for the pickup/load rule (this app has no stored load data, so nothing is checked here until you enter it). One per line: device name, max load current (A)
Uses the protected line's own R1/X1/R0/X0 entered in Tab 1.
One stage per line: name, direction (under/over), threshold (Hz), delay (s)
One stage per line: name, direction (under/over), threshold (%UB), delay (s)
⚠ Formulas built here are user-defined — click-assembled from the variables below, not independently verified against a manufacturer's manual the way the Differential and REF tabs are. Use this for a relay/scheme not already covered, with a formula you've sourced yourself.
REB500 low-impedance busbar CT adequacy — hand-verified against a real 220kV project document (reference project B, Appendix 2).
Metering/instrument-core CT check — a different concern from protection: does the CT saturate EARLY enough to protect the meter from fault current? Hand-verified against the same real document (Appendix 2, Calc 3).
One pair per line: upstream device, downstream device, prospective fault at the downstream device (kA), manufacturer selectivity limit (kA, or T for total — optional). Devices are matched to your project by name (e.g. MCCB-12 or 400 V DB-3 Incomer.MCCB-12).
One RCD per line: name, IΔn (mA), type (G = general, S = selective, R = delayed), fed from (name of the RCD upstream, blank if top), [non-actuating time s, max break time s — R only]
One circuit per line: circuit, protective device, material (copper|aluminium), insulation (pvc|xlpe), CSA mm², Ib A, Iz A, Ik max (kA), Ik min at cable end (A), [let-through I²t A²s — optional], [conventional tripping multiple — optional]
Check specific settings already entered in the relay (optional):
One bay per line: name, CT primary (A), CT secondary (1 or 5), max load (A, optional)
Relay stages — one per line: alarm|trip, V/Hz pickup (pu), delay (s)
Optional inverse-time trip curve from the relay manual — one point per line: V/Hz (pu), trip time (s)
Equipment withstand curve from the manufacturer — one point per line: V/Hz (pu), allowed time (s)
For transformers specifically: the withstand curve available here is the through-fault (IEEE C57.109) curve, which is calibrated for fault-current-range events, not sustained overload. A "too slow" result against it at low overload multiples (roughly <3\u00d7) isn't necessarily wrong \u2014 it may just mean that curve isn't validated down at that current level. This check is a useful sanity cross-reference, not a substitute for a full IEC 60076-7 loading/ageing study.
Peak voltage exceeds 3kV \u2014 a non-linear resistor is indicated. Matched against M&I Materials' published types below.
Upload a settings export directly from the relay's own configuration tool (not our CSV template) — CSV or Excel. Currently recognizes ABB / Hitachi Energy Relion-family exports (615/620/630/650/670 series) and GE EnerVista exports. Nothing is imported automatically — every element found is shown for you to review, edit, and confirm first.
| Circuit / Feeder name | Device name | Element | Pickup (A) | Curve / setting | TMS / Delay (s) i |
|---|
Covers the most common device types directly: IEC/IEEE IDMT, Definite Time, Instantaneous, LSIG, MCCB/MPCB (thermal-magnetic), MCB, Fuse, and Motor thermal. Differential (87T/87REF), Negative Sequence, and Custom Curve devices aren't supported via import yet — add those individually.
| Row | Circuit | Problem |
|---|
| Circuit | Device | Type | Voltage |
|---|
Off by default to keep everyday coordination work simple. Turn these on only if you need them — each reveals extra fields where relevant.
| Upstream / Downstream |
|---|
| Current (A) | Time (s) |
|---|
| Element | Setting range | Amps | CT | Sensor | Tap | Time dial | Curve | Remarks |
|---|
Operate current vs. restraint current. The shaded region above the line is where the relay trips; below the line it restrains. This dual-slope percentage-differential characteristic is the standard IEEE C37.91 model — pickup and slope values are this device's own settings, not a manufacturer formula.
Leave a field on "\u2014 don't change \u2014" to skip it. Only fields you actually set here are applied to every selected device.
Before trusting a faster/slower setting, confirm it still sits with a proper margin below the protected transformer or cable's own damage curve — not just below the downstream relay.
Columns are multiples of the downstream device's pickup current. Hover a cell for I, t-up and t-down. Differential elements are excluded — unit protection has no time-graded margin.
| Project | Date | ||
| Location | Doc / S/N | ||
| Contract / Client | Rev | ||
| Engineer | Fault type |