Protection Coordination Study

pandapower

Protection coordination checks whether devices operate in the right order for a chosen fault. Electrisim runs IEC 60909 short-circuit, then evaluates fuses and overcurrent (and related) devices. You get trip or melt times, complete time-current (TCC) curves, and miscoordination warnings.

When to use

• Fuse melt and relay trip times for a fault at a bus or along a line
• Time-current grading between upstream and downstream devices (complete OCR TCC for DTOC, IDMT, and IDTOC)
• A first miscoordination screen on a radial feeder

How to run

1. Place switches on lines, transformers, or bus connections in your diagram (switches are required for protection assignment).
2. Open each switch’s dialog → Protection tab. Choose Fuse (library or custom I–t curve) or OC relay (DTOC, IDMT, or IDTOC). For OCR, set subtype, inverse curve, trip times, and automatic or manual pickup currents (manual values are in amperes).
3. Click Simulate → Protection Coordination.
4. In the dialog, choose fault location (along a line or at a busbar), fault type (3ph / 2ph / 1ph), and case (max / min). Configure grading defaults on the Grading tab if switches leave fields empty.
5. Review the results dialog: short-circuit summary, tripping table (including melting time for fuses), complete I–t / TCC chart, and miscoordination list. Optionally export a .txt report.

Fault location modes

Dialog parameters

These fields are sent as ProtectionCoordinationPandaPower in the POST body together with network elements.

Switch protection settings

Per-switch parameters are configured on the Switch dialog Protection tab (see also Switch):

• Fuse — library type (e.g. Siemens NH-2 series) or custom JSON curve (t_min, t_total, x_min, x_total) plus rated current.
• OC relay — DTOC, IDMT, or IDTOC; IEC or IEEE inverse curve; TMS, grading delay, instantaneous and backup trip times; automatic or manual pickup currents in amperes. See Overcurrent relays (OCR).
• Earth-fault OCR (50N/51N), directional OCR (67), differential (87), and distance (21) — configured on the same tab; 87 and 21 use Electrisim evaluators on the short-circuit results.

At least one switch with a protection device assigned is required; otherwise the study returns an error.

Overcurrent relays (OCR)

Assign Overcurrent Relay (OCR) on the Switch Protection tab. Subtype, curve, times, and pickups are taken from that switch; empty timing fields inherit the study Grading tab defaults.

• Time grading — auto uses pandapower topological grading. manual uses the per-switch times from the Switch dialog (t_g, t_gg, tms, t_grade). Manual grading is supported for DTOC, IDMT, and IDTOC, including a complete IDTOC TCC.
• Pickup current — auto derives pickups from line ratings and the overload / CT / safety factors. manual uses I_s_a, I_g_a, and I_gg_a in amperes (not kA).
• Inverse curves — IEC 60255: standard, very, extremely, and long inverse (native pandapower OCRelay). IEEE C37.112 moderately / very / extremely inverse are evaluated by Electrisim from the same short-circuit results; trip times and TCC points are still returned.
• Evaluating engine — each relay is reported once, and the settings table shows whether it was solved by pandapower or the Electrisim evaluator. Electrisim takes over when pandapower cannot build the relay — most often because pandapower’s topological time grading requires every closed switch to sit on a line, so bus-bus ties or transformer switches make it fail. The reason is listed under Evaluation notes in the results dialog and in the .txt report.

Outputs

• Short-circuit summary — e.g. Ikss at the fault bus (kA).
• Tripping table — per switch: device type, tripped/melted flag, activation current (activation_parameter_value, kA), trip/melt time (trip_melt_time_s, s).
• Time-current chart — log-log TCC (Chart.js): complete relay/fuse characteristic (inverse segment and definite-time steps for IDTOC/DTOC) plus fault trip points.
• Miscoordination warnings — pairs of devices whose trip times are closer than the grading margin (t_diff).
• Export — optional .txt download with the same summary fields.

Prerequisites and tips

• Valid network topology with external grid (or slack) and in-service switches on protected branches.
• For results comparable to pandapower fuse examples, match fuse types per feeder, avoid duplicate fuses on both ends of the same line unless intended, and align external-grid short-circuit strength (s_sc_max_mva) with your reference case.
• OCR relays require matplotlib in the backend environment (pip install matplotlib).

Limitations

• Primary path is short-circuit based; overload (scenario=pp) is optional when enabled in the study dialog. For motor-start voltage dip studies, use Motor Starting Analysis.
• IEEE inverse curves, earth-fault OCR, directional OCR, differential (87), and distance (21) use Electrisim evaluators on SC results (not native pandapower device classes). DTOC, IDMT, and IDTOC with IEC curves use pandapower OCRelay where the network allows it, otherwise the Electrisim evaluator with the same Switch dialog settings.
• Line-end duplicate switches report identical branch currents by design.
• Subscription required in the cloud app (same gating as other premium analyses).

Technical references

pandapower v3.3.2 — Protection · Short-circuit (IEC 60909)