Power Systems Lab · 18 modules · all computed in your browser

Live relay view

All 11 fault types plus evolving, cross-country and broken-conductor faults: relay targets, scope, sequence networks and how-to-test guides.

Test presets

Bolted A–G at 50 %: POTT + 87L, the reference case.

Control panel

Fault type (phase selection)

Line-to-ground · ground involved

Distance from A50 %

Rf (each phase)0 Ω

Rg (to ground)0 Ω

Inception angle on Va90°

Relay settings and equipment problems

Pilot scheme

Autoreclose

Stuck breakerCT saturation

87L enabledPermanent fault

Fault current

0.00 kA

First trip

none

Live single-line · 230 kV two-source line · AG

⚡ AGphase Aphase Bphase CRf 0 Ω · Rg 0 Ω · inception 90°

Learn it

A shunt fault connects the three sequence networks at the fault point. How they connect depends only on which phases touch each other and the ground, so every one of the 11 types maps to one of four pictures: series (SLG), parallel without N0 (LL), N2 ∥ N0 (LLG), or N1 alone (three-phase). Open conductors are series faults between two points, with the networks in parallel (one open phase) or in series (two open phases). The relay then sees V and I at its own terminal, which are linear combinations of the sequence quantities.

Quiz · 0/5

1. A BC fault through Rf in each phase. What does the BC phase loop read?
2. Why does LLLG give exactly the same currents as LLL?
3. Which elements respond to a broken conductor that does not touch the ground?
4. In the LLG sequence connection, what increases if Rg goes up?
5. An evolving AG → ABG fault during single-pole open. What should the relay do?

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