This simulator follows the full protection chain on a 100 MVA, 13.8 kV, 50 Hz generator: abnormal condition, CT and VT measurement, relay pickup and timing, latched 86 lockout, trip-coil energization, breaker opening and verification that current has actually been interrupted. Apply a fault or abnormal condition, change relay settings, break the trip circuit, and see which element operates and whether the generator is truly isolated.
• A 3D cutaway of the generator protection zone with a trip chain (measurement, relay, trip coil, breaker), orbit controls and a component legend. • A condition selector and twenty sliders covering power, voltage, frequency, fault contribution, negative-sequence current, CT gain, and pickup and delay settings for each element. • Live elements list for 87G, 51, 32, 40, 46, 27, 59, 81, 24, 86 and 50BF with pickup progress and latched targets, plus failure toggles for trip DC, trip wiring, a stuck breaker, relay supply and breaker-failure backup. • Current, state, 87G characteristic and impedance-plane charts, guided experiments, a verification bench, a diagnostic challenge and an exportable event log.
87G compares terminal and neutral currents: through-faults largely cancel, internal faults add and cross the biased characteristic. 51 is inverse-time overcurrent. 32 detects reverse power (motoring), 40 detects loss of field when impedance enters a circle while absorbing reactive power, and 46 integrates negative-sequence heating. Voltage and frequency elements 27, 59, 81 and 24 cover abnormal voltage, frequency and volts per hertz. 86 latches a lockout, and 50BF calls upstream backup if the breaker fails to clear.
A relay operating only means a trip command was issued. The breaker still needs a healthy DC supply and intact trip wiring, and then it must open mechanically and interrupt the current. For an internal fault the generator's own field keeps feeding the fault while flux decays (0.5 s time constant), even after the breaker opens. This is an RMS teaching model with prescribed fault values, illustrative settings and simplified CT and breaker behavior. It is not a certified relay-setting or coordination tool, and it needs a WebGL-capable browser for the 3D view.
It compares the currents entering and leaving the generator stator winding. For an external fault the currents largely cancel and the relay restrains. For an internal fault they add, the differential current rises above a slope-biased pickup and the relay operates quickly.
Because operating only issues a trip command. The breaker can still stay closed if the trip DC supply is lost, the trip wiring is broken, the mechanism is stuck, or the opening time has not yet elapsed. The diagnostic challenge in the lab is built around telling these causes apart.
For an internal stator fault, opening the terminal breaker removes the grid's contribution but the generator itself still supplies the fault until its field decays. This model shows that decay with a 0.5 second time constant after excitation is suppressed.
No. Settings, the loss-of-field circle, heating constants and delays are illustrative teaching values. The lab does not include stator ground-fault, out-of-step or synchronism-check protection and does not replace a protection study or manufacturer guidance.