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STEPSS

Disturbances

Disturbances define the sequence of events during a dynamic simulation. Disturbances need to have a continuity. All disturbance commands follow the format:

time(s) COMMAND parameters

Continue Solver

Section titled “Continue Solver”

Defines solver settings. Must be the first line of the disturbance file:

time(s) CONTINUE SOLVER disc_meth max_h(s) min_h(s) latency(pu) upd_over

Discretization method (disc_meth):

  • TR — Trapezoidal
  • BE — Backward Euler
  • BD — BDF2

Jacobian update override (upd_over):

  • ALL — Update all injectors and network
  • NET — Update only network
  • ABL — Update only injectors
  • IBL — Update all injectors and network
  • NOT — Do not override

Example:

0.000 CONTINUE SOLVER BD 0.0200 0.001 0. ALL

Stop

Section titled “Stop”

Signals the end of the simulation. Must be the last line:

time(s) STOP

Example:

100.000 STOP

Trip Line (BREAKER BRANCH)

Section titled “Trip Line (BREAKER BRANCH)”

Open or close breakers of a line:

time(s) BREAKER BRANCH name_of_line orig_break(0/1) extrem_break(0/1)

Example — opening both ends of a line at t=10t = 10 s:

10.000 BREAKER BRANCH 1044-4032 0 0

Trip Machine / Injector

Section titled “Trip Machine / Injector”

Open or close the breaker of a synchronous machine or injector:

time(s) BREAKER SYNC_MACH name_of_machine breaker(0/1)
time(s) BREAKER INJ name_of_injector breaker(0/1)

Example:

10.000 BREAKER INJ L_11 0

Three-Phase Short-Circuit (Impedance)

Section titled “Three-Phase Short-Circuit (Impedance)”

Apply a three-phase fault with specified impedance to ground. This requires two commands — one to apply the fault and one to clear it.

time(s) FAULT BUS name_of_bus rfault [xfault]
time(s) CLEAR BUS name_of_bus

The fault has an impedance of rfault + j*xfault to ground:

  • rfault and xfault are in Ω
  • If xfault is omitted, a fully resistive fault is assumed

Example — 100 ms bolted fault:

10.000 FAULT BUS 1044 0. 0.
10.100 CLEAR BUS 1044

Three-Phase Short-Circuit (Voltage)

Section titled “Three-Phase Short-Circuit (Voltage)”

Apply a fault where the post-fault voltage is specified. Internally, RAMSES creates a temporary shunt admittance BfaultB_{fault} at the faulted bus and iteratively adjusts it using a secant method until the bus voltage matches the target value to within ±0.5%\pm 0.5\%. The injected currents are ix=Bfault vxi_x = B_{fault}\, v_x and iy=−Bfault vyi_y = -B_{fault}\, v_y. Up to 10 correction steps are attempted; if convergence is not reached, the simulation halts with an error message.

time(s) VFAULT BUS name_of_bus Voltage_after_fault(pu)
time(s) CLEAR BUS name_of_bus

Example — 100 ms fault with 0.5 pu residual voltage:

10.000 VFAULT BUS 1044 0.5
10.100 CLEAR BUS 1044

Change Parameters (CHGPRM)

Section titled “Change Parameters (CHGPRM)”

Modify model parameters during the simulation.

Branch Parameters

Section titled “Branch Parameters”
time(s) CHGPRM BRANCH name_of_line MAGN/PHAN ±increment

Shunt Parameters

Section titled “Shunt Parameters”
time(s) CHGPRM SHUNT name_of_shunt QNOM ±increment

The increment is in MVAr and is per-unitized internally by RAMSES.

Exciter Parameters

Section titled “Exciter Parameters”
time(s) CHGPRM EXC name_of_equipment name_of_parameter ±increment [MVAr/%] duration(s)

Units: No unit = absolute, MVAr = per-unitized by SnomS_{nom}, % = percentage of original.

Duration: 0 = step change, > 0 = ramp over given duration.

Example — ramp voltage setpoint by +10% over 10 seconds:

10.000 CHGPRM EXC g1 V0 +10 % 10

This means the parameter V0 of the exciter of synchronous machine g1 is ramped by +10% between 10 and 20 seconds.

Torque Controller Parameters

Section titled “Torque Controller Parameters”
time(s) CHGPRM TOR name_of_equipment name_of_parameter ±increment [MW/%] duration(s)

Units: No unit = absolute, MW = per-unitized by PnomP_{nom} of the machine, % = percentage of original value.

Duration: 0 = step change, > 0 = ramp over given duration.

Example — ramp active power setpoint by +1 MW over 10 seconds:

10.000 CHGPRM TOR g1 P0 +1 MW 10

This means the parameter P0 of the torque controller of synchronous machine g1 is ramped by +1 MW between 10 and 20 seconds.

Injector / Two-Port / Discrete Controller Parameters

Section titled “Injector / Two-Port / Discrete Controller Parameters”
time(s) CHGPRM INJ/TWOP/DCTL name_of_equipment name_of_parameter ±increment [MW/MVAr/%/SETP] duration(s)

Units: No unit = absolute, MW or MVAr = per-unitized using the system’s SbaseS_{base}, % = percentage of original value, SETP = the increment is the new setpoint value.

Duration: 0 = step change, > 0 = ramp over given duration.

Example — load increase of 50% active and 30% reactive over 60 seconds:

10.000 CHGPRM INJ L_11 P0 +50 % 60
10.000 CHGPRM INJ L_11 Q0 +30 % 60

This means the parameter P0 (resp. Q0) of the injector L_11 is ramped by +50% (resp. 30%) between 10 and 70 seconds. If L_11 is a load model, this simulates a load increase.

Export Jacobian Matrix

Section titled “Export Jacobian Matrix”
time(s) JAC 'name_of_filename'

Required solver settings:

$OMEGA_REF SYN ;
$SCHEME IN ;

Export Load Flow Snapshot

Section titled “Export Load Flow Snapshot”

Takes a snapshot and exports the load flow at a specific time:

time(s) LFRESV 'name_of_filename'

Next Steps

Section titled “Next Steps”