عربي
Consultancy · study

Fault ride-through (FRT) studies

Fault ride-through is the rule that a plant stays connected and supports the grid through a voltage dip. We show in EMT that your plant rides through the required voltage-time profile and injects reactive current the way the code asks.

Discuss a project Read the case study
Ride-through check · voltage against the curveIllustrative
00.510123t (s)V (pu)fault
Margin to the curvelowest point– puat least 0 pu
Power back to 90%after clearing– mslimit 500 ms
Voltage after the faultsettled level– puat least 0.85 pu
When it's needed

When you need it.

  1. The grid code asks for proof of low-voltage, and often high-voltage, ride-through.
  2. The plant is converter-based, so ride-through depends on control settings.
  3. Protection or control settings changed and compliance needs confirming again.
  4. Behaviour during a real event has to be squared with the compliance file.
Method

How we run it.

  1. 01

    Define

    Take the ride-through profile and current rules from the grid code.

  2. 02

    Apply

    Apply the specified fault types and durations at the connection point.

  3. 03

    Check

    Check voltage recovery, fast fault current, timing and staying connected.

  4. 04

    Edges

    Test the edges: deepest dip, longest fault, weakest grid.

  5. 05

    Record

    Pass or fail against each criterion, with annotated waveforms.

Tools and scenarios

Every scenario through every study.

  • PSCADFault simulation
  • Vendor control modelsIBR and HVDC
  • PowerFactory · PSS®ERMS screening
Ride-throughReactive currentPower recoveryVoltage recoveryRepeated faults
Strong grid
Weak grid
Balanced faults
Unbalanced faults
Long clearing times
Low and full output

Weak grid · Voltage recoveryOn the weak grid the voltage recovered slowly and crossed the curve at 1.8 s. A retuned voltage loop clears it.Unbalanced faults · Reactive currentNegative-sequence current was below the requirement in unbalanced faults. A setting change brought it in.Long clearing times · Power recoveryAfter a 250 ms fault, power took 600 ms to recover. A faster ramp brings it under 500 ms.Weak grid · Repeated faultsThree faults in a minute used up the chopper’s energy rating. The design now has margin for them.

25 checks · 4 led to a change · every case scripted and rerunnable
Deliverables

What you get.

  • ReportFRT compliance report mapped to each grid-code clause
  • WaveformsAnnotated voltage and current waveforms for every case
  • SettingsThe control settings used, and anything they depend on
  • ModelValidated model files behind the result

How we check it

Results map clause by clause to the code's acceptance criteria, and we name the worst-case scenarios rather than one nominal run. Assumptions and settings are written down for independent review.

Selected work

Related case studies.

Case 03 · SSO and compliance40 MW battery: SSO screening and NESO complianceImpedance scan, Nyquist, voltage injection, FRT and FFCI from one model.Case 02 · EMT modellingGenerator EMT model checked against site measurementsA full PSCAD model with excitation, stabiliser and protection, validated on site.
FAQ

Questions engineers ask.

Is FRT the same as fast fault-current injection?
They're related but distinct. FRT is the requirement to stay connected through a voltage profile; fast fault-current injection (FFCI) is the reactive/active current the plant must supply during the dip. An FRT study typically checks both.
Why test the weakest grid case?
Ride-through and current injection are hardest to achieve when the grid is weak, because the same current produces larger voltage excursions. The weak-grid corner usually governs compliance.
Do FRT settings interact with stability?
Yes. Aggressive ride-through and current-injection tuning can affect small-signal and control-interaction behaviour, which is why FRT is often assessed alongside stability and SSO screening.
Next step

Have a study like this coming up?

Discuss a project [email protected]

Related: Consultancy hub · 40 MW battery case study · EMT & grid-code compliance · SSO / impedance studies