voltage [kV]An Introduction tothe Simulation Program XTAP for
the Analysis ofElectromagnetic Transients inPower Systems
Fault onphase b600
400
2000−200−400−600

20406080time [ms]© 2022 Central Research Institute of Electric Power Industry

https://www.xtap.org/
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Central Research Institute ofElectric Power Industry

Power System Simulation Methods
Simulation by voltages and currents
Simulation by phasors

EMT Simulation
Three-phase, waveform-level
solution

EMT: Electro-MagneticTransient

1 μs

1 ms

Phasor
Simulations

Steady-State
Simulations

Positive-sequence,phasor solution

Positive-sequence,phasor solution

Transient stability andfrequency stabilitysimulations.

1s10 sTime Scale

Power flow, fault, voltage
stability and small-signal
stability simulations.

Steadystate
2Central Research Institute ofElectric Power Industry

EMT versus Phasor

voltage [kV] EMT simulation … calculates voltage and current waveforms actually occurringin a power system.
600
4002000−200−400−600

Steady-state operation

Fault onphase b20

Overvoltages on phases c and a

406080time [ms]phase
phasea phase cbSurge overvoltage on phase c

Since the EMT simulation
gives detailed waveforms ofall phases, momentary
overvoltage and current
values are obtained. It is
suitable for detailed
simulations of a particularpart of a power system.

 Phasor simulation … calculates 50- or 60-Hz voltage and current phasors in apower system.
The phasor simulation traces
voltage [p.u.]

3LG fault (symmetrical fault)
10

Steadystate
operation

Generator swing

time [s]Fault cleared
12

3

45

the variations of themagnitudes and the phaseangles of voltages andcurrents and ignores their
momentary variations. It is
suitable for simulations of alarge power system.
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Central Research Institute ofElectric Power Industry

XTAP (eXpandable Transient Analysis Program)is an industrial-grade EMT or waveform-level simulation program.

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Central Research Institute ofElectric Power Industry

XTAP (eXpandable Transient Analysis Program)is equipped with a waveform plotting tool with usefulfunctions, a line/cable constants calculation tool, anautomated consecutive simulation function, a statisticalsimulation function, a PV panel modeling tool, and so on.

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Central Research Institute ofElectric Power Industry

Components and Models
 Comprehensive electrical and control components.
 Synchronous generator model with saturation andtorsional dynamics.
 Line models (π equivalent, constant-parameter andfrequency-dependent).
 Transformer models (2, 3-winding and autotransformers).
 HVDC and FACTS converter models (line-commutated,PWM and MMC AC/DC converters; SVC and STATCOM).
 PV power generation systems.
 User-defined models: You can create your own models –You can even draw your own icons for them!
 DLL-defined blocks.
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Central Research Institute ofElectric Power Industry

Applications
 XTAP can be used not only for traditional EMT

simulations but also for new simulation needs.
 Abnormal Overvoltages, Currents and Oscillations: Lightning, switching and black-start overvoltages.
 Transformer and induction motor/generator inrush currents.
 Ferroresonance and subsynchronous resonance.

 Power Quality Assessments:
 Harmonics, flicker and voltage interruptions/drops/swells.

 Performance Studies of Power Electronics

Converters:

 HVDC systems, FACTS devices, power electronics converters used inrenewable energy (PV and wind) generation systems and battery
storage (EV) systems.
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Central Research Institute ofElectric Power Industry

2S-DIRK versus Trapezoidal
 XTAP uses the 2S-DIRK method for the numerical integration. It is

inductor voltage [V]mathematically guaranteed that the 2S-DIRK method neverproduces fictitious numerical oscillation due to sudden changes
of inductor currents and capacitor voltages unlike the trapezoidal
method used in other programs.
2S-DIRK
Simple Test Circuit

control systemwith step output
1A0A00h = 1 ms

204060time [ms]80100

Trapezoidal with CDA

100 mH

inductor voltage [V]controlledcurrent source10 Ω1002000−2000204060time [ms]801008Central Research Institute ofElectric Power Industry

Strong Research Base XTAP has been developed with incorporating

recent research results obtained at CRIEPI: The 2S-DIRK (two-stage diagonally implicit Runge-Kutta)
method is used for the numerical integration of differentialequations. It is especially suitable for power-electronics(switching-circuit) simulations.
 A practical three-phase (unbalanced) steady-state
initialization method is implemented.
 A robust and efficient solution method, in which the NewtonRaphson (NR), the biaxial NR and the Katzenelson algorithm
are combined, has been developed and is used to solve
nonlinear circuit equations.
 An efficient sparse-matrix manipulation algorithm accelerates
the solution process.
 The last two are patented but free to use in XTAP.
9Central Research Institute ofElectric Power Industry

User Community and Development
 User Community

Others

Universities
 In Japan, all T & D companies use
XTAP as their standard, and major
manufacturers, engineering
companies, universities and research
institutes form a user community.
The total number of users is more
Manufacturers
than 3,300 as of Sep. 2021.

T &Dcompanies

Eng. companies

 Development
 Hokkaido Electric Power, Tohoku Electric Power, TEPCO Holdings(Tokyo Electric Power), Hokuriku Electric Power, Chubu ElectricPower, Kansai Electric Power, Chugoku Electric Power, Shikoku
Electric Power, Kyushu Electric Power, Okinawa Electric Power andElectric Power Development Company financially support thedevelopment, and CRIEPI performs the development project.
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Central Research Institute ofElectric Power Industry

Education Opportunities
 XTAP comes with a 178-page manual and 42

introductory and practical test cases for self-learning.
 A summary of XTAP is given in the IET Book below.
 Courses by EMT specialists are offered in Japan (English
on-line courses can be arranged).

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Central Research Institute ofElectric Power Industry

Web Site - www.xtap.org

XTAP is available to everyone for free of charge andcan be downloaded from this site.
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XTAP
https://www.xtap.org/© 2022 Central Research Institute of Electric Power Industry