This document summarizes a simulation of transient skin effect in DC railway systems using MATLAB/Simulink. It discusses: 1) The need to model skin effect in the time domain rather than frequency domain to distinguish starting and fault currents. 2) Using a step series algorithm to calculate remote short circuit current for skin effect calculation. 3) The design of a circular cylinder model, application of step voltage signals, and calculation of frequency dependent current response. 4) A complete Simulink model and S-function model flowchart for remote short circuit simulation.

1. Simulation of Transient Skin Effect of DC
Railway System Based on
MATLAB/Simulink
By
Shridhar B. Kulkarni
Roll No 1529010

2. Contents
• Introduction
• Structure of DC railway system
• Design of circular cylinder
• Step voltage signal and current response
• Step series method
• Calculation of frequency current
• Complete Simulink model of remote Short circuit
• Flowchart of S - function model

3. Introduction
• Classic calculation of skin effect based on frequency domain is
not suitable for time-domain simulation
• Difficult to distinguish starting current and fault current
• Key technique is calculation of remote short circuit current for
calculation of skin effect
• Step series algorithm

4. Structure of DC railway system

5. Design of circular cylinder

6. Step Voltage Signal and Current Response
• When t = 0 of step voltage signal
means angular frequency is also infinity
inside current density is infinitesimal
Therefore, current can be defined as
• When t =

7. Step series method
• In the form of discrete sampling, the voltage signal can be
expressed by
• The sampling voltage signal can also be expressed by unit
step signal as,
• Calculate all the current response of every step voltage
signal and make these currents combined in time domain.
The result can be expressed as

8. Calculation of frequency current
• The skin effect impedance of frequency is derived from
Maxwell’s equation
• At a given frequency , the impedance of a solid cylindrical
conductor is given by
Where ,
• Therefore, the current could be calculated by,

9. Complete Simulink model of remote Short circuit

10. Flowchart of S - function model

11. THANK YOU