Surge arresters constitute an indispensable aid to insulation coordination in power systems and they are the primary protection against different types of overvoltages (lightning or switching). They are generally connected in parallel with the equipment to be protected to divert the surge currents. The paper presents an approach to teaching high-voltage laboratory using specially designed exercises that can be done using MATLAB R2007. This paper presents a MATLAB-based technology to simulate residual voltage test, long duration withstand test, and operating duty test on arresters. Evaluation of the simulation with more than 30 students is very positive in terms of their developing confidence in and understanding of this simulation. ß

No abstract

A positive temperature coefficient (PTC) device is a passive component used to protect against overcurrent faults. In this paper, dimensions of a PTC device connected in series with a circuit breaker that can act as a current limiter has been calculated. When the current flowing through the device exceeds the current limit, the PTC device warms up above a threshold temperature and the electrical resistance of the PTC device suddenly increases several orders of magnitude to a tripped state where the resistance will typically be hundreds or thousands of ohms, greatly reducing the current. This feature allows power system to use a cheap circuit breaker in series with the PTC device to disconnect the circuit. In this paper, by helping heating equations and simulations with finite element method, the PTC device cross-sectional area and its thickness has been calculated.

In this paper, a family of high-order compact finite difference methods in combination with Krylov subspace methods is used for solution of the nonlinear sine-Gordon equation. We developed numerical methods by replacing the time and space derivatives by compact finite-difference approximations. The system of resulting nonlinear finite-difference equations is solved by Krylov subspace methods. The behavior of the compact finite-difference method is analyzed for error estimate and computational cost. Numerical results are presented to verify the behavior of high-order compact approximations for stability and convergence. The accuracy and efficiency of the proposed scheme are also considered.

No abstract