Based on the demand of the power quality 's harmonic monitor and the specialty of large scale programmable logic device, this paper advances a frame of a 24-bit float point FFT module in FPGA.

In the end, using the developed program ETHP (Electric Traction Harmonic Penetration), an actual large scale network is studied, and the calculation results are analysed.

Under a suitable condition, this paper gives an existence theorem for harmonic maps from surfaces to certain Riemannian manifolds in a large scale.