High voltage electrical reactor in series is the main supporting equipment for reactive compensation and harmonic treatment. The electrical reactor and capacitor bank are connected in series, to restrict switching surge current effectively, inhibit higher harmonic, improve system voltage waveform, and play an important role in safe operation grid and reactive compensation. Iron core electrical reactor is made by epoxy casting of high quality silicon steel sheet and coils. The products have the features of low costs, small volume and no leakage.