As we know, the TF method is more sensitive to changes in the power transformers at higher frequencies. Although measurement based on low voltage impulse (LVI) is definitely faster than that based on swept frequency method (SFM), the available frequency band is narrow because of the typical microsecond impulse. In this paper, the characteristics of the nanosecond impulse in the frequency domain were investigated. A test System based on Nanosecond low voltage impulse was developed. The proposed method was applied to a 10kV/100kVA distribution transformer in the laboratory. Measurement results with two different impulses were compared.

Based on Wagner field cancellation method, the paper presents a simplified method to calculate the induced overvoltage on transmission lines excited by lightning striking on tower. Firstly the square-wave response of lightning-induced voltage is calculated, and then the responses produced by other excitations can be calculated by Duhamel integral. This method can reflect the time-varying characteristic of the induced overvoltage. The simulation results show that the amplitude of lightning current and the length of upward leader have greater impacts on the induced overvoltage.

For rapid production decline, difficult production stability ability in low permeability reservoirs, establishment of effective injection-production system between injection and production wells is proposed to curb production decline. The effectiveness of an injection-production system should contain two aspects, supplementing enough energy to layer on time and overcoming starting pressure gradient. Completely fractured injection-production well arrangement is simplified into an injection-production one-way flow model, and layer pressure calculation formula is derived by separating variables while single-phase flow. Formulas of determining terminal parameters and driving pressure gradient of an effective injection-production system are gained by demanding for time limits on layer pressure and letting production well’s B.H.P (bottom hole pressure) equal or a bit bigger than a minimum pressure. Results show that the efficiency of a completely fractured well arrangement is related to permeability, oil viscosity, reservoir thickness, well spacing, well draining, production rate, and maximum producing pressure drop. The bigger the production rate, the smaller well draining should adopt, and the driving pressure gradient will also become bigger. For a certain reservoir, several sets of effective injection-production systems are possible, and which effective injection-production system is the best should determine by the principle of cost-effective development.