In order to further improve the insulation performance of fiber reinforce plastic (FRP) materials used in electromagnetic pulse (EMP) simulators, the flashover characteristics of FRP materials with different surface roughness and groove, i.e., those who are easily achieved and have a prominent effect, are investigated in 0.1 MPa SF₆ under nanosecond pulse voltage with a rise time of 20–30 ns. The experimental results show that surfaces with different roughness have no significant influence on the flashover voltages of the FRP insulators, and both the convex grooves made of FRP and the convex grooves with nylon rings inlaid to form projections can improve the surface flashover voltage of epoxy FRP insulators under nanosecond pulse, in which the effect of the former surface is more obvious. For the insulators with convex grooves made of FRP, it is found that the root of the FRP protrusions breaks down after a number of shots with the occurrence of carbonization channels and spots, which is nonexistent for the nylon projections. Combined with the test results of surface characteristics, the surface roughness and the secondary electron emission yield (SEEY) are not key factors of flashover characteristics in SF₆ under nanosecond pulse, arguably due to the fact that the energy needed for an incident electron to ionize an SF₆ molecule is lower than that to excite two secondary electrons. Hence, the flashover performance cannot be improved by adjusting the surface roughness, and the flashover channel is principally governed by the macroscopic distribution of electrical field which can be changed by the convex groove. Breakdown phenomena of FRP protrusions indicate that the bulk insulation performance of resin FRP is weaker compared to pure resin because of its composite structure, as well as the impurities and voids introduced in the manufacturing process. The results are instructive for the design of FRP insulation structures in the compact EMP simulator.

The Fiber Reinforced Plastics (FRP) with vacuum forming technology has high structural strength and excellent insulation property, and is widely used in EMP (Electromagnetic Pulse) simulation devices. In order to improve the insulation performance of FRP and meet the requirements of the supporting structure for insulating materials in MV (Megavoltage) EMP simulation equipment, the effect of groove shape on the insulation performance of FRP insulators was studied. The experimental object is the cylinder insulators with different grooving technologies. The insulation environment is 0.1 MPa SF6, and here we use the circuit to output the nanosecond pulse with the rising edge of approximate 30 ns. The result shows that in SF6, different from the vacuum condition, the concave grooves of different shapes and sizes have no significant influence on the flashover voltage along the surface of insulators, which indicates that the secondary electrons production on the surface of insulators may not be the main reason for the flashover process along the surface in SF6. The result also indicates that convex grooves can reduce the electric field on the development path of the flashover channel and change the angle between the development path of the streamer and the electric field on the surface of the insulator, thus improving the withstand voltage of the insulator. Besides, in the experiments of samples with convex grooves, the bulk breakdown phenomenon of insulator and its convex grooves were observed, showing that there is a competition between the bulk breakdown in the insulator and the flashover along the surface of insulator whose phenomenon may be related to the impurities (bubble or dust) introduced along the glass fiber during the manufacturing operation.

Now piezoelectric (PZT) sensor is typically used to detect and locate partial discharge (PD). However, optical fiber sensor is a good alternative for its advantages of immunity to electromagnetic interference (EMI), potential to be installed in the transform and good multiplexing capability. Compared with other optical fiber sensor, microfiber coupler sensor (MFCS) is small, low-cost and easy to demodulate, while there are few studies on the PD detection based on MFCS. In order to prove the feasibility of the MFCS in the PD detection, a PD detection system based on MFCS is proposed. The experiment results show that the MFCS can successfully detect the ultrasonic signal from PD and it has the similar sensitivity with traditional PZT sensor. Besides, the change in the amplitudes of the ultrasonic signals when the distance between the MFCS and the PD source increases is investigated, and the relationship between the signal amplitudes and PD magnitudes is analyzed. The good performance of the MFCS indicates that it is promising for applications in monitoring the PD activity in the power transform.