A Novel Calibration Method in the Presence of Space Charge in Dielectric Materials Using the Pulsed Electroacoustic Technique

Calibration is an important part of procedures to accurate measurements of space charge in solid dielectrics. The pulsed electroacoustic (PEA) technique is one of the mostly used techniques due to its simplicity in construction, low cost and easy to implement for both plaque and cable samples. A novel method has been proposed which enables the PEA technique to be used in the presence of space charge. It is based on two measurements. Firstly, the sample with the presence of charge is measured without any applied voltage. The second measurement is carried out with a small dc applied voltage. The applied voltage should be small enough so there is no disturbance on the existing charge in the sample. The difference of the two measurements can be used for calibration. The additional advantage of the proposed method avoids the influence of the pulse voltage on calibration. A 200 µm LDPE sample was stressed at 8 kV for 60 minutes to produce a significant amount of charge in the sample. The proposed method has been used to calculate the residual charge and the result has been compared with the conventional method.