Electric Field and Temperature Characteristics of Accumulated Charge Amount in Several Polymeric Insulating Materials Using Q(t) Method and Quantum Chemical Calculation

Circuit Models of Q(t) Data and Analyses of Saturation Time Dependency on Delay Parameters

“…Note that humidity and temperature of the sample should be ideally included in the equations as parameters, but from [11] and [14], the relation appears to be quite complicated, thus their effects are not considered in this study.…”

“…8(a) indicates that initially the condenser C0 (and the sample) intake charges steeply (during less than 1 s), and then Q0(t) behaves as if it had a very small linear coefficient against time. Note that the coefficient actually has time dependency [14] so that its value changes slightly as time passes by. A main difference between numerical test and experimental PI data is the ratio of Q0(t = 1) and Q0(t = 300), and the steepness of the transient step between t = 1 and t = 300 s. In other words, experimental PI data show high-speed responsibility in the early stage of charging, and high resistance in the latter stage.…”

“…These circumstances have increased the requirement for research on the diagnoses of electrical insulators. Q(t) measurement is a diagnostic technique used for electrical insulators in power devices, cables, and other equipment [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Q(t) measurement was first demonstrated in the 1970s by Takada et al [1], and the mechanism and structure of the circuit are almost the same as those of a leakage current detector, which can detect an extremely small electric current that indicates the incompleteness and/or the defects of electrical insulation inside insulators.…”

“…Wang et al applied Q(t) measurement to detect water treeing [6], Wang et al [7], Fujii et al [8,9], and Iwata et al [10] demonstrated that the leakage current increases with electrical treeing. Uehara et al [14] demonstrated transition of the ratio of charge amount during Q(t) measurement of several polymeric materials at both room temperature and high temperature. Kadowaki et al [15] demonstrated simultaneous measurements of both Q(t) and space charges.…”

“…However, to analyze the results of Q(t) measurement and compare other experimental/simulation results, for example, the pulse electro-elastic acoustic emission method (PEA) [19], or quantum chemical calculation and molecular dynamics simulation (QM/MD), a mathematical model of Q(t) measurements and its analysis are required. Moreover, mathematical/physical models that describe the precise separation of the transition from absorbed to leakage current based on experimental results do not exist, though the separation is considered a merit of using Q(t) measurement [14], instead of other leakage current detection methods. This situation indicates substantial risks in actual diagnoses owing to the lack of proper understanding/treatment of experimentally obtained values from Q(t) measurement.…”