Hioki SM-8216, Instruction Manual, Page: 35 / 44

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6.5 Changes in the Current Flowing through an Insulator
In insulation resistance measurements, a large amount of current flows
Upon the application of the measuring voltage to the insulator. The current
gradually reduces its value with time, but it takes a time until the value
becomes stable and fixed. This phenomena is due to the combination of the
charging current, absorption current, and leakage current, and it is
generally called dielectric absorption phenomena. The equivalent circuit of
an insulator is considered as shown in Fig. 6.5.1.
Fig. 6.5.1 Equivalent Circuit of an Insulator
When a voltage is applied to the circuit, a charging current flows through a
bank of capacitors, C
0
, C
1
, C
2
,
. . . . . . .
C
n
. Firstly, C
0
is charged, and
other capacitors follow. As the charging progresses the current through R
0
constantly flows as shown in Fig. 6.5.2.
Fig. 6.5.2 Current Flowing through an Insulation Material
R
0
is an insulation resistance to be measured, but, C
0
, C
1
, C
2
, . . . . . . . C
n
Have series resistors R
0
, R
1
, R
2
, . . . . . . . R
n
. Therefore, a measurement of
R
0
only is very difficult. It is said that, with some insulation resistance
０
Charge current
Absorption current
Leakage current
Time
（Charge）
Voltage
application
Current
（Discharge）
Current
short Time