MI 3205 TeraOhm XA 5kV
Measurements
31
5.1.4 Electrical representation of insulating material
The Figure 5.1 represents the equivalent electrical circuit of an insulating material.
R iso
C p i
R p i
C iso
R iss1
R iss2
m aterial
su rfa c e
Itest
+
-
G u ard
I
PI
I
Ciso
I
Riso
I
Riss
Itest
Figure 5.1: Insulating material
where:
R
iss1
and R
iss2
................. Surface resistivity (position of optional guard connection)
R
iso
................................. Actual insulation resistance of material
C
iso
................................. Capacitance of material
C
pi
, R
pi
............................ Represents polarization effects
I
test
.................................. Overall test current (I
test
= I
PI
+ I
RISO
+ I
RISS
)
I
PI
.................................... Polarization absorption current
I
RISO
................................ Actual insulation current
I
RISS
................................ Surface leakage current
