Megger DELTA 4000, Reference Manual

Page: 34 / 48

34 DELTA 4000 ZM-AH02E
3 TESTING POWER SYSTEM COMPONENTS
method, whereas, the phase-to-phase tests are made by the
UST test method.
When testing large generator windings which have a very
high value of capacitance per phase, the maximum speci-
men capacitance measurable at a particular test voltage may
be limited due to maximum output current from test equip-
ment. For this case tests will have to be made at a reduced
voltage level or with the use of Resonating Inductor (Cat.
No. 670600).
The temperature of the windings should be above and
never below the ambient temperature to avoid the effects
of moisture condensation on the exposed insulating sur-
face. Temperature measurements when using temperature
correction curves should be based on that at the winding
surface.
Avoid prolonged exposure to high humidity conditions
before testing because such exposure may result in moisture
absorption in the insulating materials. It is desirable to make
tests on the winding insulation shortly after shutdown.
Table 3.10
Three-phase rotating machinery
Stator test connections (Motors and generators)
Te
st
N
o
.
In
su
la
ti
o
n
te
ste
d
Low voltage lead
configuration
Test con-
nections
to
windings
R
em
ark
s
Te
st
m
o
d
e
M
ea
sur
e
G
ro
un
d
G
uar
d
H
ig
h
v
o
lt
ag
e
Re
d
B
lu
e
1 A to
g
GSTg-RB
Red
&
Blue
A B C
B & C
Guarded
2 A to B UST-R Red Blue A B C C Grounded
3 B to
g
GSTg-RB
Red
&
Blue
B C A
C & A
Guarded
4 B to C UST Red Blue B C A A Grounded
5 C to
g
GSTg-RB
Red
&
Blue
C A B
A & B
Guarded
6 C to A UST Red Blue C A B B Grounded
7
A + B
+ C to
g
GST-
GND
A,
B,
C
– –
May require
Resonating
Inductor
Equivalent Circuit Remarks
A Phase A winding
B Phase B winding
C Phase C winding
G Ground
Note: Short each winding on itself if possible.