Megger INGVAR, User Manual

Page: 49 / 72

BH0654BE ZP-BH05E 49
8 APPLICATION EXAMPLES
Measure the instantaneous trip
time
1]
Increase the current to an ample margin
above the tripping level.
2]
Start an injection and read the time on the
display.
8.2 Testing the ratio of a
current transformer
This test determines whether or not a current trans-
former has the correct ratio. During the test, current is
injected into the primary side of the current transform-
er, and the current in each secondary winding is meas-
ured using INGVAR’s second ammeter ("A-METER 2").
WARNING
Make certain that you observe all appli-
cable safety regulations and precautions
associated with dielectric strength on the
secondary side. The secondary side of the
transformer must be closed during the
injection!
1]
Basic setting:
OPERATE OFF
AMMETER1, UNIT AMPERE
2]
Connect the INGVAR output to the primary
terminals on the current transformer.
3]
Connect INGVAR’s second ammeter ("A-
METER 2") input to the current transformer
winding that is to be tested. Make certain
that this winding is not connected to any
other circuit.
4]
Activate "A-METER 2" in the "V/A METER"
menu option under the "A-METER 2" menu
heading.
5]
Select "A-METER 2 NOM I" and set the nomi-
nal secondary current for the current trans-
former. You might, for example, set it to 5 A.
6]
Select "A-METER 2 UNIT", and then select
“CT ratio".
7]
Press
TIME
.
8]
Set the desired primary current, whereupon
both the primary current and the actual ratio
will appear on the display.
Example
1000 A injected into a transformer with a ratio of
5000/5.
5.107s
1.00kA
5000/5 A