REF 542plus switchbay protection and control unit
Manual Part 3: Installation and Commissioning
1VTA100004-en DMS,2001-10-04
REF542
plus
: Installation and Commissioning
36 / 80
5.5.2 Voltage transformer
The same polarity test or patch test is run with voltage transformers. The difference is
that the battery is connected to the secondary side and the analog DC test instrument
to the primary coil of the voltage transformer.
The test setup for checking a core is shown in the following figure.
V
+
–
N
A
a
n
e
n
+
–
Figure 17:
Polarity test of voltage transformers
Every core must be tested here.
If the Variac described in the current transformer section for recording the magnetiz-
ing characteristic has a sufficiently high output voltage (e.g. 500 V), it can also be
used to run a qualitative test of the voltage transformer transformation ratio. The
Variac voltage is applied to the primary side of the voltage transformer and a voltme-
ter is used to measure the secondary voltage at the corresponding transformer or pro-
tective cabinet terminals.
5.5.3 Current sensor
Because the current sensor, the Rogowski coil, is an air-core coil, it must be sub-
jected to the same polarity test as the current transformers.
The test design is shown in the following diagram. A higher voltage value may be re-
quired for the battery.
+
–
P2
P1
V
+
–
S2
S1
Figure 18:
Polarity test of current sensors (Rogowski coil)
The transformation ratio is tested exactly as with a current transformer. The display in
the REF542 protection and control unit can also be checked at the same time. It is not
necessary to record a magnetizing characteristic with the Rogowski coil, because it is
an air-core coil with no saturation characteristics.
