Test Circuit
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Safety is a large concern. The following images show some steps of the setup. There are areas available for double-checking setup before taking actual measurements. The motor contactor below is used to cause the transformer to short circuit to show a fault.
motor contactor
Below is the short circuit part of the test circuit.  On the left side is a current transformer that was used to measure the current through the shorting circuit. The fuse box on the right has fuses which we blew to stop the short circuit. The small black wires coming off of the side of the contactor are connected to a switch. When the switch is flipped, the short circuit is then working. After a few cycles (or 1/10 of a second), the fuses blow and the short circuit is no longer conducting current. This prevents damage to the transformer. The other small black wires connect to the relay and as soon as the short circuit turns on, the relay starts collecting data.
Short Circuit
A diagram of the shorting circuit is below.
short circuit
A close-up of the fuse block is below.
fuse block
Events are triggered as shown in the diagram below.
event trigger
Current transformers (shown below) are used to decrease the current before it is input to the relay. The current is measured on both the input and output of the transformer.

current transformer
The SEL-421 relay below is used for measuring the current. Then the measurements are collected on a PC and converted into waveforms for analysis.
SEL relay

A block diagram of the test circuit is available at the following link. It's a large image and may take a while to download.
Block Diagram of Test Circuit

The first test circuit we created was using an existing 25kVA transformer. Pictures of this are available at the following link.
Initial Test Circuit
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For problems or questions regarding this web site, contact eevicmaki@vandals.uidaho.edu
Last updated: 4/26/07.
University of Idaho, Moscow, Idaho.