In high revenue areas such as universities, shopping malls
and business centres, taking CT’s offline for testing is not
an option, so a reliable live CT test alternative is required.
Live CT testing using admittance…
A component of a good CT’s characteristic performance is
a low admittance value. This admittance value can be measured while in-circuit using the 505B (pictured).
The 505B is placed in series with an in-circuit CT and it
superimposes a small 1.6kHz signal onto the live 50 or 60Hz
secondary metering circuit.
A filter on board the 505B extracts the 1.6kHz admittance
reading and from this a quick determination is made on the
CT’s general health.
Admittance testing only adds an extra 10 minutes to a polyphase
meter test and is quickly becoming part of a routine test requirement
for some utilities.
The 505B can perform the following measurements:
Voltage and current at 50 or 60Hz.
1.6kHz admittance test on a CT secondary.
1.6kHz admittance test on a CT secondary plus the complete metering loop.
VA burden of the metering loop downstream from the test block, or at the CT secondary terminals.
VA burden of the metering loop from VT secondary terminals or at its test block.
A USB interface is also provided on the front panel for downloading results data to a PC.