Raptor
60
Low Power CT
This template is identical to the one described above, so we
refer to that for its use.
Indeed, different systems have appeared on the market to
carry out the same function as a classic CT, but with
advantages over it (economic, size, lack of saturation, etc.)
for certain applications, especially in low voltage.
Different systems are used but, for our application, we are
only interested in knowing what converts the primary current
into a low level voltage, proportional to this current, and
consequently they are tested the same.
However, the linearity and angle acceptance criteria
between primary and secondary may vary depending on the different types of sensor.
AC Resistance
The contact resistance of circuit breaker poles,
sectionalizers, busbar connection points, and cables, etc.
must be verified during any start-up or maintenance of
primary equipment. This resistance is characterised by its
low value, around tenths of micro-ohms. The only way to
measure them is via the 4-wire measurement, which
consists of injecting a current of sufficient value so as to
generate sufficient voltage drop to be measured with
certain accuracy.
Dividing the voltage value obtained by the current value
injected, we obtain the impedance (Z) of the cross-section
between the two points where the voltage measurement
cables are connected.
However, for practical purposes, we are only interested in the real part (resistance R) of
the total impedance, which is the result that we obtain from measuring in Alternating
Current.
To obtain this real part, we must also measure the phase angle. This is the aim of the test
template.
Template configuration:
The template is configured as follows:
• Generator: Pass-through turn
• Time display; As timer in seconds (8 s, maximum length of high current
injection)
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