SEECO SENSE digital current and voltage sensor
devices are true sensors in that they do not physically transform primary
phase current and voltage to produce secondary output signals like
traditional oil-filled or dry-style instrument transformers.
Instead, the sensor unit digitizes phase current and voltage and
accurately reproduces (real time) in phase proportional sinusoidal current
and voltage waves for communication with meters, relays, rtu's and other
customer load devices.
Both current and voltage sensor devices utilize
induction to produce the desired output signals. The current
monitoring mechanism employs a current sensing coil (Rogowski Coil), which
is used to sense the line current and generate safe, low voltage outputs.
The coil operates on Faraday's law, which states that the total
electromotive force induced in a closed circuit is proportional to the
time rate of change of the magnetic flux linking the circuit. If the
current varies sinusoidal with time at a constant frequency, the output
can be stated as Erms=2πf
H Irms where H is the coil sensitivity.
The output voltage of the current sensing coil is equal
to the derivative of the instantaneously primary current. The
polarity of the output voltage will be determined by Lenz's law, which
states "the induced current in a loop is always in a direction as to
produce a flux opposing the initial change in flux." In other words,
the induced voltage will change phase by 180 degrees when the current
The voltage monitoring mechanism employs a voltage
sensing rod, which is used to sense the electro magnetic field of the line
voltage and generate a low level voltage output. Like the current
sensing coil, the voltage sensing rod operates on the principle of
induction. When an electro magnetic flux field moves, the motion of
the magnetic lines cutting across a conductor forces free electrons in the
conductor to move, producing current. The process is called
induction since there is no physical connection between the field and the
conductor. The current generated by the sensing rod is then
converted into a low level voltage output.
Utilizing sensing mechanisms that digitize and
reproduce, rather than transform phase current and voltage, permits device
designs that are lighter in weight, more compact, ultra safe and very
economical. The emergence of this new technology solves many of the
problems faced by design engineers when confronted by space, weight and
mounting limitations in compact substations and transmission and
distribution line monitoring applications.
For additional information on
SEECO SENSE digital current and voltage sensors, please view the following pages: