The current sensor is based on the Rogowsky coil principle and consists of a single
air-wounded coil. Due to the lack of an iron core, the saturation effects of
conventional current transformers do not exist anymore. Current sensors are thus
well suited for the deployment of distance and differential protection functions.
The current sensor output is a voltage signal, proportional to the derivative of the
primary current being measured. The numerical integration of the signal is
performed by the DSP in the REF 542plus unit. The current sensors cover a range
between 0.5 to 2.0 of the rated current. The 80 A current sensors, for example, are
very suitable for applications between a current range of 40 A to 160 A. Other
current sensors are defined for the range 120 A to 480 A, 320 A to 1280 A and 800
A to 3200 A.
The voltage sensor is based on the resistive divider principle. Therefore, the voltage
sensor is linear throughout the whole measuring range. The output signal is a
voltage, directly proportional to the primary voltage. The following Fig. 4.8.1.-1
and Fig. 4.8.2.-1 shows a combined sensor. The current and voltage sensors are
encapsulated into a single resin unit. Therefore, they are referred to as "combined"
or "combi sensors".
A050502
Fig. 4.8.1.-1
Combined sensor
Coupling electrode is incorporated in the sensors, for voltage detecting systems
(VDS).
4.8.2.
Binary inputs and outputs
The REF 542plus unit acquires the primary objects status with auxiliary contacts,
which are read by binary inputs, and sends commands using binary outputs. Several
signals coming from other components are also monitored. Among others, the
following operations are implemented using binary inputs and outputs:
26
REF 542plus
REF 542plus
Multifunction Protection and Switchbay Control
Unit
Technical Reference Manual
1MRS755859
