FUNCTION CHARACTERISTICS
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NA011 - Manual - 05 - 2022
CPU board
This circuit board contains all the circuits necessary for performing the analogue and digital pro-
cessing of the signals.
Analog processing
The following are envisaged:
• Anti aliasing filter circuits, .
• Amplifier circuits for conditioning the input signals,
• Reference voltage adjustment circuits for the measurement A/D converter.
The relays uses a DSP processor operating at 40 MHzThe input currents are sampled at a frequency
of 64 samples per period by means of a dual conversion system which allows the attainment of infor-
mation pertaining to polarity and amplitude with high resolution. The measurement criterion allows
precise measurement of even those signals having a unidirectional component, such as transient
currents with overlapping exponential, which typically appear during faults.
The circuit board also houses the output relays with the corresponding command and control cir-
cuits, communication circuits, buttons, LCD display, LEDs and the key switch.
CPU
A 32 bit DSP is provided.
The following are envisaged:
• Real Time Clock circuits with oscillator and super capacitor,
• RS232 communication port,
• RS485 communication port,
Memories:
• Ram: high speed static memory
• Flash memory,
• EEprom memory: used for calibration data storage,
Input board
Phase current inputs
Traditional CTs
Three phase current inputs with secondary nominal currents independently selectable at 1 A or 5 A
through DIP-switches.
Low power CTs
Three phase current inputs with primary nominal currents independently selectable through DIP-
switches and software.
Residual current input
Measured residual current
One residual current input with secondary nominal current selectable at 1 A or 5 A through DIP-
switches.
Calculated residual current
Residual current is calculated by the vector sum of the three phase currents, measured by three 1A
or 5A CTs or by three LPCT type sensors.
MMI (keyboard, LED and display)
The MMI module (Man Machine Interface) includes:
• An eight keys 8 keyboard,
• A backlight 16x2 LCD display,
• Eight signalling LEDs,
• RS232 communication port.