ABB ret650, Technical Manual, Page: 569 / 670

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ADx
Controller ADx_High
ADx_Low
ADx
IEC05000296-3-en.vsd
IEC05000296 V3 EN
Figure 251: Simplified drawing of A/D converter for the IED.
The technique to split the analog input signal into two A/D converter(s) with different
amplification makes it possible to supervise the A/D converters under normal
conditions where the signals from the two A/D converters should be identical. An
alarm is given if the signals are out of the boundaries. Another benefit is that it
improves the dynamic performance of the A/D conversion.
The self-supervision of the A/D conversion is controlled by the ADx_Controller
function. One of the tasks for the controller is to perform a validation of the input
signals. The ADx_Controller function is included in all IEDs equipped with an analog
input module. This is done in a validation filter which has mainly two objects: First is
the validation part that checks that the A/D conversion seems to work as expected.
Secondly, the filter chooses which of the two signals that shall be sent to the CPU, that
is the signal that has the most suitable signal level, the
ADx_LO or the 16 times higher
ADx_HI .
When the signal is within measurable limits on both channels, a direct comparison of
the two A/D converter channels can be performed. If the validation fails, the CPU will
be informed and an alarm will be given for A/D converter failure.
The ADx_Controller also supervise other parts of the A/D converter.
17.1.5 Technical data
Table 476: Self supervision with internal event list
Data Value
Recording manner Continuous, event controlled
List size 40 events, first in-first out
1MRK 504 135-UEN A
Section 17
Basic IED functions
563
Technical manual