u1x2x1u1x2x1ADxControllerADx_HighADx_LowADxIEC05000296-3-en.vsdIEC05000296 V3 ENFigure 347: Simplified drawing of A/D converter for the IED.The technique to split the analog input signal into two A/D converter(s) with differentamplification makes it possible to supervise the A/D converters under normal conditionswhere the signals from the two A/D converters should be identical. An alarm is given if thesignals are out of the boundaries. Another benefit is that it improves the dynamicperformance 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. TheADx_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 partthat checks that the A/D conversion seems to work as expected. Secondly, the filterchooses which of the two signals that shall be sent to the CPU, that is the signal that hasthe 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 thetwo A/D converter channels can be performed. If the validation fails, the CPU will beinformed 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 dataTable 573:Self supervision with internal event listData ValueRecording manner Continuous, event controlledList size 40 events, first in-first out1MRK 506 335-UUS A Section 17Basic IED functions745Technical manual
