Section 4 Analog inputs4.1 IntroductionAnalog input channels in the IED must be set properly in order to get correct measurementresults and correct protection operations. For power measuring and all directional anddifferential functions the directions of the input currents must be defined in order to reflectthe way the current transformers are installed/connected in the field ( primary andsecondary connections ). Measuring and protection algorithms in the IED use primarysystem quantities. Consequently the setting values are expressed in primary quantities aswell and therefore it is important to set the transformation ratio of the connected currentand voltage transformers properly.The availability of CT and VT inputs, as well as setting parameters depends on the orderedIED.A reference PhaseAngleRef must be defined to facilitate service values reading. Thisanalog channels phase angle will always be fixed to zero degrees and all other angleinformation will be shown in relation to this analog input. During testing andcommissioning of the IED the reference channel can be changed to facilitate testing andservice values reading.4.2 Setting guidelines4.2.1 Setting of the phase reference channelAll phase angles are calculated in relation to a defined reference. An appropriate analoginput channel is selected and used as phase reference. The parameter PhaseAngleRefdefines the analog channel that is used as phase angle reference.The initially connected phase-to-earth voltage is usually chosen as PhaseAngleRef. Aphase-to-phase voltage can also be used in theory, but a 30 degree phase shift between thecurrent and voltage is observed in this case.If no suitable voltage is available, the initially connected current channel can be used.Although the phase angle difference between the different phases will be firm, the wholesystem will appear to rotate when observing the measurement functions.1MRK 506 334-UUS A Section 4Analog inputs89Application manual
