For Solar PV systems that utilise a SMA Power Reducer Box (for control over active output power limitation setpoints by the grid operator), access using Modbus to read the active power limitation setpoint value is not possible. Nor can the value be read from the inverters or other plant devices using Modbus.

Instead, you can use a HTTP retriever and regex to scrape the value from the Power Reducer Box's internal web server (in this case, at IP address 1.2.3.4).

{
   "dataSources":[
      {
         "xid":"DS_158029",
         "name":"Power Reducer Box",
         "enabled":true,
         "type":"HTTP_RETRIEVER",
         "alarmLevels":{
            "PARSE_EXCEPTION":"NONE",
            "DATA_RETRIEVAL_FAILURE":"INFORMATION",
            "SET_POINT_FAILURE":"NONE"
         },
         "purgeType":"YEARS",
         "updatePeriodType":"MINUTES",
         "quantize":true,
         "retries":2,
         "setPointUrl":"",
         "timeoutSeconds":30,
         "updatePeriods":5,
         "url":"http:\/\/1.2.3.4\/index.php?module=PlantStatus&action=index",
         "purgeOverride":true,
         "purgePeriod":1
      }
   ],
   "dataPoints":[
      {
         "xid":"DP_172704",
         "name":"Active Power Limitation Setpoint",
         "enabled":true,
         "loggingType":"ON_CHANGE",
         "intervalLoggingPeriodType":"MINUTES",
         "intervalLoggingType":"INSTANT",
         "purgeType":"YEARS",
         "pointLocator":{
            "dataType":"NUMERIC",
            "ignoreIfMissing":false,
            "setPointName":"",
            "settable":false,
            "timeFormat":"",
            "timeRegex":"",
            "valueFormat":"###.#",
            "valueRegex":"(?<=L3: )(.*)(?=%)"
         },
         "eventDetectors":[
            {
               "xid":"PED_028817",
               "type":"LOW_LIMIT",
               "alarmLevel":"INFORMATION",
               "limit":99.0,
               "durationType":"SECONDS",
               "duration":60,
               "alias":""
            }
         ],
         "plotType":"STEP",
         "unit":"%",
         "chartColour":"",
         "chartRenderer":{
            "type":"TABLE",
            "limit":10
         },
         "dataSourceXid":"DS_158029",
         "defaultCacheSize":1,
         "deviceName":"Power Reducer Box",
         "discardExtremeValues":false,
         "discardHighLimit":0.0,
         "discardLowLimit":0.0,
         "intervalLoggingPeriod":15,
         "intervalLoggingSampleWindowSize":0,
         "overrideIntervalLoggingSamples":false,
         "purgeOverride":true,
         "purgePeriod":1,
         "textRenderer":{
            "type":"PLAIN",
            "useUnitAsSuffix":true,
            "unit":"%",
            "renderedUnit":"%",
            "suffix":""
         },
         "tolerance":0.0
      }
   ]
}