Thanks for that response.
I tried the first version and it worked well with 30 seconds.
But I think I 5 minutes update interval is for the most usecases okay with a trigger to refresh if the state is changing.
When I can link 2 channels on one Item that will be the fix for me 
Thanks @rossko57
I run into a weird behavior.
Sometimes the Openhab Item switches to 0 Voltage.
I don’t know why, u can see at the log that the item is really switching from like ~230V to 0V
2021-04-13 16:42:26.615 [vent.ItemStateChangedEvent] - S4_Voltage changed from 229 to 0
2021-04-13 16:42:26.619 [vent.ItemStateChangedEvent] - S4_Power_Total changed from 0.589 to 0.03
2021-04-13 16:43:14.935 [vent.ItemStateChangedEvent] - S4_Current changed from 0.0 to 0.17
2021-04-13 16:43:14.940 [vent.ItemStateChangedEvent] - S4_Power_Total changed from 0.03 to 0.59
2021-04-13 16:43:14.943 [vent.ItemStateChangedEvent] - S4_Voltage changed from 0 to 228
Here u can see the log of the Tasmota device.
I know I got a timestamp problem (summer / winter in Germany)
But this is the log for the time.
In every log entry the voltage is at ~230Voltage.
So why does the Openhab Item changes to 0 Voltage !?
The smartplug is running all time so there is no voltage drop.
15:41:14.429 MQT: tele/Steckdose_04_Spuelmaschine/SENSOR = {"Time":"2021-04-13T15:41:14","ENERGY":{"TotalStartTime":"2021-04-10T23:42:25","Total":0.588,"Yesterday":0.000,"Today":0.588,"Period":1,"Power":76,"ApparentPower":80,"ReactivePower":26,"Factor":0.95,"Voltage":228,"Current":0.351}}
15:42:14.421 MQT: tele/Steckdose_04_Spuelmaschine/STATE = {"Time":"2021-04-13T15:42:14","Uptime":"0T07:14:44","UptimeSec":26084,"Heap":27,"SleepMode":"Dynamic","Sleep":50,"LoadAvg":19,"MqttCount":1,"POWER":"ON","Wifi":{"AP":1,"SSId":"Raspberry","BSSId":"DC:39:6F:14:1E:B0","Channel":7,"RSSI":58,"Signal":-71,"LinkCount":1,"Downtime":"0T00:00:03"}}
15:42:14.430 MQT: tele/Steckdose_04_Spuelmaschine/SENSOR = {"Time":"2021-04-13T15:42:14","ENERGY":{"TotalStartTime":"2021-04-10T23:42:25","Total":0.589,"Yesterday":0.000,"Today":0.589,"Period":1,"Power":76,"ApparentPower":80,"ReactivePower":26,"Factor":0.95,"Voltage":229,"Current":0.352}}
15:43:14.433 MQT: tele/Steckdose_04_Spuelmaschine/STATE = {"Time":"2021-04-13T15:43:14","Uptime":"0T07:15:44","UptimeSec":26144,"Heap":27,"SleepMode":"Dynamic","Sleep":50,"LoadAvg":19,"MqttCount":1,"POWER":"ON","Wifi":{"AP":1,"SSId":"Raspberry","BSSId":"DC:39:6F:14:1E:B0","Channel":7,"RSSI":56,"Signal":-72,"LinkCount":1,"Downtime":"0T00:00:03"}}
15:43:14.444 MQT: tele/Steckdose_04_Spuelmaschine/SENSOR = {"Time":"2021-04-13T15:43:14","ENERGY":{"TotalStartTime":"2021-04-10T23:42:25","Total":0.590,"Yesterday":0.000,"Today":0.590,"Period":1,"Power":21,"ApparentPower":39,"ReactivePower":33,"Factor":0.54,"Voltage":228,"Current":0.170}}
15:44:14.388 MQT: tele/Steckdose_04_Spuelmaschine/STATE = {"Time":"2021-04-13T15:44:14","Uptime":"0T07:16:44","UptimeSec":26204,"Heap":27,"SleepMode":"Dynamic","Sleep":50,"LoadAvg":19,"MqttCount":1,"POWER":"ON","Wifi":{"AP":1,"SSId":"Raspberry","BSSId":"DC:39:6F:14:1E:B0","Channel":7,"RSSI":58,"Signal":-71,"LinkCount":1,"Downtime":"0T00:00:03"}}
15:44:14.397 MQT: tele/Steckdose_04_Spuelmaschine/SENSOR = {"Time":"2021-04-13T15:44:14","ENERGY":{"TotalStartTime":"2021-04-10T23:42:25","Total":0.591,"Yesterday":0.000,"Today":0.591,"Period":0,"Power":10,"ApparentPower":12,"ReactivePower":7,"Factor":0.85,"Voltage":230,"Current":0.053}}
After some time, the voltage jumps from 0 Voltage to ~230 Voltage again…
I dont know why its fixing itself !?
The update interval is set to 300seconds.
without any rule by myself.
Did someone have an idea why this behaivor happen sometimes ?