I have to deliver power to a sensor which is 500 meters far away from the mains. Sensor needs an 12V DC power supply, and the DC power supply needs to be powered from the mains. Battery is not an option and I have to use SMPS for the sensor. The power delivery(power cables to the sensor) will be indoors(inside a bridge). Sensor sinks less than 10mA current. No voltage regulation needed.
I have two choice:
Either I will power the DC supply in the vicinity of the mains, and send the power to the sensor which is 500 meters far away by using twisted shielded cable. This is in Figure 2 below. Or I will power the DC supply through 500 meters of AC cables and power the sensor at the vicinity of the DC supply. There will be no direct lightning strike ect. but EMI might occur.
In terms of noise the closer the power supply to the sensor it is better because the sensor output quality is affected by the power supply noise.
As in Figure 2, I was planning to send the power to the sensor by 500m DC cable and was planning to install TVS diodes and caps at power supply rails before the sensor.
In terms of noise and EMI, is it better to use the wiring scheme in Figure 1 instead? If I use the 500 mains cable do I still need astra components for over voltage or noise? Which way requires less effort or caution?