PoE is an option. You could get an old switch with power over ethernet ports and then you just need a poe to regular dc converter at each PI.
For example a 24 port 100 mbps switch for 32$ , adtran netvanta 1234 poe :
https://www.ebay.com/itm/164302111135If you don't mind reducing your bandwidth to 100 mbps and having non-standard ethernet cables, you could just use 4 of the wires to send DC voltage through the unused pairs.
Basically, do passive poe, see
https://en.wikipedia.org/wiki/Power_over_Ethernet#PassiveIn a passive PoE system, the injector does not communicate with the powered device to negotiate its voltage or wattage requirements, but merely supplies power at all times. The common 100 Mbit/s passive applications use the pinout of 802.3af mode B (see § Pinouts) – with DC positive on pins 4 and 5 and DC negative on 7 and 8 and data on 1-2 and 3-6.
You'd have to buy passive poe injectors or make some "adapters" to inject the voltage into the unused pairs at the switch / patch panel and take it out when it comes to the pi ... you know the 100 mbps ethernet only uses 2 pairs, wires 1,2,3 and 6 ... so 2 unused wires can be ground, 2 unused wires can be some voltage...
You can figure out the voltage drop over 30 meters easily.. for example you know AWG24 wires typical in ethernet cables have around 85 ohm per km resistance, and you use two in parallel so the resistance will be half, or around 50 ohm per km, or 0.05 ohm per meter, and you'll have 60m of wire (to the device and back)
Assuming you'll do 19v input and the device consumes 100 mA (you'll use a dc-dc converter to convert 19v to 5v so your peak 220mA is basically less than 100mA peak on higher voltage) ...
So 19v in, 100mA , 60 m of wire at 0.05 ohm ... v = i x r = 0.1 x 60m x 0.05 = 0.3v drop ... instead of 19v you'd have 18.7v
Here's an adapter which takes power from passive poe (as explained above) jack, 18v..60v input , and exposes a standard 100mbps ethernet and a barrel jack with 12v at up to 1.2A :
https://www.ebay.com/itm/202914660285 There's also kits of the injector and the splitter :
https://www.ebay.com/itm/121100493562Another example of set of injector and splitter, 5 pack for $13 :
https://www.ebay.com/itm/282049940669