The turns ratio is defined by the Ethernet controller used. Whereas 10 Base-T often uses turns ratios of 1 : 1.414 or 1 : 2.5 on at least one of the lines, 100 and 1000 Base-T almost exclusively work with a turns ratio of 1 : 1. This is because the number of secondary turns is so large – due to the high primary inductance combined with a higher number of turns than with 10 Base-T – that they can no longer be accommodat ed on a small ring core. Winding with twisted wires is also no longer possible, which can still be tolerated for 10 Base-T, but leads to a de terioration in transmission properties for 100 Base-T.

The minimum insertion loss and the maximum values for return loss, crosstalk and common mode rejection are also defined over the entire frequency range.

https://passive-components.eu/lan-transformers/#:~:text=The%20relevant%20Ethernet%20standards%20for,by%20the%20Ethernet%20controller%20used.

The FL ISOLATOR is used for electrical isolation in copper-based Ethernet networks.
In industrial environments, potential differences pose a constant problem with regard to interference-free data transmission.
The high-quality isolation for up to 4 kV provides reliable protection for Ethernet devices and interfaces. This results in considerably higher immunity to interference in industrial applications.

No power supply required
Dielectric strength of up to 4 kV
Protection against aggressive environmental influences, particularly harsh industrial environments, thanks to coated PCB
Electrical isolation of data cables and cable shielding
Extended temperature range of -25°C to +85°C
Mounting on EN DIN rails
Continuous insulation voltage of 250 VRMS
Shipbuilding approval in accordance with DNV GL

https://www.meso.biz/en/products/ni-1000/

• Connector:
1 x RJ45 jack (device)
1 x RJ45 jack (external)
1 x screw terminal for equipotential bonding
• Data transfer rate up to 10/100/1000 Mb/s
• Supports PoE devices
• Supports PoE 802.3at/af/bt with 48 V and up to 90 W
• Inductive galvanic isolation
• 6 kV Isolation (10 / 700 us)
• Arrest capacity: 1000A (8 / 20 us)
• Ignition voltage: 68 V
• Operating temperature: 0 °C ~ 50 °C
• Housing material: plastic
• Dimensions (LxWxH): ca. 70 x 25 x 25 mm
https://www.kauppasatama.fi/tuote/62619/Delock-Network-Surge-Protector-6-kV-RJ45?gclid=EAIaIQobChMIptLLn-a18wIVgtKyCh2maw4aEAYYAiABEgI28vD_BwE

The only power put out by a standard Ethernet port is the transmitted power. Typically this will be ±2.5 volts differential signals with a nominal 100 Ω source resistance. This equates to 50 mA or 250 mW measured between the two transmit signal conductors. This occurs only when a packet is being transmitted.

Standard Ethernet does not provide any power for connected devices. It only carries the transmit and receive signals.