There are as many naming conventions and philosophies as there are panel builders.
I don't follow any 'industry standard' because I find it hard to follow and I've got no formal training in it. Ladder diagrams drive me nuts, likely through inexperience TBH.
For AC power circuits, its the usual "L1", "L2", ect. If I want to be more granular to help me when wiring or troubleshooting, I'll extend it to "L1-1" or "L2-4a" as that helps keep things straight when following a wire. It tells me what line & voltage to expect, and what components are at either end when referring to the wiring diagram.
For terminal blocks, I number the blocks and then label the wires with what blocks & components they connect. For a row of terminal blocks I'll name them "TB01" "TB02" etc. For different groups of blocks I'll start a new series:
240VAC L1 blocks: TB001-TB0nn
240VAC L2 blocks: TB021-TB02n
24VDC V+ blocks: TB101-TB1nn
24VDC V- blocks: TB201-TB2nn
Other groups are numbered similarly, including new series of block numbers if the group is located outside of the main panel. So...
24VDC V+ blocks in the operator panel: TB501-TB5nn
You get the picture. The numbers don't tell anyone what the voltage is or what the circuit does, but it makes following the wires easy through the diagram and when you've got your face deep in the panel.
Same for components. Circuit breaker 1 is "CB01" and for relays & contactors I'll extend it a bit to include the terminal numbers. I use the "NN/nn-NN/nn" format, where NN is the component and nn is the terminal.
So a wire might have "TB01-K05/A1" on it. That tells me that wire connects TB01 to relay K1's A1 coil terminal.
In the photo I posted, check out the 3rd wire from the right. Without looking at a diagram, I can tell that wire connects Switch 1, terminal 01, to the UB1's X215 terminal. The "UB1" is a breakout board for a UCCNC motion controller, and X215 is one of the NPN inputs. So that wire is sending a signal to the motion controller when the switch (pushbutton, likely) is activated. And the wire is blue, meaning it's a 24vdc signal.
The wire at the far right: "SW02, terminal 3B" is a low-numbered switch - probably an estop, especially since simple function switches rarely have more than one set of contacts. It's connecting to the breakout board (UB1) at a 0Vdc terminal - another clue that it's an estop wire. My guess is that wire is the signal wire from the main estop switch, and SW02/1 or /2 are the other switch contacts used to kill the main power contactor.
And the wire is red, which is possibly a no-no is NFPA79-land, but I restrict red wires to estop circuits unless they're AC at non-line voltages (i.e. the 100VAC conductors between my toroid transformer and the dc rectifier are big, fat, red cables).
It helps to label everything on the diagram first, then print out batches of labels for the circuit or section of the wiring you're doing at the moment. As you can see on the diagram I posted the labels are mostly in green. I initially add them to diagram in red font, and then change them to green when I've installed the labeled wire. Helps having the computer right next to the working area, of course.
Are there wires labeled 'backwards'? Of course. I could have TB01-K1/14, or it could be K1/14-TB01. I just pick whatever makes sense to me and try to stick with it as I visualize how the electrons are moving along.
I'm quite sure there are better ways to do this, but it's working for me.
