Review of optical isolation due to ground potential difference and communication port damage

Substation renovation review: When the ground potential difference is measured to be more than ten volts, why does the copper cable port break first?

Published: 2026-09-20 EB-LINK Views: 1065 Ground potential difference, optical isolation, circulating current, serial port

Damage to communication ports in outdoor areas of substations is often attributed to lightning strikes. ReviewOptical isolation renovation of a 220kV substation communication networkAccording to the repair reports and measurement records, the reason that is closer to the truth is the continuous circulation formed by the ground potential difference, which is more common and more continuous than lightning strikes.

Circulation is the norm, spikes are occasional

The outdoor switchyard and relay protection room each have a grounding grid. When fault current or unbalanced load flows through the grounding grid, a potential difference will appear between the two points. A difference of more than ten volts was measured on site before and after the switch operation. The duration was not long, but the operation was repeated every time. The two ends of the serial port cable are connected to the devices on both sides respectively, which turns this difference into a loop current. The current enters the interface chip of the transceiver and the main control board along the signal line. The port is thinned again and again until it no longer recovers after a certain operation.

Prioritize the transformation of channels across the ground network

Not all copper cables are equally dangerous. The basis for judgment is whether the channel spans two different reference grounds. Sites are sorted by impact:

For telecontrol and data collection channels across buildings or across field areas, the equipment at both ends is grounded independently of each other;
The serial port line from the outdoor cabinet to the indoor host has a long path and a large coupling area;
The short wires inside the same screen cabinet are close to the reference ground at both ends, so the processing can be postponed.

For the first two categoriesThree-in-one data optical transceiverOr replace the two-way data optical terminal. The fiber itself is insulated and disconnected between the two grounds. The port no longer bears the circulation current. This is alsoCommunication transformation plan for electric power and new energy stationsThe reason why optical isolation is placed at the front of the transformation sequence.

The reserved copper cables need another set of protection

The short wires and local debugging ports in the screen cabinet generally still retain copper cables. This part relies on single-point grounding, shielding layer processing and surge protection devices to control risks, and cannot be solved by optical cables. EB-LINK recommends registering the two types of passages separately during renovation to avoid using protective measures in the wrong location on site.