电力通信系统

We've completed the OPGW installation across the 68 km transmission line route. The cable has 24 single-mode fibers — G.652.D. Now we need to splice the fibers at each of the 14 splice points, roughly every 5 km. What's your splicing plan and what splice loss target are we aiming for?

We're using a core-alignment fusion splicer with active clad alignment. Splice loss target is less than 0.03 dB per splice — at 14 splice points, that means a total splice loss of under 0.42 dB across the entire route. After each splice, I do an OTDR shot from the nearest access point to verify the splice quality immediately — the splice should show less than 0.05 dB on the OTDR trace with no reflectance peak. Each splice joint closure is sealed with heat-shrink and pressurized with dry nitrogen to prevent moisture ingress.

Once all 14 closures are spliced, we'll do the end-to-end OTDR test from the substation at one end to the substation at the other. What's the acceptance criteria for the end-to-end link?

For this 68 km route on G.652.D fiber at 1550 nm wavelength, the fiber attenuation coefficient is ≤ 0.22 dB/km. So the maximum allowed end-to-end attenuation is: 68 × 0.22 = 14.96 dB for the fiber, plus 14 × 0.05 = 0.7 dB for splices, plus 1 dB for connectors at both ends. Total budget: approximately 16.7 dB. Our target is to be below 15 dB — if we exceed that, we need to identify which splice or fiber section is causing the excess loss and rework it. After OTDR, we'll also do a bidirectional test and a chromatic dispersion check for the DWDM channels.

The SDH transmission network for the new 220 kV substation is configured. We have STM-4 links to the adjacent substations east and west, providing 622 Mbps capacity in each direction. The EMS data, teleprotection channels, and voice services are all mapped onto the SDH payload. I'm ready to test the end-to-end connectivity to your regional dispatch center.

From our side, I see the STM-4 optical signal received at -18 dBm — that's within the receiver sensitivity range, good margin. I'm pinging the substation RTU — response time 3 ms, stable, no packet loss. Now let's verify the teleprotection channel. We use a direct fiber channel with a guaranteed latency under 5 ms end-to-end. Run a loopback test on the protection channel.

Loopback test running. Protection signal sent from the line protection relay at the substation, through the SDH network, to the dispatch center, and looped back. Round-trip time: 3.8 ms — well within the 5 ms limit. The BER test on the E1 circuits shows error-free performance over a 24-hour test period. All 12 E1 circuits for teleprotection, SCADA, and voice are within specification. One thing to flag — we should configure an alternate route for the protection channel. If this single fiber route is cut, the teleprotection is lost. The redundancy via the microwave link to the north substation should be set up as a backup path with automatic switchover.