24 fiber optic cable.

[Mlmlzx]

Dear sirs,

I have read that 24 and 48 pairs of optical fiber cables are often used. Recently,for 220 kV double circuit line, i found 24 pair of cables used. They were 6 in a bundle.

How protection schemes develop from them?

It appears that relay signals, like distance relays signal travel through them to trip breaker at the other end.

But what about the bandwidth?

Regards,

 

[davidbeach]

Most protection traffic is very low bandwidth, lots of channels can be multiplexed into a single fiber pair. 87L traffic can benefit from a dedicated pair, but things like SEL's Mirrored Bits don't need dedicated pairs.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[saladhawks]

The utility that I work uses single mode fiber optic cable between Receiving Stations for line differential protection.

We have used both multi-plexed and point-to-point fiber optic circuits. Overall, the bandwidth requirements for tele-protection are extremely small compared to the capabilities of fiber optic cable.

 

[djs]

For very long runs, bandwidth can be an issue. With fiber there is a rating called Minimum effective modal bandwidth. It is the product of bandwidth by distance. The shorter the run, the higher the bandwidth can be used. For very long runs, the available bandwidth decreases considerably. One reason single mode fiber may be used in place of multimode.

 

[sushilksk]

Protection scheme requires very low bandwidth. In extreme case, 6 pair will be more than enough for double circuit line. In practical, it may work with only 2 pair.

Additional fibers may be used for other communication related applications like leasing to telecom operators.

 

[thermionic1]

Often if a SONET ring is used, there are fibers on the OPGW that are merely patch (thru) points to other stations. The same can be said of SCADA, security, etc.