UK Curious how the UK EHV network fits together? Check out this map site

[UKMeterman]

Ever curious how the nation grid and DNO networks fit together? This map site might help Open Infrastructure Map - https://openinframap.org/#14.53/51.5092/-0.01187

 

[Julie.]

Interesting map, though is is missing the 11kV segment that feeds us of the Errol substation (only part of route shown).

I had been wondering about the HV/EHV lines that have 6 cable sets as two either side of the pylon, are they:

• Simply parallel pairs of 3-phase
• Separately protected 3-phase sets (in which case can it run for any length of one set fails, or is there load shedding at next sub-station?)
• 6-phase for whatever reason?

Maybe @UKMeterman or @Julie. will have an answer?

Just picked this up.

When there are 6 cable sets on a transmission tower, this means there are two circuits, they may be operated in parallel or actually split off at some point to two different destinations or sources.

In the main the two circuits are split between sides, but this isn't necessarily always the case.

Looking at one side, the centre bundle 'sees' a phase each side (top/bottom), the top, only one conductor below, and the bottom bundle 'sees' one other conductor bundle and the ground. This means that each phase would end up with different reactances to each other!

This is a problem with distance protection as the x/r would be different for each phase so you need different characteristic angles (RCA) on the relay for each phase, which isn't possible.

So the cables are transposed, on a 90km line L1 will spend 30km at the top, 30km in the middle and 30km on the bottom etc to balance things out.

With two circuits and longer lines, all 6 bundles may be transposed to balance between phases and between circuits, when this occurs obviously the circuit-per-side isn't maintained over the whole length.

The number of conductors in each bundle also gives a rough idea of voltage - more conductors in a bundle - higher voltage; although this isn't always true, as a particular circuit may be associated with say a power station interconnector whose rating is fairly low, so a single, or twin conductor bundle, but still at 400kv (would normally be 4 conductor bundle for 400kv, 1 may be 132/275kv 2 may be 275kv usually).

Basically you could make an educated guess at the voltage, and layout based on sides and bundle sizes, and it would be fairly reasonable.

(However the moment you say it confidently out-loud; this will be one of those exceptions!!)

 

[UKMeterman]

Just picked this up.

When there are 6 cable sets on a transmission tower, this means there are two circuits, they may be operated in parallel or actually split off at some point to two different destinations or sources.

In the main the two circuits are split between sides, but this isn't necessarily always the case.

Looking at one side, the centre bundle 'sees' a phase each side (top/bottom), the top, only one conductor below, and the bottom bundle 'sees' one other conductor bundle and the ground. This means that each phase would end up with different reactances to each other!

This is a problem with distance protection as the x/r would be different for each phase so you need different characteristic angles (RCA) on the relay for each phase, which isn't possible.

So the cables are transposed, on a 90km line L1 will spend 30km at the top, 30km in the middle and 30km on the bottom etc to balance things out.

With two circuits and longer lines, all 6 bundles may be transposed to balance between phases and between circuits, when this occurs obviously the circuit-per-side isn't maintained over the whole length.

The number of conductors in each bundle also gives a rough idea of voltage - more conductors in a bundle - higher voltage; although this isn't always true, as a particular circuit may be associated with say a power station interconnector whose rating is fairly low, so a single, or twin conductor bundle, but still at 400kv (would normally be 4 conductor bundle for 400kv, 1 may be 132/275kv 2 may be 275kv usually).

Basically you could make an educated guess at the voltage, and layout based on sides and bundle sizes, and it would be fairly reasonable.

(However the moment you say it confidently out-loud; this will be one of those exceptions!!)

I do know of cases where the circuit is 275KV one side and / 400KV the other (look at the connections to ELLAND) and another circuit where the plylon says 400kV but it 275 kV on the system schmatic (Usk power station)