power grid topology
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overview
a hyperscale data center requires 100mw to 1gw of power—comparable to a medium-sized city. this cannot be delivered through urban distribution infrastructure.
transmission vs distribution
voltage levels
- transmission: 115kv-765kv (bulk power, long-distance)
- subtransmission: 33kv-138kv (intermediate)
- distribution: 4kv-35kv (local delivery to buildings)
- secondary: 240v/415v (to individual premises)
capacity differences
- distribution designed for neighborhood-scale loads (residential, small commercial)
- hyperscale requires direct transmission tap at 138kv+
- urban substations are space-constrained and capacity-limited
why 500mw cannot use urban distribution
physical impossibility
- urban distribution wires are thermally limited for neighborhood-scale loads
- drawing 500mw-1gw would cause catastrophic thermal failure
- existing urban wires lack current-carrying capacity
the straw analogy
urban distribution is like drinking a lake through a straw. the water (power) exists, but the delivery mechanism (distribution wires) cannot physically handle the volume.
what urban upgrade requires
- build new high-voltage transmission corridors through neighborhoods
- acquire land for massive substations (urban land: $500k-1m+/acre)
- excavate city streets (navigating gas, water, sewer lines)
- underground high-capacity cables
- timeline: 48-72+ months minimum
rural alternative
- tap existing transmission line in rural corridor
- build greenfield substation on $10k-30k/acre land
- connect directly at 138kv+
- timeline: 18-36 months
substation economics
| factor | urban | rural |
|---|---|---|
| land cost/acre | $500k-1m+ | $10k-30k |
| configuration | indoor (gis required) | outdoor (ais possible) |
| new substation cost | $15-50m+ | $3-7m |
| timeline | 48-72 months | 18-36 months |
gis = gas-insulated switchgear (10-20% footprint of air-insulated, but expensive)
ais = air-insulated switchgear (standard, cost-effective)
case study: northern virginia
northern virginia (data center alley) exemplifies grid constraints:
- 250+ data centers, ~6,000mw active
- transmission grid in eastern loudoun county now constrained
- dominion energy: 7-year wait for new large customer connections
- july 2024: lightning strike on 230kv line caused 1,500mw of data centers to switch to backup
sources
- miso transmission cost estimation guide
- dominion energy investor presentations
- pjm interconnection data
- iec 60038 voltage standards