Power Transmission
Why This Matters
Your generator produces electricity, but it sits by the river or on the hilltop, not inside your workshop or home. Getting power from where it is made to where it is needed without losing most of it along the way is the central challenge of electrical infrastructure. Without transformers and proper wiring, a generator 500 meters away is nearly useless. With them, a single generator can power an entire settlement.
The Transmission Problem
Electricity flowing through wire generates heat. That heat is wasted energy. The formula that governs this loss is the single most important equation in power transmission:
Power loss = I² x R
I = current in amps
R = resistance of the wire in ohms
Notice that loss depends on the square of current. Double the current, quadruple the losses. This is why sending high current over long wires is catastrophically wasteful.
A Practical Example
Your water wheel generator produces 500 watts at 12V. You want to send this power to your workshop 200 meters away using 12 AWG copper wire.
Current at 12V: I = P/V = 500/12 = 41.7A
Wire resistance: 12 AWG copper = 0.0053 Ω/m
Total wire (200m out + 200m return): 400m x 0.0053 = 2.12Ω
Power lost in wire: I² x R = 41.7² x 2.12 = 3,685 watts
You are trying to lose 3,685 watts in wire that is only carrying 500 watts. This is physically impossible — what actually happens is the voltage drops so severely that barely anything arrives at the other end. Your workshop gets almost nothing.
The Solution: Step Up Voltage
Same 500 watts, but at 240V instead of 12V:
Current at 240V: I = 500/240 = 2.08A
Same wire resistance: 2.12Ω
Power lost: 2.08² x 2.12 = 9.2 watts
From 3,685 watts lost to 9.2 watts lost. That is the entire reason power transmission systems use high voltage. Transformers make this possible.
Warning
High voltage is lethal. 240V through wet skin can deliver 240 mA — instantly fatal. Every high-voltage line, transformer, and connection must be treated as a death hazard. Insulate thoroughly, ground properly, and keep high-voltage components out of reach.
Transformer Construction
A transformer transfers electrical energy between two circuits through electromagnetic induction. It only works with AC (or pulsating DC).
How Transformers Work
Two coils of wire wound around the same iron core. AC current in the primary coil creates a changing magnetic field in the core. That changing field induces voltage in the secondary coil.
The voltage ratio equals the turns ratio:
V_secondary / V_primary = N_secondary / N_primary
Step-up: more secondary turns → higher output voltage
Step-down: fewer secondary turns → lower output voltage
Example: You want to step 12V AC up to 240V AC for transmission.
Ratio needed: 240/12 = 20:1
If primary has 50 turns, secondary needs: 50 x 20 = 1,000 turns
Power in equals power out (minus small losses), so:
V_primary x I_primary = V_secondary x I_secondary
12V x 41.7A = 240V x 2.08A = 500W
Voltage goes up, current goes down proportionally. The power stays the same.
Building a Transformer
Step 1 — Prepare the core
The core must be soft iron or electrical steel. Critically, it must be laminated — built from thin iron sheets (0.3-0.5 mm) insulated from each other with varnish, paint, or even paper.
Why laminated? Solid iron cores develop eddy currents (circulating currents induced in the core itself). These waste energy as heat. Laminations break up the eddy current paths and can reduce core losses by 90% or more.
Sources of laminated cores:
- Old transformers (microwave oven transformers, power supply transformers)
- Electrical motor stator cores
- Ballasts from fluorescent light fixtures
If you must make your own: Cut thin iron sheets (from tin cans with tin removed by acid, or from sheet metal hammered thin). Stack them with paper or varnish between layers. Clamp or bolt together.
Core shapes:
- E-I core: E-shaped pieces alternating with I-shaped pieces. Most common in small transformers. Easy to wind.
- Toroidal: Donut shape. Most efficient but hardest to wind.
- Shell type: Core surrounds the coils. Good magnetic coupling.
Step 2 — Wind the primary coil
Wrap magnet wire around one leg of the core. Count turns carefully. Wind in neat layers, insulating between layers with paper, tape, or cloth.
Wire gauge for primary: Must handle the full primary current without overheating. For a 500W, 12V primary: 41.7A requires at least 8 AWG wire. This is thick and hard to wind. Consider using multiple thinner wires in parallel.
Step 3 — Insulate between windings
Wrap several layers of insulation (cloth, paper, tape) over the primary before winding the secondary. The insulation must withstand the full secondary voltage without breaking down.
Step 4 — Wind the secondary coil
Wind the secondary over the insulation layer, on the same core leg. Again, count turns carefully.
Wire gauge for secondary: Handles secondary current. For 500W at 240V: 2.08A requires only 18 AWG or thicker.
Step 5 — Insulate and mount
Wrap the completed assembly in insulation. Mount in a protective enclosure. Label the primary and secondary terminals clearly.
Tip
Scavenging is far easier than building from scratch. A microwave oven transformer can be rewound for different voltages. The core is already laminated and high-quality. Remove the original secondary winding (carefully — the HV winding produces 2,000V), keep the primary, and wind a new secondary with the turns ratio you need.
Transformer Efficiency
A well-built transformer is 90-98% efficient. Losses come from:
| Loss Type | Cause | Mitigation |
|---|---|---|
| Copper loss (I²R) | Resistance in windings | Use thicker wire |
| Core loss (eddy currents) | Circulating currents in core | Use laminated core |
| Core loss (hysteresis) | Magnetization energy lost each cycle | Use soft iron / electrical steel |
| Flux leakage | Not all flux couples both coils | Keep windings close together on same core leg |
Wire Selection
Copper vs Aluminum
| Property | Copper | Aluminum |
|---|---|---|
| Conductivity | Excellent (reference standard) | 61% of copper |
| Weight | Heavy (8.9 g/cm³) | Light (2.7 g/cm³) |
| Strength | Good | Poor (breaks easier) |
| Corrosion | Develops patina, still conducts | Oxidizes; oxide is insulating |
| Availability | Motors, house wiring, plumbing | Overhead power lines, some house wiring |
| Connection | Solders and crimps easily | Requires special techniques |
Recommendation: Use copper for all connections, indoor wiring, and short runs. Consider aluminum only for long overhead transmission lines where weight matters and you can use mechanical (bolted) connections.
Warning
Never directly connect copper wire to aluminum wire. The junction creates galvanic corrosion that increases resistance over time, eventually causing overheating and fire. Use approved bi-metal connectors, or separate with a steel bolt-and-washer terminal.
Gauge Selection by Distance and Current
For a 12V DC system (where voltage drop is critical):
| Distance (one way) | 5A Load | 10A Load | 20A Load | 40A Load |
|---|---|---|---|---|
| 10 m | 18 AWG | 16 AWG | 14 AWG | 10 AWG |
| 25 m | 16 AWG | 14 AWG | 10 AWG | 8 AWG |
| 50 m | 14 AWG | 10 AWG | 8 AWG | 6 AWG |
| 100 m | 10 AWG | 8 AWG | 6 AWG | 4 AWG |
For higher voltage AC systems (120V+), voltage drop is less of a concern, and wire gauge is primarily determined by current-carrying capacity (ampacity).
Poles and Insulators
Building Utility Poles
For overhead transmission lines, you need poles to keep wires safely above ground.
Pole material: Straight, rot-resistant wood. Cedar, locust, or treated pine. If unavailable, any straight tree trunk works, but expect shorter lifespan.
Pole specs for a community grid:
| Parameter | Specification |
|---|---|
| Height | 6-8 meters (20-25 feet) above ground |
| Burial depth | 1.5-2 meters (5-6 feet) |
| Diameter | 15-25 cm (6-10 inches) at top |
| Spacing | 30-50 meters (100-150 feet) |
| Lean | Slight lean away from line tension |
Setting poles:
- Dig a hole 1.5-2 meters deep
- Place the pole and pack rocks around the base for stability
- Fill and tamp firmly
- Add guy wires (rope or wire anchored to stakes) for the first and last poles and at corners
Insulators
Wire must not touch the pole or ground. Insulators keep the wire electrically isolated.
Best insulators:
- Ceramic (from old power lines, toilets — porcelain is excellent)
- Glass (bottles, particularly the necks)
- Dry hardwood (temporary, deteriorates with moisture)
Simple bottle insulator: Wire a glass bottle neck to the pole crossarm. Run the transmission wire through or over the bottle neck. Glass has extremely high resistance and handles rain well.
Crossarms: Bolt or lag-screw a horizontal wooden beam across the top of each pole. Mount insulators on the crossarm with spacing of at least 30 cm between wires.
Tip
Scavenge ceramic insulators from any downed power lines. They are designed for the job, rated for high voltage, and nearly indestructible. Even broken pieces can be drilled and mounted.
Line Stringing
Tension: Wire must be taut enough to stay clear of the ground but not so tight that temperature changes (expansion/contraction) snap it. Leave visible sag — about 1-2% of span length. For a 40-meter span, 40-80 cm of sag at mid-span.
Clearance: Minimum 5 meters above ground at the lowest point of sag. Higher over roads or paths.
Splicing transmission wire: Overlap 15-20 cm and wrap tightly with smaller wire. The joint must be mechanically strong (the wire hangs from it) and electrically sound (loose joints arc and burn).
Distribution Systems
Single Phase
The simplest distribution: two wires (hot and neutral) from the transformer secondary to each building. One wire carries the “hot” AC voltage, the other is the neutral (grounded) return.
Generator → Step-up transformer → Transmission line → Step-down transformer → Buildings
|
Hot ──┤
├── Load
Neutral ─┤
├── Ground rod
This is sufficient for a small community. Every building gets the same voltage (whatever the step-down transformer provides).
Split Phase (120V/240V)
A center-tapped secondary winding provides two voltages:
┌─── Hot A (120V to neutral) ───┐
│ │
├─── Neutral (center tap) ──────┤── To building
│ │
└─── Hot B (120V to neutral) ───┘
Hot A to Hot B = 240V
Hot A to Neutral = 120V
Hot B to Neutral = 120V
This is the standard North American residential system. It provides 120V for lights and small loads, and 240V for heavy loads (stoves, heaters, motors) — all from one transformer.
Service Entrance
Where the distribution line connects to a building:
- Service drop — wire from the pole to the building
- Weather head — keeps rain out of the wire entry point
- Meter point — where you measure consumption (if tracking usage)
- Main disconnect — a switch or breaker that kills all power to the building
- Distribution panel — fuses or breakers for individual circuits inside the building
Warning
Every building must have a main disconnect switch accessible from outside. In a fire or emergency, you need to kill power to the entire building instantly without entering it.
Protection Systems
Fuses
Every circuit needs a fuse rated below the wire’s capacity. The fuse must blow before the wire overheats.
| Wire Gauge | Ampacity | Fuse Rating |
|---|---|---|
| 14 AWG | 15A | 15A |
| 12 AWG | 20A | 20A |
| 10 AWG | 30A | 25A or 30A |
| 8 AWG | 40A | 35A or 40A |
Building fuses for higher currents: Use calibrated wire. Tin-plated copper wire of a known gauge will melt at a predictable current. Test each batch by intentionally overloading (outdoors, safely) and note the blow point.
Circuit Breakers
A circuit breaker is a reusable switch that opens automatically when current exceeds its rating. Scavenge them from electrical panels in buildings.
How they work: A bimetallic strip bends when heated by excess current, releasing a spring-loaded contact. Some also have an electromagnetic trip for short circuits (instant response).
Maintenance: Test breakers periodically by pressing the test button. If a breaker trips repeatedly, find and fix the fault — do not replace it with a higher-rated one. That defeats the purpose and lets your wiring overheat.
System Grounding
The entire distribution system must be grounded:
- Generator frame — grounded to a rod at the generator site
- Transformer neutral — grounded at each transformer
- Service entrance — grounded at each building
- Equipment grounds — every metal enclosure connected to ground
Ground rods: Copper-clad steel rods (scavenge from building sites) or copper pipe driven at least 2 meters into earth. Connect with heavy wire (6 AWG or larger) to the neutral bus bar at each distribution point.
Ground resistance: Moist soil provides lower resistance. Dry, rocky, or sandy soil has poor grounding. In poor soil, use multiple ground rods spaced at least 2 meters apart and connected together.
Tip
Test ground resistance by measuring voltage between the hot wire and the ground rod. It should be very close to the voltage between hot and neutral. A significant difference means poor grounding. Drive the rod deeper, add more rods, or water the soil around the rod.
Load Balancing
If your community grid has multiple buildings, distribute loads as evenly as possible across phases and circuits. Unbalanced loads cause:
- Higher neutral current (overheating the neutral wire)
- Voltage fluctuations (some buildings get too much, others too little)
- Generator inefficiency
Practical load balancing:
- Inventory every building’s total connected load (watts)
- Assign buildings to circuits so each circuit carries roughly equal load
- Stagger heavy loads (do not run the workshop motor and the community oven on the same circuit)
- Schedule high-draw activities at different times
Metering and Monitoring
At minimum, you need to know:
- Voltage at the generator and at each building (a simple voltmeter or multimeter)
- Current on each circuit (a clamp ammeter or shunt resistor with voltmeter)
- Frequency if running AC (listen for the hum — 50 Hz is a low hum, 60 Hz slightly higher)
Track daily usage patterns. Know when peak demand occurs. This lets you plan generator capacity and maintenance windows.
Building a Small Community Grid: Step by Step
Step 1 — Site the generator. Near the power source (water wheel, wind turbine). Protect from weather. Ensure access for maintenance.
Step 2 — Build or install the step-up transformer. Match the generator output voltage and desired transmission voltage.
Step 3 — Set poles and string transmission wire. Follow the route from generator to the settlement center. Use proper insulators at every pole.
Step 4 — Build or install the step-down transformer. Located at the settlement, steps voltage back down to usable levels (12V DC, 120V AC, or 240V AC depending on your system design).
Step 5 — Run distribution lines. From the step-down transformer to each building. Use overhead or buried cable.
Step 6 — Install service entrances. Main disconnect, fuse panel, and ground rod at each building.
Step 7 — Wire buildings internally. Individual circuits for lighting, outlets, and heavy loads, each with its own fuse.
Step 8 — Test everything. Verify voltage at every point. Check ground connections. Test every fuse by briefly overloading.
Step 9 — Commission. Start the generator, energize the grid section by section, monitor for problems.
What’s Next
With power transmission infrastructure in place, put it to use:
- Lighting — the first and most impactful use of distributed electricity
- Telegraph — long-distance communication over wire
- Energy Storage & Batteries — buffer power for when the generator is offline
Power Transmission — At a Glance
The core problem: Power loss = I²R. High current over long wires wastes most of your power as heat.
The solution: Step voltage up with a transformer. Higher voltage = lower current = dramatically lower losses.
System Element Key Specification Transformer ratio V_out/V_in = turns_out/turns_in Core Must be laminated iron (not solid) Poles 6-8 m tall, 1.5-2 m buried, 30-50 m apart Insulators Ceramic, glass, or porcelain — never bare wood Wire Copper preferred; aluminum for long overhead runs only Ground rods 2+ meters deep, copper-clad, at every transformer and building Protection hierarchy:
- Main fuse at generator output
- Fuse at each transformer secondary
- Main disconnect at each building
- Individual circuit fuses inside each building
- Ground connections everywhere
Safety rule: Any voltage over 50V can kill. Treat every wire as live until you personally verify it is de-energized. One-hand rule for all high-voltage work.