The standard voltage for electrical outlets changes around the world. Although most countries in the Americas have a voltage of 110-127V, other continents mainly use 220-240V. However, this only applies to the residential and light commercial sectors. In large commercial and industrial buildings, electrical installations use even higher voltages, such as 277/480V and 347/600V.
The instantaneous power supplied by an electrical circuit is the product of voltage and current. Assuming the load is kept constant, a higher supply voltage allows for a lower current. When designing an electrical installation, the selection of the nominal voltage involves a trade-off between current and voltage – when one increases, the other decreases.
Make sure your electrical installation design is safe and efficient.
Benefits of current reduction in electrical circuits
Industrial processing machines consume significantly more energy than household appliances and office equipment. If a low voltage such as 120 V is used in this case, a very high current will be required to provide sufficient power.
- For example, a 900-watt household appliance consumes only 7.5 amps of current at 120 V, but a 150 kW industrial machine would draw 1,250 amps at 120 V.
- Such a high current requires very large conductors, wasting copper and making installation much more expensive.
- On the other hand, a 600V power supply reduces the current to a much more manageable 250A.
- If the 150 kW equipment uses three-phase voltage, the rated current is further reduced to 144A, requiring an extra conductor.
Also consider that circuit breakers and other protections are sized based on current. For example, a 1250A circuit breaker is considerably more expensive than a 250A circuit breaker. Larger protection devices are also bulkier and heavier, which makes their installation more complex.
Current reductions don't just save on wiring and electrical components – consider that losses in a conductor are proportional to current squared. In other words, doubling the current increases heat losses by four, while 1/2 the current reduces losses by 1/4. In a large industrial installation with thousands of meters of electrical circuits, the savings from reducing current can be significant.
Of course there is a lower limit to how much the current can be reduced since it involves an increase in voltage. Higher voltage requires more isolation and additional protective measures for personnel. A conductor carrying 100A at 120V is much less threatening than a conductor carrying 12A at 1000V, even though both deliver 12 kilowatts.
Handling high voltage safely
A high voltage installation requires two fundamental elements to be safe: adequate insulation according to the voltage level and physical isolation measures to prevent accidental contact. Of course, the installation must also meet the National Electrical Code and any applicable local building codes.
To ensure continued safety, insulation must be tested at regular intervals; Damaged insulation increases the risk of arc fault, threatening personnel and equipment. Additionally, insulation deteriorates more quickly when exposed to extreme temperatures and chemical agents. The test is performed with a device called a megohmmeter, which applies a test voltage to the insulation to measure its performance. The difference with a conventional multimeter is that the megohmmeter applies a much higher test voltage, suitable for high insulation levels.
Transmission and distribution lines use much higher voltages than homes and businesses, precisely because they need to transport large amounts of energy. A low voltage transmission line would be prohibitively expensive and very impractical, requiring many kilometers of large conductors.
- Voltage is increased at power plants to a level suitable for transmission and then reduced by substations for distribution.
- Pole transformers perform the final step down for residential and commercial use.
- Industrial users often reduce transmission voltage with their own substations due to their high demand for electricity.
To achieve a safe and efficient installation, the best recommendation is to hire professional electrical engineering services from the beginning of the project. They can specify the most suitable voltage for each appliance and equipment, with corresponding electrical protections.
Final Recommendations
Electricity is the fastest and most efficient energy supply method known to modern civilization, but its capacity also makes it dangerous when not handled. When designing electrical installations, increasing voltage reduces current, which allows for smaller conductors and protective devices. However, the design must also take into account the risks of higher voltages with appropriate isolation and protection measures, combined with regular testing.
Energy efficiency measures are strongly recommended, as they reduce the total power consumed by an electrical installation. For a given voltage, this allows for smaller conductors and protective devices. For example, a high-brightness HID bulb consumes more than 450 watts, while an equivalent LED product typically consumes less than 150 W – a given circuit capacity can serve three times as many bulbs in this case if they are LED.
