The Power Behind Street Lights: Voltage, Current, and Lighting Systems
Street lights are essential for ensuring safe and secure environments in urban and suburban areas. But what power do they run on? This article explores the different types of street lights and the electrical currents that power them. We'll cover everything from the early era of incandescent lights to modern LED systems, detailing the voltage and current involved in each process.
Early Incandescent Street Lights and Arc Lights
The history of street lighting dates back to the early 20th century, with the first significant changes in technology occurring in the 1930s and 1940s. Early incandescent street lights, used in cities and towns before the widespread adoption of other lighting systems, relied on a series-parallel wiring configuration. These lamps were typically 50 to 100 watts and operated at around 6.6 amps, with a total circuit voltage ranging from 1,000 to 2,000 volts. This setup was necessary to provide the required wattage across a large number of bulbs in a continuous string.
Modern Lighting Systems: Airfield Runway Lights and Arc Lights
Airfield runway lights, which are critical for safe night flights, are still wired in series with voltages ranging from 1,000 to 8,000 volts. These high-voltage systems are used because the number of bulbs can range from hundreds to thousands, ensuring that the lights are bright and visible for pilots. The current in these systems is typically around 6.6 amps, which is sufficient to power the high-intensity lamps used in runway lighting.
Street Lights and Voltage in the UK and US
In the United Kingdom, street lights typically run on 230 volts alternating current (AC). This voltage is standard mains voltage and is consistent throughout most of the country. The UK's motorways, a part of the national highway system, are illuminated by 400 watt high-pressure sodium lamps at intervals of 100 yards. Power distribution to these lamps over such a long distance necessitated significant infrastructure challenges in the past. However, the specifics of how this was achieved can vary and are subject to detailed engineering studies and reports.
In the United States, the voltage used for street lighting can range from 120 volts to 480 volts, depending on the jurisdiction and the specific distribution system in use. These variations depend on the local electrical grid and the needs of individual cities and towns. For instance, smaller communities may use 120 volts, while larger municipalities might use 240 or 480 volts to power their streetlights.
Lighting Pillars and Voltage Converters
The voltage supplied to the lighting pillar is typically 230 volts AC in the UK. However, the lighting fixtures themselves may contain a voltage converter circuit to suit the specific luminaire. This conversion ensures that the light source, whether it be an incandescent bulb, a fluorescent tube, or an LED, receives the correct voltage to operate efficiently and effectively.
Traffic Lights: A Different Voltage
Traffic lights operate on a different voltage from street lights. Most traffic signals use 24 volts DC, generated by the controller computer. This direct current is used to activate relays, which in turn allow the flow of 120-volt or 240-volt alternating current (AC) to power the actual bulbs or LEDs. The transition to LED technology has been a major shift in recent years, as it significantly reduces energy consumption and improves the longevity of traffic lights.
For example, in the United States, traffic signals and their controllers run off 120 volts AC. In the past, light bulbs were embedded in sockets to illuminate glass or plastic lenses, but this has given way to LED technology over the last 15 years. LEDs require less energy, last longer, and offer better light quality, making them an ideal choice for modern traffic control systems.
Conclusion
The power behind street lights and other public lighting systems has evolved significantly from the early days of incandescent bulbs to the current use of LED technology. The choice of voltage and current depends on the specific application, whether it be for general street lighting or traffic signals. Understanding these differences is crucial for ensuring optimal performance and energy efficiency in public lighting systems.