Control Circuits for Streetlights

Interesting answers, but misleading. Your key word is street lighting.

Street lighting uses the most economical lamp source available, high pressure sodium (HPS) or metal halide (HIT). These sources do not respond well to being switched frequently (most manufacturers limit this to 6 per day). Interestingly, fluorescent is rarely used in street lighting, except maybe in tunnels and walkways, and respond better to frequent switching.

Presence detection is never used on street lighting:

• the PIRs and wiring are too complex
• it is difficult to cover a street with multiple PIRs
• they are too unreliable
• they are subject to vandalism
• do not respond well to large fluctuations in temperature
• there are legal implications with lighting turning off unexpectedly

Timeclocks are rarely used on street lighting, and never in public streets, only in amenity areas:

• they are unreliable and require regular attention for changes in summertime
• cannot respond to unusual circumstances, such as fog or bad weather
• do not respond well to large fluctuations in temperature
• have legal implications to the relevant authority if the lighting turns off unexpectedly or at the wrong time

Photocells are used almost exclusively. If you look closely at some lanterns, you will see the culprit mounted on top of one of the fittings. This is wired to a contactor in the street lighting column, which will energise the whole circuit. There is generally a failsafe contact, such that photocell failure or destruction will trigger the circuit permanently on. The system is fit and forget; there are no timings to set, and the system will repsond to fog or snow etc. You may see a number of vertical rods around the detector, which are usually interpreted as lightning protection, but are there to keep birds from depositing their lunch

One alternative is an impulse contactor, which receives a timing impulse sent along the mains, from a central control. These are increasingly rare.

A recent project here in New Zealand was Wellington's Waitangi Park, which used a lighting control system called C-Bus. In general however, local councils do not have the inclination, budget, or wish the legal exposure associated with failed street lighting. One accident or injury can cost many $100,000s, even just to defend a case, so the energy saving associated with complex controls is non-sensical.

I am a member of this forum, but at the moment I don't remember my password, so I am answering as a Guest.

BabyGuiness offered a very good answer. Here are some more items to consider.

1. If the street lights are spaced very far apart, such as only at intersections in a residential neighborhood, the best way is with individual photocontrols on each luminaire. The lamps will come on at dusk and go off at dawn year round. Most luminaires will come with a twist lock receptacle on top in which you can mount the photocontrol. Some will even come with the control mounted as an integral part of the luminaire. If not, you can mount them on a bracket adjacent to the luminaire.

2. If you are lighting a major thoroughfare you might want all the lights to come on at the same time. You can install a photocell at the source of the power and it will energize the circuit at dusk, but this is limited capacity and only works for a few lights. You can also use a relay in conjunction with a photocontrol to energize the circuit at dusk. The relay should be normally closed. That way if the photocontrol fails the circuit will come on and stay on all the time instead of staying off all the time. Most relays are going to be 30 amp or 60 amp. If you exceed that, you can cascade relays or use a pilot wire. The pilot wire would be hot during the day time and would hold several normally closed relays in the open position. Then it goes off at dusk, allows the relays to close, and energizes the lighting system.

3. Timers are not normally used on street light systems because it gets dark at different times during the year. If you were doing an area lighting project, such as a large parking lot at a shopping mall, then you could use a time to turn the lights off after the mall is closed. The says some energy because the lights are not on all night, but may cause some security problems.

4. Street lighting systems are rarely set up in series anymore. I haven't seen a series street lighting ciruit in over 30 years.

Jim Cartwright