How Surge Protection Devices (SPD) Work for LED Street Lights?

What is SPD?

Before we get to the idea of a surge protection device, we first need to understand what a surge is. A surge is a transient overvoltage beyond the normal operating voltage. Essentially, a surge is an intense pulse that occurs for only a few millionths of a second.

Hazards of Surges

The hazards of surges are mainly divided into two types: catastrophic hazards and cumulative hazards. Catastrophic hazard refers to a surge voltage that exceeds the capacity of the equipment. The equipment will be completely destroyed or have greatly reduced service life. Cumulative hazard refers to the cumulative effect of multiple small power surges that lead to the deterioration of semiconductor device performance, equipment failure and shortened life, and finally lead to the shutdown or productivity decline. Without a surge protection device, a lot of electronic equipment, instruments, and communication lines will be under attack by both of these hazards and eventually become ineffective. This includes outdoor LED street lights. So it is necessary to have surge protection devices for outdoor luminaires like street lights, flood lights, landscape lights, lawn lights, courtyard lights, parking lot lights, etc.

What is SPD?

A surge protection device (SPD) is a kind of electronic device that provides safety protection for all kinds of electronic equipment, instruments, and meters and communication lines. When the electrical circuit or communication line experiences an external interference that suddenly produces a peak current or overvoltage, the surge protection device can conduct and shunt those intense pulses very quickly to prevent the surge from damaging other equipment in the electronic circuit. A good surge protection device should be capable of repeating these functions as specified to achieve true protection.

Why is SPD Required for LED Street Lights?

1. Outdoor LED street lights are usually powered by a power supply that converts alternating current to direct current. The power supply voltage required by the LED semiconductor is relatively small. This is different from the instantaneous high voltage withstanding ability of traditional high voltage street lamps. The LED street lights themselves don’t have the ability to withstand peak currents and overvoltages from outside. So it is necessary to use surge protection devices for LED street lights.
2. As a typical outdoor LED lighting application, LED street lights have a high initial cost. The payoff is built in through lower wattage requirements, lower maintenance costs and longer life. In order to prevent failure of street lamps installed outdoors during the payback period of about 5 years, street lights should have high durability and reliability. Transient surges in alternating current lines are a major threat to street lamps. So it is necessary to take some effective measures to prevent surges from damaging street lights.
3. In fact, not only lightning strikes will cause induced surges, but the on/off of inductive or capacitive loads, short circuits of ground electrodes or power supplies can also produce pulses in the power line, causing damage similar to lightning strikes. Therefore, it is very important to consider circuit protection units to eliminate on-site faults caused by the electrical environment.

How Does SPD Work for LED Street Lights?

The way to protect the street light from surge damage is to block high voltage/current transient interference from entering the lighting fixture. Therefore, a surge protection device (SPD) can be used in outdoor LED street lighting applications to suppress surge energy and minimize the impact on lighting equipment.

When there is an abnormal increase in voltage in the power line, the resistance of the surge protection device will drop sharply to guide the surge out of the protected equipment's power line. When the surge is over, it will automatically reset to a high impedance state. You can think of the SPD as a sluice gate, and the surge as a flood. Under normal circumstances, the gates are closed, but when a flood is anticipated, the gates open quickly so the water can be diverted.

There are two main types of SPD module configurations:

1. Parallel Connection

2. Series Connection

The SPD takes the surge so the protected equipment can survive. Over time, the SPD will come to the end of life due to the many surges it endures. It sacrifices itself so the protected equipment can live.

SPD with Flasher for LED Street Lights

From customer feedback, we have gathered that they are unsure whether the SPD installed in the LED street lighting system is working properly after a period of operation or is damaged. There is no clear indication, which brings uncertainty to their street lighting maintenance.

So when we designed a street lighting solution for a customer, we specifically integrated the SPD with a mini flasher into the LED street lighting system to meet their needs. This allows maintenance staff to determine the condition of the surge protection device based on the flasher signal.

If you also have similar needs for a street lighting system, feel free to contact us.