The choice of the nominal value of the protective machine for a street garland begins with an accurate calculation of the total power of all connected light devices and determining their starting currents. If you ignore this step and install the protection device at random, you risk getting constant false positives in the cold or, worse, overheating of the wiring and ignition with a short circuit. Properly selected protection should be guaranteed to cut off emergency currents, but at the same time withstand short-term voltage throws, characteristic of the operation of LED and lamp systems.
The specifics of operation in the open air dictates strict requirements not only for electrical parameters, but also for the design of the device itself. An automatic switch installed in an unheated shield or on the facade is exposed to temperature, humidity and ultraviolet changes, which can significantly change the characteristics of its releases. So the question is, what exactly is it? switch-off choose, requires an integrated approach, taking into account the type of load, the cable cross section and environmental conditions.
Calculation of total power and load current
The first step in the selection of protective equipment is to determine the full power of the entire light installation. You need to add the power of all the garlands, searchlights and decorative elements that will be powered by one machine. A standard formula is used to transfer power by current. I = P / Uwhere P is the total wattage and U is the mains voltage (usually 220-230 volts). The resulting value will show the working current that will flow through the wires and switching equipment in normal mode.
However, a simple calculation of the working current does not take into account an important nuance: initiation currents. At the time of switching on the garland, especially if it uses transformers or old incandescent lamps, the current can briefly exceed the nominal 5-10 times. Modern. LED garlands with pulsed power supplies also create current throws due to the charge of the input capacitors. If the machine is picked up too close to the working current, it will perceive these throws as a short circuit and instantly turn off the power.
For the correct selection of nominal value, it is recommended to add a margin to the design current in the amount of 20-30%. This will allow the system to work stably even with small fluctuations in voltage in the network or when connecting additional consumers in the future.
Selection of time-current characteristics
A critically important parameter in the choice of protection is the time-current characteristic of the cleavage, which is denoted by the Latin letters B, C or D. For household socket groups and lighting, type B or C machines are most often recommended. The difference between them lies in the range of currents of instant electromagnetic cutoff, in which the machine is triggered without delay.
Automatics with characteristics «B» are intended for lines with active load, where the starting currents are minimal. They work when the denomination is exceeded by 3-5 times. If your street lighting consists solely of low-power LED tapes without massive power supplies, this option may be suitable, providing maximum sensitivity to leaks and closures.
However, for most street decorations, where pulsed power supplies or mixed load are used, the best choice will be the characteristic. «C». These devices withstand a short-term excess of current 5-10 times, which allows you to safely survive the moment of turning on the garland without false knocking. Installation of a type D machine for garlands is usually not required, as they are designed for powerful electric motors with huge starting currents.
The effect of temperature on the work of the disengagement
The heat disengager of the machine, responsible for protection against overload, works on the principle of heating the bimetallic plate. This process is directly dependent on the ambient temperature. Standard calibration values for circuit breakers are specified for a temperature of +30°C or +40°C, which is the norm for heated spaces.
When installing a shield with a machine gun on the street in winter, the temperature can drop to -20 ° C and below. In such conditions, the “cold” automatic machine will require much more current to heat the plate and then turn off. In fact, its real bandwidth will grow and it may not work on time when the cable overloads, which creates a fire hazard situation. Conversely, in summer in the sun, the body can heat up, causing premature operation.
To compensate for temperature changes, when installing street lighting, it is necessary to take into account correction coefficients or choose machines with an extended temperature range. Some manufacturers produce series specifically designed for use in the extreme north or tropics, where the operating range is from -50°C to +70°C. The use of conventional household models in unheated street shields requires special care and current reserve.
⚠️ Attention: If the circuit breaker is installed in an unheated street shield, its actual shutdown capacity may decrease in winter and increase in summer. It is recommended to choose the nominal value taking into account temperature corrections or use thermostabilized models.
Requirements for the degree of protection of the IP housing
Street operation of electrical equipment involves exposure to moisture, dust, snow and direct sunlight. A conventional household machine installed in open form on the facade will quickly fail due to corrosion of contacts or moisture entering the mechanism. Therefore, the key parameter is the degree of protection of the case, marked with the code. IP.
For street garlands and control boards, the minimum level of protection is IP44This means protection from solid objects larger than 1 mm and water spray falling from any direction. However, for reliable long-term work, it is better to focus on the class. IP65 or IP66. Such devices are fully protected from dust and withstand powerful jets of water, which is critical when washing the facade or heavy oblique rain with snow.
Often, the machines themselves do not have a high class of protection, so they are placed in special sealed boxes. When choosing a box, make sure it is made of UV-stable plastic that will not crack in the cold and crumble under the sun. It is also important to have osmal entries for the cable, which will ensure the tightness of the entry and exit points of the conductors.
The need to install a RCD or difavtomat
Protection against overload and short circuit, which provides a conventional machine, does not save a person from electric shock. Street lights are at high risk: people can touch wires with their hands, snow and rain create a conductive environment, and insulation can be damaged mechanically. Therefore, the connection circuit must necessarily include a protective shutdown device (CCD) or a differential automatic.
For street lighting and garlands, it is recommended to install an ultrasound with a leakage current of no more than 30 mA (0.03 A). This value is safe for humans and allows you to turn off power at the slightest violation of isolation. If the lighting perimeter is large and the total natural leak current is large, it is permissible to use a 100 mA RCD on the input, but individual groups of garlands are still better protected with more sensitive devices at 30 mA.
There is a common misconception that LED lights are safe and do not require an ultrasound. This is not the case: garland power supplies have pulsed transducers that create high-frequency interference and can have significant leakage currents to the housing. In addition, if the cable is damaged by a snowdrift or an ice crust, it is the ultrasound that will prevent tragedy if someone decides to fix the decoration.
☑️ Checking connection security
Comparative table of characteristics of machines
For convenience of choice, we will give comparative data of various types of protective devices that can be used in the street lighting circuit. The choice of a particular model depends on the total power of your garland and operating conditions.
| Type of device | Rated current (A) | Characteristics | Recommended application |
|---|---|---|---|
| 1P machine | 6-10 A | B | Low-power LED garlands (up to 2 kW) |
| 1P machine | 10-16 A | C | Mixed load, garlands with transformers |
| diffautomatic | 16 A/30 m | C | Full protection (current + leakage) for street outlet |
| 2P machine | 10 A | C | Phase and zero breaks for enhanced security |
Why you can not use aluminum cable for garlands
Aluminum has high oxidability and low plasticity. In the cold, it becomes fragile, and in places of contact with copper terminals of the machine, an oxide film is quickly formed, increasing resistance and the risk of heating. For street garlands, use only copper cable with crosslinked polyethylene insulation (for example, VVGng-LS or specialized street brands).
Connection schemes and installation of equipment
Installation of protective automation for street lights should be carried out in compliance with all electrical safety standards. Connection is usually through an intermediate sealed box, which houses an automatic machine, an RCD and, if necessary, a cache or photo relay for automatic inclusion. All connections inside the box must be made through terminal pads or shells, twisting in street conditions is categorically unacceptable.
The cable going to the garland should be fixed so as to exclude its tension and damage by wind. The cable entrance to the garland body should be raised upwards or protected by a visor so that the water drains without flowing inside. If the garland is suspended at a height, provide convenient access for maintenance and replacement of burned out elements without the need to climb the ladder each time under tension.
When assembling the shield, observe the color code of the wiring: phase wire L (usually white, brown or red) is connected to the input of the machine, zero N (blue) goes to the zero bus or directly to the RCD. Grounding conductor PE (yellow-green) must be continuous and connected to the garland body if it is metal or to the grounding circuit.
Use a comb tire to connect the machines inside the shield, if there are several. This provides a more reliable contact and neat look than the jumpers from individual pieces of wire.
Common mistakes in the organization of food
One of the most common mistakes is the use of conventional sockets and extension cords for street connection. Plastic of such devices can not withstand ultraviolet and frost, becoming brittle, and the lack of tightness leads to moisture entering the contacts. The result is a short circuit or failure of the machine due to corrosion.
Also, there is often neglect of calculating the cable cross section. House owners take a thin wire "only glow", not taking into account that at a line length of 20-30 meters, the voltage drop can be significant, and the short circuit current at the end of the line is insufficient for instantaneous operation of the machine. This can lead to the fact that when closing the machine will not knock out, and the cable will warm up along the entire length.
Another problem is the “curling” of wires of different metals (copper and aluminum) without the use of special transition terminals. In street conditions where humidity is increased, the copper-aluminum galvanic pair breaks down very quickly, leading to heating, sparking and eventual fire. All connections must be made through brass or bimetallic terminals.
⚠️ Attention: Never leave the connection points of the wires just wrapped in tape on the street. Ordinary PVC tape in the cold blubbers and peels off, and in summer floats. Use only shrink tubes with adhesive layer or sealed couplings.
Maintenance and seasonal conservation
After the end of the holiday season, street wiring must be preserved. Even if the machines and cables have a high protection class, prolonged exposure to aggressive environments can lead to the accumulation of dirt, salt (if the reagent is used on the roads) and moisture in the gaps. It is recommended to turn off power, dry the shield and, if possible, dismantle the garlands for storage in a dry room.
Before the next season, be sure to conduct a visual inspection of the cable for damage to the insulation by rodents or mechanical ruptures. Check the tightening of contacts in the machine and the RCD, as from the heating and cooling cycles, the metal can slightly “float”, weakening the connection. Contact lifts should be carried out regularly, at least once a year.
If the circuit breaker is triggered during the operation of the garland, do not rush to turn it on again. First, find and eliminate the cause: check the integrity of the garland, the lack of water in the connections, the serviceability of power supplies. Re-inclusion of the machine on a faulty chain can lead to its failure or fire at the site of the defect.
The main rule of safety: the protection machine is selected by the cross section of the cable, not by the power of the garland. The cable must withstand the current of the machine, and the machine must protect the cable.
Can I use one machine for home and street lights?
Technically possible, if the total power does not exceed the nominal value of the machine and the cable cross section. However, this is bad practice. When the protection is triggered, you will be left without light in the whole house or on the street. In addition, the street line has higher risks of current leaks, which can lead to frequent false RCD shutdowns, de-energizing the interior.
Which cable is best used to connect street lights?
The best choice is a copper cable brand VWGng-LS (for gasket in corrugated) or a specialized cable KG (the cable is flexible) with rubber insulation, which does not smack in the cold. For temporary installations, cables marked “for street use” with double insulation are also suitable.
Why does the machine knock out when the garland is turned on?
There may be three reasons: (1) The total power of the connected devices is exceeded. (2) There has been a short circuit in the wiring or the garland itself (moisture, insulation damage). (3) The automatic machine is not properly characterized (e.g., type B instead of C) and reacts to the initiation current as an accident.
Do I need to ground the metal elements of the garland?
Yes, if the garland has a metal frame, supports or housings of lamps made of conductive material, grounding is mandatory. This ensures that when the phase breaks down on the body, the voltage will go to the ground, and the automatic or RCD will instantly turn off the power, protecting people from electric shock.