As far as town or street lighting is concerned, the current social, economic and cultural situation has set certain guidelines in which the following factors are all important:
• Quantity and quality lighting appropriate to conducting normal activities in towns, villages and roads at night.
• Energy-saving lighting system, while at the same time maintaining light levels appropriate to each situation.
• Environment-friendly designs that make as little impact as possible on the consumption of natural resources, in terms of:
a. The biggest possible percentage of recyclable materials.
b. Robust products with a long service life.
c. Reliable, low failure rate products.
d. Products that cannot be manipulated by third parties who disregard their proper use.
e. Low implementation cost designs that will give a swift return on the investment.
f. Easily implemented designs without any need for works or additional costs.
What are the rules involved in attaining the best lighting system?
Each country is trying to optimise the aforementioned factors by means of directives, regulations, standards, etc. and by way of the type of installation:
1) There are regulations for new installations that make it compulsory to use energy-saving methods. For example, in Spain we have Royal Decree 1890/2008 of 14 November with its regulation on outdoor lighting installations’ energy efficiency and its complementary technical instructions. Specifically, ITC-EA 02 requires lighting adjustments at low traffic times for over 5 KW installations.
2) Appropriate maintenance must be carried out on existing installations and simple actions can be taken to achieve greater benefits:
a. Replacement of old lamps for new, more efficient ones. For example, the use of new 100 to 140 lm/W metal halide lamps that perform better than the previously used mercury ones, and better than some high pressure sodium ones.
b. Maintaining the luminaires: cleaning the reflectors, the luminaire glass or polycarbonate covers and checking the optic group sealing, all of which will ensure that the light generated by the lamps reaches its destination.
c. Changing the standard equipment for Bi-Power control gears (We will define its operation below).
What is the best type of product for the easiest street lighting efficiency?
La respuesta a ésta pregunta la encontraremos en los equipos de Doble Nivel de potencia tipo “SMI” con respuesta astronómica. A continuación se exponen las razones más importantes:
The answer to this question lies in the Bi-Power system control gears timed with astronomical response “SMI”-type. The most important reasons for this are:
• Because it is independent, its needs no other installation element, additional circuits or other auxiliary components on control panels or in the luminaire.
• The investment is small but the benefits are immediate.
• The equipment is reliable, given that the failure rate after 10,000 operating hours is less than 0.1%.
• The equipment is robust and withstands the high luminaire temperatures. • It is economical, costing very much the same as single level equipment.
• 90% of the materials used to make it can be recycled (copper and magnetic steel).
• Easy to install.
• Low cost and swift return on investment. For example, a complete “SMI” for a 150W, high pressure sodium or metal halide lamp can result a saving if the cost of a KW per hour is to the order of €0.15, we will have saved the equivalent of €26.11; i.e. the cost of the equipment is recovered in approximately one year.
What is Dual Power Level equipment and how does SMI technology work?
Bi-Power control gear is a ballast designed to save energy in installations, normally of the street lighting type. It is based on the fact that at certain times of night the light level can be reduced (up to 40% of the power) without any perceptible loss of visibility, but with significant energy savings.
250W 2P _ 2P magnetic system 250W
100W 2P _ 2P magnetic system
The ballast is fitted with an additional winding that increases nominal impedance and reduces the lamp’s power. The change from one power level to another is brought about by a switching relay.
On ignition, the ballast works at nominal level supplying the lamp with its maximum or nominal level, both in terms of power as well as regards to luminous flux. At a particular time during the night, the additional winding will be connected by means of interaction with the control relay, thus reducing the power consumed and the luminous flux, uniformly and without significantly diminishing visibility.
For timed, SM (without command wire) models, the changeover to reduced power level occurs after a set time which is determined as of lighting switch-on (see the following figure).
SM (without command wire) models graphic
Unlike the above, the changeover to reduced power level in SMI models is brought about using an algorithmic calculation done by a microprocessor. Astronomical response means that, throughout the entire year, the changeover to reduced power level is practically always simultaneous.
Electronic ballast 2P technology 150W
The SMI -2…+5 hour standard model works as follows:
• The average operation over the last four nights is calculated.
• The mid-point for the night is calculated.
• The reduced power level is enabled two hours before this average point.
• The equipment will adhere to this reduced level for five hours after the mid-point is reached.
• A total of seven hours at reduced level.
SMI standard model (fig. 1)
• The response of this standard model installed in Madrid would be as seen in the following table.
• Yellow reflects operating hours at nominal level, while the orange represents reduced level operating hours.
• If you want to extend the reduction hours, you can use SMI (-3…+5h, -3…+7h or -3…+9h: the latter setting means that the nominal power level would not be restored in the morning).
SMI standard model (fig. 2)
Some frequently asked questions about SMI system installation and/or maintenance are answered below:
Why can I not change the level as soon as I switch on the lamp?
Because switching on is always done at maximum power level at the start in order to stabilise the lamp, in accordance with manufacturers’ recommendations. The control and protection are disabled for 5 minutes.
What does it do over the first few days when the data has not yet been memorised?
It considers a standard night-time duration of 11 hours. This average of the aforementioned, 5.5 hours, would serve as the basis on which to apply the reduction -2…+5 hours.
What happens when there is a power cut and the lamp has been switched off?
Whenever there is a power cut, when the supply is restored, the equipment switches on again at maximum power level and starts to calculate according to the memorised average, thus that night the reduction will not meet the sought-after efficiency (It has no memory or internal control of real time).
How is the system protected against mains overvoltages?
Whenever mains voltage exceeds 260V (which would only last for a matter of milliseconds) the equipment changes over to reduced power level, even during nominal power operating times. In this situation, when the mains returns to 250V, the equipment will return to maximum power if operating at that time interval.
ELT SMI control gear is characterised by the following features:
• It counts the nights when the switching-on time is over 4 and under 18 hours.
• 500 ms is the power-out time in order to start timing. Moreover, this is the minimum interval without mains power which ensures a timing re-start.
• It supports mains micro-cuts up to 10 ms, which is the maximum time without mains power for which the programme will not restart, continuing on with the timing from the previous point (whether or not the lamp switches off).
• If the lamp switches off for reasons other than mains power cuts, equipment timing will continue.
It is worth noting that the SMI system is also implemented in our electronic equipment for HID lamps and in our LED Driver range for street lighting.
Jesus Barrado, Technical Department
