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|Prague, Czech Republic|
|Ing. Arch. Patrik Kotas|
|Zumtobel Licht GmbH|
The Prague underground plays an irreplaceable role in the concept of municipal public transport, in particular with respect to the everyday load of all surface transport routes. Moreover, Prague - as a historical city - bears the heritage of confined development, a number of relatively small areas and protected historical monuments so that the reliable operation of the underground is absolutely critical for the life of the metropolis.
The progressive modernization of older underground stations and new construction has also brought new views on the operation of lighting systems. The concept of luminaires with DALI gears was selected after overcoming initial problems with the search for an optimum technical solution.
The method of operation of a lighting system in the underground has partially different requirements when compared with other constructions. Reliability together with achieving the necessary intensity of lighting in accordance with applicable standards is the first requirement. Next is economy of operation, easy and comprehensible control and the possibility of status monitoring. Platform lighting represents a specific issue, as described below.
An emergency lighting system that is always powered from a station central battery, together with other important underground technologies remains a special part.
The complete control and monitoring system of a lighting system is subsequently based on DALI communication into which, in addition, relevant technological elements are incorporated. The aim of the solution was to fulfil the main requirements of Metro Praha as listed below:
1. Safe operation of luminaires.
2. Ensuring the required lighting-technical parameters under all operational statuses.
3. Possibility of both local and remote control.
4. Automatic tests of emergency luminaires.
5. Economical operation, automatic dimming in link to daylight, timing modes, constant level of illuminance.
6. Monitoring of the lighting system as a unit, visualization both in the underground station and on the central control panel.
7. Obtaining background information for the purposes of repair and maintenance planning and reduction of operational costs.
8. Use of already verified control system technical platform.
• 13 Prague underground stations fitted with luminaires with DALI gears, others in construction.
• A total of 6,000 intelligent luminaires installed so far.
• Automatic dimming in link to daylight, timing modes.
• Remote and local control of luminaires and switching components in switchboards from the central control room.
• Data transfer from individual luminaires (status, defects, burning hours) in the central control room.
• Automatic modification of the operational mode of luminaires according to current outside temperature.
• Luxmate Professional control application is operated on the PLC GE Series 90-30 platform to ensure maximum operational reliability.
• Special application for automatic tests and emergency lighting status assessment.
• Cimplicity central visualization displaying lighting and switchboard technology in stations.
• Special application for transfer of values of daylight omni-directional sensors between stations.
• Access to the control application of any station from any connecting point within underground technological network.
• Cimplicity visualization for maintenance personnel in the stations of supervisors of individual lines.
• Local visualization in stations on Pro-face touch panels or panel PCs.
The Prague underground consists of 54 stations while 3 others are currently under construction. The first stations were opened in 1974 and Střížkov, Prosek, Letňany are the latest stations to be commissioned in 2009. Until 1997 when the company Zumtobel installed the first lighting control system (still without DALI at that time) here, lighting control in the stations had been fitted with a system of local light sensors only.
Luminaires in each station can be classified on the basis of more criteria; for our purposes we will use classification between luminaires designated for public and non-public areas.
All luminaires in public areas are controlled with the DALI protocol; this applies to the emergency luminaires only in non-public areas.
Naturally, operation of the underground lighting system is subject to a number of (in particular safety) regulations that have a principal effect upon the method of control of luminaires.
Besides automating commands, authorized operators also participate in operation actively, whose interventions are always overriding with respect to the Luxmate control system.
This feature distinguishes the project fundamentally from the usual solutions where the achievement of the maximum level of automation or savings in power consumption or the creation of light effects is usually the main goal.
Luminaires with a higher IP level fitted usually with 18W, 36W or 58W T8 lamps are largely used for lighting. Special luminaires with similar lamps are installed on the platforms and some stairs.
Control of luminaires:
It is possible to separate the method of control in a simplified way between digital and electric when electric control is disconnected from one or more luminaires from the power supply voltage.
The Luxmate control system project based on DALI does not deal with electrical control, but it is forced to respect all consequences of such operations.
All luminaires connected to Luxmate/DALI are operated in the appropriate light scene during standard operation. Rooms with daylight are controlled automatically in accordance with the data from the central daylight sensor; the lighting of other areas is set to the required values within a static scene.
A special case is the lighting of the platform edge. In order to avoid creating a stroboscopic effect for the train driver, the luminaires above the platform edge have to create a continuous band of light without a break. However this produces an unnecessarily high level of platform illumination both from the viewpoint of energy consumption and, above all, as a source of relative glare to the driver of the approaching train. DALI control is used to reduce the intensity to a reasonable level here.
Electric control is performed by manual intervention of the operator directly from the switchboard or from the station supervisor working site. Remote control is possible from the underground central control room. Control circuits of contactors to which larger or smaller groups of luminaires are connected are always switched by means of switches.
All DALI gears are set so that lighting up of luminaires to 100% intensity takes place in the case of a loss of DALI or LM-BUS control signal.
Luminaires return to the previous operational status after the defect has been remedied.
The system is based on the already well-proven Luxmate Professional control system with a specially modified software component for operation on the PLC GE Series 90-30 platform. This variant was developed by Zumtobel exclusively for the Prague underground in order to achieve maximum reliability, also on the HW side.
LM-DALIS convertor units are positioned in individual light switchboards and connected to the spinal LM BUS bus bar.
Connection of the Luxmate BUS bus bar with PLC GE is carried out with Westermo opto-converters that allow extension of metallic interconnections without the risk of communication interference. Ethernet connections for PLC integration with other parts of the technology are designed using a similar method.
Visualization of the complete technology runs on HMI Cimplicity while details from all underground stations fitted with the lighting control system are available in the system operator’s workplace. Visualization of local technology only runs on a panel-touch PC in the respective station. The visualization displays the status of the monitored devices of switchboards and details of individual luminaires and it allows commands to be given remotely for both the technological part of the switchboards and for the lighting control system.
The locations of all important components such as contactors, controllers, switches, circuit breakers and protectors are monitored in all light switchboards. This data is designated as technological points and is used for the correct assessment of luminaire status.
This close linking of the switchboard technology with the lighting control system resulted in a special modification of processing status information from the lighting control system when an open contactor or circuit breaker does not cause the generation of error messages from the connected luminaires but masking of these statuses will occur instead and the information on the open contactor (circuit breaker) will override them.
The system operator has the possibility to re-route the currently measured values of daylight on the omni-directional sensor from any station to any other station. This method ensures sufficient redundancy in the event of a sudden station sensor failure.
Emergency luminaires are connected permanently to 220 V DC, they are provided with DALI gears and controlled by the Luxmate central control system.
Some luminaires are installed in public areas and are controlled on the basis of daylight intensity, others are turned on continuously and some are turned off in the basic mode.
Monitoring of the emergency luminaires is extraordinarily important as passenger safety is the most important operational aspect.
Emergency luminaires are also currently installed in hazardous areas such as switching stations, transformer stations, cable spaces, cable channels and ventilation shafts. An application for testing emergency lighting, allowing testing luminaires in stations and related lighting technology and assessment of the results of tests including their archiving is available in the system operator’s workplace.
Zumtobel has been a supplier of the lighting control system for the Prague underground since 1997. The concept of station lighting has undergone substantial development from a low number of incorporated luminaires through large units controlled in ON/OFF mode up to the DALI digital system during this period.
The DALI system has found a unique possibility of application for the construction of a system guaranteeing maximum operational safety thanks to both its reliable function and provision of all operational data for further processing.
It is obvious that this “industrial” application can also be inspiration for other technically focused projects in which somewhat different aspects than we are used to in the case of “normal” DALI projects will be applied.
On Monday, 16 April, three winning projects were selected for the DALI Award 2012.
See the Winner of the DALI Award 2012.