TUNNEL LIGHTING – DESIGN
& CONTROL
Research and Development
Sector -
I. DESIGN OF
TUNNEL LIGHTING
I.2. PROGNOSES ABOUT THE
hourly charts of luminance L20 AND TRAFFIC INTENSITY ICAR
I.3.
COMPUTING THE ANNUAL HOURLY CHART OF THE NECESSARY LUMINOUS FLUX
I.4. OPTIMIZATION OF ARTIFICIAL LIGHTING OF
ROAD TUNNELS
II.
COMMUNICATION SYSTEM OPERATING PRINCIPLES
II.1. HIERARCHY
LEVELS AND OPERATING PRINCIPLES
II.2. SUPERVISORY CONTROL AND DATA
ACQUISITION
III. HARDWARE OF CONTROL SYSTEM
III.1. CONTROLLER FOR SUPERVISORY CONTROL
III.2. EMBEDDED CONTROLLERS FOR TUNNEL LIGHTING
III.3. LUMINANCE-METERS FOR CURRENT
MEASUREMENT OF L20 AND LTH
III.4. DIMMING DEVICES FOR HIGH
PRESSURE DISCHARGE LAMPS
IV. SOFTWARE OF
CONTROL SYSTEM
I. DESIGN OF TUNNEL LIGHTING
I.1. INTRODUCTION
The
necessary luminance Lth [cd/m2] of the road surface in the
threshold zone, immediately after entering the tunnel, is determined by the
condition:
(1) Lth ³ R.L20.
The
level of adaptation luminance L20 [cd/m2] of a driver approaching the
tunnel is determined for 20-degree zone of observation measured from a distance
equal to the breaking distance to the tunnel entrance. The parameter R [1,2] depends
on the conditions of movement in the tunnel (one-way vs. two-way traffic), the
kind of lighting installation, and the traffic intensity ICAR [car/h].
The
annual maintenance costs for tunnels without ventilation (up
to 800 m long) mostly depends on the annul
expenses for artificial lighting. Their extent depends on the annual hourly
charts of the access zone luminance L20 and traffic intensity Icar.
The necessary working power for illuminating a unit area of the road is
proportional to the luminance determined from equation (1), and the parameter
k:
(2) p(t)=k.Lth(t)=k.R(ICAR(t)).L20(t), [W/m2].
The
parameter k [(W/m2)/(cd/m2)] is a basic quality factor of the lighting system –
specific power for achieving a unit luminance on the road. It depends on the
type of the lamps used, on the luminous intensity distribution of the
luminaires [14], on their placement in relation to the road (centrally or
laterally), and on the indicatris of road pavement reflection [25]. The
calculated necessary specific power is provided by the simultaneous work of
luminaires from a number of circuits. The optimal number of circuits for day
lighting is determined by solving an optimization task with the objective of
minimizing annual maintenance costs [21].
When step control of the day lighting is used, the optimal number of
circuits can be quite large. This is one way of decreasing the over-expenditure
of electricity caused by inaccurate adherence to condition (1). Further
improvement in the control of the lighting in the threshold and transition
zones can be achieved by providing a possibility for smooth adjustment of the
intensity of lighting of the lamps in some circuits [19]. The control of the
luminous flux is not done individually for each luminary, but rather, it is
centralized, with a special dimming device for the whole circuit [22].
Fig.1.1 shows an example of such control devices [20]. Non-dimmable
luminaries 1 and dimmable luminaries 2 in the threshold and transition zones
are connected to lighting control panel 3, respectively with n circuits with circuit closers 4, and (m-n) circuits with special dimming devices
5. The total number of circuits is m.
Lighting control panel 3 is connected to a controller of the lighting 6. The
latter is in turn connected to a luminance-meter 7 for measuring the adaptation
luminance L20, and a luminance-meter 8 for measuring the luminance Lth
of the road surface in the threshold zone and the traffic intensity ICAR
(when a vehicle passes through the field of the luminance-meter, the sudden
change in the road surface luminance is recorded).
Fig.1.1. Control of the tunnel lighting
with two kinds of circuits – with dimming and without dimming of the luminous
flux of the luminaries
I.2. PROGNOSes ABOUT THE
annual hourly charts of THE access zone luminance L20 AND TRAFFIC
INTENSITY ICAR
The
annual hourly charts of the access zone luminance L20[365,24] and
traffic intensity ICAR[365,24] are used to calculate the annual
chart of the luminous flux FNEED[365,24]
necessary to meet the lighting requirements for the threshold and transition zones
[1,2]. The annual chart is part of the input data for the optimization task.
Obtaining
an annual hourly chart of the luminance L20
is not a problem if there is a tunnel with similar entrance
exposure and working monitoring system in exploitation. In this case the
easiest way is to use the annual hourly chart of L20 for the
previous year directly from the database of the system. Before using the chart
it has to be re-scaled using the highest for the new tunnel value of L20,
calculated by (1).
When data from a similar tunnel are not
available, the annual hourly chart of L20 can be calculated from the
regional monthly charts of daylight for sunny, mixed and cloudy days [7]. A statistically reliable data for the ratio
between the different type of days for every month [3,21], the maximum value of L20 for the new tunnel, the hourly measurements of L20 for one
sunny day, information about the day of the measurements, and the geographic
exposure of the tunnel entrance is needed. A satisfying prognostic result for L20
can be received with a method that takes into account the trace of the
sun for the specific parallel.
The annual hourly chart of traffic intensity ICAR can be obtained from the road authorities. They
have weekly, monthly and seasonal charts of traffic intensity.
Similar approach was used for solving the
optimization task for a tunnel on highway “Hemus” in
Given the parameters of the tunnel,
the annual hourly charts of the adaptation luminance L20 [cd/m2], and the traffic intensity ICAR [car/h], the computation
of the annual hourly chart of the necessary luminous flux for the threshold and
transition zones is done in the following sequence [19]:
Ø For
every hour of the year (1-8760), for the given parameters of the traffic (Table
1), the given hourly charts of the adaptation luminance L20 [cd/m2], and the traffic
intensity ICAR
[car/h] (Fig.1.2), the class of the tunnel (Table 1) and its
coefficient R[I]
(Table 2) are determined. Here I
denotes the index of the hour;
Ø From
the calculated values R[I],
the annual hourly chart of the road surface luminance at the beginning of the
threshold zone in the tunnel, LTH[I]=R[I].L20[I],
is determined;
Ø The
maximum value LTH_MAX [cd/m2] of all values LTH[I] during the year is found;
Ø Given
the general requirements for decreasing the luminance from the middle of the
threshold zone to the end of the transition zone [1], the graph of the
luminance in the threshold zone, LTR_l=LTH_MAX*(1.9+l/v)-1.4,
is plotted. Here l [m]
is the distance from the beginning of the threshold zone to the point, at which
LTR is determined, and v [m/s]
is the speed limit in the tunnel;
Ø The
line LTH_MAX (up
until the middle of the threshold zone) and the curve LTR_l=LTH_MAX*(1.9+l/v)-1.4
(from the middle of the threshold zone to the end of
the transition zone) are integrated numerically. From the value
obtained for the conditional area, S [(cd/m2)*m], the conditional
length of the threshold and transition zones, l_CONDITIONAL =S/LTH_MAX [m], is computed;
Ø The
necessary luminous flux for achieving the luminance, LTH_MAX, is calculated using the width of
the road WK [m]
and the specific coefficient of the lighting installation LE [(lm/m2)/(cd/m2)]. The latter corresponds to the efficiency of
the particular kind of tunnel luminary and its mounting. FNEED_MAX=LTH_MAX*l_CONDITIONAL*WK*LE [lm];
Ø The
annual hourly chart of the necessary luminous flux FNEED[I] for creating luminance LTH[I] is computed from the formula FNEED[I]=FNEED_MAX*LTH[I]/LTH_MAX;
Ø The
so-computed luminous flux for each hour of the year can be achieved by
different combinations of circuits of luminaries, with different levels of dimming
of the lamps. If a circuit is non-dimmable, the lamps work at their nominal
flux yield (luminous efficiency), while if a circuit is dimmable, the lamps
work at a level of the flux yield that depends on the level of dimming.
Table 1.
Class of the tunnel
according to the requirements for artificial lighting (see [2]).
|
Type of traffic through
the tunnel |
One-way |
Two-way |
||||||||||
|
Traffic intensity [vehic./h] |
>1500 |
500÷1500 |
<500 |
>400 |
100÷400 |
<100 |
||||||
|
Traffic type |
Ñ |
̀ |
Ñ |
̀ |
Ñ |
̀ |
Ñ |
̀ |
Ñ |
̀ |
Ñ |
̀ |
|
Tunnel class |
4 |
3 |
3 |
2 |
2 |
1 |
4 |
3 |
3 |
2 |
2 |
1 |
Ñ – mixed traffic including
bicycles; ̀ – motorized traffic only
|
||||||||||||
Table 2. Recommended
values for R (see [2])
|
Stopping distance |
60 m (60
km/h) |
100 m (80
km/h) |
120 m (100
km/h) |
|
Tunnel class |
|||
|
4 |
0.05 |
0.06 |
0.10 |
|
3 |
0.04 |
0.05 |
0.07 |
|
2 |
0.03 |
0.04 |
0,05 |
|
1 |
Only day and night duty lighting (<6 cd/m2) |
||
Fig.1.2.
Annual hourly charts of the adaptation luminance L20 [cd/m2], the
traffic intensity ICAR [car/h], and the necessary luminous flux FNEED
[klm] for the threshold and the transition zones of the tunnel
I.4.
OPTIMIZATION OF ARTIFICIAL LIGHTING OF ROAD TUNNELS
The annual operating costs consist of the cost
of the consumed electricity, the price of lamp replacement during the year, the
labor costs associated with cleaning the lighting fittings, and amortization
deductions.
The lighting fittings in the threshold and transition zones are arranged
in circuits, and are powered from a central panel. Usually, the circuits are
controlled with circuit closers that provide a simple on/off mode (100% or 0%)
of the lighting fittings, depending on the access zone (adaptation) luminance L20
at the tunnel entrance. Modern lighting installations allow for smooth group
control of the luminous flux of the light sources by dimming the nominal
luminous flux of each of them. The problem of finding the optimal number of
circuits, as well as of how many of these circuits should be dimmable, can be
formulated as an optimization problem. The data consist of hourly values of the
luminous flux needed to produce the required luminance of the road surface at
the threshold and transition zones during the year. These values are calculated
based on the characteristics of the particular tunnel, on annual hourly charts
of the access zone luminance L20, and on the traffic intensity ICAR.
From the hourly values of the luminous flux, the hourly values of the necessary
electrical power can be computed. The latter enter into the calculation of the
cost of electricity. Since the ratio of the flux to the necessary power (the
so-called yield) decreases as a
larger percentage of the nominal flux of the lighting fitting is dimmed (see
Fig.1.3), the most cost-efficient combination of dimmable and non-dimmable
circuits in the lighting installation is not immediately obvious. Every
combination of dimmable and non-dimmable circuits contributes to the overall
operating costs both in terms of different setup prices, and in terms of
consumed electricity that depends on the particular dimming schedule for each
hour during the year.
Fig.1.3.
Characteristics of a high-pressure sodium lamp
FL
= 1 corresponds to luminous flux of the lamp equal to 48000 lm; PL = 1 - to
lamp power of 400 W; FL/PL = 1 – to
flux-yield of 120 lm/W; UL = 1 – to lamp
voltage of 105 V; I = 1 – to current through the lamp equal to 4,3 A
The objective of the
optimization problem is to determine the optimal total number of circuits m, and of those, the number of dimmable
circuits (m-n), so that the operating
annual expenses for the lighting installation are minimal. The hourly values of
the luminous flux necessary for ensuring safe transition through the tunnel are
known (see Fig.1.2). The problem data include also the costs of raw materials,
equipment, and labor during the construction and maintenance of the lighting
installation, as well as the prices of electricity for the three zones of a
24-hour period (night, day, and peak).
The exact expression for the objective function is:
(3) Z = CEN + CMAINT + CA
= min,
where:
CEN is the annual cost of electricity for
lighting, determined from the calculated chart of necessary electric power
given a particular combination of working dimmed and non-dimmed circuits for
every hour of the year;
CMAINT is the cost of maintenance of the lighting
installation (lamp replacement, labor costs, etc.);
CA is the annual payments, including interest,
on a loan taken out in order to build the lighting installation. If a loan has
not been taken out, the interest is assumed to be equal to the interest paid on
money deposited in a bank. This accounts for the fact that the money should not
lose its value by investing it in the construction of the lighting installation
as opposed to holding it in a bank.
I.4.1. Calculation
of the annual cost of electricity for lighting
The cost of
electricity CEN is
determined from the values PNEED[i] [kWh], the power needed to sustain the necessary
luminous flux FNEED[i] [klm]
for every hour i during the year (FNEED[i] was illustrated in Fig. 2). The necessary
power is computed as:
(4) 
.
The first term contains a summation of the
power consumed by all non-dimmable circuits, while the second term contains a
summation over all dimmable circuits. YIELD,
the yield of the non-dimmed circuit, is the nominal lighting yield FLnom/PLnom
from Fig.1.3. YIELDDIM[j], the yield of the jth dimmable circuit, depends on the degree of dimming of j. It equals FL/PL, with FL varying
between 10% and 100%.
The price of electricity, e[i], EUR/kWh, is different depending on the hour zone
within a 24-hour period (night, day or peak), in which the particular hour
falls. Choosing a time interval Δt equal to 1 hour, the annual cost of electricity can be written as
(5) 
.
I.4.2. Calculation of the
annual cost of maintenance of the lighting installation
The cost of maintenance
consists of expenses for lamp replacement, as well as expenses for cleaning the
optical systems of the lighting fittings. It can be computed from the
expression:
(6) 
,
where the notation is as follows: eL – price of a single lamp, eL_CH
– cost of lamp replacement and cleaning the optical system of a lighting
fitting, NL – total number
of the lamps in a circuit, TDIM
(respectively, TNODIM) – annual use of a dimmable
(respectively, non-dimmable) circuit in hours, TL_LIFE – nominal life of the lamps used in hours.
I.4.3. Calculation of the
annual payments on a loan
Today’s
cost of a loan of size K, paid over T equally long periods, and charging
interest rate of r per period, can be
computed to be (see the concept of “present value” in [24]):
(7) 
.
In our case, K is the amount of capital investment necessary for the
construction of the lighting installation. We assume that each time period is a
year. r is therefore the annual
interest rate. K is calculated from:
(8) 
,
where:
KLUMIN
is the cost of purchase of luminaries;
KLINE
is the cost of building the
circuits;
KDIM_APAR is the cost of purchase and installation of
dimmable circuit apparatus;
KNODIM_APAR is the cost of purchase and installation of
non-dimmable circuit apparatus.
The components of the cost of capital investment themselves are computed
from the following formulas:
(9) 
,
where FNEED_MAX
[klm] is the maximum value of necessary luminous
flux in the annual hourly chart, eLUMIN [EUR] is the price of a single luminary, FLUMINARY [klm] is the luminous flux of the luminary;
(10) 
,
where m is the number of circuits, eLINE_COST [EUR/m] is the price per meter of a circuit
line (the price depends on the number of circuits m, because the cross-section of the line has to be different for
different m), length_line is the length of the circuit lines in meters
(it equals the length of the threshold and transition zones);
(11) 
,
where eDIM_APAR_COST [EUR] is the cost of a single dimmable circuit apparatus (it is different for different total number of
circuits m because of the different
power it controls);
(12) 
,
where eDIM_APAR_COST [EUR] is the cost of a single apparatus for control of non-dimmable
circuits (automatic fuse and
circuit closer). Again, this cost
depends on the number of circuits m, because the apparatus has to control
different power.
It
is assumed that in terms of present value, the first two components of the
annual operating costs (CEN and CMAINT)
remain the same over the years. This assumption can be made, because the annual
inflation is approximately equal to the base interest rate on bank deposits.
The present value calculation is therefore applied only to the costs associated
with repayment of the loan, but not to the costs associated with increase in
the prices of lamps, labor, and electricity.
The optimization problem is solved for an
example of an annual hourly chart of the adaptation luminance L20,
taken from real annual measurements of the natural luminance for the region of
the city of Sofia [7] and from measurement data of the hourly variation of the
luminance L20, obtained with a specialized luminance-meter on a
sunny day at the entrance of a tunnel on the “Hemus” highway that faces
southwest. Based on data for the average monthly traffic intensity on the
“Hemus” highway, and on actually recorded hourly traffic over a week, an
example annual hourly chart of the traffic intensity ICAR is put
together. The traffic through the tunnel in consideration is one-way, with a
speed limit of 80 km/h, and only motor
vehicles are allowed.
Using the algorithm described in [21], a C++
program was written to compute the annual costs by enumeration. The goal was to
observe how the three types of costs change for each configuration. We consider
discrete levels of dimming for the lamps (multiples of 10%), up to 9 circuits,
and up to 4 dimmable circuits. We compute all possible outcomes for the present
costs of equipment, labor, and electricity in