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ilp archive : journals
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public lighting no. 55 vol. 14
April-June 1949
- Editorial p53
- Major Changes p53
- Restrictions on street, sign and window display lighting was lifted on April 2nd. Thousands of
citizens flocked to the Metropolis to witness the great "switching on" - there were so many that
congestion was caused at key points. The crowds massed in the streets to see the advertisement sign lighting
and shop window lighting - improved street lighting added to the general cheerfulness and convenience of
the crowds. In some cases full advantage has been taken to restore the street lighting - however much
pre-war lighting was quite inefficient, there was a lack of equipment due to the ravages of war and disuse
over the years, and there were other problems due to local vandalism and the difficulty of obtaining
suitable material for replacement. Some local authorities were hesitant to act in the absence of official
notificaiton with reports only appearing the press.
- The Gas Industry was nationalised on May 2nd and is now grouped under its central authority and the various area boards.
- RoSPA recently published statistics showing the number of accidents and fatalities on the roads both by
day and night - which make despondent reading. A special week, backed by the MoT, was devoted to this special cause.
- Lighting: Anti-Social Behaviour, Lighting: ARP, Lighting: Safety, Statistics: Accident Data
- Annual Conference - Llandudno p53
- The programme has now been published.
- APLE: Conference
- Annual Conference - Llandudno p54
- Description of Llandudno.
- APLE: Conference
- Annual Conference - Column and Lantern Demonstration p54
- The Llandudno authorities have given the Association permission to you the grass decorative plots
running down the centre of the promenade and the columns and lanterns to be seen will cover both Group A
and Group B, gas and electricity. It is also hoped to show bollards, road signs, motor tower wagons,
ladders and syphon emptying outfits etc. Arrangements are in hand for the manufacturers of accessories,
such as clock controllers etc., to show some of their products.
- It has not been possible to arrange an indoor exhibition nor to stage a "live" outdoor demonstration.
So the Conference sessions will be devoted to manufacturers on September 14th.
- APLE: Conference
- Annual Conference - Programme p55
- Program for the Conference
- APLE: Conference
- Road Accident Statistics 1937 - 1947 p56
- Extract from Road Accident Bulletin No. 24 by RoSPA.
- Statistics: Accident Data
- Street-Lighting Installation, Shipley p57
- Details of installation in Shipley.
- Lighting: Installations
- Rare Honour for Mr. Howard Long p57
- The Illuminating Engineering Society has elected Mr. Howard Long, M.I.E.E., F.I.E.S.
an Honorary Member. Only twice before in the history of the Society has this honour been conferred. He
was also an original Association of the APLE.
- Lighting: Personnel
- Members of Council - Annual Election p57
- A brief description of the present constitution of the Council.
- APLE: Organisation
- Laboratory Of Light - The Civic Services From Within p58
- Sheffield have 26,000 street lamps in 670 miles of streets.
- Scientific Certainty
- The efficient working of this network is the responsibility of the Lighting Department. In Matthew Street,
the Department maintains an unusual laboratory. In a black painted room, street lighting experts ensure by scientific tests that
only the finest lighting equipment is used. The laboratory staff have also designed and built test apparatus. Before equipment
can be tested, the fuel source (gas or electricity) must be of a known standard. The first duty of the laboratory
is to check the quality and control the pressure of gas, and the voltage of electricity.
- A Shattering Test
- Samples from each batch of gas mantles first undergo the "shock test" on a machine which subjects them to 2000 vibrations
whilst they are illuminated. Any weakness in design or construction is exposed. Those which survive this test are then checked
for light output. The effectiveness of this examination is shown by the fact that Sheffield uses only 1½ mantles
a year for each burner nozzle compared with between two and six mantles in other areas. With mantle consumption in Sheffield
of 40,000 a year, this economy becomes appreciable.
- The voltage of electricity supplied for street lighting purposes may vary by as much as 6%, the statutory
maximum tolerance. A 1% voltage drop causes a 5% loss of light output. This renders the mains supply unsuitable for testing
electric lamps so, for testing purposes, the laboratory generates its own electricity.
- Up To Standard
- Over 21,000 100W lamps and over 5000 500W lamps were used for street lighting. Sample specimens of the 100W lamps
are tested for light output and length of life. Every 500W lamp is tested before use against a "standard" lamp of given
light output, the original "standard" lamp being supplied by the the National Physical Laboratory.
- Defeating Dirt
- In each month of 1947, an average of 40.49 tons of solid matter was deposited on each square mile on an industrial
district, compared with only 11.55 tons deposited on a residential district. This presents a problem with the cleaning
and maintenance of 2,500 refractor units in use on the main traffic routes. Regular tests are now made on glasses from
different districts and at different seasons of the year, and it has been found that the light absorption of glasses
in operation varies from 2% up to much as 45% in 15 days. The deposit alters according to season and district; it is
increased by fog and winter weather. In practice it has been found impracticable to clear refractor units efficiently
while they are in position on the 25ft. standards. Instead 150 units are replaced each day and brought into the department
for cleaning and maintenance.
- Careful Control
- Street lamps are normally controlled by clockwork time switches or relays, either individually or in groups. This
system is not regarded as sufficiently flexible for traffic bollards, and these are therefore controlled by light-sensitive
photo-electric cells and relays, which react automatically to daylight and darkness. The accuracy of thousands of clockwork
mechanisms and much delicate electro-magnetic control equipment is a further responsibility of the testing laboratory.
- Lighting: Control, Lighting: Maintenance, Lighting: Statistics
- Lancashire Section p59
- Report from a meeting in Bury where 70 delegates attended. Since 1920, when street lighting more or less
consisted of haphazard pools of light, traffic conditions had altered considerably, but there had been
very little change in street lighting. Statistics showed that good lighting paid. The cost of road accidents
far exceeded the cost of good lighting. Petty crimes, which were best done in the dark, could also be prevented
by good street lighting.
- A wide variety of subjects were briefly discussed at the "Open Forum".
- Members were taken on a tour of the Lighting Department's workshops and of the street lighting in Bury.
- APLE: Sections
- Scottish Section - Spring Meeting p60
- The papers "Control of Electric Street Lighting Installations - Practical Consideration" by A. J. Ogle, B.Sc., A.M.I.E.E., F.I.E.S. and
"Stairlighting" by J. M. Ward, W. D. Brassington and C. J. Chicholm were read and discussed. The
attendance was over 60.
- Since the Formation Meeting held on May 28th, 1948, the Scottish Section have enjoyed a successful and busy year.
The Inaugural Meeting was held in Dundee on 5th November 1948. In addition, the Committee have held five meetings during
the year.
- APLE: Sections
- Control Of Electric Street Lighting Installations: Practical Considerations by A. J. Ogle, B.Sc., A.M.I.E.E., F.I.E.S. p61
- Paper given to the Scottish Section.
- Lamps are to be lighted and extinguished, and the means of achieving this range between the individual control of a
single street lamp by its own controller: hand switch, clock, synchronous motor switch or light actuated relay - to the
control from one point only of every street lamp connected to a large electricity supply system.
- Between these limits lies a whole gamut of control arrangements embracing small and large groups of street lamps controlled
by master time switches, cascade relays or simple manual push button. These may be used in connection with switch cores integral
with street mains or with overhead switch wires (making use of a common neutral in return) with pilot conductors incorporated
in the general distribution system actuating contactors to operate groups of lamps or with public lighting conductors
to which individual lamps or groups of lamps are exclusively connected. Also included are those methods whereby group
control is effected by superimposing parasitic currents (DC or high frequency AC) over an electricty distribution network
from a central point.
- Hand Control
- Manual control of street lamps is essentially archaic and uneconomical and it does not merit serious consideration, although
it does possess the advantages accompanying a daily patrol such as the speedy and regular reporting of lamp failures or damaged
equipment.
- Time Switches
- These are the most popular methods of automatically controlling lamps, either individually or in groups:
- Hand Wound: These are actuated by a spring-wound clockwork lever movement which requires winding at intervals for 15 days. Originally, the switch
contacts were actuated by a mechanism known as a "hand-set" dial in which the times of lighting and extinguishing depend upon the
positions of striking levers or arms relative to a dial geared to make one revolution in 24 hours. The striking arms,
"in" and "out" are manually set relative to the dial to correspond to the required times of lighting and extinguishing.
These are changed according to the gradually changing seasons of the year. The next development was the "solar" dial to
replace the hand-set dial. This consists of a train of gears working in conjunction with a specially shaped cam or link motion
which is astronomically compensated and automatically compensated and automatically positions the striking arms each day
so that the times of lighting and extinguishing are related to thechanging times of dusk and dawn throughout the year. In
adddition to the automatically moving dusk and dawn arms, the dial may be fitted with fixed arms to increase the number of
switching operations at selected times. The solar dial can be designed for a schedule of operations to suit particular
geographical regions according to their latitude.
- Electrically Wound: An electric motor winds the spring of a clock movement. There are two types: (i) Continuously
wound movement, escapement controlled. The spring is capable of operating the switch alone of 36 hours in the case of an
interruption of supply. Certain switches have an additional fitment which corrects the escapement time to frequency time; (ii)
Periodically wound movement, escapement controlled. Once every eight hours the electric motor winds up the spring, which
has a 36 hour reserve to maintain the clock during interruption of supply. These are comparatively expensive and are therefore
normally only considered for group control.
- Synchronous Motor Driven: These switches provide a very convenient and reliable method of control and when combined
with a solar dial, are fully automatic. They have the disadvantage that each switch much be reset after an interruption of
the electricity supply.
- General Design: Should have a sufficient degree of accessibility to permit ample facility for periodic maintenance and replacement
worn parts. The setting of the time switch into commission and the resetting of the dial should be a simple operation as it is
desirable from the viewpoint of the economy that this should be done by semi-skilled labour. A short-circuiting button for testing
the lamp during the hours of daylight is a desirable feature.
- Maintenance: In-Situ: Semi-skilled labour is inspected at intervals to check for timekeeping. Skilled labour,
of the electrician type, should be available to carry out installation and minor adjustments to pass back to headquarters accurate reports
of faults.
- Maintenance: Periodic: If number of switches warrants, one or more skilled clock repairers, specially trained in this class of work,
should be engaged to carry out general repairs and maintenance. It is generally considered advisable to bring the time switch in
for overhaul and reconditioning at regular intervals to lengthen the life of the switch and to forestall breakdowns or failures.
The recommended period for switch changing is: For escapement type movements: 3 to 4 years; For synchronous motor type: 6 to 7 years.
- Timekeeping
- Escapement type movements should have an initial accuracy of timekeeping within 15 minutes per month.
- Life
- A good time switch should have a normal expectation of life of 30 years. It has been contended sometimes that, in view of the
comparatively low cost of a 10-amp synchronous motor switch, it may be more economical to run the switch for 10 or 15 years entirely
without maintenance and then discard it.
- Records
- It is very necessary to set up a system of accurate records such as: time switch, type of case, location,
date of purchase, date of installation, burning period, purchase price etc.
- Sources of Manufacture
- The ideal condition would be to limit the time switches to one manufacturer. This would permit the opportunity
to standardise on types, promote ease of maintenance and facilitate the training of staffs, skilled and semi-skilled.
- Time Switch Cases
- There are two main types of cases: (1) The type referred to as "standard" which is housed in the base of the
lamp column or is not directly exposed to the elements. This type of case should afford good general protection
from dirt, dampness, etc; (2) The "weather-proof" type which is fitted in positions where it is directly
exposed to the weather. This type usually necessitates a variety of sizes and designs depending upon the arrangement
of the wiring system of which it forms a part and upon the auxiliary equipment to be housed.
- Location of Switch
- Whether it is housed in the base of a lamp column - pole or wall-mounted - in special cupboard or in a
substation, consideration should be given to accessibility, ease of maintenance and replacement, freedom from
possible interference and the safety of the public.
- Group Control by Switch Core or Switch Wire
- An additional core is incorporated in the supply main, and the twin service to each lamp is connected to this
core and the normal neutral core which is used as a return lead. At the point of control the switch core is
connected to one phase of the system through either a handswitch or through an electrically operated time switch.
If more than one lighting or extinguishing time is required for the lamps, further switch cores will be required.
The switch core is the more desirable and more economical method of controlling lamps but it must be planned
in advance and is therefore limited to new development. Cables containing a switch core or cores are not readily
obtainable and delivery may be greatly delayed. This limitation does not exist in the case of overhead distribution
networks
- Cables Used Exclusively for Public Lamps
- It may sometimes be necessary to provide a special system of mains to supply the whole or a large part of
a public lighting instasllation e.g. where discharge lamps are required on a DC network or no general distribution
mains exist. When a public lighting cable can be laid at the same time and in the same trench as a distribution
main, the cost of the former is obviously very greatly reduced. When a new underground distributor is to be laid
the comparative cost of individual time switches as against switch core or public lighting cable depends upon
the spacing of the lighting units.
- Pilot Cable
- This is a cable or small section included in the general distribution system. Unlike the switch core or
switch wire it does not carry the current consumed by the lamps but is used to operate a contactor which
controls the conductors to which groups of lamps are connected. This method is especially useful for balancing
load on a three-phase four-wire distribution system.
- Relay Control - Cascade System
- A number of special lighting conductors arranged in separate circuits, each with a relay and a contactor
to control it, so that the contactor for each circuit is operated when the preceeding circuit becomes alive.
Each circuit is fed from a separate source of supply. In this way, very long stretches of lighting extending
over several different supply networks may be controlled from one point by a small time switch or push button.
- Remote Controls By Injection Into Distribution Networks
- Specially selected impulses are superimposed on the normal electricity supply network and are received by
suitable relays which operate indiviudal lamps or groups of lamps. The method which provides facilities for
transmitting the the greatest number of signals with the minimum amount of equipment is to be preferred.
- The location of the signal transmitters is an important consideration. They are: (a) A centralised transmitter
to serve a whole area i.e. a whole city of the whole of a Suppy Undertaking's distribution system; (b) Partly centralised
transmitters located as suitable points throughotu the supply system ("dispersed" centralised control), each of
these transmitters serving a large, but limited area; (c) Local transmitters installed on L.V. networks, each
transmitter serving one L.V. network only.
- These methods may be divided into two main groups according to their principle of operation:
(1) High frequency A.C. impulses over main distribution networks; (B) D.C. injection over low-voltage A.C.,
each network, if necessary, being controlled from a central point by pilot wires.
- High Frequency Impulses over Main Distribution Networks
- Oscillations at frequencies in the order of 10,000 to 12,000 cycles per second are injected into the main
supply network, the actuating receivers being tuned to respond to the specified frequency of the impulse and
the duration of its imposition. Added selectivitiy may be obtained by sending out the impulses in a
variety of chosen rhythms and by this means false operation by stray currents may be avoided. These systems may
be used locally on low-voltage distribution networks or, as is more usual, by injecting the signal into the
high-voltage distribution system. Every piece of the current-consuming apparatus absorbs a portion of the signal
current, and thus to provide a signal strength of four volts at all parts of the system, many kilowatts of
power may be required. The alternators employed are capable of generating high frequency currents with powers
of from 10kVA to 100kVA.
- Fully centralised systems have been installed with marked success in an apperciable number of cities.
It should be borne in mind that the success of these systems depends largely on the nature of the local
electricity supply system. Close consideration must be given to local distribution condition before
mkaing use of any of these methods on a large supply system, as their efficency and operation is greatly
affected by high voltatge switching and load changes. Consideration should also be given to the extent to
which the high-frequency impulse may spill over from one network to another. Most maufacturers of this
type of equipment, however, claim to have overcome this difficulty. The capital cost of such a fully
centralised system is apt to be high.
- DC Injection over Low-Voltage Networks
- DC Bias signals are injected into the low-voltage network at each distribution substation by means of biasing
equipment connected between the star point of the distribution transformer and the network neutral. As DC signals
cannot pass through transformers, biasing equipment is needed in every substation serving the area to be controlled.
The method is simple in principle and the apparatus required is robust in construction, easily installed and
contains no delicate mechanism required skilled equipment.
- Equipment required: At the Substation: (1) A heavy duty, car type 6-volt battery to provide the DC signal
current; (2) A biasing panel to make the connection to the low-voltage network; (3) A lighting control
unit connected to time switches. The operation of the time switch starts the lighting control unit, which
operates the biasing panel so that it sends out the DC signal of the required polarity and duration to operate
the lamps as desired.
- Equipment required: At The Lamp: This consists of a specially designed transformer type of choke so arranged
that, when connected across the supply mains, the voltage induced in the secondary winding is equal and opposite
to the primary voltage so that only the DC signal current is left to operate a simple polarised relay which
forms part of the unit. The relay opens or closes switching contacts accordingly to the direction of the
signal current. Where all lamps are to be switched off and on together the two signals of opposite polarity
are sent out i.e. two seconds positive to light the lamps and two seconds negative to extinguish them. These
signals easily operate the simple oplarised relays. Units of this type are termed "short pulse units."
When lamps are to be switched off in two groups, use is made of a similar unit to the short pulse unit,
but with the relay actuating the swtich contacts through a thermal delay strip so that a long impulse of
20 seconds is needed to switch the lamps off. These are called "long pulse units." Long pulse units are fitted
to lamps to be extinguished as dawn and short pulse units to lamps to be extinguished earlier at midnight.
When the two seconds positive bias is sent out at dusk, all the units, both long and short pulse will switch
on. When the two second negative bias impulse is set out, only the short pulse units will switch off. At
dawn a twenty seconds negative impulse is sent out which switches off the long pulse units.
- The Central Control Point (if required)
- This consists of a power supply unit to 50V DC from the 240V AC supply, a motor for timing the signals
and a relay for connecting the 50V DC supply to pilot lines connecting the substrations to the central control
point. Time switches are used to operate the master controller. Manual push-buttons are provided to give
emergency hand control. The lighting control unit in the substation is replaced by a remote control unit.
This is a polarised relay which is connected to the pilot lines and responds to the 50V impulses sent out
by the master controller, and which, in turn, operates the biasing panel. The master controlled is suitable
for operating up to 25 substations in parallel. In the normal position of the biasing panel, a short circuit
is maintained between the star point of the transformer and the network neutral. When the switch is moved to
the 'on' position, the 6V battery sends out a positive impulse over the phase wires, the neutral being negative.
When the switch is in the 'off' position, the direction of the impulse current is removed.
- Battery
- Trickle charging equipment is incorporated in the biasing panel.
- Street Lamp Units
- The "long pulse" relays require more maintenace than the "short pulse" type on account of the addition
of the thermal delay element. If a few "half night" lamps are required theyse may, with economy, be
controlled by individual time switches. The relays are very reliable. In an installation where more than
5000 are in use, the average number requiring adjustment or repair does not exceed 100 per annum. Periodic
overhaul, as in the case of time switches, is not necessary.
- Pilots
- Pilot lines are necessary if control of the indiviudal low-voltage networks is to be from a central point.
If no such pilots are available, private lines, may be retned from the Post Office. The rental charge is £8
per mile. This is not free from troubles. The pilots are energised from the central point at 50V DC
during the transmission of signals. Where bare GPO lines are used, it may happen, due to the fault or a broken
wire, that the pilot wires become energised by the GPO battery, thus operating the biasing panel and switching
on the lamps. It may even burn out solenoid coils on the panel. Mal-operation of biasing panels may also take
place when GPO testers test out pairs in their underground cabels and connect their testing battery across
a pilot pair.
- Comparative Costs
- Biasing equipment at each substation is £110 and assuming street lamp units to average £3
each and the cost of a 10A synchronous motor time switch is £5, then for 55 switching poitns on any
one low-voltage network the capital cost is equial. With any number of switching points greater than this on
a network, a saving of £2 per point is acheived, but with any less the advantage in cost lies with the
time switch. This does not take into consideration the fact that maintenance of the relay units cost
considerably less than with time switches, not to mention the cost of labour expended in resetting a
large number of indiviudal time switches after an interruption of the electricity supply.
- Conclusion
- The problem resolves itself into an economic one. Before embarking on a changeover to such a system
the public lighting engineer will do well to carefull consider the following:
- 1. Capital expenditure on control plant.
- 2. What part, if any, can be allocated to load control other than public lighting.
- 3. Estimated running cost per annum including amortisation of capital.
- 4. Is it desirable to have all one's eggs in one basket?
- 5. Comparison with existing methods of control in effectiveness and cost.
- 6. To what extend can existing methods such as pilot wires, public lighting conductors, cascade switching
can be integrated with a CMS and to what extent is it desirable.
- 7. Can a fairly reliable estimate be made of the increase in the number of electric lamps?
- There is much to be said in favour of "dispersed" centralised control and the restriction of the centralised
control to low-voltage networks, several of which can be grouped for operation into urban areas. Each group
may be controlled from a central point by the use of the telephone or pilot wires usually provided
between substations or by private lines rented from the GPO.
- From an installation and maintenance point of view there is a strong case for controlling lamps in
groups by the simplest of all means - a straightforward service from a low-voltage main including the provision
of a public lighting core or cores, or provision for a switch wire when an overhead low-voltage network is
erected near a public highway.
- It is impossible to avoid speculations which arise from the nationalisation of the electricity
supply undertakings. It is interesting to ask ourselves to what extent are lighting authorities prepared to
modify their local, sometimes parochial, ideas to conform with a national lighting time-table applied over
a large area and even to what extent are lighting authorities prepared to accept a lighting and extinguishing
service provided by the Electricity Board.
- Lighting: Control
- Inauguration of Sodium Street Lighting and Rythmatic Control at Seaview Road Sub-station, Wallasey p66
- Details of installation at Wallasey
- Lighting: Installations
- The Structure of the Gas Industry under the Gas Act, 1948 by J. R. W. Alexander, M.A., LL.B., F.C.I.S. p67
- Description of the new nationalised Gas Industry.
- Other
- Adverts:
Poles Ltd,
Londex Ltd,
Stanton Ironworks Co., Ltd,
Siemens Electric Lamps And Supplies Ltd.,
Imperial Chemical Industries Ltd.,
Broads Manufacturing Co. Ltd.,
Automatic Telephone And Electrical Co., Ltd.,
Holophane Ltd.,
Willey And Co. Ltd.,
Wardle Engineering Co., Ltd.,
Stewarts And Lloyds Co., Ltd.,
REVO Electric Co., Ltd.,
British Electrical Development Association, Inc,
The British Thomson-Houston Co. Ltd.,
Concrete Utilities Co., Ltd.,
Brighton Lighting & Electrical Engineering Co., Ltd.,
Ford Motor Company Ltd.,
Triplex Safety Glass Co., Ltd.,
Standard Telephones And Cables Ltd.,
Metropolitan Gas Meters Ltd.,
Eagle Engineering Co., Ltd.,
Engineering And Lighting Equipment Co. Ltd.,
Vauxhall Motors Ltd.,
The Horstmann Gear Co., Ltd.,
Gowshall Ltd.,
James Keith And Blackman Co., Ltd.,
British, Foreign And Colonial Automatic Light Controlling Co., Ltd.,
Falk, Stadelmann Co., Ltd.,
William Sugg And Co., Ltd.,
Metropolitan Vickers Electrical Co. Ltd,
Sangamo Weston Ltd. and
The General Electric Co., Ltd.
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