Introducing ELV Equipment

Jag Morar BSc CEng MIET

TfL

Directorate of Traffic Operations

The views expressed in this presentation are not necessarily

those of TfL

Overview of Presentation:

• Electricity at Work Regulations – 1989

• IEE Regulations

• Standards for Controller and signalling

equipment

• ELV controllers

• Signalling Equipment

• Conclusions and sum-up

Electricity at Work Regulations 1989

Places duty upon us (Employers, Employees,

Designers, Manufacturers, Approval Authorities

and suppliers of Electrical equipment) to comply

with the regulations.

To this extent the most significant statement is in

Regulation 4 (1):

Regulation 4(1)

“All systems shall at all times be of such

construction as to prevent, so far as is

reasonably practicable, danger”

‘Danger’ means risk of death or personal injury through:

• Electric Shock, Fire or Explosion initiated by Electrical Energy

Regulation 4 refers to the Electrical System which means all

constituent parts of the electrical Installation and and covers

construction and maintenance

Related Regulations

4(1)

Systems Constructed to

prevent Danger

Reg 5 -

Strength and

capability

Reg 11 -

Excess currentReg 6 -

Environment

Reg 8 –

Earthing and

other

Precautions

Reg 7 -

Insulation

Reg 9 -

IntegrityReg 13 - Safe

WorkingReg 13 -

Isolation

Reg 10

Connections

Regulation 6

Requires that:

‘electrical equipment should be suitable for the

environment and conditions of use to which it may

reasonably foreseeably be exposed to such as:

• Mechanical damage

• Effects of weather and natural hazards

• Wet dirty, dusty or corrosive conditions

• Flammable or explosive substance such as dust vapour

or gases

to ensure that any danger which may arise from such

exposure will be prevented so far as is reasonably

practicable’

Duty Holder’s responsibility

The onus is on the specifier and managers (or duty holders in the organisation), who know the activities undertaken and the environment concerned, to select

the appropriate equipment

So is it now ‘Reasonably Practicable’ to specify ELV for the full system?

IEE Regulations – BS7671

These regulations assist us in specifying and developing

precautions that help us comply with the Requirements of

the Electricity at Work regulations. In particular Regulation

411-02 specifies how we can provide Protection Against

Electrical Shock by using SELV supplies.

BS 7671 defines the ELV supply as being less than 50V ac

or less than 120V ripple free DC. In the UK the ELV supply

for signalling equipment is generally 48v AC

SIGNALLING STANDARDS

• BS 7987 (2001) – Road Traffic Signal systems:

– Provides the Electro Technical specification for controllers

and signal heads. It therefore specifies the operating voltage

and currents and absolute voltage limits for signal ‘on and off’

conditions.

– ELV output voltages specified in section 5.1.2 are only

recommended voltages; therefore are not mandatory

– Recommended voltages are 40v, 50-0-50v and 55-0-55v AC

– The signal classification K is only in terms of current output

per signal drive

SIGNALLING STANDARDS

• TR2500 (Issue A) – Specification for Traffic Signal

controllers:

– Among other things, this specification defines the electrical

supply and safety requirements by identifying the applicable

classification from the Harmonized Document HD638 for

equipment to be used in UK

SIGNALLING STANDARDS

• TR2523 (Issue A) – Traffic Control Equipment Interfacing

Specification:

– Specifies signal output as mains Voltage for the normal RAG

signal heads

– Specifies mains supply for regulatory signs

– Specifies mains solar cell input

– Specifies an auto transformer capable of dimming outputs at

120, 140 and 160 Volts AC

– Specifies mains supply for auxiliary equipment such as OTUs,

OMUs etc.

– Only specifies 48v ELV supplies for nearside signals, tactile

units and demand indicators

SIGNALLING STANDARDS

• CLC/TS 50509 (Aug 2007) – Use of LED Signal

Heads in Road Traffic Signal Systems: – CENLEC document published on 28 Sep 2007

– It is still under development and currently only acts as

guidance for evolving LED signals

– It specifies operation of LED optical units at 40, 42, 48

and 230 volts AC at the input terminals

– It will be subject to a review within 3 years when it may

be withdrawn, or revised, or entered into the work

programme to be developed into a full standard.

– Comments should be sent to Technical committee,

EPL526, for Road Traffic signals

Why use 48V AC?

• It is as high as we could safely go to allow for volt drops

and also still keep within the ELV limit specified in the IEE

regs.

• This voltage has been the UK signalling industry norm for

some years

• AC (42V) is also the norm for ELV operation in Europe

ELV CONTROLLERS - Where are we now?

• PEEK – 48v AC – (PTC1/Trojan or EC2 (Dutch equivalent to PTC-1)

– The EC2 ELV (42V AC) controllers installed in

Netherlands drive ASTRIN compliant LED signals with a

power consumption of between 7 and 15W (in bright)

• Microsense – AC, 48V rms– Sentinel

• Siemens – Rectified AC, 48V rms. Negative wrt to

protective earth – ST900

Rectified 48v AC – negative wrt to 0v

Why use DC?

• DC Switching circuits are easier to control using devices

such as FETs with low series voltage drop when switched

on

• Lamp monitoring of all signals including nearside signals is

much simpler with DC

• 48v AC could still cause relatively high level of induced

voltages on adjacent cabling and therefore problems like

correspondence or conflict faults as we have seen in

London on some applications with nearside signals

• Largest supplier in UK has elected to go down this route

SIGNALLING EQUIPMENT

• TfL has evaluated the following LED signals:

– TechMiracle - 230v

– Gelcore - 230v

– PEEK - 230v and 12v DC

– Siemens - 230v

– Microsense - 48v

– Coeval - 12 to 15v

– Monitron – 48v

Signalling equipment is still generally designed to work at

mains voltage

NEW ELV SIGNALLING EQUIPMENT

• PEEK – currently in the final stages of releasing a new (CLS based) LED product for operation at both 230 and 48 volts AC

• Microsense – 3G LED , capable of operating at both 230 and 48 volts AC (15W bright, 4W dim)

• Siemens – 48v Helios CLS LED signals plus 48v regulatory signs (11w bright, 3w Dim – cf 28/11w for standard LED with lamp monitoring)

Advantages of using ELV controllers with

LED signals

• Power saving through the use of LED signals

• Cabling simplified because you do not need to allow for

separate LV cabling

• Full and safe ELV installation becomes practicable and a

real alternative

Cable Losses

• TS50509 specifies a maximum drop of 5%

• UK requirements in TS50509 allow us to cope

comfortably with voltage drops in both bright and

dimmed states

• Volt drops may become a problem but in most

cases should be overcome through a proper

electrical design and cabling

Volt drop at 70oC over 100m (x2)

1.125151.0

0.9121.0

0.75151.5

0.6121.5

Volt drop per

optic -V

Power

W

Cable size

mm2

Conclusions

1. ELV controllers in conjunction with low power LEDs

signals will finally enable suppliers, users and approvers

to specify, develop and construct traffic control systems

that prevent Danger to the public and maintenance

engineers

2. CENLEC standard TS50509 needs considerable work to be

done for it to be easily interpreted without ambiguity.

Major users, developers and in particular the statutory

approvers need to be fully involved in developing this

standard such that LED signal heads can be developed

and used confidently with any supplier’s ELV controller

Conclusions

3. Both HD638 and TR2500 need to be updated to

include ELV signalling equipment

4. Volt drops could become an important

consideration for sites with long cable runs.

Excessive volt drops could result in signals

working erratically but at majority of sites this

should not be a problem if we use very low

power (≈12W) LED signals

Conclusions

5. Siemens advise that technically the ST900 can be used with any signal that complies with CLC/TS 50509. However, until this spec is formally ratified as an EN standard, the responsibility for the safe performance of the system as a whole would need to be agreed

6. The current status of the market is such that ELV controller can only be used confidently with the supplier’s own ELV signals because the lamp monitoring cannot be guaranteed when operated with other supplier’s signals

Finally

• Standardisation of ELV LED signals and

controllers should be a major concern for the

Traffic Management Authorities

• Without standardisation, the larger authorities

such as TfL, and maintainers will need to stock a

large inventory of parts

• Without standardisation, Authorities will

potentially be locked into buying controllers and

signals from one supplier

Final thought

ELV signals may well be the traffic industry’s

answer to the recent government announcement

to replace all conventional lamps with eco- bulbs

Thank you