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Topic Title: 2 phase sports flood lighting
Topic Summary: Does anyone have experience with this system?
Created On: 24 February 2010 11:28 AM
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 24 February 2010 11:28 AM
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jeepster

Posts: 11
Joined: 02 February 2006

I am looking at a problem with an installation on a large sports field with 12 x 20 meter columns, the columns have 4 or 5 floodlights at 2200 watts each.
The system is wired in what looks like a 2 phase system - each 4 core armoured cable supplies 2 x circuits of 2 phases and no neutral? This gives 400 volts to the lamps?
This is a system I am not familiar with and was wondering if anyone can offer any more information on how it works and the pros and cons of this system? Would sizing cables be any different to a single or 3 phase system?
 24 February 2010 12:44 PM
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Inrush

Posts: 707
Joined: 19 December 2007

While I cannot comment on the lighting aspect of the design, you can essentially treat each pair of light fittings as a single phase circuit but supplied with 400 Volts.

This type of connection has the advantage of a reduced design current and associated Voltage drop in the final circuit (due to the increased supply Voltage).

If the total load (on the suppying DB) is unbalanced you effectively have an unbalanced delta connected load, and your imbalance will flow in the phases not the neutral, therefore the total loading on the board supplying the columns will need to be calculated using phasor addition.

Edited: 24 February 2010 at 12:56 PM by Inrush
 24 February 2010 12:53 PM
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broadgage

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Larger sizes of discharge lamp are often designed for use on 400/415 volt supplies, with suitable control gear.
In most cases the lamps are different from those intended for 230/240 volt supplies.
If any re-lamping is required take great care that the correct lamps are used.
The higher voltage lamps are normally more efficient, and as pointed out above, the higher supply voltage reduces losses in the sub circuit cables.
The voltage drop, in volts for a given size cable and current will be exactly the same on 230 volts or on 400, but it will be a smaller percentage of the higher supply voltage.
 24 February 2010 01:05 PM
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jeepster

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Joined: 02 February 2006

Thanks to Inrush for your reply,

The system was installed in 1995 and we are looking at the electrical test results following a periodic inspection and test.

The armoured cable has failed its Zs test. ( double the permissable)

Some of the armoured cables ( 4 core) are 280 meters long (from supply pillar to column) but only 6mm csa. The measured current on a phase is 25 amps.If this was a single or 3 phase system the cables would be undersized. You suggest that an advantage of this system is reduced design current and associated voltage drop. Would this 6mm be sufficient? It seems well undersized to me.
 24 February 2010 01:22 PM
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OMS

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Some of the armoured cables ( 4 core) are 280 meters long (from supply pillar to column) but only 6mm csa. The measured current on a phase is 25 amps.If this was a single or 3 phase system the cables would be undersized.


How do you determine that - a 6.0mm armoured buried direct will take a good 35A per phase

I presume that the cable is three core and presents at each column where any pair of phases are selected to supply the individual ballast for each lamp - perhaps one cable down either side of the field feeding 6 columns on each side. If so this sounds a fairly typical high mast installation - cable may be a tad mean in terms of sizing (personally I would have used a 16mm for robustness and SWA CSA but that is conservative).

Regards

OMS

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Failure is always an option
 24 February 2010 01:38 PM
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jeepster

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Look at the volt drop
 24 February 2010 02:03 PM
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OMS

Posts: 19668
Joined: 23 March 2004

Originally posted by: jeepster

Look at the volt drop



But the load isn't all "lumped" at the end of the run is it - essentially you have a progressive voltage drop - the load diminishes as the cable length increases so applying 25A at the end of 280m is wholly inadequate as a means of determining volt drop.

Add to that the fact the cable is not fully loaded and operating in a ground temperature of well under 30C and it's quite likely that the volt drop isn't actually a problem

Although my comments above relate to a specific wiring arrangement - I don't know how this is wired

Regards

OMS

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Failure is always an option
 24 February 2010 05:04 PM
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GJH

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Joined: 24 January 2008

I have worked on this type of lighting, we changed all of the control gear which was in a pillar at the bottom of the column as it was all old and falling apart. And even doing this some of the lights didnt work.

We changed the lamps (2KW each) and on close inspection the internal wiring of the fittings had all burned up! It had gradually broken doen the insulation and was burning off the lugs.

These fittings were 8 years old. In the end the manufacturer had advised we replace all the fittings with new ones as we had tried to rewire them with silicon heat resistant cable, this lasted about a day.

I have a magnetic thermometer which i used on the fitting, the outside temp was 0 degrees C and after 25mins of being turned off the fitting was still 100 degrees! Thats how hot they get!

The heat had caused all of the faults. The company i was working for replaced all of the fittings i think, but it cost thousands!!
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