Voltage drop Solution ?

Tony S

Senior Member
I’ve just put a similar supply in, single phase 25kVA over 4000Ft. The source was 433V stepped up to 3.3kV, a 25mm² 3c SWA cable and then stepped down to 240V. Volt drop at FLC 0.55%
The savings on cable and cable laying more than made up for the cost of the transformers.

25mm² = 2AWG
 

kwired

Electron manager
Location
NE Nebraska
I’ve just put a similar supply in, single phase 25kVA over 4000Ft. The source was 433V stepped up to 3.3kV, a 25mm² 3c SWA cable and then stepped down to 240V. Volt drop at FLC 0.55%
The savings on cable and cable laying more than made up for the cost of the transformers.

25mm² = 2AWG
@ 4000 feet it very well may be the better method cost wise. Might not be at only 500 feet though. Plus you had a different voltage at the end then what you started with so some transformation was going to happen anyway, though you probably had 240 available at the supply end.
 

Tony S

Senior Member
230,240,250V in the UK is a bit of a sore point, all I’ll say is the EU harmonised voltage is baloney, it’s normally 245V.

Supply end is a grain drier with two 1000kVA transformers plus a 1000kVA methane powered generator all at 433/250V 3Ph. Most of the year they export to the grid.

The boss didn’t want to see the plant from his new house nor did he want the OH line from the DNO (PoCo). 25kVA is more than enough for a modern house, the last thing we need in the UK is air conditioning.

By going up in voltage we saved 4.5 tons of cable, cut the number of joints from five to just one, installation was easier. The only thing I got moaned at for was the 75 tons of sand to bed the cable in the trench!
 

powerplay

Senior Member
500'
95 A at 240
250 Al mcm
4% drop

what load profile
continuous?
what % motors?
how sensitive to drop, rated for 220?
what is the actual source v > 240? Often is
etc
- Home and greenhouse with Ballasts
- pretty continuous.
- negligible Motors I believe outside A/C
- Ballasts I assume drop lights out with Voltage Drop
- I believe it is 240volt
 

powerplay

Senior Member
Agree
Need load details

also most 240 stuff will run fine at 220 and 120 at 110
Factor in likely closer to 245-250 than 240 and even better

how stiff is the supply
if the service is 100 kva and long load 20 kva not bad
if service is 50 may be an issue

I haven't seen the Supply yet... Heard it was a Pole Mounted Transformer and wonder if it is an 25KVA. Service of 50KVA would be an issue for 20KVA load?
 

Ingenieur

Senior Member
Location
Earth
I haven't seen the Supply yet... Heard it was a Pole Mounted Transformer and wonder if it is an 25KVA. Service of 50KVA would be an issue for 20KVA load?
hard to say
it was just to illustrate the smaller the motor/service ratio the less droop upon starting

I would leave as is
explain the options to the owner
be forthright
doesn't matter now or later, cost should be comparable
run for a while and see if you have issues
if so, address them

93 A connected
but if a residence and greenhouse factored probably much lower

most ballasts will operate fine at 200 or 108, 10% drop
their v dip ride through is even lower
 

powerplay

Senior Member
hard to say
it was just to illustrate the smaller the motor/service ratio the less droop upon starting

I would leave as is
explain the options to the owner
be forthright
doesn't matter now or later, cost should be comparable
run for a while and see if you have issues
if so, address them

93 A connected
but if a residence and greenhouse factored probably much lower

most ballasts will operate fine at 200 or 108, 10% drop
their v dip ride through is even lower

Client mentioned "Brownout" You thinking the approx $11k in Transformer step up and down would do little?
 

Ingenieur

Senior Member
Location
Earth
Client mentioned "Brownout" You thinking the approx $11k in Transformer step up and down would do little?
Are you saying this is up and operating?
if so you must make measurements
v at each end
i
again while starting the largest motor

something doesn't jibe
 

kwired

Electron manager
Location
NE Nebraska
Client mentioned "Brownout" You thinking the approx $11k in Transformer step up and down would do little?
We may want to know exactly what was meant when the term brownout was mentioned.

There is a big difference between a little dimming of lights vs a big enough voltage sag that contactors actually drop out, or running motors would actually stall or come near stalling.
 

powerplay

Senior Member
We may want to know exactly what was meant when the term brownout was mentioned.

There is a big difference between a little dimming of lights vs a big enough voltage sag that contactors actually drop out, or running motors would actually stall or come near stalling.

I am heading there today from an ongoing issue to find out what "brown out" means because it is being described by someone limited in electrical knowledge... he was told it needed step up and down Transformers to overcome the distance and wanted an Quote.
 

AKElectrician

Senior Member
To step up the Voltage on an very long underground Cable run, is it possible to install an step up transformer, or would the Load continue to brown out from an undersized cable Feeder that feeds the transformer trying to step up the Voltage? Thanks for any feedback!
Probably wont work, but... Is it possible to hit a higher tap on the transformer??? Run your voltage a little higher to compensate for the load end?
 

Smart $

Esteemed Member
Location
Ohio
Probably wont work, but... Is it possible to hit a higher tap on the transformer??? Run your voltage a little higher to compensate for the load end?
Where there is a single constant-current load it would work. Where there are several loads and the current draw will vary over time, the fluctuation in voltage drop may be considered excessive. For example, the lights may flicker substantially on the start of a motor, or perhaps simply and noticeably vary in brightness.
 
Top