Customer MVA load maximums for different utility service voltages 1

[rockman7892]

Is there a standard rule of thumb or guidelines for what maximum MVA load utilities will serve to customers (large utilities, etc..) for given service voltage classes.

For instance:

- For 34.5kV distribution lines is there a typical threshold load that utilities will serve customers from this voltage?
- Same with 138kV, 230kV and other common service voltages?

Common example would be if a customer is being served by 34.5kV and wants to add load that will exceed the utilities max allowance for that voltage class service would they commonly have to discuss with utility an option for getting a higher service voltage provided to the site?

 

[dpc]

The capacity of a service is limited by the current. It is not economical to provide 10,000 A at 12.47 kV. Multiple services are possible, but generally at some point, higher voltage is necessary. Most distribution feeders are 600 to 1200 A. Services over 600 A probably will require an express feeder. Another factor is proximity to the utility substation and available voltages.

 

[bacon4life]

Since there is often a 10x or more step between available voltages, I would surprised to find a general guideline.

Are you thinking of:
1-adding a new load tapped of an existing line with no upgrades required?
2-adding a new load after upgrading the upstream grid and/or substation?
3-service from a new onsite substation?

In my area:
1-A random section of our grid routinely needs upgrades when more than 100 A is added.
2-Express feeders at 15 kV would be in the 200-600 amp range.
3-Industrial substations might be much larger than distribution stations. In my area the utilities often negotiate with industrial customers as to whether the power is sold at the high voltage or the lower voltage side of the substation.

 

[waross]

A rule of thumb for motor (with exceptions):
When the HP is greater than the amperage, it is better to go to a higher voltage.
Is there any similar, loose rule of thumb for service voltages?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[davidbeach]

Serving 300MVA at 34.5kV is not unheard of. True thing, but no other details possible.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[waross]

Wow. That'll stop an old Timex.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Mlmlzx]

as per CIBP manual, 320 MVA for 220 kV as per gujarat norms, and 500 MVA for 220 kV as per central electricity authority norms..

 

[Mlmlzx]

rule of thump is approx one-fourth MVA for sub tl category.

 

[che12345]

Dear Mr. rockman7892 (Electrical)
"...Is there a standard rule of thumb or guidelines for what maximum MVA load utilities will serve to customers (large utilities, etc..) for given service voltage classes...."
1. It varies from location to location. Technically it depends on:
a) the utility voltage levels available in the location,
b) the voltage, current , short-circuit rating of the switch-gear that are readily/economically available on the market,
2. In the location I am in:
a) any load <=45kVA supplied by 230V single-phase or 230/400V 50Hz,
b) any load >45kVA may be supplied by 22kV, 66kV or 230kV 50Hz.
Che Kuan Yau (Singapore)

 

[davidbeach]

45kVA is way too small to consider anything above 600V. Way too small.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[Parchie]

@rockman7892,
How about using the empirical formula for determining the most economical voltage for any transmissions line?
V = 5.5 x sqrt(L/1.6 + P/[(pf)(Nc)(150)])

where: P is the power to be delivered in kVA; pf= power factor; Nc = no. of circuits; and L in kilometers of line.​