Average Power Transformer Inventory

Sure--a Ouija board.

I'm certain an average number exists but I see no value in knowing this number. I suspect an average number per type of load (household, industrial business, office business, etc.) would be a more valuable number to a utility. A utility will be able to crunch their own numbers to discover this trend.

They would own enough, with some spares.

There is a manner to arrive at the number. The characterization of this "manner" would be considered unscientific to some.

What are you really asking, and why? Homework, job interview, your job, idle curiosity, or just fun?

I am developing a solution for Power transformer remote monitoring.I would like to know if this market is scalable and on an average what is the transformer fleet population for a utility - operational + inventory.

What exactly do you need to monitor?

They only have three categories they fit into.

1:Online and working.

2:Off line on purpose.

3: Online but not working.

If the case of category number three the customer will let you know soon enough that their power is out which does not cost anything to the utility to find out.

Unless they have made changes to their system and now have too many, or not enough. -- JHF

As many as was prudent, practical, and necessary, yes and no...

https://www.elp.com/articles/powergrid_international/print/volume-18/issue-5/features/transformer-maintenance-key-to-grid-resiliency.html

https://www.hsb.com/TheLocomotive/TransformerAssetManagement.aspx

Depends on the size of the utility company and their experience with the need to replace them. Ice storms, fallen trees, foolish kids driving too fast, older fools driving drunk, sober jerks driving carelessly, lightning strikes, periodic replacement and many other factors must be considered.

Scientific method is the relative use of common sense and the appropriate formulation. The formula for this is: N = I_S + F_T + F_K + O_F + A_J + L_S + P_R This is an integer always greater than 1

Good Luck, Old Salt

In reference to post #7-----

I_s = Ice Storms F_t - Fallen Trees F_k = Foolish Kids O_f = Older Fools S_j = Sober Jerks L_s = Lightening Strikes P_r = Periodic Replacement A_j = All Other Junk (as a second unknown to make you do some calculus)

Good Luck, Old Salt

Since you are starting from scratch, you have to feel your way, say using a Drake formula or equivalent.

Find total magawatts consumed

Find number of utility companies

Find the power generated by a utility company.

Find their locations.

Find the area size served.

Find the population served.

Determine typical power consumption per person or household. This will vary according to locale (urban, rural, cold, hot etc).

Determine size of transformers used, and under what conditions, and numbers. Transformer manufacturers?

Now you have a general idea of the approach, start researching the figures. This means internet searching, and contacting people (surveys). Where you can't find figures, take a punt, or ask people in the know for a guesstimate.

There may be a company that has knowledge along the lines of what you need. Dig further into government reports.

There are also companies that will do surveys for you. Start saving.

You won't get an answer quickly.

n+1

Very good and prsctical question, based on a sound research premise. Hopefully, someone who works at a utility will reply, something like, we have 47,000 metered customers, and maintain the grid for most of them. We have about 19,000 trnasformers in service (several different kinds), and keep on average, about 2000 in a couple of locations. Now that would be helpful and based on actual knowledge, unlike this post, or the 15 above it.

Sorry, I was interrupted and did not have time to finish.

N+1 => (N = Quantity of known size of transformers required to service an area) + 1 Spare.

The quantity is determined by customer load plus line loss multiplied by transformer efficiency divided by service area size restrictions.

The grid design is based on the utility operations management requrements, available generation node size & quantity, location of generation node(s), distribution line size, voltage level, line location restrictions, and area zoning restrictions.

Many utility companies still operate their transformers at 110-125% of rated capacity to attain maximum efficiency which regularly puts the equipment at risk of failure when the ambient temperature gets too high and requires additional critical spare units for backup. (This increases the overall quantity of transformers the utility must own.)

In order to answer the question with any real degree of accuracy; you must identify the utility operations management philosophy, apply it to the system design, and then do the math.

Your inventory count method does not account for different types of transformers.

As for your comment that many utilities operate their transformers above rating, I agree that this is a common practice but not for the reason you stated. The customers have control of the loads not the utility. No homeowner when adding a window air conditioner notifies the utility of the added power they will be taking. They may have to hire an electrician to provide a suitable outlet and breaker from their power panel but that's about all that will be done. So the loading will creep up to 125% of the transformer rating before a new distribution configuration happens.