When a distribution transformer becomes overloaded and must be replaced with a larger unit, there is the cost of the new transformer, the cost of having a utility crew remove and replace the existing transformer, and the cost of re-inventorying or disposing of the old transformer.
The cost of changing out one 50 KVA distribution transformer, and replacing it with a 75 KVA unit is well over $3,000. The cost of replacing a substation transformer can exceed 1 million dollars.
At some point in time, when the population of PHEVs and EVs increases, a large number of distribution and substation transformers are going to have to be replaced with larger units. Whether this happens when they fail or under a planned regimen will depend on whether utilities know where vehicles are being recharged.
The problem is exacerbated if vehicles are recharged during the day when transformers are already heavily loaded.
It’s difficult to assign a number to the total hidden cost of having to replace transformers to allow for charging the batteries of PHEVs and EVs, but it’s worthwhile to see how great the hidden cost might be.
If it’s assumed one distribution transformer will have to be replaced for every 10 PHEVs or EVs sold, and, as noted earlier, if there are 87 million PHEVs or EVs on the road in about 19 years, it would cost, at $3,000 per unit, over $25 billion to replace the distribution transformers serving homes.
Also, if it’s assumed that one substation transformer will have to be replaced for every 5,000 PHEVs sold, then, using the same math and a $1,000,000 replacement cost, an additional $17 plus billion will be required for substation transformer replacements.
The more units charged during the day, the sooner this cost will be incurred.
Ideally, PHEVs and EVs should be charged during nighttime, off-peak hours.
This could be accomplished if charging stations have a timer that only permits charging between 10 pm to 6 am. Such a timer couldn’t be used at charging stations in downtown areas, but could be required for charging stations located in homes.
Unless utilities know where PHEVs and EVs are being recharged, they will always have to react in an emergency mode when a transformer fails.
If, however, utilities are notified by the electrical contractor whenever a charging station is installed, utilities could develop a plan for replacing distribution transformers before they fail.
Electrical contractors will have to install 240-volt charging stations in the home since most such installations will require adding wiring from the service entrance, and possibly also replacing the existing service entrance. The large, 480-volt, quick-charge charging stations in downtown areas or commercial buildings will also be installed by electrical contractors.
Contractors will probably need permits and could be required, with an appropriate law, to report to the local utility where these charging stations are installed.
This isn’t an entirely satisfactory solution since many vehicles will be charged using the 120-volt outlet in the garage, but it could help reduce the number of times a utility has to respond to an outage where an overloaded transformer has caused several homeowners to be without electricity.
The complexity and cost associated with distribution transformers becoming overloaded as the result of recharging the batteries of PHEVs and EVs is significant, and should become part of the dialog surrounding the advent of these vehicles.
How can emergencies be minimized?
How much will it cost to replace transformers?
What will be the hidden cost borne by the consumer?
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