Growing pains

 City’s transformer capacity needing second separate sub-station for new load increases

In February 2015, a report on the utility’s substation, prepared by Mike Thielen, Utilities Plus Energy Services, the electrical engineer for the City of Mountain Lake, was presented to the Utility Commission.

The 2015 report identified these following concerns:

+ The transformer and other equipment is 41-years-old.

+ At 41 years, that means there is a 10% chance of transformer failure.

+ At 50 years of age, the failure rate is 50%.

+ A transformer maximum load should not exceed 6,250 Kva (a KVA is simply 1,000 volt amps).

+ With the current load growth, the transformer will reach 6,250 KVA by 2024.

+ Transformer failure would result in outages that are costly, requiring overtime and the purchase of diesel fuel to operate the Municipal Power Plant’s generators, and/or temporary equipment rented to provide electricity to the city.

+ Recommended the construction of a second separate substation which would reduce the interruption of service to customers. The estimated cost of a second separate substation was estimated at $1.5 million to $1.75 million.

According to Mountain Lake City Administrator Wendy Meyer, “One sentence from the 2015 report was prophetic, “The transformer capacity does not leave any spare capacity for new load increases by new customers over-and-above normal load growth.”

“Growing pains” at Milk Specialties (MSC) will call for the need for additional power in 2016. They will be adding a reverse osmosis polisher to treat and allow re-use of the “reject water” from their reverse osmosis process. This water is currently sent to a pond adjacent to their property. The Minnesota Pollution Control Agency (MPCA) has mandated that the water be treated after November 30, 2016.

In addition, MSC wants to add another 1000 horsepower (HP) for additional equipment. This will require larger transformers and lines on the property. In addition, this additional horsepower will cause problems for the existing substation.

This new equipment to be installed at Milk Specialties (MSC) brings load growth above normal load growth and moves the need for a second separate substation from some point in the future – to today.

In order to support MSC’s needs, it was determined by the commission and the Mountain Lake City Council, that the upgrades, including a new sub-station of quality construction to provide long-term electrical service to Mountain Lake’s residents and businesses, should be undertaken now.

It may be necessary to generate power locally from the generators at the Municipal Power Plant at times after MSC installs the equipment, and before the sub-station is complete.

The new sub-station will be located on the east end of the city, near the industrial park.

At the Monday, April 18 meeting of the city council, the call went out for bids for the equipment necessary for the new substation.

The major pieces of the project, 10/14 MVA transformer, 69KV circuit switcher and air-break switch, and 5KV indoor switchgear, are being bid now, with the remainder of the project to be bid when the delivery date of the major pieces is known. The transformer is expected to arrive anywhere from 26-to-52 weeks after the bid is awarded.