Shoreline Substation transformer ready to rock and roll

This new transformer sits on top of pendulum bearings that keep it from toppling when the ground shakes


The new Transformer Bank 73 at the City Light Shoreline Substation may not look very different to you than any other heavy piece of equipment in our system – until you look under it.

It sits on a set of rollers designed to allow the heavy machine to slide back and forth during an earthquake, and to return it to its original position when the shaking stops.

The Shoreline transformer is only the second transformer in the United States to use this base isolation technology. The first was installed in Vancouver, Wash., by the Bonneville Power Administration. Leon Kempner, principal structural engineer and seismic program manager at BPA, helped to introduce the technology to City Light.

The specific device used in Shoreline is called a triple pendulum bearing – a series of concave plates and a center post that are free to slide during strong ground motion. These bearings act as a type of shock absorber, allowing the transformer to glide back and forth in a pendulum motion, trading movement for force. This reduces the stress on the transformer and is connections during an earthquake, and helps to keep it balanced.

Past earthquakes in the region have toppled transformers, damaging radiators, conservators, gaskets and cracking porcelain parts. Each transformer costs more than a million dollars and takes about a year to replace, so losing multiple transformers in an earthquake could be devastating for the Seattle area.

This upgrade was developed and designed by Robert Cochran, a senior civil engineer at City Light. “Incorporating base isolation with high voltage transformers is something I have been working on for years and finally came together this year,” he said.

Robert will present a paper on this topic at the 2015 ASCE’s Electrical Transmission and Substation Structures Conference in Branson, Mo.

Hydro excavators help save time and money

Nate Thomas, left, and James Sauls use a hydro excavator to clear soil and debris from their work area.

New hydro excavator technology has improved the ability of City Light crews to clear soil and debris in preparation for construction – resulting in increased efficiency, lower costs and fewer errors.

Instead of using a metal augur, hydro excavators use high-pressure water jets and suction hoses to clear the area around poles and underground vaults, where water often gathers. The use of a water jet instead of a metal drill and shovels greatly reduces the risk of damaging other equipment that may be underground, such as gas, water, electric, sewer, or communications lines.

“We used to encounter unmarked utilities on a fairly regular basis,” explains Richard Moralez, Manager of Electrical Services and Construction at the City Light South Service Center. “The use of hydro excavators has helped us to avoid a lot of damage.”

Underground utility equipment is often decades old and unmarked, meaning crews frequently aren’t able to see it until it is too late. The result – in the past – was typically equipment damage that had to be repaired by City Light or other utilities.

Using a hydro excavator means any damage is minimal to nonexistent when crews encounter unforeseen underground equipment. The most common damage is only minor nicks from the suction tube. This vast improvement in technology saves the utility money and reduces construction times – meaning lower costs for our customer-owners.

There are several additional benefits to using hydro excavators. Water and debris are vacuumed up into a large capacity tank on the work truck, which can then easily be disposed of at City Light’s new decant facility. The decant facility pretreats the water and solids using a carbon filtration system, allowing for cost-effective disposal while complying with all federal, state and local environmental regulations.

If crews encounter contaminated soil on the job, they are able to localize and dispose of it at the South Service Center decant facility or other certified facilities. Samples of the material can be collected and identified, allowing the information to be shared with the rest of the city’s utilities, increasing safety and reducing costs.

Another important benefit is reduced wear and tear for crew members. Crews no longer need to clean and shovel dirt off of metal augurs and then hand-shovel dirt back into the area post-construction. Instead, they can use the much gentler and more effective hydro excavator to clear the work space, and then refill the area with clean backfill material from a separate dump truck. This has the added benefit of leaving the construction space with the best possible appearance when they leave the job, so that when a restoration crew comes in, there isn’t much left to clean up. Instead of needing three or four trucks in a fleet, crews may need only one truck to get the job done.

“The utility first started using hydro excavators periodically within the last 10 years, but has greatly increased its usage recently as we’ve found it to result in much lower incidences of damage,” said Moralez.

Although City Light is not liable for damage to unmarked utilities, it’s still an inconvenience to the customer who may go without cable, telephone, or water service during repairs.

“The real success story is the improved service to the customer,” Moralez said.

Copper Thieves Disrupt Electric Service, Risk Lives

When thieves break into electric utility facilities to steal copper, they not only risk their lives, but they disrupt power for customers and drive up operating costs that can lead to higher prices.

A man who apparently intended to steal copper from a Puget Sound Energy substation in Renton was critically injured Wednesday when he cut into a transformer’s wiring. Read the full story here .

Copper thieves have targeted Seattle City Light in the past also.

Customers can help the utility protect the reliability of energy delivery and enhance public safety by paying attention to any unusual activity around substations or other electric facilities, Security Manager Doug Williams said.

“If you see something suspicious, call 9-1-1,” Williams said. “Let’s be a partner on this.”