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Important Message from Glendale Water & Power

Post Date:09/06/2019

Important Message From Glendale Water & Power - Rolling Outages

Dear Glendale Water & Power Customers,

We at Glendale Water and Power want to apologize for the sudden power interruptions that were implemented this past week and the inconvenience to our customers caused by these interruptions. Unfortunately, we experienced a major impact to our distribution infrastructure exacerbated by the increasing summer temperatures which in turn created an emergency situation and forced us to reduce power to specific affected areas in the City.

In late July, our Rossmoyne substation experienced an unprecedented accident when an auxiliary transformer exploded and caused severe damage to one of two main transformer banks at the facility. This substation is a major anchor for the City’s power infrastructure and ties to three other substation sites those being the Scholl, Howard and Fremont stations (see maps here). Following the accident we were left with a single transformer bank to carry all customer power demands from that site. While one portion of this substation has been down, and we have been working on repairs, ordering parts and overseeing inspections, many of our customers that were being served by this substation were rerouted to other areas so the pressure on this substation was alleviated.That in turn added pressure to the other areas.

In addition to having limited use of the Rossmoyne substation, the original accident at that site created a cascading effect and caused a distribution station cable failure at our Scholl substation. This cable was just recently replaced in June 2019 and underground cables of this type are designed to last 30 years or more. However the power surge from the accident and the elevated heat from additional energy routing through these cables led to portions of the cable melting and failing.

This cable failure combined with high temperatures reduced our ability to compensate for the damaged transformer bank at Rossmoyne and led to a failure alarm notification from the remaining transformer bank at the station. This dangerous combination presented an emergency situation and an imminent threat to the remaining system infrastructure.Therefore we had no choice but to immediately start emergency outages of one hour increments in three specific areas to reduce the stress on the system and ensure we did not incur any further damage to our remaining infrastructure.

Our system is designed to have redundancy for reliability purposes so that the loss of a single component does not interrupt the delivery of electricity to the customer. This is especially true in the hotter summer months when high day time temperatures and minimal cooling through the evening and late night hours increase the demand for energy throughout the day with no real relief in the off-peak hours. Our system, like any electrical system, experiences overheating issues under these seasonal circumstances but in this case the combination of the explosion and cable failures resulted in the loss of both our first and second level contingencies thus creating a more severe problem.

Our outstanding maintenance crews literally worked around the clock to repair the secondary cable failure which was completed early Sunday morning.This enabled us to regain a certain amount of our contingency and to end the emergency outage procedure. This will now allow us to utilize all of our remaining resources without risk until the transformer repairs at Rossmoyne substation can be completed in approximately two weeks.

From the onset of this emergency situation we began to utilize media platforms immediately available to the City and GWP. This allowed us to provide information we had available at the time and to forecast what the affected customers could expect as quickly as possible.These platforms included our web pages, social media and GTV 6. As soon as it was determined that the outages would need to continue we utilized our reverse 911 phone messaging service and sent notifications to the cell phones, emails and land lines of those directly affected.Unlike a planned event or a construction project where we have the opportunity to give advanced notice this was an emergency and the unpredictable nature of the event made notification much more challenging.That being said we will use the lessons learned from this situation to improve upon our response for future events when and if possible.

Despite advances in demand forecasting, it remains to a great degree situational and uncertain. It also can be difficult to predict production, since power supply resources, distribution systems and transmission lines can fail unexpectedly due to weather extremes or other problems. The transmission system is the backbone of GWP’s service provision effort, bringing energy from the Grayson Power Plant and remote supply sources to substations, the distribution system and then to our customers. Ensuring the reliability and stability of each segment of this complex process is the critical task we are faced with on a minute by minute basis each and every day.Ensuring proper contingency and redundancy in that critical effort is essential whether it is in the generation/supply or transmission/distribution components.

Reliability is a top priority for GWP. Based on our history of outage management compared to other similar sized utilities and as recognized by the American Public Power Association as a Platinum Level Public Power Provider, it was without question an unprecedented action that we were forced to take. Thank you and our sincerest appreciation to all of our customers for their understanding and patience.

Glendale Water & Power

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