Outages, offline generators leave New Orleans vulnerable during heavy rain

During prior events when 25 cycle power was diminished, Entergy power was relied upon more, and 25 cycle power was rationed, and sometimes refused. The worst case of such rationing and refusals occurred during the flooding on August 5, 2017.

Over half of the machines which provide antiquated 25 cycle power to drainage, water, and sewer pumps across the city’s east bank are currently out of service, the New Orleans Sewage and Water Board said,  sinking the utility’s ability to quickly move water off streets during severe spring storms below its own stated needs.

The utility posted an update on its website this week. While similar convergences of failures have occurred during past rainstorms, it is rare to have such concurrent outages happen during dry weather.

During prior events when 25 cycle power was diminished, Entergy power was relied upon more, and 25 cycle power was rationed, and sometimes refused. The worst case of such rationing and refusals occurred during the flooding on August 5, 2017.

In their posting, dated April 4, the Board said that steam-powered turbine-generator 4 was out of service for at least ten days due to unspecified “mechanical issues.” A suite of five smaller electro-motive diesel generators called EMD’s, intended as backups to the utility’s main turbines, are also all unavailable, though the agency claims four of the units could be back in service this week. Finally, one of five “frequency changers” which convert 60 cycle power supplied by Entergy New Orleans to 25 cycle power was noted as out due to inspection, cleaning, and scheduled repairs, work expected by the agency to take four to six weeks. 

The utility is left with natural gas-fired turbine generator 5 and four frequency changers. Two other turbine generators – numbers 3 and 1 – were decommissioned in 2021 and 2022 respectively.

In total, the combined loss of the seven machines brings the Board’s ability to supply 25 cycle power, which among other uses runs approximately half the east bank’s drainage pumps, down to 35.75 megawatts, less than half its theoretical maximum of 72.25 megawatts and significantly below the maximum amount of power drawn during heavy rainstorms.

That top level need has fluctuated in past Board statements, ranging between 42 and 52 megawatts. Should four of the EMD’s return to service this weekend, the agency would have 45.75 megawatts available, theoretically enough for a large storm, but leaving them no redundancy should additional equipment fail while and after rain is falling. 

The failures come at one of the worst times of the year for storms. April is one of the rainiest months in New Orleans, according to a decade of data published in the Board’s most recent financial audit. From 2011 to 2021, April was at least third in monthly rankings five times, including its status as the rainiest month of 2013, 2015, and 2016. Recent years have brought significant April storms in 2019 and 2021, when 25 cycle power was equally constrained.

The effects of 25 Hz power shortages would be felt most acutely during rainstorms where most of the 25 cycle pumps are located, in the section of the east bank west of the Industrial Canal (known as “Old City” to the Board) and in the Lower Ninth Ward. 

All of New Orleans East and most of the west bank have drainage powered by 60 cycle power from Entergy New Orleans or by diesel fuel, so they would be insulated from the failures. 

While there are also a number of 60 cycle pumps in “Old City,” just under two thirds of the drainage capacity there and in the Lower Ninth Ward is handled by 25 cycle pumps, including at three stations where 25 cycle is the only power available. Two of those stations, located on North Broad Street, drain an area from the Central Business District out to Mirabeau Avenue, including the French Quarter, Treme, the Seventh Ward and large portions of Mid-City. The third exclusively 25 Hz station drains the western portion of Lakeview.

At a City Council committee meeting last month, Board Executive Director Ghassan Korban touted the $300 million power complex now being constructed at the agency’s Carrollton Plant. The project, with its centerpiece Entergy New Orleans substation designed to tap directly into more reliable power from nearby 60 cycle transmission lines, is intended to replace much of the unreliable 25 cycle generating equipment, including the currently out of service turbine 4 and the EMD’s. However, Korban also said the project will not be able to feed power to the Board’s 25 cycle pumps through an array of new frequency changers and distribution facilities until the fourth quarter of 2024 at the earliest, leaving the city dependent upon the older equipment for nearly two more years.

Turbine 4 unreliable

In response to questions from The Lens, a Board spokeswoman said that the “mechanical issues” on turbine 4 were related to two valves on the machine’s main steam inlet: the trip throttle valve and the governor control valve. 

Both valves are involved in regulating the speed of the turbine, a delicate, complicated process which is most difficult when another turbine is being brought online or taken offline, and the two units need to be synchronized to ensure their power signatures match. Currently, the Board only has two 25 cycle turbines – numbers 4 and 5.

The T4 repairs this month are not out of the ordinary. The turbine-generator, which was installed in 1915, has spent much of the last decade under repair. It underwent tens of millions of dollars of federally-funded post-Katrina rehabilitation from 2012 to 2018, followed by two years in service. In late 2020 it was taken down for reasons which remain unclear, returning in July, 2021. Currently, it is the Board’s workhorse for 25 cycle power, running over 300 days in 2022 according to the Board’s power logs.

However, despite all of the work performed on the unit, T4 has proven to be very unreliable. The turbine generator or its main breaker tripped eleven times in 2022, representing over half of a larger group of 19 events through the year when the machine stopped while it was running, could not be started, or had to be shut down due to various issues. In at least five cases, the machine or its main breaker tripped while or shortly after synchronization with turbine 5. In six other cases, turbine 4 simply tripped without any apparent interaction with turbine 5.

Other than the numerous trips, one T4 shutdown incident appears to be of serious concern. During a four day outage after it tripped during synchronization and could not be restarted during a September 3rd rainstorm, T4 was reported in the power logs to be suffering from a difficulty maintaining vacuum. That failure was characterized more generically as “mechanical issues” in a state-mandated Board report sent to the City Council and the New Orleans state legislative delegation. The inability to sustain adequate vacuum – formed as flowing pressurized steam condenses while transferring energy to spinning turbine blades connected to an electrical generator – can be a death knell for such machines. Turbines 1 and 3, which also ran on steam, both suffered from repeated vacuum problems before they were permanently shut down.

EMD’s and frequency changers out often and long

Four of the five EMD’s are out of use due to an “air compressor issue,” according to the Board’s website. In response to emailed questions, the Board said the compressor was required to start all the EMD’s, and the particular problem was a failed interface display. They said the display was due to be replaced this week, and afterward four of the EMD’s could be placed back in service. 

EMD outages are frequent, even more so than for T4. While the EMD’s play a vital backup role when other machines are unavailable and during the summer when rain is more frequent, they do not do so completely successfully because they are unreliable units. On over 40 different days in 2022 problems were noted in Board logs with EMD’s, either in being unable to warm them up, to start them after warm-up, or to keep them running once started. 

The problem cited for the fifth EMD currently out of service is “auxiliary radiator fan issues.” For over a year, all five EMD’s have been undergoing upgrades to reduce their noise output.The Board said in response to questions that a return to service date for the fifth EMD could not be determined, because testing of the fan upgrades on the unit was ongoing. 

Frequency changer 4’s outage, listed as “scheduled repairs,” is part of an effort to rehabilitate the two 6 megawatt frequency changers located at the Board’s station “D” on Florida Avenue at the People’s canal.

The station D frequency changers are usually the first units turned on to supplement turbine power to drainage pumps during a rainstorm. Like almost all of the Board’s power fleet, they suffer from deferred maintenance. In 2017, Veolia recommended as part of their systemwide assessment that both units be cleaned, and that frequency changer 3 have all its wiring replaced

A contract to perform that work was issued in 2022 to Jay Industrial Repair of Alabama, and work on frequency changer 3 began on May 31 last year. Like the work currently occurring on frequency changer 4, the repair work for frequency changer 3 was anticipated to only last a matter of weeks. The unit did not return to service for over five months.

Editor’s note: A few minutes after the publication of this article, the Sewerage and Water Board announced the restoration to service of three of the five EMD generators, bringing their total available 25 cycle power up to 43.25 megawatts. While this is marginally above the lower end of what the utility claims is required for drainage in a large rainstorm, the long record of EMD unreliability and the continued outages of turbine 4 and frequency changer 4 leave the city in a heightened state of vulnerability to flooding. 

Matt McBride

Matt McBride is a freelance reporter covering infrastructure for The Lens. He began his reporting career with his blog "Fix the Pumps," covering post-Katrina flood protection construction by the Corps...