Two recent hurricanes in the USA combined to create one of the worst natural disasters the country has ever had to deal with. Entergy was the utility most severely affected, but its effective restoration efforts meant quick relief for its customers.
It is a fact of modern day business practice that utilities have to be well prepared for every eventuality that may affect supply. However, sometimes no matter how well acquainted with emergency procedures that prepare for the worst, circumstances will conspire to challenge in ways that were previously incomprehensible.
In April 2004, US energy company Entergy drilled for a Category 4 storm, striking New Orleans with severe flooding. On 29 August 2005, a Category 3 storm, raging under the name Katrina, hit the Mississippi coast with sustained winds of 200 km/h. New Orleans was soon after a city 80 per cent underwater in scenes that verged on the apocalyptic. Just under a month later, a second major hurricane hit Entergy’s service territory. The two storms combined to become one of the greatest natural disasters that the USA had ever been confronted with, and with 1.9 million customers having lost power, Entergy was facing a situation that would test its restoration capabilities and efforts as never before.
Figure 1. Katrina affected one third of Entergy’s service territory
As soon as Entergy became aware that Katrina was likely to strike its service territory, the company activated its System Command Centre in Jackson, Mississippi and moved a multi-disciplinary team in to lead the work that was to follow after the storm had left its trail of destruction. It also galvanized Transmission Command Centres in Jackson and New Orleans, and Distribution Centres at Utility Operations headquarters in Louisiana, Mississippi, Texas and Arkansas.
For the power plants, a Fossil Emergency Response Centre was created in Texas. In view of the approaching storm and severe flood warnings, one of the first defence actions this Centre took was to shut down the generation units at the Michoud power plant. Single units at other plants under threat were isolated from the grid and placed in islanding mode, allowing them to generate electricity to power their own auxiliary systems. Core teams were to remain at these plants around the clock to monitor equipment and conduct damage assessments.
Looking in the eye
On 30 August, as Katrina blew its final gusts, those preparing to come out from the barricades and conduct damage assessments for Entergy could not have dared imagine the scenes that would greet their eyes. The storm had created the largest number of power disruptions from a single event in the company’s history.
Sixteen units generating a total of 4613 MW had been affected. At the height of the storm, all units were either shut down or isolated from the grid to protect equipment. The majority of these were operational again shortly after the storm had passed; however, six units, representing 888 MW of capacity, suffered extensive flood damage and will not be available for operation until repairs have been completed.
The worst affected was Michoud, which flooded as expected. This damage could have been a lot worse if it had remained in operation as the sustained floodwater of up to 1.8 m could have spurred turbine fires and generator hydrogen explosion events.
Figure 2. Part of the damage assessment procedure in the aftermath of Rita saw Entergy deploy helicopters
Katrina affected one-third of Entergy’s service territory. Some 4828 km of transmission system were knocked out of service, more than 45 060 km of distribution lines were impacted upon and 263 substations and 1550 feeders were taken out.
Facing such a mammoth restoration task, Entergy recruited thousands of workers from other utilities through Mutual Assistance Agreements. This provided an entirely different set of logistical problems. Several ‘tent cities’ were built to safely house the restoration workforce and hundreds of support personnel were drafted in to help cater for and prepare them. Crews would often find themselves working in flooded, mosquito infested areas and had to be inoculated against disease. Security personnel had to be assigned to those entering areas where security was a concern.
Once the damage had been assessed crews began restoring essential services such as hospitals, police and fire departments and sewer and water utilities. Entergy adopted an outside-in strategy that focussed on restoring power on the perimeters of affected areas, then working into more severely impacted areas. Backbone feeders with major trunk lines that support large electrical loads were the first priority.
Toward the end of September, as crews had restored power to the majority of the 1.1 million customers affected by Katrina, and work was well underway to restore power in the most severely affected areas, the second hurricane struck.
The second blow
Hurricane Rita hit land near the mouth of the Sabine River on 24 September and although also classed as Category 3, it created even greater damage to the transmission system than Katrina. Its impact was also felt harder as it severed the ties between generation and load East-to-West, plunging the area from Conroe, Texas to Jennings, Louisiana into darkness.
Creating 810 000 outages and impacting upon all four states Entergy operates in, Rita was the second worst storm in the company’s history.
In total Rita affected 14 generation units. All were available for operation shortly after the storm had passed as Entergy took every precaution necessary, and sometimes even unnecessary, to protect its assets. At the height of the storm, 12 units, with a capacity of 3143 MW, were either shutdown or isolated from the grid to protect equipment. As a precaution in Arkansas, Entergy lowered the levels of lakes Catherine and Hamilton by around 30 cm below normal to provide extra margin in case Rita caused heavy, extended rainfall. Such rainfall did not accompany Rita in the end, but it highlights the depth of preparation.
This preparation was again highlighted as the company also proved its flexibility by reacting to lessons learnt just days earlier from Katrina with the decision to reduce the number of core team personnel at plant sites. Smaller core teams were stationed at Sabine, Nelson, Lewis Creek and Toledo Bend during the hurricane. Sabine was also shut down and removed from service in case of flood damage, which again did not materialize. Precautionary action was also taken with regard to asbestos as the high winds battered the asbestos insulated equipment at Nelson and Sabine.
Figure 3. Flooding at the Paterson power plant
Part of the damage assessment procedure after Rita saw Entergy deploy helicopters as it sought to survey its battered distribution network. The second major hurricane in as many months hit and impacted upon almost every area Entergy operated in, leaving little room for mercy in its wake. Once the damage had been assessed, the decision was taken to mobilize large numbers of the workforce that had been exhausted from the Katrina restoration effort, to begin giving the power back Rita had taken.
The second storm brought with it over 800 000 new outages that had to be restored and crews soon began replacing 29 000 distribution poles and bringing 522 transmission lines and 715 substations that had been affected by both storms back in to service. Having worked together to create devastation in the region, the two storms were now essentially in competition for personnel, materials and other necessary resources to repair their trail.
Katrina and Rita individually caused a scale of destruction rarely seen before, so it is perhaps somewhat remarkable that power has now been restored to all 1.9 million customers (who are able to accept power) affected by the back-to-back hurricanes.
In the 42 days following Katrina, power was being restored to customers in Mississippi, Louisiana and in the New Orleans area at the rate of nearly 26 000 each day. In the 21 days after Rita made landfall, each day power was restored at an average rate of 38 000 customers in Arkansas, Louisiana, Mississippi, New Orleans and Texas. Entergy recruited a workforce of 16 000 and coordinated them to repair the worst damage ever incurred on its system, restoring more than six times the previous number of customer outages.
The effort did not come without costs. As its customers grew fearful of sky-rocketing energy prices, Entergy’s New Orleans unit filed for Bankruptcy Protection a month after Katrina. It also planned to borrow $200 million from its parent company to help cover costs, expected to total around $475 million. Some analysts predict that Entergy will face a final cost of around $1 billion.
However, as the government prepares to distribute $250 billion of federal aid, Entergy should prepare itself for a well-deserved slice of content in the fact that it conquered chaos and helped bring back order and normality.