CenterPoint Energy Super Bowl LI Coordination and Hurricane Harvey Operational Efforts

Transcription

1 CenterPoint Energy Super Bowl LI Coordination and Hurricane Harvey Operational Efforts 51 st Annual Transmission and Substation Design and Operation Symposium David Mercado, P.E. Real Time Operations Engineering Manager CenterPoint Energy

2 Background CenterPoint Energy s electric transmission and distribution business serves a 5,000-square-mile area that includes Houston, the nation s fourth largest city with over 2.4 million metered customers. Operating a transmission and distribution system in such a dense and populous footprint brings its own set of challenges. In this technical paper, two distinct challenges are highlighted and how CenterPoint Energy has managed these challenges are further outlined. The first challenge that is discussed in this paper involves the coordination efforts related to the city of Houston hosting the 2017 Super Bowl LI, a high profile annual sporting event that is viewed annually by over 100 million viewers around the nation. The New Orleans Superdome power outage during the 2013 Super Bowl resulted in a 34 minute interruption caused by a relay misoperation due to a relay design defect. Although the root cause of a particular power outage can be attributed to a multitude of factors, the 2013 Super Bowl outage highlights the importance of assessing the robustness and redundancy of power feeds into such large venues. In preparation for the 2017 Super Bowl hosted in NRG Stadium in Houston, Texas, CenterPoint Energy considered various system improvements to bolster the reliability in the vicinity of the area feeding the stadium along with various other logistical considerations including communication efforts, physical security, and electric operations preparation actions. The second challenge presented in this paper is associated with the operational efforts encountered during Hurricane Harvey. Hurricane Harvey was record-breaking storm that resulted in over 52 inches of rainfall in southeast Texas from August 26 th through September 4 th of Although the immediate greater Houston area did not experience the effects of high winds typically associated with hurricanes, extreme flooding due the rainfall and the threat of rivers and waterways exceeding their banks presented the greatest challenge. As a result of the high water, various issues were encountered from flooded substations to eroded transmission tower foundations. CenterPoint Energy implemented various innovative solutions to address the extreme flooding accompanied by Hurricane Harvey. Figure 1: CenterPoint Energy Service Area

3 Super Bowl LI Coordination In the aftermath of the 2013 Super Bowl partial power outage in New Orleans, CenterPoint Energy found it prudent to evaluate the robustness and redundancy of the power system feeding NRG Stadium and associated Super Bowl venues around the city of Houston in preparation for the 2017 Super Bowl hosted in Houston, Texas. CenterPoint Energy considered various system improvements to bolster the reliability in the vicinity of the area feeding the stadium along with various other logistical considerations including communication efforts, physical security, and electric operations preparation actions. Initial Power System Evaluation CenterPoint Energy s primary distribution substation serving NRG stadium was a single breaker 138 kv substation configured as seen in Figure 2. Under this design configuration, a single 138 kv breaker failure would lead to the outage of both transmission sources to the substation resulting in a total outage of the distribution feeders feeding the stadium. CenterPoint Energy identified a relatively simple and easy to implement solution of adding a second breaker in series with the existing breaker as seen in Figure 3. CenterPoint Energy completed this design change in This solution solved the complete substation outage scenario for a breaker failure condition, but did not fully address the scenario in which NRG stadium would experience an outage from a fault on one of the transmission lines feeding the substation. Figure 2: Original substation single breaker configuration Figure 3: Revised substation double breaker configuration To increase the reliability of the transmission service into this substation if a fault were to occur on one of the transmission lines into the substation, a longer term solution was developed to convert the substation into a 138kV four breaker ring design with both transmission lines feeding the substation on opposite corners of the ring bus and the two substation power transformers on the remaining two opposite corners. This design would minimize the possibility of a transformer outage in conjunction with a fault on either transmission line sources into this substation. See Figure 4 for the long term solution that was developed for this substation. CenterPoint Energy completed this design change in 2016.

4 Figure 4: Final 4 breaker ring bus configuration Outline Departmental Roles and Responsibilities CenterPoint Energy developed a Super Bowl preparation committee team with representatives of various departments across the company. Each department was assigned roles and responsibilities to clearly outline expectations. The overall goal was to develop a coordinated organization structure to ensure prompt and coordinated response to monitor and restore gas and electric services during Super Bowl LI events. CenterPoint Energy Departments Department Roles and Responsibilities Corporate Communications o Create internal and external communication plan and oversee its implementation. o Create employee messaging. o Respond to media inquiries and create news releases as required. Corporate Security o Create physical security event plan. o Secure additional physical security resources and serve as liaison with contractors. o Monitor and oversee the implementation of the physical security plan. Customer Service o Create customer service plan to support SB LI events and oversee its implementation. o Respond to customer concerns during a SB LI event incident. Electric Operations o Follow pre-event check list such as review abnormal circuit conditions on feeder and transmission circuits supplying SB LI events, verify primary and back up feeds are capable of carrying load requirements, infrared appropriate equipment and check substation equipment. o Pre-stage personnel to efficiently and effectively respond to issue that may arise during SB LI events.

5 Gas Operations o Conduct leak surveys and repair before the event and map critical lines. o Pre-stage Gas resources to efficiently and effectively respond to gas incidents. o Gain visibility of what contractors are doing in the SB LI venue areas. Government Relations o Serve as liaison with external agencies such as City of Houston operations command center, police and fire departments. o Provide a liaison as needed to provide support to external governmental agencies as needed. Human Resources o Provide same support as normal operations. o Respond to emergent events as necessary. Logistics o Secure and stage necessary resources. Radio Communications o Maintain operational readiness of the Voice & Mobile Data Radio System (VMDRS). o Staff appropriately throughout the event. o Respond as needed. Safety o Create safety messaging for the SB LI event. o Staff appropriately to support the SB LI events. Technology o Ensure adequate infrastructure review of operation. Repair as needed. Operations o Provide appropriate IT support of tools required to operate system effectively. o Ensure appropriate staffing throughout event. Transportation o Fleet s plan to support the Super Bowl event will consist of strategically assigning technicians throughout CenterPoint s Houston service area. Fleet technicians will be working and ready to respond to any vehicle or equipment issues anywhere in the Houston area. To facilitate coordination between the various departments involved, 12 months prior to the event monthly meetings were held with all stakeholders involved. Coordination was also conducted with external entities including the Federal Department of Homeland Security, local law enforcement, City of Houston emergency management, and NFL and NRG stadium security. Electric Operations Preparation CenterPoint Energy instituted various measures to ensure increased reliability of our Distribution, Substation, and Transmission systems. The following are action plans executed in preparation for Super Bowl LI: Distribution Operations / Vegetation Management Identified and inspected 36 overhead circuits associated with Super Bowl LI venues Released and completed 25 work orders related to improvements Identified and inspected 34 circuits associated with Super Bowl LI venues for vegetation management issues

6 Major Underground Met with NRG stadium site electricians and contractors to develop testing procedures for NRG stadium equipment and response to faults. Performed VLF (Very Low Frequency) testing on the conductors feeding NRG stadium Replacement of one pad mount transformer at NRG stadium due to leaking bushings Installed 30 locking manhole covers in key major underground locations for increased safety and security. Substation Operations Figure 5: Example of a locking manhole cover Performed infrared testing at substation feeding NRG stadium Performed dissolved gas analysis on both transformers at substation Installed new ballistic fencing around distribution substation feeding NRG stadium Figure 6: Ballistic Fencing around substation feeding NRG stadium

7 Transmission Operations Inspect 138 kv transmission circuits that serve substation feeding NRG stadium Inspections resulted in the installation of avian protection on seven transmission structures and one insulator string replacement In addition to these proactive inspections and assessments, a work moratorium was placed on any scheduled work on substations, interconnecting transmission lines, and distribution circuits in the area of NRG Stadium, Downtown Houston, Airports, and any other Super Bowl related venues during the week of the Super Bowl. Super Bowl Coordination Conclusions High profile events such as the Super Bowl can have a significant impact to the host city. Ensuring increased electrical reliability can facilitate a successful event hosting contributing to enhanced safety, security, and financial success. Although it may not be feasible to mitigate every potential point of failure that may exist to the power system, prudent measures that are beyond normal business practices can be evaluated and implemented as necessary to reinforce system reliability. Hurricane Harvey Operational Efforts Hurricane Harvey was record-breaking storm that resulted in over 52 inches of rainfall in southeast Texas from August 26 th through September 4 th of Although the immediate greater Houston area did not experience the effects of high winds typically associated with hurricanes, extreme flooding due the rainfall and the threat of rivers and waterways exceeding their banks presented the greatest challenge. As a result of the high waters, various issues were encountered from flooded substations to eroded transmission tower foundations. CenterPoint Energy implemented various innovative solutions to address the extreme flooding accompanied by Hurricane Harvey. Hurricane / Flooding Preparation In the days prior to the Hurricane Harvey gulf coast landfall, CenterPoint Energy reviewed existing switching procedures for substations that have previously experienced flooding. The purpose of these procedures is to develop a temporary reconfiguration that provides a bypass in case of flood water levels rendering the substation inoperable. Those procedures were re-evaluated, updated as needed, and circulated among all parties involved in making operational decisions. Due to the unprecedented rainfall and rising water levels from nearby rivers, reservoirs, and bayous, many substations that have never previously flooded, experienced high flood water. The flooding from Hurricane Harvey resulted in 17 substations out of service or inaccessible due to high water. The following is an example of a temporary substation configuration that was developed in real time as high water was rising within the substation yard.

8 Rising water was reported at a 345 kv substation during Hurricane Harvey. Remote SCADA control was still operational although water ingress into the control house was occurring resulting in imminent damage to relays, RTU, and other control house equipment. The risks of not taking any action include degradation to system reliability, possible protection being compromised, damage to substation equipment and associated lines, and personnel and public safety concerns. An expedited engineering power flow analysis was performed to determine a substation bypass configuration that maintains system reliability integrity. Figures 7 and 8 depict the substation status before and after the temporary bypass configuration. Figure 7: Imminent Flooded Substation Configuration Figure 8: Substation Temporary Bypass Configuration Prior to executing the temporary bypass configuration at this substation, coordination was required with our system protection engineers to ensure appropriate protection at remote ends. Due to changing line impedances for the new created bypass lines, updated relay settings needed to be calculated, issued, and deployed at remote ends. As evidenced by the images below, this proactive action likely avoided further system damage and preserved reliability to the CenterPoint Energy transmission system during this extreme flood event. After the flood waters receded, the condition of the substation equipment was assessed, cleaned, and damaged equipment was replaced. Once all the substation equipment was determined to be in acceptable operating condition, the substation was returned to its normal operating configuration. This was achieved within 7 days after the substation flooding.

9 Figure 9: CenterPoint Energy Substation Flooding Mobile Substation Use CenterPoint Energy also leveraged the use of a mobile distribution substation due to the complete flooding of a key distribution substation serving a densely populated community in the Houston area. The mobile substation was installed on an adjacent church parking lot that was elevated on higher ground. Various technologies were utilized including drones, amphibious vehicles, and airboats. The load which was previously field switched to other nearby distribution substations was restored to the mobile substation within two weeks of flooding.

10 Figure 10: Flooded Distribution Substation and Use of Mobile Substation Flooding impacts on Transmission Towers Flooded substations were not the only issues faced during Hurricane Harvey. Various transmission towers located on the banks of rivers were washed out causing line lockouts. Figure 11 and 12 below show an example of a transmission line river crossing before and after Hurricane Harvey. In this case, the river

11 exceeded its banks and washed out the foundation of two towers causing the transmission line to make contact with the flood waters. After the water receded, temporary poles were set in place and the transmission line was restored. Figure 11: San Jacinto River Crossing prior to Hurricane Harvey Figure 12 : San Jacinto River Crossing after Hurricane Harvey Hurricane Harvey Operational Efforts Conclusions Hurricane Harvey was a category 4 storm that resulted in extreme flooding along the Texas Gulf Coast including the Greater Houston Area. Over 52 inches of rainfall was measured, and the damage as a result of flooding was unprecedented. During the storm there were more than 42,000 lightning strikes, a record number or tornado warnings, and flooding in areas that were beyond the 500 year floodplain. CenterPoint Energy experienced 17 substations out of service or inaccessible due to high water, 7 transmission line lock outs, and 293 distribution circuit lock outs. Some of the innovative techniques used to assess damage

12 and restore power include the use of air boats, drones, amphibious vehicles, intelligent grid, and Advanced Metering Systems. Although the impacts of a storm like Hurricane Harvey cannot be completely avoided, proactive planning and decisive operational action can help mitigate such impacts. Additionally lessons learned from previous experiences and experiences of others can be used to improve certain practices for future weather events like Hurricane Harvey.