A feasibility study commissioned by the US Army Corps of Engineers looked at more than costs and benefits to evaluate automation, staffing levels, and responsibilities at six hydroelectric plants, says Bruce Benson
A TYPICAL cost/benefit analysis of automation may identify potential annual operational savings, but could other factors contribute to a recommended solution with a higher total cost? When the Omaha District of the US Army Corps of Engineers (the District) retained black-veatch to evaluate the feasibility for increased efficiency and automation at six hydroelectric plants on the Missouri river, the study revealed additional issues beyond automation which had to be included in the analysis. The following summarises the alternatives investigated, unique issues identified, economic analysis, and recommendations.
Background
The District currently owns and operates six hydroelectric plants on the Missouri river: Fort Peck (Montana), Garrison (North Dakota), and the Oahe, Big Bend, Fort Randall, and Gavins Point power plants (South Dakota). Each plant has five full-time operators, a full-time maintenance staff, and an operator on duty 365 days a year 24 hours a day.
The plant operators normally use the Supervisory Control and Data Acquisition (SCADA) system to monitor and control plant operation. The SCADA system, called the power plant control system (PPCS), performs: supervisory control, data acquisition, alarming, sequence of events (SOE), automatic generation control (AGC), bus voltage control (BVC), report generation, and historian. Upon loss of a PPCS, the plants can be operated and monitored from the local control boards in the control room.
The Regional Hydropower Action Center (REHAC), currently located in the Gavins Point power plant control room, is staffed with five full-time controllers who collectively provide shift coverage 365 days a year, 24 hours a day. The PPCS provides access to the same plant graphic screens and remote control capabilities for the REHAC controller as are available to the plant operator.
Currently, power plants are primarily monitored and controlled by the local operator or controller through each plant’s PPCS. On a normal weekday dayshift, the REHAC controller currently monitors and controls each remote plant for a total of only two hours each day, four hours a day when maintenance personnel are not
on-site. When the REHAC has control of the plant, the local operator normally performs inspection and surveillance rounds or may request REHAC control in order to leave the control room to troubleshoot a problem, perform minor switching, and so forth.
The reservoir control centre (RCC) develops the water schedules, which anticipate generation and navigation control needs. The RCC gives the water demand to Western Area Power Administration (WAPA), which figures an overall plant MW generation requirement to meet the water demand and sends the daily energy schedule to the local plants. The RCC, WAPA, and local plant operators carefully coordinate their efforts to meet the water schedule and power requirements.
Each generator has three control modes: remote auto, local auto, and local manual.
• Remote auto – the plant operator or REHAC controller can use the PPCS to operate locally from a PPCS workstation (computer terminal) in the plant control room or remotely from the REHAC workstation.
• Local auto – the unit is operated from the control boards in the plant control room and the PPCS cannot perform control actions, AGC, or BVC.
• Local manual – the unit is controlled from switches on the unit control boards and cannot be controlled from the PPCS or the local auto switches in the control room.
Economic evaluation
Table 1 provides a summary of the economic evaluation. Based on the estimated costs, it is economically feasible to remotely control all of the plants from the REHAC. If the REHAC has 10 full time equivalents (FTEs) plus one engineering support person and one supervisor, and plant operational staffing level is reduced from five FTEs to two FTEs (24 FTEs total), keeping operators in the plants during maintenance hours to support WAPA and plant switching, then annual operating costs could be reduced by an estimated 14.5% (US$582,238). If the REHAC has 10 FTEs plus one additional support person and a supervisor, and if maintenance personnel are cross-trained to perform local operations and the plant operations staffing level is reduced to zero, then annual operating costs would decrease by 36% (US$1.4M). Once the reduced staffing level is reached, payback for making the plant and REHAC equipment upgrades required to support remote unattended operation was determined to be two to five (1.92– 4.72) years depending on the cost savings from the reduction of staffing levels.
To provide reliable, repeatable remote control of the generating units from the REHAC, the project team identified some necessary plant equipment improvements. The team also noted that existing conditions requiring maintenance should be repaired regardless of the operational mode and before considering unattended operation.
A number of alternatives for unattended monitoring of fire and security systems were evaluated. Options considered included the addition of security guards, remote monitoring by a third party, and providing video and alarm monitoring at the REHAC.
Plant operations staffing levels
Assuming that the plant equipment is modified to support unattended operation and personnel are properly trained, operating personnel are not required in the plants 365 days a year, 24 hours a day. The team evaluated the following four plant staffing level options.
• Option 1 – status quo/current staffing level assumes that plant operator and controller staffs remain at one person per shift providing coverage 365 days a year, 24 hours a day; the current staffing level requires five FTEs.
• Option 2 – reduce operator staffing level at all remote plants to two FTEs with one operator working maintenance staffing hours to support plant switching, write clearances, and perform plant inspections.and a second operator working a relief shift.
• Option 3 – reduce operator staffing level at all remote plants to one FTE with the operator working maintenance staffing hours to support plant switching, write clearances, and perform plant inspections.
• Option 4 – reduce operator staffing level at remote plants to zero. Plant maintenance personnel will be cross-trained to manually operate the plant locally when remote control is not available, write clearances, and provide switching.
Although the cost benefit of an operations staff reduction is the same for each plant, not all plants have to use the same option and therefore were considered independently. An increase in personnel call-outs is anticipated if an operator is not present to respond immediately. Some of the plants have been designated as black start facilities for their states. WAPA estimates that it will take 30 to 45 minutes before these plants are ready to add generation back on their lines; therefore, a maximum one hour operator response time is acceptable and meets the NERC requirement.
A reduction of plant operator staffing levels would require revision of operator, maintenance, and REHAC controller duties, procedures, and responsibilities. Specific areas to be addressed include: plant control, reporting, writing clearances for hazardous energy control, switching, daily inspections (rounds), contractor oversight, call-out procedures, fire and security, public safety and emergency response. Because there are operators on-site performing these duties now, reduction to unattended operation must consider these responsibilities and the cost for proper training and other change management to maintain the same level of plant, personnel, and public safety performance.
It is recommended that the plant operator staffing level at the Gavins Point and Big Bend plants be one FTE because these two facilities have less equipment, require fewer clearances and are simpler to operate. All other projects should be staffed with two operators. Even with the present operating levels, it is recommended that the REHAC controller be responsible for operating units for longer periods to allow the local operator additional time for inspection rounds and maintenance switching. Although reduction of operational staffing to zero provides the most savings, maintenance would have to provide at least 25 hours per week overtime responding to call-outs and performing other operational duties, which would have substantially burdened plant staff.
REHAC controller staffing levels
The project team evaluated the level of staffing required for REHAC control, assuming that the centre will remotely operate all six plants continuously 365 days a year, 24 hours a day. The REHAC should be staffed 365 days a year, 24 hours a day to provide remote control of unattended plants. During the day shift, two controllers are required to operate and monitor the six plants. At most, 10 controllers are required to provide 24/7 two-person coverage, with two to five-person rotations. It may be possible to use only one controller during off-peak hours (10 p.m. to 6 a.m.), providing additional cost savings. Because the plants will be mostly unattended and remotely controlled, the PPCS and communication systems assume greater priority and necessitate an additional maintenance person to improve system reliability.
REHAC equipment
If the REHAC is going to be staffed with two controllers responsible for operating all six plants a majority of the time, it would need to be relocated from the Gavins Point control room and expanded. Before evaluating a different location, the team had to define the REHAC. Someone who thinks of a centralised control centre may envision a large facility used as a showcase for others, complete with wall-to-wall mapboard displays and elaborate workstations. Another individual may consider the existing layout adequate, knowing that a showcase is not required. Presently, the REHAC requires operating space for one person with four computer monitors to view and control the plants. Except for two additional monitors, it basically has the same layout as the plants – two workstations mounted into a control desk console.
Minimum space requirements were identified for a REHAC control desk console with two controller workstations, each with three control monitors, a security monitor, and two large overall District river system displays. Restroom and kitchen facilities are also required. Equipment space for an engineering workstation, communication, and redundant PPCS servers is required, but this equipment does not have to be located in the controllers’ working area.
REHAC location
The REHAC is currently located in the Gavins Point control room. The current location does not have space for the recommended configuration, and location of the REHAC controllers in the plant control room interferes with local switching and maintenance activities. Alternative locations were evaluated.
For unattended operation, the REHAC will serve as the centre for all operations and as the primary point of contact for support for energy (generation) and voltage control. WAPA dispatchers will contact the REHAC to have them start and stop a unit, condense, and perform transmission line loading relief. The REHAC will become the primary station for all reporting. The REHAC will also be the primary point of contact for RCC located in the division office in Omaha, Nebraska.
REHAC personnel will monitor flows during nesting season for the endangered shoreline birds, the least turn and the piping plover. These birds nest near the water, and it is critical to their survival that flows not vary from the tight constraints during the birds’ nesting season.
If the power plants are not staffed 24/7, plant fire and security information will most likely be routed to the REHAC when there is no staff working at the plant. This will give the REHAC the responsibility for contacting local authorities or plant personnel. In the event of a complete unit shutdown or a critical failure, the REHAC controller will call the plant manager to determine which project personnel should respond.
If the District wants visibility and exposure for the hydro power programme with the public and management, Omaha is the clear choice for the REHAC location. Locating the REHAC together with RCC water control and District technical staff would be beneficial. If the REHAC were located at Oahe, the REHAC operation would be located in the plant that was the most significant in terms of importance to the electrical grid and WAPA. Maintaining the REHAC at Gavins Point, however, offers the advantage of lowest cost and minimises impact to existing controller staff.
The REHAC provides a variety of functions for a diverse group – each with their own priorities. What could be considered an advantage for one group could be a disadvantage for another. For instance, locating the REHAC in Omaha has its advantages for District management, but is the last location WAPA would select because it would not be located in a plant.
The study resulted in a recommendation to relocate the REHAC to Oahe power plant, which is important to WAPA for providing over 700MW area control error (ace), load following, and black start capabilities. The Gavins Point plant has fewer generating units and can be unattended more than Oahe. Also, Oahe is more centrally located to all six of the plants for the PPCS technical support person stationed in the REHAC. Having the controllers at Oahe yields an additional benefit because one of the two controllers on duty may be able to respond to certain critical plant alarms and WAPA requests.
Risk issues for unattended plants
Because the plants are always staffed (365/24/7), the community has developed a reliance on each plant for additional support services that do not have a direct cost-benefit comparison but should be considered by the District before de-staffing any plant. The following is a list of the services currently provided by the plants:
• Emergency shelter during severe weather for residents and campers.
• Log and monitor float plans of personnel on the river.
• Response to local emergencies, such as capsized boats in tailrace.
• Monitor the marine radio channel and providing assistance to boaters if necessary.
• Operator records a daily telephone message indicating flows for the benefit of fishermen.
• 24-hour contact for US Army Corps of Engineers and rangers.
• Weather data from the National Weather Service is manually entered into the PPCS or weather station readings e-mailed daily with a monthly report issued to the Weather Bureau.
• Garrison plant – Need automatic weather and Lake Audobon data reporting system – information required by RCC.
• Garrison plant – Provide switching at Pick City substation for WAPA (five miles from the plant).
• Garrison plant is the primary and secondary energy source and sole water source for the City of Riverdale, North Dakota, the Garrison Dam National Fish Hatchery, Corps outside maintenance facilities, and all Corps downstream campground and recreational facilities. The plant is also the sole energy source for the Bureau of Reclamation Snake Creek station. The hatchery utilises electric heat for the pallid sturgeon; therefore, there is limited response time for operations to restore power (heat) in the winter before the possibility of losing fish. Time required to restore power and water would increase if the plant is unattended.
• Big Bend – Plant provides potable water to the campground, supply is manually controlled.
When the plants are unattended, the above duties would need to be reassigned to others. Oil spill detection and delayed response is another issue that needs to be addressed. The District will review these issues, determine the organisation’s responsibility with respect to each issue, and identify mitigations to minimise negative impacts to the public and the hatchery that could result from operational changes.
Author Info:
For additional information, contact Carlos Araoz. Tel: +1 916 364 2933 or email: AraozC@bv.com
TablesTable 1