Customer: Louisiana Hydroelectric

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Case History: POWER MANAGEMENT

Customer:	Louisiana Hydroelectric
Location:	Sidney A. Murry Jr. Station, Corps of Engineers Old River Control Auxiliary Structure, Lettsworth, Louisiana
Project:	Auxiliary Structure Gates Power/Control Modifications
Operating System:	Linux 2.0.x

Customer Background:: Louisiana Hydroelectric opened in response to a need for a non-polluting, less costly power source for Vidalia, Louisiana. A site approximately 40 miles south of the town was selected for the new facility. The plant started full-scale operations in 1990. It was designed to rely on the Mississippi river's natural flow and elevation drop at the Old River Control complex, therefore not needing a large impoundment dam. It was also built in accordance with the U.S. Army Corps of Engineers existing water management objective with minimal impacts on the surrounding environment. The station operates more continuously than most run-of-the-river hydro plants, with a capacity factor of approximately 55% and an estimated availability in excess of 99%. It is currently under an approved 42-year power purchase contract with Louisiana Power & Light. Vidalia purchases 6% of the power with an option to purchase up to 15% of the generated power.
(Note: Information on the background of Louisiana Hydroelectric was obtained from the National Renewable Energy Laboratory of the US Department of Energy. Hardcopy of DOE/Ch10093-206, DE93000081, October 1993, is available from National Technical Information Service, US Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161).

Project Background:: The Louisiana Hydroelectric in conjunction with the New Orleans District of the Corps of Emgineers, manages three main structures to optimize water flow for power production. These structures are: the Hydroelectric Structure, the Low Sill Structure and the Auxiliary Control Structure. The Hydroelectric Structure controls the water flow in order to provide power and electricity to the destinations they serve. The Low Sill Structure is a dam regulating water flow from the river during high flow currents. The Auxiliary Control Structure is a regulating dam which also provides the backup system for the Hydroelectric Structure, monitoring any change in the water level for necessary adjustment. In all these structures, the water flow is controlled by gates; increasing or decreasing the flow of water. The gates of the Hydroelectric Structure must be lowered to a 40% opening when the destination is no longer accepting electricity. As the gates close, water backs up on the dam and the gates of the Auxiliary Structure must change position to keep the water level and flows relatively constant. Currently, the position of the all gates are adjusted manually.

Customer Needs:

Louisiana Hydroelectric approached AccessWare with the following needs:

a software package that would provide automatic control of Auxiliary Structure gates at the Corps of Engineers Auxiliary Structure, in response to an alarm condition at the Hydroelectric station.
a software package that would provide, at both the COE Administration/Maintenance Building and the Hydroelectric Control Room, dynamic graphics to indicate real-time gate positions and headwater/tailwater levels at the Auxiliary Structure, Low Sill Structure and Hydroelectric station.
a software package with operator password security and the ability to maintain a historical log of all operations.

The Access Machine Solution:: For this project Louisiana Hydroelectric purchased two AccessPoint Complete Basic packages and two ViewOperator Clients along with a ShadowPath and Application Access Toolkit. Custom services included the configuration of screens and databases and the development of custom interlocks and sequencing.
AccessWare's solution will insure a quicker, more accurate response to emergency conditions at the hydroelectric station. The automation of the auxiliary gates removes the possibility of human error and allows immediate initiation of the necessary gate position changes. Constant communication between structures provides up-to-date real-time information to the user. The historical subsystem logs all events and alarms for accurate plant history information, which is easily retrievable when needed.

AccessPoint Software Specifics:

Graphics - This system will include full color dynamic graphics, custom screens specifically tailored to the project, including the following graphic screens:
- Overview screen indicating Auxiliary Structure, Low Sill Structure, Gates, Hydro station and head and tail water levels at the Auxiliary and Low Sill Structures, Hydro station and the Emergency Standby Generator Systems.
- Auxiliary Structure with six gates indicating the position of each gate, head and tail water levels.
- Low Sill Structure indicating head and tail water levels.
- Hydro station indicating head and tail water levels.
- Overall control system and interconnecting cabling with status of each component.
- Emergency standby generator system at Auxiliary Structure with current and voltage of utility and generator system and status, common trouble and alarm of generator.
Historical Logging - A historical event logging file will be provided to permanently record operator actions, COE/Hydro Plant System status, alarm conditions, and other historical operations. This file can continuously print on the logger printer and/or may be viewed on-line at operator command.
Interlocks and Sequence - A custom application will be provided to allow custom interlock and sequence control of the COE Auxiliary Structure gates. Controls and interlocks will be performed by software only (at the master station), based on specific inputs, and shall not require user input to initiate. Manual control of the gates from the Louisiana Hydroelectric's Station Control Room shall not be possible while in interlock mode. Interlock and sequences shall include:
- Move the COE Auxiliary Structure gates to a present position in the event of an alarm condition generated at the Hydroelectric station.
- Auxiliary Structure gate position will be User defined on a daily basis by COE Operator Interface only or through a series of calculations to be performed by the software, based on head and tail water levels and flows.
- Provide analog levels of tailwater and headwater from the COE Auxiliary Structure, Low Sill Structure, and Hydro Plant to both the COE Auxiliary Structure and Hydroelectric station operator interface at each facility.
Password Protection - Four levels of password access will be provided.
Alarms - The Software shall allow the alarm status of any control or monitored function to be displayed at all times on any current graphic or screen. The two most recent alarms shall also be included on the current graphic. A multi-page display shall indicate the current standing alarms and a Level 4 password shall be the only operator allowed to accept the alarms individually or globally at any time.
Operator Interface System - An operator Interface system shall be provided at both the COE Auxiliary Structure and the Hydroelectric Station Control Rooms. This interface will include full color graphics and all operational features of the SCADA system, limited by the security system. The Operator Interface system will provide for operational features only; system configuration must be performed via the master station system console.
Link Modems - A set of three external link modems will be provided to connect between the Remote Operator Interface and the master stations. The modems will be multi-dropped to allow for automatic failover to the backup master station in the event of failure of the primary master station.

Applications by Location:

Hydroelectric Plant (8 gates)
AccessPoint will display head water and tail water positions for three structures. For each structure's gates, AccessPoint will calculate water flow from polled head and tail water value, and polled gate position (represented in feet). The total water flow through the structure will be calculated and displayed. The emergency condition that invokes automatic control of the Auxiliary Structure gates is tripped by a power failure occurring at the Hydroelectric Station. This condition will automatically move the Hydroelectric Station gates to a 40% opening. AccessPoint will poll and represent this breaker as a digital on/off status. The Auxiliary gates will be automatically moved based on Corps of Engineers (COE) entered values and the number of available-to-move gates.
Auxiliary Structure (6 gates)
Automatic control of the Auxiliary Structure gates commences upon detection of an emergency condition. Each gate will be controlled automatically in 15 second intervals. When an emergency condition is detected, a procedure for selecting the gate opening begins. Once AccessPoint knows which gates to move, it will notify each gate activator as to the movement direction, desired opening in feet, and that the movement is occurring in automatic rather than manual mode. Digital Output addresses in the RTU will be used to trigger alarms local to the gate location. Other Digital Output addresses will be used to mimic the operations of the raise, lower and stop buttons on each control panel, triggering the movement of each gate. These operations will be controlled by a master process or event manager (AccessPoint client program).

The distance to move the gate is retrieved from the numbers entered daily by the COE and is based on the number of available gates. In automatic mode, each movement action is based on which mode a gate is operating in, which direction the gate is moving, and the desired height of the gate. The height value will be compared within the gate movement action to the last position of the gate. When the current gate position is equal to the desired position, the stop button is activated.
For each gate, AccessPoint will poll motor-current analog values to determine motor availability, gate position analog value, and a 480- volt power source digital signal. In addition, AccessPoint will poll each control panel at each gate, and the structure's analog head water and tail water value.
Sill Structure (11 gates)
At the Sill Structure, AccessPoint will monitor the head and tail water levels. Gate positions will be entered into AccessPoint manually each time the gates have been manually adjusted (by the COE field engineer). Water flow for each gate and total water flow will be calculated and displayed.
Maintenance Area - backup generators
AccessPoint will monitor the status of three automatic transfer switches in the Generator Room. It will also monitor an analog value for downward incoming voltage.

Access Machine
Benefits:

Improved response time - the automated process will decrease the time necessary to respond to problems or changes in the water flow. This helps improve customer satisfaction as well.
Economic gain - the automated system allows for an immediate reaction to controlling the water flow. The faster the gates are adjusted the faster the generated power is adjusted to the correct level, saving money and time.