Hydroelectric Generating Station SCADA

Location

Southern California

Customer

Imperial Irrigation District

Background

The Imperial Irrigation District (IID) regulates the distribution of irrigation water for the Imperial Valley in Southern California. Six hydroelectric generating stations are installed on the network of irrigation canals where there is an opportunity to generate power. These stations are unmanned and are located in remote desert areas. The stations are controlled via radio from a System Operating Center (SOC) using a Harris SCADA system.

Reason for the project

The existing SCADA system hardware had become obsolete. IID wanted to replace the specialized SCADA equipment with conventional Programmable Logic Controllers (PLCs) in order to obtain an open system that would have a longer life expectancy. IID also wanted to invest in a control system platform that would suit their plans for enhanced system functionality and improved response time with the future installation of a system wide fibre optic network.

Scope of the project

The principal contractor for the project was AEG Automation. Universal Dynamics was responsible for the development of the PLC programs, CRT based operator station configuration, and Oracle database application software. The system was designed for control either from the CRT operator station or from the Harris SCADA master system at the IID SOC.

In addition to the PLC logic program, several custom loadable modules were developed for the PLC to perform specialized functions. Loadable modules were used to create a time stamped event handling system in the PLC, interpret and record all operator actions, and interface the PLC to a Sequence of Events Recorder with 1 millisecond resolution. The event time stamping was synchronized using GPS satellite clocks to obtain system wide time accuracy to within a few milliseconds.

An Oracle database was used to log system data and events. The events and operator actions recorded by the PLC are interpreted by the Oracle database to produce verbal descriptions of the events for display to the operator. There are more than 40,000 unique events that can occur in the system. The Oracle system was also configured to produce summary reports of system power generation, alarms, inhibited alarms, field inputs, which had been placed off scan by the operator, and maintenance tags which had been placed on field devices.

The CRT operator station was protected by operator password with multiple levels of security clearance and included a select-before-operate scheme for all field devices such as circuit breakers and water gates. All information displayed to the operator included flags to indicate the quality and reliability of the information, which is particularly important because the hydro stations are unmanned. The CRT operator station software configuration utilized in excess of 100,000 unique tags.

Benefits from the project

The improved data collection and recording enable IID to better diagnose the cause of lost generation and thus increase generation revenues. The system wide accurate time stamping of field events, such as circuit breaker trips, alarms, and operator actions, enables faster resolution of faults and improved system reliability. Automated reporting of disabled alarms and field inputs which have been placed off scan in the PLC help to avoid situations where damage could result to the generators due to missed alarms.

The new PLC based control system platform is well suited for future expansion of the system such as installation of a high-speed fibre optic communications network and the addition of improved local automatic controls for the generators.