Power Systems Application Brief

Power Monitoring

The Problem

The use of electricity in our daily lives has become a commodity which we take for granted. It is the job of people like John A. Demcko, P.E., Senior Consulting Engineer for the Arizona Public Service Company, to keep power flowing and quickly analyze any problems which occur. To simplify this job, much of the equipment used has been automated. A digital fault recorder or DFR plays an integral part in the automation.

Power Systems Monitoring

A DFR is a data acquisition system used by the electric utility companies and other producers of electrical power to monitor power generating and transmission equipment under stressed conditions. When a power system becomes over-stressed for a prolonged time, a blackout may occur. The voltage and current on transmission lines and at generating plants can be monitored by devices called protective relays. It is the job of the protective relay to monitor the condition of the power generation and transmission equipment and initiate the appropriate reaction if an over-stressed condition occurs. DFRs are typically installed as an after event monitor to allow the appropriateness and effectiveness of the protective relays to be assessed. The DFRs are supplied with sophisticated hardware and software to allow these events to be saved to memory or transmitted via modem to an engineering office for analysis within minutes of an over-stressed condition. A Master Station (MS) in the engineering office receives the data from the DFRs in the field.

Analysis for Reliability

The data transmitted back to the MS must subsequently be analyzed for the pertinent information so that the appropriate decisions can be made to ensure reliable power system operation. The problem is finding a powerful data analysis package to accomplish this. Several of the DFR manufacturers provide some analysis software for use with the records captured on their individual DFRs. DADiSP can import from the de-facto DFR data export format supported by many DFR manufacturers worldwide and provide sophisticated data analysis. This data analysis is particularly suited to the requirements of the power utilities in their daily operation. The power of DADiSP was readily apparent when the Arizona Public Service company had a question about the validity of an analog panel meter measuring the generator field voltage at one of their power plants. No on-site personnel were available to address the problem.