Paper Presentations

Impact on Power Quality of Restoration of Air-Conditioning Load Following Service Interruption
Nosh Medora, Exponent Failure Analysis Associates
Alexander Kusko, Exponent Failure Analysis Associates

The electric utility industry has been concerned with “cold load pickup” on primary feeders following service interruptions. The effect has not been recognized, except as “switching” in the power quality domain. In a hot day, the air-conditioning load is usually a major component of the feeder load. That load component can triple for up to an hour while all of the air-conditioners thermostats call for maximum cooling. The effect depends on the ratio of actual MW to installed MW before the service interruption. The consequences on power quality include voltage sag, feeder fuse blowing and feeder circuit breaker tripping.

Puerto Rico Electric Power Authority Power Quality Monitoring and Benchmarking Project
Professor Efrain O’Neill-Carrillo, University of Puerto Rico - Mayaguez

The Puerto Rico Electric Power Authority (PREPA), have tracked SAIDI and SAIFI indices during the past 20 years. However a record of voltage sags, swells and momentary interruptions does not exist. PREPA is the sole utility for the entire Island. The clients that assume the major costs of power generation and transmission are in the industrial sector. These clients are also more sensitive to sags, swells and momentary interruptions. Given Puerto Rico’s industrialized economy, and due to a growing concern of clients about the integrity and availability of their power delivery systems, PREPA has found the need to pay more attention to power quality issues. PREPA is working on establishing a program for continuous power quality monitoring on the electrical system. With this system statistics of power quality will be gathered, mainly voltage sag performance for the entire island. This project is in the first stage, the site selection process. We are considering aspects such as substations sites with demand meters that have power quality capabilities that are not being utilized, regional distribution of substations and transmission centers, lightning flash density, topography, faults incidence, and critical loads. Students from the University of Puerto Rico-Mayagüez have actively participated in this first phase of the project.

Using Distribution Relays To Monitor Power Quality Problems And Take Corrective Action
Jim Mack, SEL

Utility companies and power delivery independents IPO’s are expected to provide uninterrupted and unmolested power in today’s competitive marketplace. To meet the challenge they must learn to use every available resource at their disposal. Today’s relaying systems have the ability to sample system quantities at a sufficient rate to monitor voltage swells, sags, and harmonics and capture these waveforms when abnormal conditions are present. Moreover, with advanced programming logic these relaying systems can take action to correct these very problems that they detect in real time. The result is a smart power delivery system that can and will react much more quickly that possible with human intervention. This paper will discuss how to set up and program protective relaying systems to perform system switching and control. Several practical examples will be presented for consideration.