In the last decade, several manufacturers have successfully developed and demonstrated many new devices for the enhancement of electrical power distribution. The EPRI Custom Power Program was instrumental in the development of many of these power quality devices (PQD), such as the dynamic voltage restorer (DVR™), the distribution static compensator (DSTATCOM™), the medium voltage static transfer switch, the flywheel energy storage and the solid-state breaker (SSB).
During the early 1990s an EPRI study of 750 industrial and commercial utility customers indicated that an improvement in electrical service quality was desirable and a utility-provided solution was preferred. Additionally, a large percentage of those experiencing power quality problems were willing to pay a premium for power quality solutions. Changes in the regulatory environment will also continue to impel changes in the electric power delivery system. This article describes how a power quality park project currently underway is convincing companies and organizations involved that custom power technologies, as applied in a premium power park configuration, represents a significant opportunity to meet the needs of commercial and industrial customers.
Premium Power Park - Evolution
In 1992, the concept of the custom power park, also known today as the premium power park (PPP), was introduced by Westinghouse (now Siemens FPQD) in order to meet customer needs. According to this concept, the tenants of an industrial or commercial office park would be provided with a guaranteed level of electrical service quality made possible by new custom power devices. In 1999, EPRI selected the team of Host Utility American Electric Power (AEP) and Systems Integrator Siemens PT&D to jointly develop, implement and evaluate the PPP concept, both technically and economically, at an existing industrial park in Ohio. The project consists of three phases to take place over two years. Phase 1 will deal with the creation of design guidelines and methodologies of a Premium Power Park, including the interrelationships of customer needs and available solutions, and the various architecture tradeoffs as well as implementation of a UCA-based system control function. Phase 2 is the implementation of a premium power park utilizing several different PQDs from different manufacturers, working together in an industrial park environment with both underground and overhead features to the distribution system. Phase 3 consists of monitoring and analysis to evaluate the effectiveness of the implemented design methodologies, the cost effectiveness of the design and to collect lessons learned.
Providing Quality Power to Customers
The original concept for a PPP provided for the distribution of different levels of power quality enhancements to provide solutions to various customer needs in a park setting (Figure 1). With multiple levels of service available, customers could select the level of power quality to best meet their needs. The justification for paying higher rates would be based upon customer need for the selected level to avoid costly downtime and production scrap as well as the savings achieved by not purchasing, operating and maintaining internal power conditioning equipment.
In the original park concept, a centrally controlled, local distribution system could serve a wide range of customers with differing energy and power quality needs with multiple feeders. The customers could be sensitive to voltage sags and swells or affected only by long outages, or they could impact the distribution system and neighboring customers by injecting distorted currents (harmonics) or cause voltage flickers. The central control center would control and monitor the distribution of power quality and reliability for the customers within the park. The control center receives power from multiple feeders and combines it with any alternative energy sources such as fuel cells or on-site generation. Then the center distributes the power to park customers, communicates with various types of PQDs located within the park and provides a coordinated response to any power quality event. However, when the cost for installation of the multiple overlapping distribution systems was considered, a second approach for a distributed scheme was conceived. In this arrangement the various PQDs would be moved out into the park to the point of use. This would permit customers to connect directly to the distribution system for “standard” power or through a specific PQD tailored to their specific needs. Some customers may even segregate their loads into standard and sensitive and accept multiple feeders.
Essentially, there are two basic configurations for premium power parks. These are called the substation premium power park and the distributed premium power park, with each having a great deal of variation within the approach. The two concepts are illustrated in Figures 2 and 3. In the substation PPP system, all of the PQDs are located in a central substation and multiple levels of distribution feeders are created internally and distributed externally in the park. In a distributed PPP system, shunt-connected and series-connected devices are installed at customer locations based upon their individual needs.
The application of the two configurations is largely driven by economics and customer need. At a “greenfield” site, where the distribution system is being designed in conjunction with the park design in a brand new development, a Substation PPP approach can be implemented easily. For existing industrial or commercial sites, a distributed PPP approach allows the offering of premium power service without entirely replacing the existing distribution system. Both configurations require the integration and coordination of multiple PQDs.
The site selected for the distributed PPP project was an established industrial park initially developed in the 1960s as the Delaware Industrial Park in Ohio (Figure 4). There are currently eleven industrial customers within this multi-acre park, and it is about 80% occupied. These customers are primarily light manufacturers having some miscellaneous service activities. The diversification of this customer base provides a wide array of electrical service needs, and the distribution system is a mixture of overhead and underground. Collectively, the park represents about 14.4MW of demand to American Electric Power.
A PPG Industries plant and The Nippert Company are by far the largest electrical customers, representing 9.2MW of load. PPG had experienced voltage sags and interruptions disrupting its production of automotive and industrial coatings, resulting in downtime, damaged material and disposal costs. The Nippert Company casts copper 24 hours a day and has concerns about outages lasting longer than an hour to an hour and a half, which would jeopardize their product and equipment if the caster temperature falls. The remaining nine customers within the park represent just over 5MW of load. A variety of businesses include the manufacturing of fiber products, corrugated containers, plastic films, color adhesives, wood trusses and specialty inks. Many of these facilities house a high level of technology, making their manufacturing extremely susceptible to power disturbances and variances (Table 1).
The project officially kicked off in the summer of 1999 with initial efforts focusing on data collection on the feeders in and around the Delaware Industrial Park and customer participant interviews. Interviews with PPG and Nippert helped to gain an understanding of the issues affecting their operations within the park and to categorize the sensitivity to power quality issues of the equipment used in their processes. PQ specifications were then prepared based on the data obtained. For the PPP application, the matrix of devices was created and then compared with PQ specifications to determine which devices to select for further investigation. This PQ device matrix is extensive and includes over fifteen medium voltage PQ devices available in the industry from nine equipment suppliers.
AEP performed circuit modeling by using a three-phase short-circuit/load-flow program that can simulate events on the AEP distribution system. The output data assisted in determining how the PQ devices will be integrated into the circuit and if they will provide positive results for each of the customer participants. A total of six power quality monitors were installed at critical locations within the park to measure existing conditions and to obtain data to analyze and determine the types of events seen on the system. Current transients, harmonics and sags have been observed. This information is used in conjunction with the PQ specifications and PQ device matrix to select the proper PQ device for each customer application.
At this time, device selection and the system design is being reviewed and finalized. Monitoring will continue during implementation of the Distributed PPP design. Comparison and analysis of before and after data will be produced showing the benefits the premium power service has provided to the served customers. Continued cooperation by both park tenants and equipment vendors will enable this project to run smoothly and will lead to a successful demonstration of the PPP concept.