Rasheek Rifaat

Critical considerations for utility/cogeneration inter tie protection scheme configuration

Special considerations must be given to protection systems for inter ties between cogeneration plants and existing host utility power systems. The considerations are reviewed in light of contemporary experience with mid size cogenerating plants. Typical inter tie configurations are deliberated with emphasis on implications on the design of relevant protection systems. Protection schemes are presented and evaluations to their advantages and disadvantages are given. The importance of examining the protection scheme requirements during the conceptual design stage of a cogenerating plant is demonstrated. >

Comprehensive Design of Electrical Installations by Integrating System Configuration and Operational Safety Aspects

The design of a power system has to be comprehensive in regard to the system traditional design configuration aspect as well as its operational safety aspect, such as management and maintenance. The comprehensive design has to survey and define both aspects during the different design phases and during the overall operational life cycle of the system. A new methodology has been suggested to close the gap between the traditional system design integrity studies and their counterpart studies associated with system operational safety aspect.

Architecture Impact on Integrity of Electrical Installations: Cut&Tie Rule, Ring Configuration, Floating Node

An electrical distribution architecture has a vital impact on the performance of an installed system throughout its lifecycle. The architecture of an installation involves the configuration, the choice of power sources (utility and alternate power source), the definition of the different distribution levels, and the choice of equipment. Previous papers have introduced a language program for analyzing and transcribing the instructions of the safety procedures for each working zone and of the integrity procedures for each source node versus the loss of service continuity (the Parise program). Each node presents a kit of instructions as a logic gene, describing a complete and reversible evolution of the component switching means from an opening status to a closing one. This paper deals with the architecture of a power system and the combination of procedures in the operation on a nodes system. It will show the impact of the architecture on the comprehensive procedures for a complex system. To enhance the integrity of power system analysis and operation, the design could adopt the cut&tie rule, introducing ring configuration and floating nodes. The suggested advanced approach assists in the elaboration of the procedures for switching from one set or configuration of a power system to another and will help the training of operators in defining the instructions to be used in the development and the operating of each power system.

Utilizing third harmonic 100% stator ground fault protection, a cogeneration experience

Third harmonic, 100% stator ground fault protection schemes are becoming economically viable for small and mid size generators used in cogeneration applications. Practical considerations must be observed in order that such schemes are successfully applied for different machines. This paper introduces an experience with the applications of 3rd harmonic schemes in cogeneration applications and depicts their advantages and limitations. For a 50 MVA generator, actual measurements of produced third harmonics are portrayed and analyzed. In light of the experience and analysis, applications of certain third harmonic scheme configurations are contemplated.

Considerations in applying power bus protection schemes to industrial and IPP systems

Increases in fault current levels and in-plant generation installations have necessitated further discussions on bus protection. This paper involves such discussions and deliberates the need for bus protection in medium-voltage systems. It discusses considerations for the applications of relay schemes and current transformers to present-day bus-bar protection. The importance of examining current transformer saturation is presented. Current transformers transient cases are introduced where computer simulation of the protection system is encouraged. The overall bus protection concept is presented from the perspectives of independent power producers and industrial system engineers. Actual cases for bus faults and bus protection schemes are referenced.

Considerations for generator ground fault protection in mid size cogeneration plants

Generator ground-fault protection aspects are analyzed for midsize cogeneration plants. In these plants, the generators may be connected to a common generator bus. The overall bus-connected system should be considered when applying generator high-resistance grounding schemes. Calculations are reviewed for sizing generator neutral-ground resistance and evaluating third harmonic originated in the scheme. The relevant applications of third harmonics in applying 100% stator ground-fault protection schemes are examined. Practical considerations are presented for establishing selectivity of ground-fault protection schemes in the case of a common generator bus.

Architecture impact on integrity of electrical installations: Cut&tie rule, ring configuration, floating node

An electrical distribution architecture has a vital impact on the performance of an installed system throughout its lifecycle. The architecture of an installation involves the configuration, the choice of power sources (utility and alternate power source), the definition of the different distribution levels, and the choice of equipment. Previous papers have introduced a language program for analyzing and transcribing the instructions of the safety procedures for each working zone and of the integrity procedures for each source node versus the loss of service continuity (the Parise program). Each node presents a kit of instructions as a logic gene, describing a complete and reversible evolution of the component switching means from an opening status to a closing one. This paper deals with the architecture of a power system and the combination of procedures in the operation on a nodes system. It will show the impact of the architecture on the comprehensive procedures for a complex system. To enhance the integrity of power system analysis and operation, the design could adopt the cut&tie rule, introducing ring configuration and floating nodes. The suggested advanced approach assists in the elaboration of the procedures for switching from one set or configuration of a power system to another and will help the training of operators in defining the instructions to be used in the development and the operating of each power system.

Independent power producers (IPP) perspectives and experiences with WSCC requirements for generator model validation tests

After two regional blackouts in 1996, The Western Systems Coordinating Council (WSCC) instituted guidelines to verify that, for grid connected generators, the stated data represents accurate information that could reliably be used in the dynamic modeling of the system. This paper demonstrates an experience with the applications of WSCCs test guidelines to mid size units built and commissioned by independent power producers (IPPs). The paper addresses concerns with the excitation and voltage control systems and their limitations. An example of a generation unit connected at the end of a long line is discussed to demonstrate variances associated with testing and operating under extreme conditions. The concerns and issues discussed are of importance to IPPs beyond the WSCCs system as many other reliability councils are adopting rules similar to those established by WSCC.

Risks From Utility Supply Disruption

This article elaborates on the properly required protection and how its operation will prevent the undesired consequences to the ICG owner, the utility, and the general public. This article also discusses actions that take place when the utility supply is disrupted, creating an islanding condition and states reasons why protection required by regulatory agencies, local utilities, and documents such as IEEE Standard 1547 IEEE Standard for Interconnecting Distributed Resources with Electric Power Systems are required of an individual ICG. Consequences of not having the protection in place can damage the generator and/or its prime mover plus be a hazard to public safety. Examples of these consequences are given. This article will provide a clearer understanding to ICG owners of why they are required to have specified protective equipment in place.

Protection scheme considerations for common generator bus configurations used in cogeneration plants

The author discusses the applications of protective relaying schemes in modern power cogeneration plants with common generator bus arrangements. Main protection system philosophy and scheme characteristics are considered. Emphasis is given to the attributes of common generator bus configurations. High resistance neutral grounding protection sensitivity and coordinate ability are addressed. Critical considerations are identified to be evaluated in the case of plants connected to multi-tap utility transmission lines.<<ETX>>