Graphical coordination program aids system relaying at Consumers Power

Consumers Power Company has installed over 7,000 miles of underground residential distribution (URD) power cables since 1965. Until 1978, both URD primary and secondary cables had concentric neutral wires. Since 1978, all secondary URD cable installed has been triplex. The primary neutral wires are tinned copper.

This paper presents how a major U.S. gas transmission and storage company restored gas storage peaking capacity by repowering obsolete gas turbine compressor units. Consumers Power Company’s Ray Field located in Macomb County, Michigan, USA, was developed as a 44 BCF working capacity gas storage field in 1966. Due to the high deliverability, the field is operated as a peaking reservoir, handling rates as high as 500 MMCFD on injection and 1,200 MMCFD on withdrawal. Ten (10) 2,750 horsepower gas turbine driven 4-stage centrifugal compressor units were installed in the mid to late 1960’s at the field. The compression is operated 2, 4 and 8 stage, as needed, to cover storage pressures of 450 to 1800 psig. Each centrifugal compressor is driven by a Pratt Whitney (PW) GG-12 Gas Generator firing into a Cooper-Bessemer (CB) RT-27 Power Turbine. By 1980 parts and maintenance services for the PW GG-12 Gas Generator became very expensive to non-existent. Aircraft use of the GG-12 (JT-12) had been phased out. Consumers Power, with 13 of these turbines on their system, was becoming the only remaining user. In the mid 1980’s four (4) of the Ray Field gas turbine compressor units were replaced with two (2) 6,000 horsepower reciprocating engine compressor units. These replacements maintained the deliverability of the field and provided salvageable engines and other parts to maintain the six (6) remaining turbines. However, by 1993 maintenance parts returned as a major problem as well as unit availability on the 6 remaining turbine units. In 1994 Consumers Power committed to a gas turbine unit repowering program as the preferred choice over unit replacement. Two (2) refurbished Solar Centaur T4500 Gas Turbine drives were purchased and installed to repower 2 of the obsolete turbine units. These installations have been very successful. Existing compressors, foundations, piping, coolers and auxiliary systems were re-used with only minor modification. The complete installed cost for repowering was about 33% of the cost experienced for replacement. Installation was completed within eight (8) months of project commitment. The low emission rates from the Solar SoLoNOx Combustors allowed short lead time (6 months) on air emissions permit. New sound attenuation enclosures met the new local noise ordinance and replaced equipment that had been a source of local complaint. PLC based controls improved reliability and flexibility of operation. The additional horsepower available from the T4500 Turbine (4,300 vs 2,750) allows for increased future capacity. Because of the success of the Ray Turbine Repowering Project, Consumers Power has committed to 2 more refurbished Solar Centaur T4500 Units to repower PW/CB Turbines at the St Clair Compressor Station. Solar is scheduled to delivery these 2 units by year-end 1995 for installation in 1996.

Are regulated and potentially unregulated combination gas and electric utilities natural monopolies?

There is a need for performance information on small windmills intended for interconnected operation with utility distribution service. The owner or prospective buyer needs the data to estimate economic viability and service reliability, while the utility needs it to determine interconnection arrangements, maintain quality of power delivered by its line, and to answer customer inquiries. No existing testing program provides all the information needed, although the Rocky Flats test site comes close. To fill this need for Michigan, Consumers Power Company and the Michigan Electric Cooperative Association helped support a two-year program at Michigan State University involving extensive performance testing of an Enertech 1500 and a 4-kW Dakota with a Gemini inverter. The performance study suggested measurements necessary to characterize SWECS for interconnected operation. They include SWECS energy output to a-c line, miles of wind passing the rotor, var-hour metering for average var consumption, and recording watt, current, and voltmeters to assess SWECS output variability. Added instruments for waveform measurement (to assess power quality) are also needed. Typical data taken at the MSU test site are used to illustrate the techniques and preliminary data from a current project is given. Finally, conclusions about SWECS performance are listed.

This paper presents the protective relay settings of tie line tripping and design of load-shedding scheme for an integrated steelmaking industrial power system to ensure system stability after a severe fault contingency on an external utility power network. The transient stability analysis of the industrial power system with the equivalent external Taipower system has been executed for an actual fault contingency in 2005. The mathematical models of 13 cogeneration units in the plant and several large generators of a nearby Taipower thermal plant are included in the computer simulation to solve the system transient response for the fault contingency to verify the accuracy of the models used. To prevent tripping of critical loads due to an external fault contingency, the undervoltage and under/overfrequency relays with proper settings are applied for the tripping of external and internal tie lines. To restore system stability of the industrial power system for the islanding operation after tie line tripping, load shedding is designed to disconnect a proper amount of noncritical loads by considering the governor response and protective constraints of cogeneration units. According to the transient stability analysis of the industrial power system with the proposed protective relay settings and load-shedding scheme, it is found that the voltage sag and oscillation problem caused by fault contingency in the external Taipower system can be mitigated if the tie line tripping is executed in time to prevent the shutdown of critical loads and tripping of cogeneration units.

Motor management relays can enhance protection by locking out a motor after a trip or a stop until the motor has cooled enough to restart the motor. This feature enhances motor protection because it insures the start will not cause the motor temperature to exceed the thermal damage curve. As with any protective relay setting, correct settings are important, but with restart protection they can be particularly difficult due to the fact that they prevent restart of the process that is driven by the motor. Topics to be discussed in this paper include: motor hot cold ratio, RTD biasing, learned motor starting data, motor starting margins, running cool time constant and stopped cool time constant. Each of these values will be discussed in detail and will be shown with a case study that unnecessarily prevented restart of motor.

The relay protection settings performed in the largest thermal powerplant (TE 'Nikola Tesla B') are reffered and explained in this paper. The first calculation step is related to the coordination of the maximum stator current limiter settings, the overcurrent protection with inverse characteristics settings and the permitted overload of the generator stator B1. In the second calculation step the settings of impedance generator protection are determined, and the methods and criteria according to which the calculations are done are described. Criteria used to provide the protection to fulfill the backup protection role in the event of malfunction of the main protection of the transmission system. are clarified. The calculation of all protection functions (32 functions) of generator B1 were performed in the project 'Coordination of relay protection blocks B1 and B2 with the system of excitation and power system protections -TENT B'.

Dispersed generations (DGs) have its vital importance in the increasing power demand scenario. The penetration of the new generating facilities like wind, solar power etc has serious effects on the stability and the reliability of the power system. As this penetration increases, there will be a corresponding increase in the fault current level of the system which could result in fault current over duty burden. Existing power system equipments like circuit breaker capabilities and protective relay settings which are already designed for a system without considering the DGs, will not have the required ratings to withstand this severe condition. Thus, the most important challenge is their reliable integration with the Main Grid. To overcome this problem, there is a need for protection system redesign or a complete system up-gradation, which could be very expensive. The use of Fault Current Limiters (FCLs) is one of the most economical and effective solutions for the above said problem. This paper discusses the use of Superconducting Fault Current Limiters (SFCLs) as a Unidirectional Fault Current Limiter (UFCL). SFCLs are the ‘invisible elements’ in the power system under normal operation and is visible only when a fault occurs. Through this paper, reliable integration schemes for the Variable Capacity Micro Grids (VCMGs)/Renewable Energy Generation (REG) using USFCL is introduced. Simulation studies were conducted using PSCAD and numerical analyses were done to explain the effectiveness of the proposed protective system. Also, a PSCAD model of USFCL for unsymmetrical fault analysis is proposed. The proposed integration schemes prove to be reliable as it ensures an improved power quality of the micro grid and retains the protective co-ordination of the relays, thus, helping in the use of the existing protective system effectively when the VCMGs/REG are installed in the power system.

The conventional relay protection setting calculation method considers the internal interference of the transformer and obtains the setting value quickly, which leads to large harmonic interference of the transformer and affects the secondary setting calculation results. Therefore, the setting calculation method of the power transformer relay protection based on the Electrical Transient Analysis Program (ETAP) is designed. The harmonic transfer characteristics of the power transformer are extracted, and the harmonic interference of the power transformer is proposed. Then the ETAP software is adopted to establish the calculation principle of the power transformer relay protection setting and improve the calculation accuracy of the secondary setting. Through comparative experiments, it is verified that the second fixed value of the algorithm is close to the actual fixed value and can be applied to real life.

Bulk power high voltage interconnected generation presents special protective relay design setting considerations for the associated HV switchyards or substations. The concerns and suggestions presented in this document were developed during this writer's protective relay reviews or surveys of approximately 35,000 megawatts of oil, gas, coal, and nuclear generating stations.

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Reviews the book "Output and Productivity in the Electric and Gas Utilities, 1899-1942," by Jacob Martin Gould.

What explains the choice of corporate political strategy in environmental politics? Drawing on recent models of actor strategy formation in political economy, this article argues that basic material interests of firms are translated into strategies in the context of institutional environments. I advance a typological model that posits how distributional effects—positive versus negative—and perceived regulatory pressure—low versus high—interact in leading firms to adopt one of four ideal-type strategies: opposition, hedging, support, and non-participation. This article examines the model through the case of corporate strategies in the making of the European Union’s Emission Trading Scheme. The article contributes to theory-building on business strategy in environmental politics by offering a probabilistic explanatory model, and it flags hedging strategies as an increasingly prevalent form of business behavior.