Paul S. Hamer

Acceptance testing of electric motors and generators

A comprehensive inspection and acceptance test program for electric motors and generators is outlined. Recommended electrical and mechanical inspections and tests are described, and bearing housing and shaft vibration limits are recommended for all types of electric machines. The mechanical test procedures and vibration limits as described are proposed for inclusion in future editions of IEEE and NEMA standards. An inspection and test matrix for highly critical special-purpose and less critical general-purpose machines is given.<<ETX>>

Considerations for generation in an islanded operation

This paper discusses the conceptual design and operation of an isolated power system, recognizing the reality that generator or turbine trips will occur. The level of reserve generating capacity must be set with proper balancing of capital expenditures and operating costs against revenue lost in a production shutdown. The way that reserve capacity is provided is as important as the amount of reserve; seemingly adequate reserve can turn out to be badly insufficient if it is not well distributed across the available reserve sources.

Zone Based Protection for Low Voltage Systems; Zone Selective Interlocking, Bus Differential and the Single Processor Concept

Time based coordination and protection is the normal basis for coordinating low voltage power distribution systems. Enhancements, such as zone selective interlocking and bus differential protection, may be used to accelerate protective devices. However, these improvements may be costly, difficult to implement, and may not function as expected using commonly available technology. Nevertheless, the potential benefit of fault clearing speed and selectivity are more valued in todaypsilas arc-flash and reliability conscious environment than ever before. The writers shall discuss some issues associated with these traditional improvements, pitfalls to avoid and, more effective ways to implement zone-based protection to achieve fast fault protection while maintaining complete selectivity for a broad range of fault magnitudes, system configurations and load types.

Design, fabrication, and back-to-back test of 14200 HP, two-pole cylindrical-rotor synchronous motor for ASD application

This paper describes the design aspects, fabrication, and testing of a 14200 HP, two-pole, cylindrical-rotor synchronous motor used with a load commutated inverter (LCI) adjustable speed drive (ASD) to drive a refrigeration compressor for a refinery alkylation plant. The motor design aspects include extensive finite-difference analysis of the rotor cage assembly and laboratory bench-testing of a wedge assembly to verify finite-difference analysis results prior to fabrication. Torsional and harmonic analysis results are also presented. Special considerations are discussed regarding rotor heating due to harmonic currents and mitigation methods for handling the harmonic currents and heating. Mechanical design aspects are presented of the rotor cage, including rotor slot design, wedge, and end ring assembly. Two motors and drives were built, for companion projects, allowing for verification of the rotor-cage assembly by a back-to-back test. Test preparation, setup, and results are presented including rotor temperature mapping, vibration data, and torsional results. Finally, test results are compared with calculated values.

Transient recovery voltage considerations in the application of medium voltage circuit breakers

Medium voltage circuit breakers can fail to interrupt three-phase fault currents when power systems have transient recovery voltage (TRV) characteristics which exceed the rating of the circuit breaker. This paper examines the application of 13.8 kV generation and load switchgear for an oil refinery in which circuit parameters as originally designed would have exceeded the 13.8 kV circuit breakers TRV ratings had corrective measures not been taken. This paper illustrates this case and discusses the basis of TRV, how TRV is assessed, and alternative actions taken to bring circuits to within the 13.8 kV circuit breaker ratings.

Globalization of electrical safety codes and standards

As the world economic markets become more global, the interface of electrical codes and standards among countries becomes a more complex issue. The issues that need to be addressed to create harmony are as complex as the backgrounds and cultures are different. The issues include the origins and purposes of the different codes and standards and how they are administered and used in the various countries. This paper discusses the similarities and differences among the worlds safety codes and standards. It proposes strategies that could assist in developing positive harmonization.

Considerations for Generation in an Islanded Operation

This paper discusses the conceptual design and operation of an isolated power system, recognizing the reality that generator or turbine trips will occur. The level of reserve generating capacity must be set with proper balancing of capital expenditures and operating costs against revenue lost in a production shutdown. The way that reserve capacity is provided is as important as the amount of reserve; seemingly adequate reserve can turn out to be badly insufficient if it is not well distributed across the available reserve sources. The dynamic behavior of reserve capacity, as much as the amount of capacity that is ultimately available, is critical in determining how an isolated facility will behave in the wake of a unit trip or the loss of a grid connection. In this paper, experiences with detailed dynamic simulations of a range of isolated systems are described. These are related to test work and operational incidents that have provided practical calibrations. Based on simulation and experience, some guidelines are offered for configuring generation and selecting strategies for maintaining stability in large, isolated continuous-process facilities.

A new technique for the remote partial discharge monitoring of the stator insulation of high-voltage motors located in &#x201C;Ex&#x201D; (hazardous) locations

The authors present a paper on the application of a new technique for the remote on-line partial discharge monitoring of the stator insulation condition of in-service, high-voltage rotating machines. The technique applies wideband, ferrite-based high frequency current transformer sensors and high resolution measurement technology. This remote partial discharge monitoring technique has significant advantages when monitoring motors which are located in Ex hazardous gas zones in oil and gas and petrochemical facilities. The paper includes a technical review of published papers covering some of the history of the development of modern, on-line partial discharge sensors and measurement systems for rotating machines. This is followed by a comparison of the various partial discharge sensor options available and an introduction to the remote wideband partial discharge monitoring measurement technique employed by the authors. A case study from a recent pilot project (August 2011) where the new remote partial discharge monitoring measurement techniques were successfully trialed to measure partial discharge activity of in-service 10 kV motors in an oil processing facility is also presented.

Are Cable Shields Being Damaged During Ground Faults

Simulated ground-fault tests (50-700 A) of various cable, ground wire, and conduit configurations are made to determine the proportion of the total ground-fault current carried by the cable metallic shield. The percentage of the total fault current for the various return paths is tabulated, along with representative zero-sequence circuit impedances. General guidelines for protecting cable shields from damage are presented.

Continuous, remote on-line partial discharge (OLPD) monitoring of HV EX/ATEX motors in the oil and gas industry

This paper presents results from the continued application of a new technique for the remote online partial discharge (OLPD) testing and monitoring of in-service high-voltage (HV) explosive atmosphere (Ex)/atmosphere-explosive (ATEX) motors operating in hazardous gas zones. The technique employs high-current wideband high-frequency current transformer sensors located remotely from the motor under test, at the switchboard end of the HV feeder cable. Significant cost and operational benefits can be gained from this remote monitoring technique as the stator winding condition of these motors can be monitored without having to enter the hazardous gas (Ex/ATEX) zone. The work described in this paper is a continuation of that carried out by the same authors, as reported at the 2012 IEEE Petroleum and Chemical Industry Technical Conference, and includes the development of proposed condition guidelines for assessing the condition of the stator winding insulation systems of large populations of aged HV motors, based on an OLPD “league-table” database. Two case studies are presented wherein the HV stator insulation condition and reliability of in-service motors, operating in hazardous gas zones, and HV generators were assessed using both online and offline partial discharge (PD) testing and monitoring techniques. The case studies emphasize the importance of carrying out extended continuous OLPD monitoring of in-service rotating HV machines to detect underlying trends in PD activity over time. This paper concludes with how condition monitoring data can support reliability-centered maintenance and condition-based management regimes.