Motor Control Centers Research Articles

Double contingency ground fault current evaluation

Evaluation of double contingency faults in an electrical power system can be performed by a number of methods, many of which are not suitable for hand calculation. This paper describes how symmetrical component analysis and three-phase network analysis can both be used to evaluate double contingency ground faults. The two methods are compared and shown to produce the same resultant equation. These results can be used in the evaluation of the single-pole interrupting ratings of low-voltage protective devices in motor control centers and panel boards.

Multisensor Secondary Device for Detection of Low-Level Arcing Faults in Metal-Clad MCC Switchgear Panel

This paper describes the development of a multisensor device, based on four different physical phenomena, for reliable detection of low-level arcing faults in metal-clad switchgear. The proposed device was tested for actual arcing, generated on a low-voltage motor control center (MCC) panel, feeding a dry type 15kVA, 230/115 V Y/? transformer. Some results showing the performance of the developed device are presented in the paper. The device can also be applied for detection of arcing in power electronic drives, dry type transformers, gas insulated switchgear (GIS), generator bus-ducts, and other metal-clad electrical apparatus.

Gaining control with Greater Glasgow sludge management

Cutler-Hammer Motor Control Centres will provide West of Scotland Water with powerful motor starting capability for the new Sheildhall reception centres.

Cerebellar contribution to spatial event processing: Morris water maze and T-maze.

Recently, a cognitive function of cerebellar networks has been challenging the traditional view of the cerebellum as a motor control centre. Among the cognitive abilities reported to be affected by cerebellar deficits is the capacity to solve a spatial problem. We investigated the influence of a cerebellar lesion on spatial abilities by behavioural analysis of rats that had undergone surgical hemicerebellectomy (HCb; HCbed rats). Experiments were performed with a Morris water maze (MWM) and a water T-maze in both cue and place versions (visible or hidden platform respectively). Results indicate a severe impairment in coping with spatial information in all phases of MWM testing as well as in the T-maze paradigm. However, if the MWM cue phase was prolonged, HCbed rats displayed some ability to learn platform position, although at a level significantly different from controls. They succeeded in finding the platform, even in a pure place paradigm, such as finding a hidden platform with the starting points sequentially changed. Retention testing was also performed, demonstrating that HCb affects acquisition but not retention of spatial information. HCbed animals exhibit such disrupted exploration behaviour that they can display only peripheral circling, and they can acquire spatial relations only when proximal cues are available. Furthermore, in all phases of testing, platform finding for HCbed animals is essentially based on place strategies. Thus, a specific pattern of spatial behaviour, markedly different from that displayed following hippocampal or cortical lesions, characterizes cerebellar lesioned rats. These results are discussed taking into account the role in procedural learning recently assigned to cerebellar networks, demonstrating that the cerebellar circuits represent the keystone of the procedural components of spatial event processing.

Report on enclosure internal arcing tests

The improvement of electrical equipment is an ongoing process including investigative research. This is a report on research work concerning factors regarding high-energy arcing faults, the tests conducted on containment of these faults, and standards addressing arcing fault test requirements. This report is focused on low-voltage, 600 V class motor control centers (MCCs), but the issues presented should not be limited to only this type of electrical equipment. Also, the scope of this work is restricted to a high-energy arcing fault occurring in a latched or closed compartment during "normal" operating conditions and does not include arcing faults occurring in compartments when the compartment door is open.

Age‐related changes of neuronal responsiveness to melatonin in the striatum of sham‐operated and pinealectomized rats

The age-related changes and the acute effects of intravenous melatonin on the activity of striatal neurons of 1-, 3-, 6-, 12-, and 18-month-old sham-operated and pinealectomized rats were investigated. There was a decline in responsiveness from 3- to 18-months of age, although in sham-pinealectomized rats the responses were similar at 12 and 18 months; in pinealectomized rats, the neuronal responses were quite stable at early ages. In all age groups of sham-pinealectomized rats, neuronal firing decreased in most cells, and increased in only a small percentage of cells after intravenous melatonin injection (100 ng/kg). However, in pinealectomized rats, the injection of melatonin at the same doses significantly increased the firing rate of most neurons compared to that in sham-operated animals at all age-groups, while the number of neurons showing an inhibitory response decreased. These results indicate that melatonin may be involved in the modulation of the activity of striatal neurons and demonstrates an age-dependent reduction in striatal sensitivity to melatonin. They also suggest that other compounds of pineal origin may modulate the activity of motor control centers.

Program for life extension and preserving existing resources for motor control center components [nuclear plants

Many nuclear power plants have motor control centers (MCCs) installed in a harsh, radiation only, environment. Procurement of safety-related replacement devices for these MCCs is an economic burden for the stations if these MCCs have become obsolete. Identical replacement components for many MCCs installed in older plants (ITE Gould, Allis-Chalmers, Klockner-Moeller, Cutler-Hammer, etc.) are no longer available. Plants are left with the option of either retrofitting these MCCs or finding ways to extend the qualified lives of the safety-related components to minimize replacement costs. ComEd nuclear station has embarked on a program to minimize the economic burden for the replacement of Klockner-Moeller (K-M) MCC components. This paper discusses the program adopted by this station and its economic benefits to ComEd.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Self‐rehealing characteristics of a sodium current limiter and its overcurrent coordination for low‐voltage distribution system

AbstractThe sodium current limiter developed and applied for low voltage use is not a current limiting fuse but a new type of reusable current limiting device that utilizes metallic sodium as a fusible element. Excellent current limiting performance and quick self‐rehealing properties of the sodium limiter allowed highly reliable electric power systems to be obtained economically and compactly.Here we examine experimentally the rehealing properties of the sodium limiter after current limiting operation and discuss the overcurrent coordination of the sodium limiter for a low‐voltage distribution system. The results are summarized here: (1) The resistance of the sodium limiter, being between about one thousand and several thousand times its normal resistance r0 at room temperature during a current limiting operation of short circuit fault currents, changes abruptly to 30 to 40 times its ro value just after the disappearance of the fault current and falls steadily to ro. (2) The sodium limiter can recover current‐carrying capability for an overload current even immediately after a current limiting operation and maintain its capability for the following normal load current. The upper limit of the recovery of the sodium limiter is given by its overcurrent against the time characteristics under the normal condition. (3) The self‐rehealing characteristics of the sodium limiter presented here give the ability to design a low‐voltage motor control center using the sodium limiter which maintains maximum service continuity up to high fault currents.

Theories for Skilled Limb Movements .

Some of the theories that have been advanced to perform skilled limb movements are reviewed in this paper. The aspects discussed in brief include alpha-gamma control, choice of control variables in limb movements, equilibrium point hypotheses, experimental observations from simple movement studies and explanations proposed, in particular the dual strategy hypothesis. The single mechanical degree-of-freedom movements may be controlled by one of two strategies: a speed-insensitive strategy or a speed-sensitive strategy. The term strategy implies a set of rules which specify in terms of task variables and subject instructions how to choose the excitation signal, the controlling signal at the alpha motoneuron level. The two strategies differ in that speed-insensitive strategy is a result of duration modulation of the excitation pulse, whereas the speed-sensitive strategy is a result from amplitude modulation. Finally, the problem of multi-degrees of freedom movements and the role of higher motor control centres are discussed in brief.

Mouse 5HT1B serotonin receptor: cloning, functional expression, and localization in motor control centers.

Serotonin is a neuromodulator that mediates a wide range of effects by interacting with multiple receptors. Using a strategy based on nucleotide sequence homology between genes encoding receptors that interact with guanine nucleotide-binding proteins, we have isolated a mouse gene encoding an additional serotonin receptor. When expressed in cultured cells, it displayed the pharmacological profile and coupling with adenylate cyclase characteristic of the 5HT1B receptor subtype. In NIH 3T3 cells expressing this receptor, serotonin induced a decrease in forskolin-stimulated cAMP levels. This effect was blocked by pertussis toxin, indicating that the 5HT1B receptor interacts with a pertussis toxin-sensitive guanine nucleotide-binding protein. To obtain clues as to the possible function of the 5HT1B receptor, we have analyzed its pattern of expression in the adult mouse brain by in situ hybridization. Our results, together with previous autoradiographic studies, suggest that the 5HT1B receptors are localized presynaptically on the terminals of striatal neurons and Purkinje cells and that they might modulate the release of neurotransmitters such as gamma-aminobutyric acid. The predominant expression of the 5HT1B receptor in the striatum and cerebellum points to an involvement of this receptor in motor control.

Convergence of multi-modal sensory signals at thoracic interneurons of the escape system of the cockroach, Periplaneta americana

Research on the escape system of the cockroach has focused upon the role of giant interneurons in conveying information on wind stimulation from the cerci located on the abdomen to motor control centers in the thoracic ganglia. In the thoracic ganglia the ventral giant interneurons connect to a population of interganglionic interneurons referred to as type A thoracic interneurons. In this paper we have tested the type A interneurons for additional sensory inputs in the absence of ventral giant interneuron activity. We find that the cells that receive ventral giant interneuron activity are also influenced by a variety of additional sensory inputs; wind mediated activity in a pathway that descends from the head, tactile inputs from several loci, auditory stimuli and light responses. Moreover, behavioral observations indicate that at least some of these activities can alter the escape movements. The results suggest that these interneurons serve as a site of convergence for numerous types of sensory activity. They further suggest that the escape system is capable of responding to directional wind information encoded in the ventral giant interneurons in the context of a wealth of additional information.

Factors affecting higher-order movement planning: a kinematic analysis of human prehension

Past studies of the kinematics of human prehension have shown that varying object size affects the maximum opening of the hand, while varying object distance affects the kinematic profile of the reaching limb. These data contributed to the formulation of a theory that the reaching and grasping components of human prehension reflect the output of two independent, though temporally coupled, motor programs (Jeannerod 1984). In the first experiment of the present study, subjects were required to reach out and grasp objects, with or without on-line, visual feedback. Object size and distance were covaried in a within-subjects design, and it was found that both grip formation and reach kinematics were affected by the manipulation of either variable. These data suggest that the control mechanisms underlying transport of the limb and grip formation are affected by similar task constraints. It was also observed that when visual feedback was unavailable after movement onset subjects showed an exaggerated opening of their hands, although grip size continued to be scaled for object size. The question remained as to whether the larger opening of the hand during no-feedback trials reflected the lack of opportunity to fine-tune the opening of the hand on-line, or the adoption of a strategy designed to increase tolerance for initial programming errors. To address this question, a second experiment was carried out in which we manipulated the predictability of visual feedback by presenting feedback and no-feedback trials in a random order. In contrast to the situation in which feedback and no-feedback trials were presented in separate blocks of trials (Exp. 1), in the randomly-ordered series of trials presented in Exp. 2, subjects always behaved as if they were reaching without vision, even on trials where visual feedback was continuously available. These findings suggest that subjects adopt different strategies on the basis of the predictability of visual feedback, although there is nothing to suggest that this takes place at a conscious, or voluntary, level. The results of both experiments are consistent with the notion of a hierarchically-organized motor control center, responsible for optimizing performance under a variety of conditions through the coordination of different effector systems and the anticipation of operating constraints.

Organisation of intersegmental interneurons in the suboesophageal ganglion of Schistocerca gregaria (Forksal) and Locusta migratoria migratorioides (Reiche & Fairmaire) (Acrididae, Orthoptera

The subeosophageal ganglion (SOG) in insects is both a segmental centre coordinating the mouthparts and neck muscles and a suprasegmental motor control centre. Descending interneurons (DINs) and ascending interneurons (AINs) originating in the SOG project to the segmental motor centres of the ventral nerve cord and to the brain, respectively. Here, we show that there are about 300 DINs with cell bodies in the SOG, and present detailed description of the morphology of the 36 largest DINs and 17 AINs, most of which are members of bilateral pairs. Most have extensive dorsal branching usually extending through more than one of the 3 fused segmental neuromeres. All have some ventral or ventrolateral branching, but 2 DINs and 2 AINs are characterised by particularly extensive ventromedial branching. Some of the other AINs have more extensive ventral branching than the DINs. Functional implications of the overlaps of the interneurons with motor, sensory and other interneurons in the SOG support the role of these neurons in suprasegmental co-ordination with a possible subsidiary role in local motor control.

Remote fault/smoke detection for motor control centres

Commercial smoke detectors have been included in the design and installation of switchgear rooms for years. It has been assumed that the use of pendent smoke detectors provided adequate monitoring for the detection of smoke and fire in switchgear rooms. However, reports indicate that smoke detectors are not always triggered even though smoke is evident. In fact, in some cases smoke from electrical equipment was billowing out from under the doors of the switchgear rooms and still no alarm was given. The research and testing of the use of smoke detectors installed directly inside low-voltage motor control centres is described. Also, the reasons why externally mounted devices, such as the ceiling, pendent, or low-elevation smoke detectors, are not adequate in detecting smoldering or burning electrical insulation are addressed. It is concluded that, by installing smoke detectors directly inside and at the bottom of electrical equipment such as motor control centers, improved monitoring for the early detection of insulation failures and fires can be achieved.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Alternative cost-effective applications of power factor correction

Alternative cost-effective methods of applying power factor (PF) correction capacitors are discussed based on actual installations in service for up to ten years. Specific applications and test results from actual installations are presented. The purpose of these application techniques is to utilize existing electrical distribution equipment in the installation of very large values of power factor correction capacitors. It is concluded that PF capacitors can be installed at motor control centers or at the motors, thus providing maximum benefits from reduced reactive current, lower system losses, release of system transformer capacity, and minimum switching transients. Expenses associated with providing numerous traditionally sized PF capacitors, additional disconnects, and/or the installation of large and more costly automatic PF capacitor packages are minimized or eliminated. Paybacks of less than one year can be expected. >

New Life for Existing 480-V Motor Control Center (MCC) Equipment Using Vacuum Contactors

A case history is presented, indicating how an extension of life can be gained for existing 480-V motor starters by use of vacuum technology.

Control of echolocation pulses by neurons of the nucleus ambiguus in the rufous horseshoe bat, Rhinolophus rouxi. II. Afferent and efferent connections of the motor nucleus of the laryngeal nerves.

Horseradish peroxidase was applied by inotophoretic injections to physiologically identified regions of the laryngeal motor nucleus, the nucleus ambiguus in the CF/FM bat Rhinolophus rouxi. The connections of the nucleus ambiguus were analysed with regards to their possible functional significance in the vocal control system, in the respiration control system, and in mediating information from the central auditory system. The nucleus ambiguus is reciprocally interconnected with nuclei involved in the generation of the vocal motor pattern, i.e., the homonomous contralateral nucleus and the area of the lateral reticular formation. Similarly, reciprocal connections are found with the nuclei controlling the rhythm of respiration, i.e., medial parts of the medulla oblongata and the parabrachial nuclei. Afferents to the nucleus ambiguus derive from nuclei of the 'descending vocalization system' (periaqueductal gray and cuneiform nuclei) and from motor control centers (red nucleus and frontal cortex). Afferents to the nucleus ambiguus, possibly mediating auditory influence to the motor control of vocalization, come from the superior colliculus and from the pontine nuclei. The efferents from the pontine nuclei are restricted to rostral parts of the nucleus ambiguus, which hosts the motoneurons of the cricothyroid muscle controlling the call frequency.

Lessons Learned in the Environmental Qualification of Class 1E Equipment at Tennessee Valley Authority

Tennessee Valley Authority has been engaged in an extensive program for the environmental qualification of Class 1E components. This program has been conducted in accordance with the requirements set forth in various industry standards and federal regulations, including IEEE 323-1971, IEEE 323-1974, Nuclear Regulatory Commission (NRC) IE Bulletin 79-01B, NRC NUREG-0588, and the Code of Federal Regulations 10CFR50.49. Valuable lessons have been learned as a result of this program, particularly in the area of environmental qualification testing. This paper describes some unique experiences in the qualification testing of main steam isolation valve control manifold assemblies, control relays, and motor control centers.

Submersible Pumping - Long Beach Unit of East Wilmington Field: A 17-Year Review

Summary The electric submersible pump (ESP) was selected as the primary form of lift when we initiated production operations in Aug. 1965. Deviated production operations in Aug. 1965. Deviated wells with ever increasing volumes resulting from water flooding required the flexibility offered by this lift method. Many problems have been solved in the 17 years of these operations to provide a respectable run life and a sound economic provide a respectable run life and a sound economic operational basis. Introduction The ESP has been the chief form of artificial lift in the Long Beach Unit of the East Wilmington field. From Aug. 1965 through May 1983, a total of 657wells have been produced by submersible pump, with 610 active submersibles currently pump, with 610 active submersibles currently producing 476,000 B/D[75 678 m3/d] gross fluid. producing 476,000 B/D [75 678 m3/d] gross fluid. A number of improvements have been implemented over this 17-year period. These improvements have contributed significantly to reducing the failure rate from a high of 71/month in Oct. 1969 (425 wells) to a low of 10/month in March 1980(503 wells). Failures during 1982 averaged 35 a month from approximately 590active submersible wells. Thirty-two failures (610 wells) were recorded for May1983 (Fig. 2). A recent survey showed an average run life of 800 days for wells in the Ranger zone (4,000 ft [1219 m] measured depth), which has 96% of the 610active submersibles as of May 1983. The improvements are reviewed next. Feed through Mandrel and Pigtail System It was obvious from the beginning that the normal method of packing off around a narmorless section of cable through the wellhead was unsatisfactory from a safety point of view, considering wellheads 6 ft [1.8 m] apart in urban operations. A gas-saturated cable jacket would permit migration of casing head gas into the cellar and also on through the jacket of the upper pigtail to the electrical junction box-both highly unsafe operating conditions. In May 1966, THUMS, in conjunction with a wellhead manufacturer and an electrical connector manufacturer, successfully designed and implemented the feed through mandrel and pigtail system shown in Fig. 1. The system consists of a lower pigtail spliced to the top end of the power cable, an O-ring sealed mandrel through the wellhead (rated at 3 kV AC and 5,000 psi [34.475 MPa]), and an upper pigtail from mandrel to junction box. This system provides complete blockage of gasmigration through the jacket. Mandrel pins are phase-identified for correctrotation, and provide a quick means of recording the electrical provide a quick means of recording the electrical readings of the downhole system. The system also greatly expedites well servicing operations. Fig. 1 shows a typicalpigtail mandrel system with instructions for proper banding. Care should betaken for proper banding and splicing to prevent creation of potential failure points at the splice and molded connector. Solid-State Overload/Underload Controls Our initial operations used submersible pump manufacturers' panels with cumbersome dash pots or meter relays as overload/underload (OL/UL) controls. In1967, we began to use our specially designed space saving pump motor control centers (PMCC). A more reliable OL/UL control device was needed for this PMCC. In May 1970, we, in conjunction with an electrical motor engineer and an electronic engineer, installed a 4- × 7- × 5-in. [102-× 178-× 127-mm] black box in the PMCC on Well J-547 for evaluation as an OL/UL control device. After 1year's evaluation with no problems, the unit was eventually phased into service on all our wells. Improved models currently are being installed on new wells. It is believed that the solid-state control device has accomplished as much as any single improvement in lengthening run time on these wells. Isolation Transformers Dry-type auto transformers were initially used and placed in each PMCC. The early high rate of phase-to-ground cable failures prompted an engineering study that resulted in the adoption of isolation transformers. Some of the first installations of this type of transformer extended the well's run life by 2 to3 years These favorable results led to complete changeover to isolation transformers. Evaluation of Failed Equipment With the increasing failure rate in the late 1960's, production engineers began reviewing the 20 most troublesome wells to detect failure trends and recommend methods for correction. JPT p. 1321

Preventive Maintenance of Controls

Preventive maintenance is stressed as a way to save money and energy. Covered in this article are the maintenance of motor control centers, variable speed drivers, and instrumentation.