January 2007
Meissner Meissner Uninterruptible Power provides essential power solutions on a turnkey basis to a wide range of markets where power interruption is not an option. One of the lines supplied and supported by Meissner is the Eaton Powerware range which ensures performance and reliability for critical applications. See page 43
Regular FeaturesIndex to Advertisers
Drives, Motor Control, Protection and SwitchgearTrends in the use of motor protection relays E Stokes, Waller, Schweitzer Engineering Laboratories Motor protection relays are essential components in your system. A variety of such devices are available, and this article will not review the full range. What we do aim to achieve, however, is to furnish you with a basic understanding of the role and operations of such devices. The article therefore considers some fundamentals of motor protection. It should be noted that the protection elements discussed does not constitute a complete set of motor protection requirements.
Take note:
*Protection of equipment relates to thermal behaviour of the same
*Ease of setting IEDs and monitoring with same influence equipment life-time performance
*Quality is the key to successful integration and automation
About the author:
Edmund Stokes-Waller obtained his Bachelors and Masters Degrees in Engineering (heavy current) from the University of Pretoria and is registered as a Professional Engineer with the Engineering Council of South Africa. He has been involved in the area of power system protection, integration and automation at all levels (industrial and utility) for 12 years.
Edmund can be contacted on (012) 664-5930 or edmust@selinc.com Round up New VSD for air-conditioning industry
Lapp products for automation solutions
Insulation material for high voltage motors
Hitachi's improved ac servo drive series
Motor proteciton relay with communications protocol
Fieldbus compatible positioning drives
Commitment, local design and manufacture pays off
Earthing, Lightning Protection and Industrial EMCElectrical protection - a key element in mine safety: Part 2 V Cohen, CBI-electric Previously, we reviewed the requirements of electrical protection (1). Here we will review suitable strategies for ensuring electrical safety in a mining environment. Mining environments are harsh, and it is pertinent to commence with some background on protection in the mining environment.
Take note:
* Earth leakage protection was introduced to provide reliable protection against the hazards of electrocution
* The purpose of the earthing conductor is to provide a path for fault current to flow - and hence operate an over-current protection device
* Internationally a tripping sensitivity of 30 mA is required to avoid ventricular fibrillation
* In a mining environment, sensitivities of 250 mA (and even up to 1 000mA in certain cases) are preferred in order to avoid unwanted tripping
About the author:
Viv Cohen is presently CBI-electric's low voltage consultant. He is a member of the SANS 10142-1 working group. In his fields of expertise, he also represented the SABS and South African interests internationally at the IEC.
Viv can be contacted on vcohen@cbi.electric.com Lightning safety M D Grant and K J Nixon, University of the Witwatersrand This article provides a basic overview of the lightning phenomenon, the relationship between lightning and meterological phenomena and a simple, yet effective means to gauge the potential risk
Take note:
*There is no relationship between rainfall and lightning - lightning strikes regardless of how wet it is
*The lightning threat can be assessed with the flash-to-bang timing method
Secondary effects like step and touch potentials as well as a direct lightning strike can be fatal
Lightning strikes are responsible for as many as 420 deaths per year in South Africa
About the authors:
Michael Grant, principal author of the article, has a BSc (Eng) Electrical and an MSc (Eng) from the University of the Witwatersrand, where he has started his PhD in the School of Electrical and Informatio nEngineering. SInce graduating in 2004, Michael has spen this time developing a rocket triggered-lightning platform for the University to continue further research into the lightning phenomenon. He is an avid mountaineer and convenor for the Mountain Search and Rescue team in Gauteng.
Michael can be contacted on m.grant@ee.wits.ac.za
Ken Nixon holds a BSc in Electrical Engineering as well as an MSc and PhD degree from the University of the Witwatersrand, Johannesburg, where he is at present a lecturer in the School of Electrical and Information Engineering. His research interests include earthing and lightning protection, high voltage engineering and information and software engineering.
Ken can be contacted on k.nixon@ee.wits.ac.za Round up Modular multi-pole surge arresters
Earth insulation lock-out relays
Power factor improvement reduces transmission line losses
ICT - Industrial wireless communicationsFuture industrial wireless concepts based on thin access points F Seufert, Hirschmann The installation of radio networks in factory automation is still characterised by relatively expensive hardware and expensive planning and start-up costs. This article investigates the claims that both the cost of hardware and installation can be reduced, whilst having the benefit of better functionality, scalability, flexibility and extensibility.
Take note:
*Wireless networking is one of the fastest-growing technology sectors
*The wireless switch with shifted intelligence offers a superior approach to WLAN
*Wireless switch technology, with centralised intelligence, offers better functionaliry, scalability, flexiblity and extensibility
About the author:
Frank Seufert currently holds the position of products manager of the Wireless Division at Hirschmann Automation and Control, Neckartenzlinge, Germany. Hirschmann is locally represented by Industrial Automation and Control (IAC).
IAC can be contacted locally at burg@iacontrol.co.za
The case for an auto-routing WLAN backbone to solve network interruption problems C Maasch, SSE Cape Have you ever closed a tap suddenly and heard a 'knocking' sound from the plumbing system? We refer to this effect as a water hammer. In a house it is of curiosity value only - in industry its effect can be devastating. In this aticle we examine an interesting case study where non-optimal communications lead to a water hammer effect at Coega harbour. We discuss how the problem was solved.
Take note:
*An industrial WLAN requires rigorous engineering
*A WLAN can be set up to be auto-routing
*At any time, actual network topology depends on the status of the links, as determined by the auto-router
About the author:
Clive Maasch has his N6 national techical certificate in electronics, BMR marketing certificate from UNISA and a marketing diploma from Damelin College. He has 15 years sales, marketing and engineering experience in the telemetry, wireless and industrial automation market sectors. Clive currently holds the position of sales and marketing director of SSE-Group and is the managing member SSE Cape.
Clive can be contacted on (021) 552 0420 or clive@sse.co.za
Industrial information and communication systemsRound up Wireless electrical sub-metering components
Requirements for WLAN in Ex areas
VHF data modem and network management software
Honeywell unveils industrial wireless roadmap
Siemens brings two new wireless modules to market
News and ProductsASSTech acquires three new agencies
SEW competition winner
Honeywell leads in realtime process optimisation market
25 000 analytical instruments delivered
Pre-paid meter solutions for Witbank and Alexandra
Top emerging software vendor
High performance magmeter launched
Baldor acquires power systems business of Rockwell
Emerson award to Liebert
OEN partners with BBBEE consortium
A new partnership to lead the way in HMIs
Portable non-contact infrared thermometers
Winners exemplify skills and training success
Robot acquisition finalised
Pressure and level measurement and controlApplication of pulsed radar to measure the level of plastic granulate and powder H Sack, Vega Radar level measurement is growing in popularity as its benefits and its suitability for various applications are understood [1,2,3,4]. This article considers an application involving dusty, granulate plastic material and argues that pulsed radar offers both improved reliability and better accuracy.
Take note:
*Radar level sensing is not influenced by process pressure and temperature in the application described
*Dust does not adversely affect the radar signal
*Radar level gauges are available with a variety of antenna types and swivel mounts for optimal positioning
About the author:
Holger Sack has his Dipl.Ing. and currently holds a position in the product management ultrasonics, radar division at Vega Grieshaber.
Holder can be contacted at press@de.vega.com or contact Vega locally, (011) 958 1901 or john.groom@za.vega.com Round up Precision pressure switch
Innovative process pressure transmitter
Amazing level switch
Reliable level measurement in high-pressure applications
Pressure transmitter with LED display
Digital manometer with switch outputs
Standby and Backup SystemsBalancing scalability and reliability in the critical power system M J Wilson, Emerson Network Power Industry has a growing reliance on critical power supplies and a number of authors have recently tackled various aspects of this topic [1,2,3]. The topic is currently also a somewhat emotional one, emphasising the need to make rational decisions. Let's review how to make an appropriate investment.
Take note:
*When n + 1 redundancy is used, UPS modules should be sized so that the total anticipated load can be carried by three modules
*There are significant differences in how scalability applies to power systems and IT systems
*The investment in support systems needs to be weighed against their value to the business
*Critical power system availability must be 100 times greater than the availability of the systems being supported
About the author:
Mark Wilson currently holds the position of sales manager, Emergency Network Power, Liebert UPS products in South Africa. The article was sourced by Mike from Emerson Network Power's archives.
Mike can be contacted on mikejwilson@emersonnetworkpower.com
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