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 2022 - April - McGregor - Motor generators, 240V (MEN) and Isolated power supplies for signalling |
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Peter McGregorBEng (Elect) GradDip(SysEng) FIRSE JMDRailtech In NSW country areas we have historically used diesel motor generator sets to provide 120V AC power to operate signalling equipment in the field. With new technologies with electronics/inverters and the drive to use COTS (Commercial off the shelf) equipment we are using 240V commercial generator sets as opposed to the customised (e.g., Lister brand) old style generator sets at 120V AC. With updates to AS3000 and AS3010 in the past few years for generator sets are we sure that our wiring installations are up with the latest when using 240V commercial wiring practices? Signalling 120 V ac 50 Hz uses the IEC 60364 (all parts) Low voltage electrical installations IT ac power distribution system. General 240 V ac low voltage (LV) power distribution uses the TN C S ac power distribution system in accordance with IEC 60364. The general 240 V ac power supply does not provide any functional safety for signalling. Do we have the right Earthing? Multiple Earth Neutral (MEN) or are- are we using a mixture of standards? What about circuit breaker discrimination and the right earth loop- neutral impedance to ensure these circuit breakers clear under all fault conditions? Should I use an earth loop impedance tester to check? Should I consider using RCD (Residual Current Devices)s? Do I have the right installation for the signalling load? What about the surge protection requirements for my installation? Which Gen set should I use? Four pole or 2 pole for the Automatic Transfer Switch (ATS) Why do I need to choose? This paper has a brief look at some of the history with motor generator sets. Discusses some of the changes that have been undertaken over the years Look at MEN (Multiple Earth Neutral), Earthing surge protection, wiring and installation practices against current AS3000 and AS3010. Provide some recommendations for future installation of backup power supplies, motor gen sets, and surge protection using COTS equipment for signalling power supplies. |
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