Re: voltage on Neutral line, Measurements From Chile
Wow! What kind of three-phase power is this - delta or wye? Is this an example of the neutral conductor not being grounded, and just being a tap on a transformer? On Mon, 28 Jun 1999 17:10:42 -0700, Donald Kimball dkimb...@qualcomm.com wrote: At 12:08 AM 6/29/99 -0700, mvald...@netvision.net.il wrote: What voltages can I expect on the Neutral (referenced to ground) line in various countries and connection systems? Is there a limit on how high the voltage may be, both in normal and fault conditions? Some of our Cellular base stations are located in regions of Chile where power is being intentionally turned off due to low water conditions at hydro-electric plants. We have been montoring the voltage at these sites due to concerns about the battery backup system. The cell sites use 380V Line to Line, 220V Line to Neutral, 3-Phase power. During restoration of power, the voltage on neutral sometimes rises to 220V Line to Ground for several cycles. The voltage on the phases has been measured as great as 440V Line to Line for several cycles, with Line to Neutral voltages as high as 380V. There does not seem to be much power available during this transition time with the wild voltages. Preliminary measurements in Brazil are showing some of the same results. The load regulation at remote sites seems to be a problem. Don Kimball thanks in advance, Moshe Name: moshe valdman E-mail: mvald...@netvision.net.il Phone: 972-54-881334 Telefax: 972-3-5496369 Date: 29/6/99 Time: 0:08:41 -- Patrick Lawler plaw...@west.net - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: voltage on Neutral line
Hi Moshe: The voltage of the neutral with respect to the ground wire is a function of its resistance and its current: E = I * R Maximum normal current is the rating of the fuse or circuit- breaker protecting that particular circuit. For a 120-volt circuit in the USA and Canada, the current would be either 15 or 20 amperes. The resistance is a function of the wire cross-sectional area and its length. According to a licensed electrical engineer colleague, circuits in the USA are designed for a maximum 6% voltage drop, preferably 3% voltage drop at the load. This means that the voltage drop across the neutral from the load to the distribution transformer is 3% maximum, 1.5% preferable. So, the resistance is selected according to maximum voltage drop at the circuit rating. The answer to your question is that the neutral voltage varies from zero to 1.5% nominal, 3% maximum, of the supply voltage depending on load. It further varies with the distance of the point of interest from the point where the neutral is grounded. If the point of interest is within a few feet of the point where the neutral is grounded, then the neutral voltage will be a fraction of a percent. If the point of interest is near the maximum distance from the grounding point, and if the load is also at that point, then the neutral voltage will approach 1.5% nominal to 3% maximum. Fault current is a function of time. Overcurrent devices will operate according to their time-current curves. So, if you know the fault current, then you can calculate the voltage at any point along the neutral according to where the fault current is introduced and where the neutral is grounded. Fault current exists only for the period of time it takes to operate the overcurrent device (I-T curve). For a 120-volt system, you can expect about 1.8 volts drop nominal, 3.6 volts maximum, assuming a single, maximum load furthest from the point of grounding, and your measurement is also at that point. Best regards, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 858 655 3329 16399 West Bernardo Drive FAX : +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com - - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: voltage on Neutral line, Measurements From Chile
At 12:08 AM 6/29/99 -0700, mvald...@netvision.net.il wrote: Hello everyone, What voltages can I expect on the Neutral (referenced to ground) line in various countries and connection systems? Is there a limit on how high the voltage may be, both in normal and fault conditions? Some of our Cellular base stations are located in regions of Chile where power is being intentionally turned off due to low water conditions at hydro-electric plants. We have been montoring the voltage at these sites due to concerns about the battery backup system. The cell sites use 380V Line to Line, 220V Line to Neutral, 3-Phase power. During restoration of power, the voltage on neutral sometimes rises to 220V Line to Ground for several cycles. The voltage on the phases has been measured as great as 440V Line to Line for several cycles, with Line to Neutral voltages as high as 380V. There does not seem to be much power available during this transition time with the wild voltages. Preliminary measurements in Brazil are showing some of the same results. The load regulation at remote sites seems to be a problem. Don Kimball thanks in advance, Moshe Name: moshe valdman E-mail: mvald...@netvision.net.il Phone: 972-54-881334 Telefax: 972-3-5496369 Date: 29/6/99 Time: 0:08:41 - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators). - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: voltage on Neutral line
What voltages can I expect on the Neutral (referenced to ground) line in various countries and connection systems? Is there a limit on how high the voltage may be, both in normal and fault conditions? Moshe, THE's booklet, World Electricity Supplies, lists the supply voltage, frequency, and power distribution systems used in over 200 countries. You can order it through Technical Standards Services, Ltd. webpage at http://www.techstandards.co.uk/thsguide.html TN and TT power systems (IEC 950 1.2.12.1 and 1.2.12.2) are the ones usually encountered. Neutral-to-ground voltages should be less than a few (5 or so) volts even under a line-to-ground fault. Hospitals and other high-reliability installations sometimes use IT power systems (IEC 950 1.2.12.3) permitting continued operation even if a line-to-ground fault occurs-- at the cost of: * Neutral-to-ground voltage approaching the single-phase line voltage. * In a three-phase system, the other phase-to-ground voltages approaching sqrt(3) times the single-phase line voltage. This can double the required creepage and clearance distances for (to us) a tiny additional market. So we specify that our products are not to be installed on IT power systems, but may be powered by an isolation transformer that gets its power from an IT power system to create a local TN-S power system. John Barnes Advisory Engineer Lexmark International - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
voltage on Neutral line
Hello everyone, What voltages can I expect on the Neutral (referenced to ground) line in various countries and connection systems? Is there a limit on how high the voltage may be, both in normal and fault conditions? thanks in advance, Moshe Name: moshe valdman E-mail: mvald...@netvision.net.il Phone: 972-54-881334 Telefax: 972-3-5496369 List-Post: emc-pstc@listserv.ieee.org Date: 29/6/99 Time: 0:08:41 - This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: unsubscribe emc-pstc (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
