re: Safety testing after equipment repair
Rich, Your colleague may be correct in his theory, but the only 'real-life' example I am aware of relates to deterioration of a connector containing EMI suppression capacitors. The capacitors were hi-pot tested as components, were tested again as part of the connector by a second manufacturer, when incorporated into a cable assembly by a third manufacturer and finally when incorporated in the end-product: always using a D.C. voltage. Problems were identified when the dielectric broke down at the much lower normal working voltage of the connector and the connector overheated as a result (the capacitors were located in a power supply line). Subsequent tests in the lab showed that the problem resulted from the excessive hi-pot testing. Another issue I would foresee of using only a DC voltage in production is that the dv/dt can be much higher than using an AC test voltage (some of which can be set to start the ramp-up at zero volts) if the test engineer decides to use a ramp time that is too short. Another 'issue' with DC Hi-pot testers is that they usually have a high output resistance and so it is necessary to measure the applied voltage directly rather than by using a third winding on the EHT transformer as can be the case with 500 VA + AC testers (otherwise the indicated voltage is higher than the actual applied voltage). In general therefore, it seems wise to use the minimum voltage setting permitted in the standard and to select a ramp time that is long enough not to over-stress the insulation and a dwell time that is as short as permitted in the standard. If you're going to use a DC voltage, make sure that voltage indicated on any meter associated with the hi-pot tester is the actual voltage applied. Some of the more expensive hi-pot testers also have an 'ionisation' detection function that signals the existence of r.f. currents that precede breakdown, i.e, a form of partial discharge testing. Regards, Richard Hughes Safety Answers Limited. From: ri...@sdd.hp.com [mailto:ri...@sdd.hp.com] Sent: Friday, May 23, 2003 10:01 PM To: rsto...@lucent.com Cc: emc-p...@majordomo.ieee.org Subject: Re: Safety testing after equipment repair Hi Richard: is the below information true for both the AC and DC hipot methods? Some companies have contractors,subcontractors, incoming and final hipot... so it does and can occur at least 4 times, before its shipped to a customer. The theory says that the onset of the breakdown process starts with partial discharge in voids within solid insulation. Partial discharges occur more rapidly with change of voltage. Therefore dc voltages have a lower deteriorating effect than ac voltages. I have a colleague who, for this reason, insists on dc voltage for production-line tests. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi Richard: is the below information true for both the AC and DC hipot methods? Some companies have contractors,subcontractors, incoming and final hipot... so it does and can occur at least 4 times, before its shipped to a customer. The theory says that the onset of the breakdown process starts with partial discharge in voids within solid insulation. Partial discharges occur more rapidly with change of voltage. Therefore dc voltages have a lower deteriorating effect than ac voltages. I have a colleague who, for this reason, insists on dc voltage for production-line tests. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in 200305231749.kaa15...@epgc264.sdd.hp.com) about 'Safety testing after equipment repair' on Fri, 23 May 2003: I stand by my statements. You added a lot more information. In the light of that, I agree that your results are likely to be more representative than your first description suggested. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi John: There is a justification for a high-current test **where it won't cause any new damage**. The justification is that it will find bad joints in the PEC path, and stranded PEC and bond wires that have only one or two strands still intact. The high-current test will NOT find bad joints. The high-current test WILL find bond wires that have only 1 or 2 strands, and marginally for 3 strands. Finding strand damage is a function of the heat sinking provided to the remaining strands. See: http://www.ewh.ieee.org/soc/emcs/pstc/psn/ Download: 97v10n1.pdf 97v10n2.pdf These describe the experiments I performed on both strands and joints. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
UK in-service continuing compliance testing (was: RE: Safety testing after equipment repair)
All - As a matter of curiosity, are there any records of drop-out rates (for equipment that was required to be removed from service)? Short of that, any anecdotes? Are the pass/fail criteria identical to those during type testing? Richard - You say, former piece of UK legislation. As in, passed into law, or, passed away. Regards, Peter L. Tarver, PE Product Safety Manager Sanmina-SCI Homologation Services San Jose, CA peter.tar...@sanmina-sci.com From: Richard Hughes Sent: Thursday, May 22, 2003 5:15 PM Rich, Gregg, The referenced document is The Electricity at Work Regulations 1989 and they were implemented as a Statutory Instrument under the Health and Safety at Work etc. Act 1973. The former piece of UK legislation has kept many a UK electrician in gainful employment over the years. It is also why, if you come to the UK, you often see paper labels saying 'tested for safety' or the like on mains powered products. This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
I agree with Alice on the arrangement of Hi-Pot for new products, but I think the question was returned products for repair, correct. I read John W's note with interest, but I also remember a note from Rich Nute about a test he ran that pretty much pointed out that a simple continuity test served about the same purpose. Rich, I hope I'm not putting words in your mouth -- I apologize in advance if I have. If I remember Rich's much earlier note, he ran the tests with very few of the original PEC wire strands in place. Finally all of this brings up an interesting question about the aging of protective systems. Most of you know that I'm not in favor or writing or even changing standards just because one can do it, there must be some new problem that the old standard doesn't address before it should be changed. Having said all of that, how does the standard address aging of the insulation system, other than mentioning that the system should be in a well warmed condition before hi-pot? Gary This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi John: I don't think you can draw universal conclusions from just one experiment. In addition, the rate of increase of voltage is limited in the test procedures. In your experiment, there was only one increase of voltage, whereas in repeated testing, there are many. At best, we don't know if that matters or not. My test involved several different units from different manufacturers connected in parallel. The applied voltage was 60 Hz, so there was continuous change of voltage, which is the worst-case for inducing dielectric breakdown (compared to dc or an impulse). If you do a web search, you will find that the numbers I mentioned are in line with those published in web articles and research. For example, see: http://www.quin-t.com/pdfs/cequinvaramid.pdf http://www.wmea.net/partial_discharge_theory.htm http://literature.agilent.com/litweb/pdf/5965-5977E.pdf This last web site has curves showing wear-out curves for optocoupler insulation, both steady-state and impulse. These curves correspond to my findings from my tests (which were power supplies for IT equipment). I stand by my statements. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Safety testing after equipment repair
Ah Yes, emperical data; the essence of good engineering. Thank you Mr. Nute. I have performed similiar long-term tests (I hope my employer does not see this) on our iso xfmrs and component SMPS. I have recorded only (1) failure; root cause was a (latent) manufacturing defect: pressure indentation on an insulator pad that failed at hi-pot count 197. I had a (very) small xfmr, that is provides iso for a SMPS that I hi-potted at 3000Vac for approx 45 min. Detected some audio buzzing, but no breakdown. I have also hi-potted a 0.005in thick sheet of valox, using point probes, at 5000Vac for 20 min with no breakdown, but a lot of buzzing. luck, Brian -Original Message- From: Rich Nute [ mailto:ri...@sdd.hp.com] Sent: Thursday, May 22, 2003 6:23 PM To: j...@jmwa.demon.co.uk Cc: emc-p...@majordomo.ieee.org Subject: Re: Safety testing after equipment repair Hi John: My last (3) employers have required all repaired or modified units to be hi-potted. If a unit has been repaired, then the cover was removed, and the unit is no longer controlled by the oroginal production hi-pot. I think this is too stringent. Repeated hi-pot tests must be *minimised*, because of the possibility of progressive degradation of insulation. Yes, indeed, repeated hi-pot tests must be minimized. However, significant degradation of modern insulations at these low voltages and durations is doubtful for the lifetime of the equipment. Some years ago, I undertook a test to determine when an insulation would fail if subjected to a continuous hi-pot voltage. I connected several units to the hi-pot voltage for 8 hours/day. The units started failing after about 10 days. That would be about 48,000 minutes. So, we can say that we should probably not exceed 1/1000th of 48,000 minutes, 48 minutes, of hi-pot test time for the equipment lifetime. That would be 48 1-minute hi-pot tests. I don't believe any equipment would be so tested. Now, the transients are only 50 microseconds. 1.2 million transients would comprise one minute of degradation. As I recall, an industrial site would incur 5-10 such transients per day. That means, about 120,000 days for an accumulation of 1 minute of overvoltage. That's over 300 years. While repeated hi-pot tests must be minimized, the degradation due to repeated hi-pot tests is not likely to have an effect for the lifetime of the equipment. Best regards, Rich
RE: Safety testing after equipment repair
Rich, I have only one question concering the deterioration, initally tested at higher cuurent for ground bond, then over months?(time)..a lower current would be used.. is there a chart for what current might be used? based on: age humidity of installation current running thru it continously. I'd like to get a feel of whats acceptable when you go to do the test much later after the initial installation thank you, Richard, From: richhug...@aol.com [mailto:richhug...@aol.com] Sent: Thursday, May 22, 2003 8:15 PM To: ri...@sdd.hp.com; gr...@test4safety.com Cc: bar...@melbpc.org.au; emc-p...@majordomo.ieee.org Subject: re: Safety testing after equipment repair Rich, Gregg, Gregg, your memory is slipping - clearly you have been away from the UK for too long, or you're enjoying the American wine too much! The referenced document is The Electricity at Work Regulations 1989 and they were implemented as a Statutory Instrument under the Health and Safety at Work etc. Act 1973. The former piece of UK legislation has kept many a UK electrician in gainful employment over the years. It is also why, if you come to the UK, you often see paper labels saying 'tested for safety' or the like on mains powered products. Within the UK trade association for IT Equipment (EEA it was at the time) we developed a set of Guidelines to enable customers to both meet the requirements of the Electricity at Work Regulations and not damage equipment too much. We did not recommend repeated dielectric withstand testing because this could lead to premature damage to insulation, as has been pointed out already. For earth bond test we suggested that only a low current would normally be required because the equipment would have been type tested at a higher current anyway and the intention of these Regulations is to show up deterioration of products in the workplace caused by normal wear and tear. We did recommend that insulation resistance tests be conducted: we also recognised that the insulation resistance test would produce values far higher than those previously contained within IEC 380 (2 Mohms for Basic and 5 Mohms for Reinforced if memory serves) and so we recommended that successive readings be recorded so that any downward 'jumps' in resistance could be investigated further. Of course, if you try and compare readings from a cold, dry, winter day to a hot and humid summer day then that is going to give variability, as will different test equipment and a whole range of other variables. Still, it beats degrading the equipment's insulation. Since then EA became FEI who are now called 'Intellect'. Space for comments here... The EEA worked with the IEE and I believe that the IEE Guidelines are still available, for a fee. See http://www.iee.org/Publish/ Within the EEA we did not see much point in measuring leakage current (now called protective conductor current in IEC 60990) since the major component of such current for IT equipment will be due to RFI capacitors. Of course, if you can find some inexpensive test equipment that is able to provide an accurate measurement of the dc component then that's another matter... Of course, if you really wanted to be fancy then you could conduct a partial discharge test. However, most repair shops are not likely to have such kit sitting around. Regards, Richard Hughes Safety Answers Ltd From: ri...@sdd.hp.com [mailto:ri...@sdd.hp.com] Sent: Thursday, May 22, 2003 7:07 PM To: gr...@test4safety.com Cc: bar...@melbpc.org.au; emc-p...@majordomo.ieee.org Subject: Re: Safety testing after equipment repair Hi Gregg and Barry: Australia has an actual standard which lists the tests and procedures for the regular testing of equipment in use, and equipment that has been So has the UK. it was called (something like) The Electricity at Work Act generally a good thing put a dangerously and poorly implemented concept that allowed untrained unprofessionals to destroy a huge amount of IT equipment and charge the customer for it. As a result we had several thousand monitors damaged by 25 Amps being passed between the RGB Coax- grounds and PEG Another anecdote (read horror story) from the UK requirement for periodic safety testing... We had the unfortunate experience of the same UK requirement for periodic testing of Class III equipment for 25 amps from accessible conductive parts. This test destroyed a run on the circuit board, which was a failure of the 25-amp test, which resulted in destruction of the unit! The customer demanded replacement of the units because they failed the test! He did not realize that the test itself was causing the failure, nor that the test was causing destroying the unit. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send
RE: Safety testing after equipment repair
Rich, is the below information true for both the AC and DC hipot methods? Some companies have contractors,subcontractors, incoming and final hipot... so it does and can occur at least 4 times, before its shipped to a customer. Richard, From: Rich Nute [mailto:ri...@sdd.hp.com] Sent: Thursday, May 22, 2003 9:23 PM To: j...@jmwa.demon.co.uk Cc: emc-p...@majordomo.ieee.org Subject: Re: Safety testing after equipment repair Hi John: My last (3) employers have required all repaired or modified units to be hi-potted. If a unit has been repaired, then the cover was removed, and the unit is no longer controlled by the oroginal production hi-pot. I think this is too stringent. Repeated hi-pot tests must be *minimised*, because of the possibility of progressive degradation of insulation. Yes, indeed, repeated hi-pot tests must be minimized. However, significant degradation of modern insulations at these low voltages and durations is doubtful for the lifetime of the equipment. Some years ago, I undertook a test to determine when an insulation would fail if subjected to a continuous hi-pot voltage. I connected several units to the hi-pot voltage for 8 hours/day. The units started failing after about 10 days. That would be about 48,000 minutes. So, we can say that we should probably not exceed 1/1000th of 48,000 minutes, 48 minutes, of hi-pot test time for the equipment lifetime. That would be 48 1-minute hi-pot tests. I don't believe any equipment would be so tested. Now, the transients are only 50 microseconds. 1.2 million transients would comprise one minute of degradation. As I recall, an industrial site would incur 5-10 such transients per day. That means, about 120,000 days for an accumulation of 1 minute of overvoltage. That's over 300 years. While repeated hi-pot tests must be minimized, the degradation due to repeated hi-pot tests is not likely to have an effect for the lifetime of the equipment. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
I read in !emc-pstc that richhug...@aol.com wrote (in 014C7BA9.2FB45A16 .0ba45...@aol.com) about 'Safety testing after equipment repair' on Thu, 22 May 2003: For earth bond test we suggested that only a low current would normally be required because the equipment would have been type tested at a higher current anyway and the intention of these Regulations is to show up deterioration of products in the workplace caused by normal wear and tear. There is a justification for a high-current test **where it won't cause any new damage**. The justification is that it will find bad joints in the PEC path, and stranded PEC and bond wires that have only one or two strands still intact. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
I read in !emc-pstc that Rich Nute ri...@sdd.hp.com wrote (in 200305230123.saa09...@epgc264.sdd.hp.com) about 'Safety testing after equipment repair' on Thu, 22 May 2003: Some years ago, I undertook a test to determine when an insulation would fail if subjected to a continuous hi-pot voltage. I connected several units to the hi-pot voltage for 8 hours/day. The units started failing after about 10 days. That would be about 48,000 minutes. I don't think you can draw universal conclusions from just one experiment. In addition, the rate of increase of voltage is limited in the test procedures. In your experiment, there was only one increase of voltage, whereas in repeated testing, there are many. At best, we don't know if that matters or not. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi John: My last (3) employers have required all repaired or modified units to be hi-potted. If a unit has been repaired, then the cover was removed, and the unit is no longer controlled by the oroginal production hi-pot. I think this is too stringent. Repeated hi-pot tests must be *minimised*, because of the possibility of progressive degradation of insulation. Yes, indeed, repeated hi-pot tests must be minimized. However, significant degradation of modern insulations at these low voltages and durations is doubtful for the lifetime of the equipment. Some years ago, I undertook a test to determine when an insulation would fail if subjected to a continuous hi-pot voltage. I connected several units to the hi-pot voltage for 8 hours/day. The units started failing after about 10 days. That would be about 48,000 minutes. So, we can say that we should probably not exceed 1/1000th of 48,000 minutes, 48 minutes, of hi-pot test time for the equipment lifetime. That would be 48 1-minute hi-pot tests. I don't believe any equipment would be so tested. Now, the transients are only 50 microseconds. 1.2 million transients would comprise one minute of degradation. As I recall, an industrial site would incur 5-10 such transients per day. That means, about 120,000 days for an accumulation of 1 minute of overvoltage. That's over 300 years. While repeated hi-pot tests must be minimized, the degradation due to repeated hi-pot tests is not likely to have an effect for the lifetime of the equipment. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
re: Safety testing after equipment repair
Rich, Gregg, Gregg, your memory is slipping - clearly you have been away from the UK for too long, or you're enjoying the American wine too much! The referenced document is The Electricity at Work Regulations 1989 and they were implemented as a Statutory Instrument under the Health and Safety at Work etc. Act 1973. The former piece of UK legislation has kept many a UK electrician in gainful employment over the years. It is also why, if you come to the UK, you often see paper labels saying 'tested for safety' or the like on mains powered products. Within the UK trade association for IT Equipment (EEA it was at the time) we developed a set of Guidelines to enable customers to both meet the requirements of the Electricity at Work Regulations and not damage equipment too much. We did not recommend repeated dielectric withstand testing because this could lead to premature damage to insulation, as has been pointed out already. For earth bond test we suggested that only a low current would normally be required because the equipment would have been type tested at a higher current anyway and the intention of these Regulations is to show up deterioration of products in the workplace caused by normal wear and tear. We did recommend that insulation resistance tests be conducted: we also recognised that the insulation resistance test would produce values far higher than those previously contained within IEC 380 (2 Mohms for Basic and 5 Mohms for Reinforced if memory serves) and so we recommended that successive readings be recorded so that any downward 'jumps' in resistance could be investigated further. Of course, if you try and compare readings from a cold, dry, winter day to a hot and humid summer day then that is going to give variability, as will different test equipment and a whole range of other variables. Still, it beats degrading the equipment's insulation. Since then EA became FEI who are now called 'Intellect'. Space for comments here... The EEA worked with the IEE and I believe that the IEE Guidelines are still available, for a fee. See http://www.iee.org/Publish/ Within the EEA we did not see much point in measuring leakage current (now called protective conductor current in IEC 60990) since the major component of such current for IT equipment will be due to RFI capacitors. Of course, if you can find some inexpensive test equipment that is able to provide an accurate measurement of the dc component then that's another matter... Of course, if you really wanted to be fancy then you could conduct a partial discharge test. However, most repair shops are not likely to have such kit sitting around. Regards, Richard Hughes Safety Answers Ltd From: ri...@sdd.hp.com [mailto:ri...@sdd.hp.com] Sent: Thursday, May 22, 2003 7:07 PM To: gr...@test4safety.com Cc: bar...@melbpc.org.au; emc-p...@majordomo.ieee.org Subject: Re: Safety testing after equipment repair Hi Gregg and Barry: Australia has an actual standard which lists the tests and procedures for the regular testing of equipment in use, and equipment that has been So has the UK. it was called (something like) The Electricity at Work Act generally a good thing put a dangerously and poorly implemented concept that allowed untrained unprofessionals to destroy a huge amount of IT equipment and charge the customer for it. As a result we had several thousand monitors damaged by 25 Amps being passed between the RGB Coax- grounds and PEG Another anecdote (read horror story) from the UK requirement for periodic safety testing... We had the unfortunate experience of the same UK requirement for periodic testing of Class III equipment for 25 amps from accessible conductive parts. This test destroyed a run on the circuit board, which was a failure of the 25-amp test, which resulted in destruction of the unit! The customer demanded replacement of the units because they failed the test! He did not realize that the test itself was causing the failure, nor that the test was causing destroying the unit. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion
Re: Safety testing after equipment repair
I read in !emc-pstc that Peter L. Tarver peter.tar...@sanmina-sci.com wrote (in nebbkemlgllmjofmoplekemhegaa.peter.tar...@sanmina-sci.com) about 'Safety testing after equipment repair' on Thu, 22 May 2003: Or a lower potential test for mains connected equipment, such as insulation resistance. No, an IR test is not a substitute for a hi-pot test, and has a can of worms all its own. Pass values of leakage resistance are in the megohm range, but much modern equipment starts off in the 100 megohm or even gigohm range. So a degradation to 1 or 2 megohms could well be a sign of seriously-damaged insulation, but the equipment is regarded as OK. In my opinion, a value less than one-third of the initial value (preferably specified by the manufacturer) is a cause for concern. More complicated, but less deleterious, tests could include an earth leakage current test or a touch current test. Earth leakage is often appropriate but it is necessary to distinguish between resistive leakage and capacitive current. I don't know of any snags with touch current testing IF the IEC 60999 meter is used. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Safety testing after equipment repair
John - Or a lower potential test for mains connected equipment, such as insulation resistance. More complicated, but less deleterious, tests could include an earth leakage current test or a touch current test. From: John Woodgate Sent: Thursday, May 22, 2003 12:19 PM Repeated hi-pot tests must be *minimised*, because of the possibility of progressive degradation of insulation. A possible solution is to say that a hi-pot test is required if a visual inspection by a supervisor indicates that it is necessary. This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Hi Gregg and Barry: Australia has an actual standard which lists the tests and procedures for the regular testing of equipment in use, and equipment that has been So has the UK. it was called (something like) The Electricity at Work Act generally a good thing put a dangerously and poorly implemented concept that allowed untrained unprofessionals to destroy a huge amount of IT equipment and charge the customer for it. As a result we had several thousand monitors damaged by 25 Amps being passed between the RGB Coax- grounds and PEG Another anecdote (read horror story) from the UK requirement for periodic safety testing... We had the unfortunate experience of the same UK requirement for periodic testing of Class III equipment for 25 amps from accessible conductive parts. This test destroyed a run on the circuit board, which was a failure of the 25-amp test, which resulted in destruction of the unit! The customer demanded replacement of the units because they failed the test! He did not realize that the test itself was causing the failure, nor that the test was causing destroying the unit. Best regards, Rich This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
I read in !emc-pstc that Brian O'Connell boconn...@t-yuden.com wrote (in f7e9180f6f7f5840858d3db815e4f7ad1f2...@cms21.t-yuden.com) about 'Safety testing after equipment repair' on Thu, 22 May 2003: My last (3) employers have required all repaired or modified units to be hi-potted. If a unit has been repaired, then the cover was removed, and the unit is no longer controlled by the oroginal production hi-pot. I think this is too stringent. Repeated hi-pot tests must be *minimised*, because of the possibility of progressive degradation of insulation. A possible solution is to say that a hi-pot test is required if a visual inspection by a supervisor indicates that it is necessary. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Safety testing after equipment repair
Australia has an actual standard which lists the tests and procedures for the regular testing of equipment in use, and equipment that has been repaired. I believe the standard is compulsory for building sites. Regards Barry Esmore AUS-TICK 281 Lawrence Rd Mount Waverley Vic 3149 Australia Ph: 61 3 9886 1345 Fax: 61 3 9884 7272 - Original Message - From: richwo...@tycoint.com To: emc-p...@majordomo.ieee.org Sent: Thursday, May 22, 2003 6:46 AM Subject: Safety testing after equipment repair Management is asking me if we really need to perform certain safety inspections and tests after the equipment is repaired. Of course, the answer is that the inspections and/or tests are a prudent action to ensure continued safety of the product. Then they ask Does anyone else do it? Good question. Here is what we do. We intentionally tried to minimize the amount of inspections and testing. The protocol consists of certain visual inspections for such things as damaged insulation and missing fasteners; and a hypot test is specified only if the safety critical part being changed would be stressed by the test. So, let me pose the question - Does your company perform specified safety inspections and/or tests after repair of mains circuits? Richard Woods Sensormatic Electronics Tyco International This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
