Re: High temperature coaxial cable
Cable noise? Don't forget that all these esoteric materials, especially the high voltage types, demonstrate a pretty active triboelectric effect. I assume the spectrum drops a lot with the distributed capacitance, don't know how much. When the cable is first manufactured, it's pretty tight, so quiet. But when the cable ages and loosens up, it can start to become noisy. If you need low noise cable, you may wish to include such performance in your purchasing spec. - Robert - On Tue, 9 Aug 2005 08:36:29 -0700 (PDT) Bob Richards wrote: > Ian, > > You did not mention frequency range, but RG393 is > rated to 5kv (with proper connectors) and 200C. It is > good up to 1 or 2 GHz. > > http://www.pasternack.com/Search/SearchResults.asp?partNum=rg393%2Fu&RecNo=0 > > Pasternack also has some special high-voltage "C" > connectors, part num PE4950, and "SHV" connectors, > which are rated for high voltages. The normal type "N" > connectors are not rated for high voltages. > > Bob Richards, NCT > > --- "Gordon,Ian" wrote: > > > All > > Can anyone recommend a source coaxial cable rated to > > at least 4kV and > > operating temperature of at least 150C? > > Ian Gordon > > This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwellmcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: High temperature coaxial cable
Ian, You did not mention frequency range, but RG393 is rated to 5kv (with proper connectors) and 200C. It is good up to 1 or 2 GHz. http://www.pasternack.com/Search/SearchResults.asp?partNum=rg393%2Fu&RecNo=0 Pasternack also has some special high-voltage "C" connectors, part num PE4950, and "SHV" connectors, which are rated for high voltages. The normal type "N" connectors are not rated for high voltages. Bob Richards, NCT --- "Gordon,Ian" wrote: > All > Can anyone recommend a source coaxial cable rated to > at least 4kV and > operating temperature of at least 150C? > Ian Gordon > > This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwellmcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
High temperature coaxial cable
All Can anyone recommend a source coaxial cable rated to at least 4kV and operating temperature of at least 150C? Ian Gordon *** The information contained in this email and any attachments may be confidential and is provided solely for the use of the intended recipient(s). If you are not the intended recipient, you are hereby notified that any disclosure, distribution, or use of this e-mail, its attachments or any information contained therein is unauthorised and prohibited. If you have received this in error, please contact the sender immediately and delete this e-mail and any attachments. No responsibility is accepted for any virus or defect that might arise from opening this e-mail or attachments, whether or not it has been checked by anti-virus software. This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwellmcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: Coaxial cable
Actually it is called a "Z" fold as it imitates a squashed letter z when folded. The foil is folded that way so it makes continuous circumpherential contact. Not all manufacturers employ a "Z" fold or equivalent method and their coax cable's performance is degraded. The "Z" fold is much better than an overlapping non-contacting or a spiraling foil. Hans --- Gary McInturff wrote: > > Nicely put, but I want to emphasize one point. The foil in most cables > doesn't have a metal to metal contact. Where the foil overlaps itself the > polyester on the "underside" is what is in contact with the foil "outside". > The type cable you are mentioning is called an"e" fold if I remember > correctly, but I don't kno why. A lot of folks don't realize that they are > not getting foil to foil contact, just and overlap of material. > Gary > > -Original Message- > From: jrbar...@lexmark.com [mailto:jrbar...@lexmark.com] > Sent: Tuesday, November 07, 2000 8:58 AM > To: sergioro...@siemens.com.br; emc-p...@ieee.org > Subject: Re: Coaxial cable > > > > Sergio, > A "foil & braid" shield is quite common on high-speed cables. If a cable is > properly terminated and you don't have common-mode problems, most of its > radiated emissions will be from holes in the shield. Thus "optical > coverage", > the percentage of the shield's nominal area that is actually covered by > wires/conductive foil, is a reasonable approximation to the shielding > effectiveness. > > It is very difficult to braid wires in a way that achieves over 95% optical > coverage. A foil shield, with the overlap folded over so the conductive > surfaces touch, can easily achieve 100% optical coverage, but is fragile. > If a > foil-shielded cable vibrates, or is repeatedly bent, the foil will > eventually > tear. Even if end-to-end continuity is retained, this hole in the shield > can > cause a great increase in radiated emissions. By braiding wires over the > foil, > you start out with 100% optical coverage, and if/when the foil tears degrade > in > just that area to the 90-95% optical coverage of the braid. > > We used to use a type of parallel cable for Electromagnetic Compatibility > (EMC) > testing that had a foil shield. We would get about three weeks use out of > these > before they went bad and had to be thrown away because of excessive radiated > emissions. I helped develop and release an IEEE-1284 parallel cable in > 1994 > (Lexmark partnumber 1329605) that used a foil & braid shield, and we put > these > in our EMC lab. It took nine months of heavy use before the first of these > cables exhibited a noticeable increase in emissions over brand-new cables. > > John Barnes Advisory Engineer > Lexmark International > > > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > 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: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson:pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > 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: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson:pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > = Best Regards Hans Mellberg __ Do You Yahoo!? Thousands of Stores. Millions of Products. All in one Place. http://shopping.yahoo.com/ --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
RE: Coaxial cable
Nicely put, but I want to emphasize one point. The foil in most cables doesn't have a metal to metal contact. Where the foil overlaps itself the polyester on the "underside" is what is in contact with the foil "outside". The type cable you are mentioning is called an "e" fold if I remember correctly, but I don't kno why. A lot of folks don't realize that they are not getting foil to foil contact, just and overlap of material. Gary -Original Message- From: jrbar...@lexmark.com [mailto:jrbar...@lexmark.com] Sent: Tuesday, November 07, 2000 8:58 AM To: sergioro...@siemens.com.br; emc-p...@ieee.org Subject: Re: Coaxial cable Sergio, A "foil & braid" shield is quite common on high-speed cables. If a cable is properly terminated and you don't have common-mode problems, most of its radiated emissions will be from holes in the shield. Thus "optical coverage", the percentage of the shield's nominal area that is actually covered by wires/conductive foil, is a reasonable approximation to the shielding effectiveness. It is very difficult to braid wires in a way that achieves over 95% optical coverage. A foil shield, with the overlap folded over so the conductive surfaces touch, can easily achieve 100% optical coverage, but is fragile. If a foil-shielded cable vibrates, or is repeatedly bent, the foil will eventually tear. Even if end-to-end continuity is retained, this hole in the shield can cause a great increase in radiated emissions. By braiding wires over the foil, you start out with 100% optical coverage, and if/when the foil tears degrade in just that area to the 90-95% optical coverage of the braid. We used to use a type of parallel cable for Electromagnetic Compatibility (EMC) testing that had a foil shield. We would get about three weeks use out of these before they went bad and had to be thrown away because of excessive radiated emissions. I helped develop and release an IEEE-1284 parallel cable in 1994 (Lexmark partnumber 1329605) that used a foil & braid shield, and we put these in our EMC lab. It took nine months of heavy use before the first of these cables exhibited a noticeable increase in emissions over brand-new cables. John Barnes Advisory Engineer Lexmark International --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
RE: Coaxial cable
Richard, The term that I ran across many times while researching my book was "optical coverage"-- as though you put a light bulb inside the shield and measured what percentage of its light leaked out. The basic assumptions are: 1. Electric and magnetic fields inside the shield are totally blocked by the "picks" (conductive wires/strips/foil in a group), so the only leakage is through the holes between picks. 2. The fields that leak out are incoherent, and thus add as scalars (sum of magnitudes) for the peak leakage. This is a first-level approximation, and is closely related to a discussion of the shielding effectiveness of arrays of holes/ honeycomb on this mailing list a couple of weeks ago. Over a wide range of frequencies, and far enough away from the shield that the openings seem to blur together, the leakage is approximately proportional to how much of the inside/ other side of the shield is exposed to our view. But at specific frequencies, or if we get very close to a hole in the shield, we get diffraction and constructive-/distructive-interference that cause lobes and notches in the leakage fields. Some companies have tried to take advantage of this for special (high-priced) single-function cables. "Optimal braiding" selects the gauge and number of wires in each "pick" (group of wires laid parallel to one another) and carefully controls their crossing angle during construction of the cable. The idea is to create holes with a certain size and shape, and thus polarizability, and with a certain spacing lengthwise and around the cable. The authors of the articles claimed that at the design frequency they would get distructive interference, just like a diffraction grating, making the holes in the shield appear smaller than they really were. The problem that I saw with this scheme was that at other frequencies, or if you bent/pulled/deformed the cable in any way, the geometry changed and you would get an *increase* in emissions. So it always seemed more sensible to me to try to completely seal the electric and magnetic fields inside the cable/shield and not optimize just one tiny operating point. John Barnes Advisory Engineer Lexmark International author of Electronic System Design: Interference and Noise Control Techniques (Prentice-Hall, 1987) richardg%exabyte@interlock.lexmark.com on 11/07/2000 12:11:36 PM To: john_barnes.lexm...@sweeper.lex.lexmark.com cc:(bcc: John Barnes/Lex/Lexmark) Subject: RE: Coaxial cable John, Couldn't quite follow the "optical coverage" reference. Sounds like it should be "optimal coverage" for copper wire cable verses optic cable. Thanks. Richard Georgerian Technical Committee 8 Product Safety (TC-8), Vice-chair Colorado Product Safety Technical Committee (CPSTC), Chair Product Compliance Engineer Exabyte 1685 38th Street Boulder, CO 80301 USA tel.: 303-417-7537 fax: 303-417-5710mailto:richa...@exabyte.com -Original Message- From: jrbar...@lexmark.com [mailto:jrbar...@lexmark.com] Sent: Tuesday, November 07, 2000 9:58 AM To: sergioro...@siemens.com.br; emc-p...@ieee.org Subject: Re: Coaxial cable Sergio, A "foil & braid" shield is quite common on high-speed cables. If a cable is properly terminated and you don't have common-mode problems, most of its radiated emissions will be from holes in the shield. Thus "optical coverage", the percentage of the shield's nominal area that is actually covered by wires/conductive foil, is a reasonable approximation to the shielding effectiveness. It is very difficult to braid wires in a way that achieves over 95% optical coverage. A foil shield, with the overlap folded over so the conductive surfaces touch, can easily achieve 100% optical coverage, but is fragile. If a foil-shielded cable vibrates, or is repeatedly bent, the foil will eventually tear. Even if end-to-end continuity is retained, this hole in the shield can cause a great increase in radiated emissions. By braiding wires over the foil, you start out with 100% optical coverage, and if/when the foil tears degrade in just that area to the 90-95% optical coverage of the braid. We used to use a type of parallel cable for Electromagnetic Compatibility (EMC) testing that had a foil shield. We would get about three weeks use out of these before they went bad and had to be thrown away because of excessive radiated emissions. I helped develop and release an IEEE-1284 parallel cable in 1994 (Lexmark partnumber 1329605) that used a foil & braid shield, and we put these in our EMC lab. It took nine months of heavy use before the first of these cables exhibited a noticeable increase in emissions over brand-new cables. John Barnes Advisory Engineer
Re: Coaxial cable
No. The foil has lower inductance at high frequencies. The combination of foil and braid gives the best protection in a flexible cable. -- >From: "SERGIO LUIZ DA ROCHA LOURES SERGIO" >To: >Subject: Coaxial cable >Date: Tue, Nov 7, 2000, 8:14 AM > > > Group > > We are using a coaxial cable with two shields. One is a metallic mesh and > the other is a aluminium foil. This foil is known as "static foil". > What is the use of this foil? Is this used for electrostatic reasons? > > Regards > > Sérgio Rocha Loures > Siemens Ltda. - Brazil > ICN FL QEL > Tel: +55 41 341-5755 > Fax: +55 41 341-5058 > E-mail: sergioro...@siemens.com.br > > > --- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > 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: > Jim Bacher: jim_bac...@mail.monarch.com > Michael Garretson:pstc_ad...@garretson.org > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > > --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: Coaxial cable
Sergio, A "foil & braid" shield is quite common on high-speed cables. If a cable is properly terminated and you don't have common-mode problems, most of its radiated emissions will be from holes in the shield. Thus "optical coverage", the percentage of the shield's nominal area that is actually covered by wires/conductive foil, is a reasonable approximation to the shielding effectiveness. It is very difficult to braid wires in a way that achieves over 95% optical coverage. A foil shield, with the overlap folded over so the conductive surfaces touch, can easily achieve 100% optical coverage, but is fragile. If a foil-shielded cable vibrates, or is repeatedly bent, the foil will eventually tear. Even if end-to-end continuity is retained, this hole in the shield can cause a great increase in radiated emissions. By braiding wires over the foil, you start out with 100% optical coverage, and if/when the foil tears degrade in just that area to the 90-95% optical coverage of the braid. We used to use a type of parallel cable for Electromagnetic Compatibility (EMC) testing that had a foil shield. We would get about three weeks use out of these before they went bad and had to be thrown away because of excessive radiated emissions. I helped develop and release an IEEE-1284 parallel cable in 1994 (Lexmark partnumber 1329605) that used a foil & braid shield, and we put these in our EMC lab. It took nine months of heavy use before the first of these cables exhibited a noticeable increase in emissions over brand-new cables. John Barnes Advisory Engineer Lexmark International --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Coaxial cable
Group We are using a coaxial cable with two shields. One is a metallic mesh and the other is a aluminium foil. This foil is known as "static foil". What is the use of this foil? Is this used for electrostatic reasons? Regards Sérgio Rocha Loures Siemens Ltda. - Brazil ICN FL QEL Tel: +55 41 341-5755 Fax: +55 41 341-5058 E-mail: sergioro...@siemens.com.br --- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. 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: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson:pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
Re: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection
There have been endless argument about what is and is not a telecom*. It will never be settled to everyone's satisfaction. however, responding to just a little of what you said, > I would contend that TNV lines can only be those lines which are > conductively connected to public telecommunications lines/and or which can > generate telephone ringing voltages. We are trying to come up with safety criteria here. The ownership of a line is not usually important with regard to safety and in some respects ringing voltages are not the issue. The major concerns are shock and fire risk from voltages and currents on the line, and the consequences of equipment faults, lightning and power cross. The standards are trying to address the risks and have had a lot of trouble integrating such factors as contact area, voltage, source impedance, period, load sensing, legacy products, international variations, and so on, but we try, and we have been tearing our hair out on definitions. One major distinguishing feature is what telecom people have called outside plant. The exposure to lightning and power cross are critical concerns. Anyone intending to run a line to a roof or outside buildings needs to give careful consideration to what has been written for TNV1 and TNV-3 circuits regardless of what they are called, be they RS232, or just a long piece of wire. Calling a piece of wire SELV may make design rules easy and may be within the definitions, but it may be unwise if you are ignoring the risks. Bob - 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, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection
At 11:26 PM 12/1/98 -0600, Mel Pedersen wrote: > >Anyway, the intent here is that the insulation not be damaged from an > overvoltage from the TELECOMMUNICATIONS NETWORK, and I believe that the > "overvoltages" in mind included lightning strikes. Well, just my 1 cent worth would be that the "intent" of the standard would also include power lines crossing over telephone lines on a toppled telephone pole. Or, as we recently saw, even 16.6KV in the case of some druggie. I've seen the aftermath of a transformer taking down most the wires around it on it's way to the ground. Not a pretty sight. The "TNV" circuits are certainly within the product. But, I'm sure I could give a good argument over the definition of "exposed" regarding to what they attach and what potential hazard could occur. Telephone lines on a power pole are certainly more "exposed" than buried telephone lines. *** This is _strictly_ my own interpretation *** Regards, Doug - 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, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection
My comments tend to support the views of Mel Pederson rather than those of Rich Nute regarding their consideration as TNV rather than SELV circuits: 1. To meet SELV requirements the voltage must remain below 60 Vdc under fault conditions as well as tolerance limits. Compliance under fault conditions was not described in your inquiry. Otherwise the circuits within your equipment would be considered ELV circuits. If an ELV circuit, you run into problems with clause 2.10.3 restricting the use of ELV on interconnects. You may want to resolve this by specifying that your dc supply must be an SELV circuit. I would consider the coaxial cable output you described to be a TNV-1 circuit. I agree with Rich Nute, the standard does not mention "outdoors" in connection with TNV, but it does mention "overvoltages due to atmospheric discharges and faults in power distribution systems". You seem to be describing the feed to an antenna located transmitter. This sounds close enough to me to be considered a telecommunication network as described in 1.2.14.7. The note describes the internal circuit as TNV-1 and the interconnecting cable as telecommunication network (neither SELV nor TNV). Unfortunately the specifications for TNV circuits were written with telephones in mind, and do not do a good job of addressing cable TV, RF or other circuits such as yours. There is an IEC 950 WG8 antenna and cable TV project team currently addressing this issue. I would recommend applying the appropriate portions of Clause 6, explaining in your compliance report the rationale for implementing or waiving each clause. 2. IEC 950 does address lightning as mentioned above, but does so with the assumption of primary protectors on the telecommunication network. This is where the electrical code comes in. In the US the NFPA 70, 1999 edition, requires protection on these conductors. Refer to Chapter 8, particularly clause 810 and the new clause 830 on Network Powered Broadband Communication Systems. The test imposed by UL on connections such as yours from IEC 65 which consists of a 1nF cap charged to 10 kV is intended to represent lightning on cable. 3. There are requirements for Listed cable for outdoor coax cable in the US, as well as to get from the equipment through the building to the outdoors. Refer again to Chapter 8 of the NFPA 70. Obviously there are needs for insulation, flammability, ampacity and UV resistance. I have no knowlege of requirements outside US although Canada parallels many of the US code requirements for wire. Even for North American Class 2 circuits (i.e. clause 2.11 limited power) there are requirements for Listed wire. CL2, CL2P, and a host of other markings are possibilities. Check the code clause 725. Note that there is a limitation on the power source as well as the output power in these circuits. You may need redundant limiting circuits in these paths to meet the requirements. 4. IEC 950 has not yet tried to address dc supply circuits, or power feed on signal cables, except by accident. There are currently proposals in committees to introduce dc supplies and power feed, but at the moment your options seem to be to consider a 72 Vdc circuit as a hazardous circuit within the equipment. Sounds like you may have complications with interconnected accessible SELV portions. I tend to treat the incoming dc as a mains supply and provide it the same isolation as ac circuits within the switching supply which powers the product. > A CO equipment with a 48 Vdc nominal supply has coxial cable > connection to an outdoor transmitter. I have the following questions: > > 1. The coaxial cable output is conductively connected to the input. > It carries the same voltage and an amperage of 1 A (limited to 3 A > max). Assuming the input supply tolerance not to exceed 60 Vdc, > does everyone agree that this is SELV? Some of you may argue > that it is TNV-1 since it is exposed outdoors! Based on the 950 > definition of TNV, to the best of my understanding, the circuit is not > a telecommunication network voltage circuit. > > 2. 950 does not discuss protection of the equipment or user from > lightning. It should be noted that the unit also has user accessible > SELV interfaces. What type of tests or construction would you > recommend for the coaxial interface? I believe the Impulse Tests in > IEC 65 or in UL1492 should be highly recommended. > > 3. Are there any requirements for the outdoor coaxial cable? > Should it be Listed cable for North America and if so, what type of > Listed cable? Should it be Approved for Europe and if so, what type > of Approved cable? > > Assuming the power output to the cable was limited in accordance > to UL1950/EN 60 950 (ie output was limited to Class 2), should the > cable still be Listed or Approved? > > 4. Assuming the input tolerance now to be max 72 Vdc (a
RE: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection
Food for thought (or Gas Bag time depending on your perspective.) TNV circuit definition. I must be missing an update somewhere - my page shows July 26 - be gentle with me here if I'm way behind, but >From UL 1950 Third edition. 1.2.8.8 Telecommunication Network Voltage (TNV) circuit: A circuit that, under normal operating conditions, carries Telecommunication signals. A TNV circuit is considered to be a secondary circuit in the meaning of this standard. >From EN 60950 1.2.8.8 TELECOMMUNICATION NETWORK VOLTAGE (TNV) CIRCUIT: A circuit in the equipment to which the accessible area of contact is limited and that is so designed and protected that, under normal operating and single fault conditions, the voltages do not exceed specified limiting values. While this is much more vague the defining sections add to this definition. 1.2.8.9, 1.2.8.10 and 1.2.8.11 all go on to define the different TNV circuits and each of them carries the same note - which is or is not (my words) subject to overvoltages from TELECOMMUNICATIONS NETWORKS. EN60950 2.3.1 (SELV general requirements.) 2nd paragraph. If an SELV circuit is intended to be connected to a telecommunication network, consideration shall be give both to normal operating voltages generated internally in the equipment and to those generated externally, including ringing signals Earth potential rises and induced voltages from power lines and from electric traction lines, that may be received from the telecommunication network, shall not be considered. I would contend that TNV lines can only be those lines which are conductively connected to public telecommunications lines/and or which can generate telephone ringing voltages. Whether or not a line runs outside of the building and is subject to lightning is a separate issue and doesn't in and of itself classify it as a TNV line. Protection must be provided for any line regardless of its designation - TNV, SELV, or what ever. An scoreboard at an outdoor stadium has data lines - good ol' RS-232, differential drivers, or even coax lines running signals below ± 12 Vdc all of the time. These are data lines not TNV because they have no connection to the telecommunications network. But again it would possible to have telecommunication lines running next to them that could cause inductive overvoltage. I can even have a phone conversation without ever hitting a telecommunications network. Ethernet driven LAN systems are quit capable of sending voice of classically defined digital lines. They only need some intervening device to send the ring voltage to the handset. (Wherein TNV lines may be located). Digital lines can carry voice traffic and exit and enter buildings but they are still not TNV lines. There is an interim black box that decodes a "ring phone" packet or word and applies the appropriate ringing voltage etc. to the telephone handset. Independent of the digital line. That just wakes the guy at the other end up. Once its picked up the transfer of voice is strictly a digital affair. The medium itself can be either copper or glass fiber for this whole process of data transfer. Its almost always fiber if its leaving a building because of transmission distance restrictions at the high bandwidths need for voice/video transmission, but it could be copper. The overwhelming idea of TNV lines and the intent is to protect the public telecommunications network. My equipment cannot bring cripple MA Bell. Any broader definition makes virtually any circuit TNV and starts unneeded and unwanted additional regulation. The wires running through your cubical probably runs next to your phone lines and a fault if big enough could, in theory, provide an overvoltage situation through inductive couple etc to your data lines. That does not make the digital lines a TNV circuit, as clarified by the text of 2.3.1. (2.3.3 goes on to reference section 6 and TNV lines but were getting into circular reasoning here because there is no intention to connect to a telecommunications network). The protection of digital lines which are subject to lightning etc are typically done with grounded conduit transorbs and other types of things without regard for physical separation between these lines and the rest of the circuitry, again I'll refer back to the scoreboard scenario. This type of protection my not protect my electronics from destruction but neither does it pose a threat to a telecommunications network. Even though this was just my 2 cents worth I have put on my asbestos underware so fire away. Gary <> - 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, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
Re[2]: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Con
Hi Peter & Rich, 1. I disagree with Rich in that this circuit cannot be an ELV interconnection circuit. ELV circuits are not permitted as such in 2.10.2 of UL1950 (IEC950 clones) There is a single exception to this in 2.10.3. But, since this is a coaxial cable connection intended for outdoor routing as Peter has stated, it is unlikely that this exception would apply. To accurately portray this circuit as SELV or TNV, TNV-1 and TNV-3 circuits are circuits with expected overvoltage conditions from Telecommunication Networks. As this cabling is expected to route outdoors (it is still not clear to what it connects to), are telecommunication networks involved? The definition of 1.2.8.8 (TNV circuit) could apply to "any" secondary circuit, and 1.2.14.7 (telecommunication network) excludes "SELV circuits connecting units of data processing equipment", but still leaves a lot of room for interpretation. Correct me if I'm wrong here, but if this circuit connects to a telecommunications network, then it is by definition a TNV circuit, classed 1, 2 or 3 as appropriate for the intended application. Otherwise, it is likely an SELV circuit, regardless of its routing. Peter, regarding your "TNV-1 exposed outdoors" statement, 1.2.8.9 states that overvoltages from Telecommunication Networks are possible. Outdoors? It doesn't state that. However, most overvoltage conditions and Telecommunication Networks exist outdoors and I suppose its commonly assumed (there's that word again) that overvoltages and outdoor applications closely coexist. And, if this circuit is a TNV-1 circuit it must comply with the overvoltage conditions found in 6.4.1 and 6.6 (UL1950). 2. Rich has given a reasonable answer here. But it was not stated as to what this coaxial cable connects to. Other connection conditions may exist depending on the application. 3. I also agree with Rich here in that SELV, by definition, poses no shock hazard as far as safety is concerned. As for the cable itself, the cable can only be Listed if its a completely assembled cable, otherwise, it may or may not be Recognizied. But, as there are many many applications out there, as well as many many coaxial cable styles, it would be impossible to give any kind of meaningful answer here to your question, Peter. 4. Rich's answer is a good one, however, the shield braid may not always be relied upon to provide a good ground return, depending on the application. Just some of my opinions to throw back into the fray. Best regards and holiday wishes, Ron Pickard ron_pick...@hypercom.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, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection
Peter, Another 2 cents worth: About item 2, in the 9 November 1995 "Report on the meeting of the Industry Advisory Council of UL for ITE...," this very issue is addressed. UL's position at that time was to simply impose the voltage surge tests of IEC 65, sub-clause 10.1, or UL 1492, section 87, to all ITE with provisions for connection to outdoor antennas. No particular construction was specified and no requirement for an antenna discharge path was suggested. Compliance with the tests seem to be all that is required. Continuing, in the 10 June 1998, "Report of the meeting of the Industry Advisory Council of UL for ITE...," this issue was revisited. In a discussion about multi-media equipment that falls within the scope of UL 1950, it was stated that hazards not addressed in the base standard be evaluated against the requirements of a supplementary standard. The specific example given was the application of the votage surge tests. About item 3, in the same 10 June 1998 report mentioned above, UL stated their position on outdoor-use equipment and addressed coaxial cable requirements for such equipment. While your question appears to involve indoor-use equipment with connections to an outdoor antenna, I think the guidelines provided are useful. Basically, for the U.S., it seems necessary to provided a cable that is Listed for the purpose or otherwise Listed and evaluated for the application so that authorities having jurisdiction can judge suitability against the requirements of the National Electrical Code. Hope that helped with 2 of your questions. Rick Cooper MET Laboratories, Inc. 410-354-3323 Ext. 331 > ---Original Message- > From: pe...@itl.co.il [SMTP:pe...@itl.co.il] > Sent: Tuesday, December 01, 1998 4:50 PM > To: t...@world.std.com; emc-p...@majordomo.ieee.org > Subject: TNV-1 vs SELV for unit with Outdoor Coaxial Cable > Connection > > Dear All, > > A CO equipment with a 48 Vdc nominal supply has coxial cable > connection to an outdoor transmitter. I have the following questions: > > 1. The coaxial cable output is conductively connected to the input. > It carries the same voltage and an amperage of 1 A (limited to 3 A > max). Assuming the input supply tolerance not to exceed 60 Vdc, > does everyone agree that this is SELV? Some of you may argue > that it is TNV-1 since it is exposed outdoors! Based on the 950 > definition of TNV, to the best of my understanding, the circuit is not > > a telecommunication network voltage circuit. > > 2. 950 does not discuss protection of the equipment or user from > lightning. It should be noted that the unit also has user accessible > SELV interfaces. What type of tests or construction would you > recommend for the coaxial interface? I believe the Impulse Tests in > IEC 65 or in UL1492 should be highly recommended. > > 3. Are there any requirements for the outdoor coaxial cable? > Should it be Listed cable for North America and if so, what type of > Listed cable? Should it be Approved for Europe and if so, what type > of Approved cable? > > Assuming the power output to the cable was limited in accordance > to UL1950/EN 60 950 (ie output was limited to Class 2), should the > cable still be Listed or Approved? > > 4. Assuming the input tolerance now to be max 72 Vdc (a > secondary hazardous voltage circuit) which also makes the coaxial > output connection 72 Vdc, does anyone see a problem with this > type of circuit being transmitted through a coaxial cable to the > outdoor transmitter? > > Thank you all. > PETER S. MERGUERIAN > MANAGING DIRECTOR > PRODUCT TESTING DIVISION > I.T.L. (PRODUCT TESTING) LTD. > HACHAROSHET 26, P.O.B. 211 > OR YEHUDA 60251, ISRAEL > > TEL: 972-3-5339022 > FAX: 972-3-5339019 > E-MAIL: pe...@itl.co.il > Visit our Website: http://www.itl.co.il > > - > 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, > j...@gwmail.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, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
RE: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection
Hello Rich, Peter, and all distinguished colleagues: Couldn't resist... I agree that it would certainly not be SELV, however. I am not sure if one would call this ELV or TNV however. (I lean toward TNV...) 1) You have stated the following Rich: The IEC 950 definitions for TNV, TNV-1, TNV-2, and TNV-3 do not imply in any way a circuit that is "exposed outdoors." In fact, TNV is defined as "...a circuit in the equipment..." However, if you read the definition of TNV-1 circuits in clause 1.2.8.9, it states that TNV-1 is a circuit on which "...overvoltages from the Telecommunications Network are possible." I believe that the "overvoltages" referred to imply the possibility of an "exposed outdoor" TNV circuit. Continue reading, as my next answer (concerning IEC 950 lightning considerations) gives more justification for this answer. 2) You both mention that lightning surges are not considered by IEC 950, however, I believe that they are. If one considers clause 6.4.1, and the testing options for compliance for isolation from the Telecommunications Network, the 6.4.2.1 impulse test option are the ITU K.17 lightning surge (see Annex N) testing recommendations. I believe that these were developed with the transmission line characteristics of a twisted pair copper wire in mind...so I am not sure if they would be exactly applicable to your situation anyway...something to look into. Maybe the IEC 65 impulses are typical of lightning strike transmitted down Coax (I do not know IEC 65...)? Anyway, the intent here is that the insulation not be damaged from an overvoltage from the TELECOMMUNICATIONS NETWORK, and I believe that the "overvoltages" in mind included lightning strikes. It will be interesting to hear answers on 3 & 4. Just my $0.02, I could be out to lunch on this one... Mel PedersenMidcom, Inc. Homologations Engineer Phone: (605) 882-8535 mpeder...@midcom-inc.com Fax: (605) 882-8633 -- From: Rich Nute[SMTP:ri...@sdd.hp.com] Sent: Tuesday, December 01, 1998 10:49 AM To: pe...@itl.co.il Cc: Product Safety Technical Committee Subject:Re: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection Hi Peter: > 1. The coaxial cable output is conductively connected to the input. > It carries the same voltage and an amperage of 1 A (limited to 3 A > max). Assuming the input supply tolerance not to exceed 60 Vdc, > does everyone agree that this is SELV? ELV, yes. SELV, I don't know because there is not enough information. SELV is defined as a voltage source that does not exceed the limits of ELV (i.e., 60 V dc) in the event of a single fault (usually a fault in Basic Insulation). This implies that SELV is derived from a hazardous voltage source. Since you did not describe the energy source, we cannot answer your question. > Some of you may argue > that it is TNV-1 since it is exposed outdoors! Based on the 950 > definition of TNV, to the best of my understanding, the circuit is not > a telecommunication network voltage circuit. The IEC 950 definitions for TNV, TNV-1, TNV-2, and TNV-3 do not imply in any way a circuit that is "exposed outdoors." In fact, TNV is defined as "...a circuit in the equipment..." The coax cable output you describe is nothing more than a secondary circuit. It is either SELV or ELV or a Secondary Circuit. It is not Hazardous Voltage. It is not a TNV circuit (however, the definitions of TNV are sufficiently vague that any circuit, including the one described here, meeting the limits of TNV-1, TNV-2, or TNV-3 could be a TNV circuit!). Many IT products include coax cable inputs and outputs. The fact of a coax cable means nothing special with regard to the safety of the product. > 2. 950 does not discuss protection of the equipment or user from > lightning. It should be noted that the unit also has user accessible > SELV interfaces. What type of tests or construction would you > recommend for the coaxial interface? I believe the Impulse Tests in > IEC 65 or in UL1492 should be highly recommended. Neither IEC 65 nor UL 1492 consider safety from lightning. Without an isolating barrier of some sort between the coax circuit and all other circuits, or some attentuators from both the shield and the center conductor to a good ground, it is unlikely you can provide any protection against lightning. > 3. Are there any requirements for the outdoor coaxial cable? > Should it be Listed cable for North America and if so, what type of > Listed cable? Should it be Approved for Europe and if so, what type > of Approved cable? If it is a SELV circuit, then the only requirements are those of the manufacturer. By definition, there is no
Re: TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection
Hi Peter: > 1. The coaxial cable output is conductively connected to the input. > It carries the same voltage and an amperage of 1 A (limited to 3 A > max). Assuming the input supply tolerance not to exceed 60 Vdc, > does everyone agree that this is SELV? ELV, yes. SELV, I don't know because there is not enough information. SELV is defined as a voltage source that does not exceed the limits of ELV (i.e., 60 V dc) in the event of a single fault (usually a fault in Basic Insulation). This implies that SELV is derived from a hazardous voltage source. Since you did not describe the energy source, we cannot answer your question. > Some of you may argue > that it is TNV-1 since it is exposed outdoors! Based on the 950 > definition of TNV, to the best of my understanding, the circuit is not > a telecommunication network voltage circuit. The IEC 950 definitions for TNV, TNV-1, TNV-2, and TNV-3 do not imply in any way a circuit that is "exposed outdoors." In fact, TNV is defined as "...a circuit in the equipment..." The coax cable output you describe is nothing more than a secondary circuit. It is either SELV or ELV or a Secondary Circuit. It is not Hazardous Voltage. It is not a TNV circuit (however, the definitions of TNV are sufficiently vague that any circuit, including the one described here, meeting the limits of TNV-1, TNV-2, or TNV-3 could be a TNV circuit!). Many IT products include coax cable inputs and outputs. The fact of a coax cable means nothing special with regard to the safety of the product. > 2. 950 does not discuss protection of the equipment or user from > lightning. It should be noted that the unit also has user accessible > SELV interfaces. What type of tests or construction would you > recommend for the coaxial interface? I believe the Impulse Tests in > IEC 65 or in UL1492 should be highly recommended. Neither IEC 65 nor UL 1492 consider safety from lightning. Without an isolating barrier of some sort between the coax circuit and all other circuits, or some attentuators from both the shield and the center conductor to a good ground, it is unlikely you can provide any protection against lightning. > 3. Are there any requirements for the outdoor coaxial cable? > Should it be Listed cable for North America and if so, what type of > Listed cable? Should it be Approved for Europe and if so, what type > of Approved cable? If it is a SELV circuit, then the only requirements are those of the manufacturer. By definition, there is no shock hazard. (Some outdoors equipment standards specify one-half the ELV voltages for protection against electric shock.) > 4. Assuming the input tolerance now to be max 72 Vdc (a > secondary hazardous voltage circuit) which also makes the coaxial > output connection 72 Vdc, does anyone see a problem with this > type of circuit being transmitted through a coaxial cable to the > outdoor transmitter? A coax is an interesting construction from a safety point of view. Class I. The center conductor insulation is Basic Insulation. The shield braid is a ground to return the fault current in the event of failure of the Basic Insulation. End. Best wishes for the holiday season, Rich - Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 16399 West Bernardo Drive FAX : +1 619 655 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, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
TNV-1 vs SELV for unit with Outdoor Coaxial Cable Connection
Dear All, A CO equipment with a 48 Vdc nominal supply has coxial cable connection to an outdoor transmitter. I have the following questions: 1. The coaxial cable output is conductively connected to the input. It carries the same voltage and an amperage of 1 A (limited to 3 A max). Assuming the input supply tolerance not to exceed 60 Vdc, does everyone agree that this is SELV? Some of you may argue that it is TNV-1 since it is exposed outdoors! Based on the 950 definition of TNV, to the best of my understanding, the circuit is not a telecommunication network voltage circuit. 2. 950 does not discuss protection of the equipment or user from lightning. It should be noted that the unit also has user accessible SELV interfaces. What type of tests or construction would you recommend for the coaxial interface? I believe the Impulse Tests in IEC 65 or in UL1492 should be highly recommended. 3. Are there any requirements for the outdoor coaxial cable? Should it be Listed cable for North America and if so, what type of Listed cable? Should it be Approved for Europe and if so, what type of Approved cable? Assuming the power output to the cable was limited in accordance to UL1950/EN 60 950 (ie output was limited to Class 2), should the cable still be Listed or Approved? 4. Assuming the input tolerance now to be max 72 Vdc (a secondary hazardous voltage circuit) which also makes the coaxial output connection 72 Vdc, does anyone see a problem with this type of circuit being transmitted through a coaxial cable to the outdoor transmitter? Thank you all. PETER S. MERGUERIAN MANAGING DIRECTOR PRODUCT TESTING DIVISION I.T.L. (PRODUCT TESTING) LTD. HACHAROSHET 26, P.O.B. 211 OR YEHUDA 60251, ISRAEL TEL: 972-3-5339022 FAX: 972-3-5339019 E-MAIL: pe...@itl.co.il Visit our Website: http://www.itl.co.il - 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, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
