technical bulletin UTP vs STP Shielded data cables make the grade Unshielded data cables reach the limits of their performance

Transcription

1 technical bulletin Data communication technology 12/2015 UTP vs STP Shielded data cables make the grade Unshielded data cables reach the limits of their performance Business Unit Datacom LEONI Kerpen GmbH Zweifaller Strasse Stolberg Germany Telefon +49(0) Telefax +49 (0) Author: Strategic market development and standardisation We reserve the right to make technical modification LEONI Kerpen GmbH LEONI technical bulletin 12/2015 1

2 Topics dealt with in this bulletin: Types What about the shield? Types Transmission characteristics Electromagnetic compatibility a) MICE concept b) Performance comparison c) Separation distances Thermal behavior Fire behavior Equipotential bonding, earthing, shielding Conclusions There is a wide range of different types of data cables. They can be classified according to number and position of the shields within the cable structure. Thus, U/UTP data cables have no shield whatsoever. In contrast, S/FTP data cables have a pair shield made of aluminum foil and an overall shield made of tin-plated copper braid. Between these two types, there are other variants that differ in the type of shielding used. The following nomenclature illustrates the most common types. Cable types xx/x x x Overall shielding F Braided shielding S Braiding and foil shielding SF What about the shield? Individual shielding Unshielded Symmetrical element U F P Shielded vs. unshielded data cables The question as to whether shielded or unshielded data cables should be used is as old as data cables themselves. There are justified arguments for and against on both sides which constantly rekindle the long-standing controversy. There is no doubt whatsoever that the unshielded technology now so widespread worldwide meets all requirements when data rates of up to 1 Gbit/s are to be transmitted. S/FTP (PiMF with overall shielding) F/FTP U/FTP Braided shielding So why do you need a shield? It is equally true that shielded cablings offer the best protection against irradiation and radiant emittance, and this is becoming more and more critical in view of the constantly increasing transmission frequencies and the rising degree of electromagnetic contamination. So do Category 8 cables with a bandwidth of 2 GHz provide the answer to the crucial question: What about the shield? SF/UTP F/UTP U/UTP Braiding and foil shielding Figure 1: Construction Data cables over cross element Which cable design is ultimately used depends on the transmission performance required, the electromagnetic compatibility (EMC), the installation conditions, the thermal behavior, the fire behavior and the expected service life. Regional as well as historically conditioned conventions and the inertia of the installed basis also frequently affect the choice of medium. 2 LEONI technical bulletin 12/2015 LEONI technical bulletin 12/2015 3

3 Transmission characteristics Electromagnetic compatibility The capacity of data cables is defined by a set of low-frequency and high-frequency transmission characteristics which, taken together, lead to a maximum transmission frequency / bandwidth. For greater clarity, data cables are divided into Categories 3 to 8 with regard to their transmission characteristics. The correlating cabling system classes C to F A / I/II also allow a correlation to be made with the transmission rate supported (usually an Ethernet protocol). The following table shows the currently existing cable categories in connection with the typical cable design, the maximum transmission frequency and the maximum transmission rate. Unshielded data cables: The table shows that unshielded data cables can only be used up to a maximum of Category 6 A (500 MHz). The reason for this is that the so-called alien crosstalk, i.e. the mutual influencing of adjacent data cables, disturbs data transmission inadmissibly with rising frequency. Electromagnetic compatibility (EMC) describes the ability of electrotechnical devices to work satisfactorily without disturbing other equipment or being disturbed themselves. Fundamentally, the operation of electric or electronic devices should not interfere with the function of other radio and telecommunication systems. This is mainly achieved because the transient emissions of an electrotechnical device are limited on the one hand and the device must have a minimum immunity to interference on the other. a) MICE concept Environmental class The relevant cabling standards ISO/IEC and EN classify the electromagnetic load or contamination of a defined environment in terms of the so-called MICE concept. Parameter/ Level Mechanical Ingress 1 M 1 I 1 2 M 2 I 2 3 M 3 I 3 Climatic C 1 C 2 C 3 Electromagnetic E 1 E 2 E 3 Figure 3: MICE-Conzept relevant ISO/IEC and EN Shielded data cables cover the entire bandwidth up to Category 8.2 (2 GHz). The requirements with regard to alien crosstalk are met by design here. Here there are 3 electromagnetic classes E1, E2 and E3 whose demands rise in step with the index. A simple rule of thumb: The higher the category, the higher the transmission frequency and the bandwidth, i.e. the higher the performance of the data cable. Category Class Max. Frequency Typical Design Transmission rate Ethernet 3 C 16 MHZ U/UTP, F/UTP, SF/UTP up to 10 Mbit/s 5 old "D" 100 MHZ U/UTP, F/UTP, SF/UTP up to 10 Mbit/s 5E D 100 MHZ U/UTP, F/UTP, SF/UTP up to 1 Gbit/s, 2 Gbit/s *(in consulting) 6 E 250 MHZ U/UTP, F/UTP, U/FTP up to 1 Gbit/s, 5 Gbit/s *(in consulting) 6 A E A 500 MHZ U/UTP, F/UTP, U/FTP. F/FTP up to 10 Gbit/s 7 F 600 MHZ S/FTP, F/FTP >10 Gbit/s, hight reserves 7 A F A 1 GHZ S/FTP up to 25 Gbit/s, hight reserves 8.1 I (30 m) 2 GHZ F/UTP up to 40 Gbit/s not backwards compatible to Cat. 7 and 7 A 8.2 II (30 m) 2 GHZ S/FTP up to 40 Gbit/s, very hight reserves * Shielded performance fulfilled as design Figure 2: Category & class, typical design & transmission frequency Electromagnetic E1 E2 E3 Operating range Office Data center Industrial Electrostatic discharge - Contact (0,667 µc) 4 kv 4 kv 4 kv Electrostatic discharge - Air (0,667 µc) 8 kv 8 kv 8 kv Radiated radio frequency, amplitude modulated (RF - Am) 3 V/m at ( ) Mz 3 V/m at ( ) Mz 10 V/m at ( ) Mz 3 V/m at ( ) Mz 3 V/m at ( ) Mz 3 V/m at ( ) Mz 1 V/m at ( ) Mz 1 V/m at ( ) Mz 1 V/m at ( ) Mz Conducted radio frequency (RF) 3 V at 150 khz - 80 MHz 3 V at 150 khz - 80 MHz 10 V at 150 khz - 80 MHz Electrical fast transient /Burst (EFT/B) AC mains power including the protective earth Electrical fast transient / Burst (EFT/B) I/O (signal/ data/control) Surge (transient ground potential difference) - signal, line to earth 1000 V 1000 V 2000 V 500 V 500 V 1000 V 500 V 1000 V 1000 V Magnetic (50/60 Hz) 1 A/m 3 A/m 30 A/m Magnetic (60 Hz to Hz) ffs ffs ffs Figure 4: Demand MICE-Class E 1, E 2, E 3 Class E1 is usually required in the office field, whereas E2 and E3 are mainly encountered in the industrial environment. This explains why shielded data cables are often obligatory there. 4 LEONI technical bulletin 12/2015 LEONI technical bulletin 12/2015 5

4 b) Performance comparison Minimum seperation S A GHMT study comparing the performance of shielded and unshielded cabling systems on location assessed the transient emissions and immunity to interference for 1 Gbit/s and 10 Gbit/s applications. The final ranking underlines the technical superiority of shielded systems in terms of their electromagnetic compatibility. Parameter System 01 U/UTP System 02 U/UTP System 03 F/UTP System 04 S/FTP System 05 S/FTP Radiated radio-frequency disturbance field strength test DIN EN Segration Classification Separation without electromagnetic barrier Containment applied to information technology or mains power cabeling S Open metallic containment Perforated metallic containment Figure. 6: Minimum separation distances as a function of the installation ducts used and the separation class excerpt from EN ) Solid metallic containment d 10 mm 8 mm 5 mm 0 mm c 50 mm 38 mm 25 mm 0 mm b 100 mm 75 mm 50 mm 0 mm a 300 mm 225 mm 150 mm 0 mm Testing immunity to radio-frequency electromagnetic fields DIN EN Electrical fast transient/burst immunity test DIN EN Table for minimum separation distances Test relating to the immunity to conducted disturbances, induced by radio-frequency fields DIN EN A correction factor resulting from the number of electric circuits installed must now be added to the minimum separation distances determined. The minimum separation distances can increase or decrease as a function of the electric circuits installed. Power-frequency magnetic field immunity test DIN EN Electrostatic discharge immunity test DIN EN Ranking Figure. 5: Electromagnetic compatibility of shielded and unshielded systems in comparison (excerpt from GHMT study) c) Separation distances Incidentally, the degree of electromagnetic compatibility also leads to normative specifications for the minimum separation distances of data cables and energy cables installed in a jointly used installation duct. Separation class d can be used for data cables with a coupling attenuation of at least 80 db, i.e. for all data cables according to EN of Category 7 and higher. The separation class d allows the shortest distance between the parallel data and energy cable routes. This has a positive effect on the space requirements. Electrical circuit type Quantity of circuits Power cabeling factor P 1 to 3 0,2 4 to 6 0,4 7 to 9 0,6 10 to 12 0,8 20 A, 230 V, single phase 13 to 15 1,0 16 to to to to 75 5 >75 6 Figure 7: Correction factors for power supply cables (excerpt from EN ) Separation class c must be used for data cables with a coupling attenuation of at least 55 db. This usually concerns shielded cables of Category 5 and Category 6. Separation class b must be used for data cables with a coupling attenuation of at least 40 db. This usually concerns unshielded cables of Category 5 and Category 6. 6 LEONI technical bulletin 12/2015 LEONI technical bulletin 12/2015 7

5 Thermal behavior Fire behavior In conjunction with the accumulation of cables in the installation duct, the constant increase in the power transmitted via Power over Ethernet (PoE) (100W in future) can cause noticeable temperature increases in the data cables which can become inadmissible in extreme cases. The heating up of cables depends on the following factors: Power load (as a function of the PoE standard used) Cable design (in particular conductor cross-section) Number of cable bundles in the installation duct Installation environment (heat dissipation) Environmental temperature Data cables permanently installed in buildings fall under the Construction Products Regulation EU No. 305/2011, which has now come into full force for all member states of the EU. 7 different European fire classes (Aca, B1ca, B2ca, Cca, Dca, Eca and Fca) as well as 3 additional classifications (smoke development, acidity and burning drops) were designated in this connection. A is the highest fire class and F is the lowest. Ranking A ca B1 ca B2 ca C ca D ca E F Standard EN ISO 1716 FIPEC Sce n2 FIPEC Sce n2 FIPEC Sce n2 FIPEC Sce n2 EN H (mm) FS (m) 1,75 1,5 2,0 THR (MJ) The correct cable design makes a crucial contribution to minimizing the heating up of the cable. EN HRR (kw) FIGRA (W/s) Rule of thumb: The higher the category, the lower the heating up additional classification EN smoke emission s1a, s1b, s2, s3 s1a, s1b, s2,s3 s1a, s1b, s2, s3 s1a, s1b, s2, s3 nein nein EN acid liberates a1, a2, a3 a1, a2, a3 a1, a2, a3 a1, a2, a3 nein nein This is because the conductor cross-section rises in step with the increasing category; the DC resistance drops and so does the heat dissipated. EN burning drops d0, d1, d2 d0, d1, d2 d0, d1, d2 d0, d1, d2 nein nein Figure 9: Requirements of European fire classes In the example from ISO/IEC TR shown here, shielded data cables of Category 7 A show 36 % less heating up compared with unshielded data cables of Category 5. Considered according to economic and technical aspects, the use of Class B2ca will probably be required for very high safety requirements, and Cca for high safety requirements. Size of cable bundle (Quantity cable) Temperature rise C Category 5 Category 6 Category 6 A Category 7 Category 7 A Special designs with very high safety requirements (for hospitals, rest homes and kindergartens) and in escape routes: use of cables of Class B2ca In buildings with high security requirements (administrative and office buildings, multi-storey buildings, hotels): use of cables of Class Cca Figure 8: Heating up of cables as a function of the cable category (from ISO/IEC TR 29125) -36% Proposal as to the European classes to be used for fire protection cables Euroclasses Additional classes Security requirements Flame progagation / heat development Smoke production / density Acidity development / particles Flaming droplets / particles in a bulding A ca very high B1 ca very high B2 ca s1 a1 d1 very high C ca s1 a1 d1 high D ca s2 a1 d2 medium E ca low none F ca Figure 10: Recommendation for fire classes as a function of the fire risk In a shielded data cable, the cable functions as a protective shield in case of fire. The result is a significantly better fire behavior than with unshielded versions 8 LEONI technical bulletin 12/2015 LEONI technical bulletin 12/2015 9

6 Equipotential bonding, earthing, shielding System security with regard to transmission technology and the protection of persons... is achieved by means of the shielding of the data cabling and via the equipotential bonding system within the building. Here the power supply has to be realized according to the TN-S system (separate neutral and protective conductor) so that no leakage currents can flow across the data cable shields. The cable shield must have contact with the connector on both sides and be continuous in order to form a Faraday cage and thus achieve a good EMC. All-round contacting (i.e. 360 ) is the most effective solution. Health and safety requirements demand at least one one-sided connection of the shield to the equipotential bonding system of the building (for example on the patch panel). All equipotential bonding conductors run via the shortest possible distance to a common equipotential bonding rail connected with the central earthing point of the building. Equipotential bonding therefore ensures that a potential difference cannot arise between devices and that dangerous contact voltages or compensation currents do not flow through the shielding. The earthing and equipotential bonding system is realized according to ISO/IEC internationally and according to EN and EN and 2 in Europe. Incidentally, the earthing of data cable outlets is not obligatory, even when they have housings made of metal or other conductive materials. Conclusions As described above, even though unshielded cable technology is still predominant worldwide, there is a clear trend towards using shielded. The fact that cables of Category 8 (2 GHz) can only be realized with a shield demonstrates the technical limits of unshielded cables. The Technical Bulletin also demonstrates many more advantages of shielded cables which allow real customer benefits, thus providing numerous arguments for using them. In the comparison of the transmission characteristics, the electromagnetic compatibility, the thermal behavior and the fire behavior, the shield is the downright winner. 10 LEONI technical bulletin 12/2015