Shielded cable
A shielded cable is an electrical cable of one or more insulatedconductors enclosed by a common conductive layer. The shield may be composed of braided strands of copper (or other metal, such as aluminium), a non-braided spiral winding of copper tape, or a layer of conducting polymer. Usually, this shield is covered with a jacket. The shield acts as a Faraday cage to reduce electrical noise from affecting the signals, and to reduceelectromagnetic radiation that may interfere with other devices (see electromagnetic interference). The shield minimizescapacitively coupled noise from other electrical sources. The shield must be applied across cable splices.
In shielded signal cables the shield may act as the return path for the signal, or may act as screening only.
High voltage power cables with solid insulation are shielded to protect the cable insulation and also people and equipment.
Signal cables
The common method to wire shielded cables is to ground only the source end of the shield to avoid ground loops. However, in airplanes special cable is used with both an outer shield to protect for lightning and an inner shield grounded at one end to eliminate hum from the 400 Hz power system.[1]
Applications
The use of shielded cables in security systems provides some protection from power frequency and radio frequency interference, reducing the number of false alarms being generated. Best is to keep data or signal cables physically separated by at least 3 inches (75mm) from 'heavy' power circuits which are in parallel.
Microphone or "signal" cable used in setting up PA and recording studios is usually shielded twisted pair cable, terminated in XLR connectors. The twisted pair carries the signal in a balanced audio configuration.
The cable laid from the stage to the mixer is often multicore cable carrying several pairs of conductors.
Consumer use screened copper wire with one central conductor in an unbalanced configuration.
Also see: High-end audio cables
Power cables
Medium and high-voltage power cables, in circuits over 2000 volts, usually have a shield layer of copper oraluminum tape or conducting polymer. If an unshielded insulated cable is in contact with earth or a grounded object, the electrostatic field around the conductor will be concentrated at the contact point, resulting in corona discharge, and eventual destruction of the insulation. As well, leakage current and capacitive current through the insulation presents a danger of electrical shock. The grounded shield equalizes electrical stress around the conductor, diverts any leakage current to ground. Stress relief/ cones should be applied at the shield ends, especially for cables operating at more than 2kV to earth.
Shields on power cables may be connected to earth ground at each shield end and at splices for redundancy to prevent shock even though induced current will flow in the shield. This current will produce losses and heating and will reduce the maximum current rating of the circuit. Tests show that having a bare grounding conductor adjacent to the insulated wires will conduct the fault current to earth quicker. On high current circuits the shields might be connected only at one end. On very long high-voltage circuits, the shield may be broken into several sections since a long shield run may rise to dangerous voltages during a circuit fault. However, the shock hazard of having only one end of the shield grounded must be evaluated for the risk. The maximum recommended shield potential rise is 25 volts. IEEE 422 and 525 lists the cable lengths that would limit shield potential to 25 volts for a single point ground application.[2]
| Size Conductor | One Cable per Duct (ft) | Three Cables per Duct (ft) |
|---|---|---|
| 1/0 AWG | 1250 | 4500 |
| 2/0 AWG | 1110 | 3970 |
| 4/0 AWG | 865 | 3000 |
| 250 kcmil | 815 | 2730 |
| 350 kcmil | 710 | 2260 |
| 400 kcmil | 655 | 2100 |
| 500 kcmil | 580 | 1870 |
| 750 kcmil | 510 | 1500 |
| 1000 kcmil | 450 | - |
| 2000 kcmil | 340 | - |
for your philippine electrical concerns...needs...installation...orders...safeelectrical2013@gmail.com
METRO MANILA PHILIPPINES
WIRE AND CABLE SUPPLIER IN METRO MANILA
WIRE AND CABLE SUPPLIER IN QUEZON CITY
WIRE AND CABLE SUPPLIER IN LUZON
WIRE AND CABLE SUPPLIER IN VISAYA
WIRE AND CABLE SUPPLIER IN SUBIC
WIRE AND CABLE SUPPLIER IN CLARK
WIRE AND CABLE SUPPLIER IN THE PHILIPPINES
WIRE AND CABLE SUPPLIER IN THE PHILIPPINES
ELECTRICAL SUPPLIER IN METRO MANILA
ELECTRICAL SUPPLIER IN QUEZON CITY
ELECTRICAL SUPPLIER IN LUZON
ELECTRICAL SUPPLIER IN VISAYA
ELECTRICAL SUPPLIER IN SUBIC
ELECTRICAL SUPPLIER IN CLARK
ELECTRICAL SUPPLIER IN PHILIPPINE INDUSTRIAL PARK
ELECTRICAL SUPPLIER IN PHILIPPINE ECONOMIC ZONE
ELECTRICAL SUPPLIER FOR PHILIPPINE FOREIGNERS
ELECTRICAL SUPPLIER FOR PHILIPPINE PROVINCES
ELECTRICAL SUPPLIER IN PHILIPPINES BATANES
ELECTRICAL SUPPLIER IN PHILIPPINES LAOAG
ELECTRICAL SUPPLIER IN PHILIPPINES CLARK
ELECTRICAL SUPPLIER IN PHILIPPINES SUBIC
ELECTRICAL SUPPLIER IN PHILIPPINES MANILA
ELECTRICAL SUPPLIER IN PHILIPPINES BATANGAS
ELECTRICAL SUPPLIER IN PHILIPPINES LEGASPI
ELECTRICAL SUPPLIER IN PHILIPPINES BORACAY
ELECTRICAL SUPPLIER IN PHILIPPINES PALAWAN
ELECTRICAL SUPPLIER IN PHILIPPINES PUERTO PRINCESA
ELECTRICAL SUPPLIER IN PHILIPPINES ILOILO
ELECTRICAL SUPPLIER IN PHILIPPINES BICOL
ELECTRICAL SUPPLIER IN PHILIPPINES CEBU
ELECTRICAL SUPPLIER IN PHILIPPINES BOHOL
ELECTRICAL SUPPLIER IN PHILIPPINES SURIGAO
ELECTRICAL SUPPLIER IN PHILIPPINES DUMAGUETE
ELECTRICAL SUPPLIER IN PHILIPPINES BACOLOD
ELECTRICAL SUPPLIER IN PHILIPPINES CAGAYAN DE ORO
ELECTRICAL SUPPLIER IN PHILIPPINES SURIGAO
ELECTRICAL SUPPLIER IN PHILIPPINES BUKIDNON
ELECTRICAL SUPPLIER IN PHILIPPINES ILIGAN
ELECTRICAL SUPPLIER IN PHILIPPINES ZAMBOANGA
ELECTRICAL SUPPLIER IN PHILIPPINES BUTUAN
ELECTRICAL SUPPLIER IN PHILIPPINES GENERAL SANTOS
ELECTRICAL SUPPLIER IN PHILIPPINES ZAMBOANGA
ELECTRICAL SUPPLIER IN PHILIPPINES DAVAO
ELECTRICAL SUPPLIER IN PHILIPPINES CAGAYAN DE ORO
ELECTRICAL SUPPLIER IN PHILIPPINES CAGAYAN DE ORO
FOR YOUR PHILIPPINE ELECTRICAL CONCERNS...NEEDS...INSTALLATION...QUOTATION...ORDERS
KINDLY EMAIL US: SAFEELECTRICAL2013@GMAIL.COM
SAFEELECTRICALONLINE@GMAIL.COM
FOR YOUR PHILIPPINE ELECTRICAL CONCERNS...NEEDS...INSTALLATION...QUOTATION...ORDERS:
KINDLY EMAIL US: SAFEELECTRICAL2013@GMAIL.COM
SAFEELECTRICALONLINE@GMAIL.COM
FOR PHILIPPINE INQUIRIES LIKE LIGHTNING ARRESTER SUPPLY AND INSTALLATION
CONTACT US:
FOR PHILIPPINE INQUIRIES LIKE LIGHTNING ARRESTER SUPPLY AND INSTALLATION
CONTACT US:
FOR PHILIPPINE INQUIRIES LIKE LIGHTNING ARRESTER SUPPLY AND INSTALLATION
CONTACT US:
MOBILE NUMBERS: SMART: +63 09079522099
+63 09214026477
GLOBE: +63 09273919600
+63 09157920129
SUN: +63 9227192434
+63 09336253505
WIRELESS LANDLINE: +63 4068727
+63 4922566
LANDLINE: +63 4317553
HURRY..CALL US...NOW!!!!
THANK YOU FOR YOUR ORDERS AND INQUIRIES...
LIGHTNING ARRESTER SUPPLIER AND INSTALLER IN THE PHILIPPINES
ELECTRICAL FENCE SUPPLIER AND INSTALLER IN THE PHILIPPINES
LIGHTNING ARRESTER SUPPLIER AND INSTALLER IN METRO MANILA
ELECTRICAL FENCE SUPPLIER AND INSTALLER IN METRO MANILA
LIGHTNING ARRESTER SUPPLIER AND INSTALLER IN THE PHILIPPINE ECONOMIC ZONE
ELECTRICAL FENCE SUPPLIER AND INSTALLER IN THE PHILIPPINE ECONOMIC ZONE
LIGHTNING ARRESTER SUPPLIER AND INSTALLER IN THE VISAYA REGION
ELECTRICAL FENCE SUPPLIER AND INSTALLER IN THE VISAYAS REGION
LIGHTNING ARRESTER SUPPLIER AND INSTALLER IN THE MINDANAO
ELECTRICAL FENCE SUPPLIER AND INSTALLER IN THE MINDANAO
FOR YOUR LIGHTNING STRIKE PROTECTION...LET US HELP YOU AVOID SUCH ACCIDENTS...
BEFORE IT IS TOO LATE...BEFORE IT IS TOO LATE...
WHEN LIGHTNING STRIKE HIT YOU..
I GUARANTEE YOU..YOU'LL NEVER LIVE TO TELL YOUR EXPERIENCE...
DON'T BE THE NEXT VICTIM...PROTECT YOURSELF..YOUR FAMILY..YOUR BUSINESS AT ALL TIMES..
INSTALL A LIGHTNING ARRESTER IN YOUR PLACE...DO IT NOW BEFORE YOUR CAUGHT UNAWARE...
IF YOU HAVE LIGHTING PROTECTION INSTALLED...
YOU'LL HAVE PEACE OF MIND...YOU CAN SLEEP WELL EVEN WHEN LIGHTNING STRIKES...
YOU KNOW YOUR WELL PROTECTED...
IN YOUR HOME, IN YOUR PLACE OF BUSINESS AND IN YOUR PROPERTIES...
HURRY..CALL US...NOW!!!!
THANK YOU FOR YOUR ADVANCE ORDERS AND INQUIRIES...
"PHILIPPINE FOREIGNERS AND PHILIPPINE PROVINCES ELECTRICAL SUPPLIER
AND SERVICE PROVIDER"
"SAFE ELECTRICAL SUPPLY AND SERVICES"
No comments:
Post a Comment