Reliability Scope l l What is reliability Reliability
Reliability Scope l l What is reliability ? Reliability parameters. Failure characteristics Sources of failures in communication system
Reliability Definition l Generally defined as the ability of a product to perform as expected over time l Formally defined as the probability that a communication system performs its intended function for a stated period of time under specified operating conditions
Reliability Definition l Mathematically, this may be expressed as, where is the failure probability density function.
Reliability parameters l l l MTBF : Total operating time divided by the number of failures. MTBF is the inverse of failure rate. MTTR : Mean Time To Repair (MTTR), is the time taken to repair a failed hardware module. Availability = MTBF + MTTR
Reliability Hardware Failure characteristic Bath tub curve
Reliability Hardware Failure characteristic Infant Mortality l This class of failures cause newly manufactured hardware to fail. l Mainly due to manufacturing problems like poor soldering, leaking capacitor etc. l These failures can be detected during system burn in tests in factory.
Reliability Hardware Failure characteristic Random Failures l Random failures can occur during the entire useful life of a hardware module. l These failures can lead to system failures. l Normally Redundancy is provided to recover from this class of failures.
Reliability Hardware Failure characteristic Failures due to Wear Out l Mainly due to degradation of component characteristics will cause hardware modules to fail. l can be minimised by preventive maintenance
Reliability Sources of failures in FOP system
Reliability Sources of failures Source End copper cable 1. Break in cable 2. Interference 3. Short circuit due to moisture Back Precautionary Measure Use multistranded conductor and armoured cables Shielded cables for high speed data circuit Jelly filled cables are used
Reliability Sources of failures Source Connectors 1. Poor soldering 2. Improper fitting 3. Bad quality of connector Precautionary Measure Skilled technicians, Use of factory crimped cables We ensure connectorisation done as per OEM Back
Reliability Sources of failures Source Terminal equipment 1. Common failure point: Power supply, Transceiver module 2. Application card failure 3. 4. 5. Improper grounding Rodent problem Aging Back Precautionary Measure Dual power supply Dual transceiver port Backup channel is provided on another application card in same equipment. Proper grounding is ensured Sealing of cable entries. Regular preventive maintenance
Reliability Sources of failures Source Precautionary Measure Fiber optic patch cord & FDF 1. Break in patchcord 2. Attenuation due to improper connecter fitting 3. Break in fiber in FDF Laid through PVC conduit Use of FC/PC type connector. Back Proper marking of fiber in FDF and proper harnessing of field patchcords in the box.
Reliability Sources of failures Source Under ground FOP cable 1. Break in cable 2. Attenuation due to bending Back Precautionary Measure Laid through HDPE conduit Laying of FOP cable along with HV power cable is avoided. Burrried under ground at least 2 ft. 90 degree sharp bends
Reliability Sources of failures Back Source Precautionary Measure FOP Joint Box 1. Conductor snapping 2. Breaking of fiber in splice protector 3. Corrosion of splice protector due to moisture in grace Following things are ensured l OPGW conductor is tightly fitted in joint box. l Complete sealing of joint box l OPGW and joint box is properly mounted / fitted on tower.
Reliability Sources of failures Back Source Precautionary Measure OPGW conductor 1. Conductor snapping Good quality OPGW accessories are used. 3. Breaking of OPGW due to electrical fault. Aging 4. Theft 2. OPGW is grounded on every tower. Backup is provided through Ring architecture Regular maintenance of OPGW is carried out by transmission Div. l. In some area fencing is done at the bottom of tower l. Joint boxes are painted with Black color l. Joint boxes are kept at height as much as possible.
Reliability Thumb Rules l l l l Use good quality hardware from reputed vendor Get manufacturer test reports Carry out FAT Do proper installation and commissioning Ensure proper installation during SAT Keep system documentation ready to minimise downtime. Carry out periodic maintenance. Asses life of HW and replace it in time.
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