In transport practice there are no vibrations that consist only of a single frequency. It is recommended that for non armored cables pulling tension shall not exceed 5 kg/mm2 for copper conductors and 3 kg/mm2 for aluminium conductors. Electrical Failure. Lack of care with equipments already installed (see Figure 10. With insulated cables, erection errors that can lead to failures are larger; most common deficiencies are listed below: Pulling tension must be in accordance with the type of cable and the instructions of the manufacturer must be followed. Defective restoration of insulation, using non suitable materials and techniques (, Poor tightness of joints and terminations, allowing the, Poor cutting, preparation, continuity and earthing of metallic screen and armor, if existing (, FAT & SAT Not Conducted or Improper Conducted. PD-signal detection is the first step in executing an online predictive-testing program. • air-insulated and gas-insulated circuit breakers Such inquiry is conducted using scientific analytical methods such as electrical and mechanical measurements, or by analyzing failure data such as product reject reports or examples of previous failures of the same kind. Inappropriate storage of equipments and materials that is possible to find at the warehouse areas of manufacturers and contractors, but also in Owners installations, are a first step to a quick deterioration of those pieces, a fact that sooner or later will lead to failures that can be disastrous. Using the typical failure rate for a given type of equipment and the mean time necessary to repair it, PRA looks at the probability of failure of each type of electrical power equipment and, depending on the number of redundancies built into system design, can be used to predict availability, number of failures per year, and annual downtime. The cancelled MIL-STD-1629A is the military standard that establishes requirements and proce-dures for performing a FMECA, to evaluate and document, by failure mode analysis, the potential impact The process can prove challenging for individuals that don’t have experience … Electrical surges and failures can seriously damage this kind of valuable, fragile equipment. EXECUTIVE SUMMARY Failure analysis techniques for the evaluation of electrical and electronic components during aircraft accident investigation have been identified and examined. This paper does not intend to be an in-depth document, but we try to refer most common causes of failures of electrical systems, equipments and materials. If working control, FAT and SAT are not performed, a simple wiring mistake may cause protections and/or circuit breakers tripping command, remote protection or remote trip not to actuate, situation that can lead to the total failure and destruction of the system. PD will not simply go away. New technologies and techniques are improving detection of damaging heat and failure-predicting partial discharge. The process can prove challenging for individuals that don’t have experience diagnosing electrical-equipment problems. According to the National Fire Protection Association in 2011 an estimated 47,000 home structure fires and 16,400 non-home structural fires were attributed to an electrical malfunction or failure. Poor knowledge of systems and equipments and poor training of personnel. During this step, NTS will collect information about how the device failed and when it occurred. • arresters Design errors and deficient equipments and materials specification. A typical example of use of inappropriate tools is crimping operation of cable jointing connectors and terminals and C connectors (for copper bare cable of earthing grid), when a duly calibrated mechanical, pneumatic or hydraulic crimping tool suitable for the terminal to be crimped is not used and the the matrix employed is not compatible with the cross section of the cable and/or the dimensions of the connector. When stored in reels or in similar packages, if cable ends are not be protected against the ingress of moisture, water, dust and other contaminants, the insulation will be damaged and suffers a premature ageing, this meaning that there is a risk of short-circuit and consequently cables are subjected to failures. 4) Use only qualified and certified manufacturers, carriers and contractors. The destruction of cable reels is a typical example (see Figure 7), but damages in the insulators (cracks) of high voltage equipment (circuit breakers, disconnectors, instrument transformers, column insulators, etc.) The first step in a root cause failure analysis is data collection. Lack of a Quality Management System and poor or lack of quality control. The complex transportation environment always results in a frequency composition (frequency spectrum) with individual frequencies having different amplitudes. Common errors in hot-dip galvanization are faulty picking and degreasing of the surface, poor surface cleaning and insufficient thickness of zinc coating (According to applicable standards the thickness of zinc coating depends on environment aggressiveness and of the type and dimensions of metallic profiles used in manufacturing process). Under this assumption, any one particular system will survive to its calculated MTBF with a probability of 36.8% (i.e., it will fail before with a probability of 63.2%). An initial PD investigation will establish a baseline that can be compared with future testing results. ), due to the use of unsuitable calculation tools or a wrong evaluation of the data available may cause a permanent overload of those equipments, which leads to overheating and dielectric breakdown, or the destruction of equipments if they cannot withstand short-circuit thermal and electromechanical stress. It is common to test a representative sample of failed devices as well as those that are worki… He holds Bachelor’s and Master’s degrees from Purdue Univ. Among those reasons it is important to emphasize: Experience shows that power transformers, cables (including joints and terminations), accessories of overhead lines (insulators, clamps, connectors, etc.) following twenty-five years investigating a wide and diverse array of electrical and electronic equipment failures including explosions, fires, and injuries. • motors and generators. The fire causes ranged from electrical distribution and lighting equipment to household appliances. Hence, the risk of failures of equipments and materials is also high. The second part is a constant failure rate, known as random failures. Insufficient tightening of bolts and nuts, namely in equipments subjected to vibrations and rotating machines, may cause unfasten and loose bolts and nuts that risk destroying equipments. Limited Edition... Book Now Here. TÜV SÜD operates Failure Analysis Centres in Singapore and in other major production centres around the world to provide manufacturers of electrical and electronic products and components with failure analysis testing, material and product evaluation services, and reliability testing. A measure to avoid failures in important equipments, such as power transformers, overhead lines, generators and medium voltage motors, and materials It must be referred that electrical equipments and systems, namely overhead lines, substation busbars and power transformers require an Infrared (IR) thermography, which is a non-contact and non-destructive way to detect problems in electrical systems. Several factors contribute for those errors and deficiencies and to expedite equipments without their correction; most common factors for such a situation are: One manufacturing error that unfortunately is much more common that the desirable are defects in welding processes (It is recommended that quality of electric arc welding shall be in accordance with the following standards: EN ISO 3834, EN ISO 15609-1, EN ISO 17635:2010, EN ISO 17636-2:2013 and EN ISO 17640:2010) such as existence of fissures or gaps, porosities, incomplete fusion of welding cord, existence of scoria/detritus, affected areas due to welding over temperature and heterogeneity of the welding cord (This type of error is also common in site works); Figure 4 shows some of these defects. 25% Off on Electrical Engineering Shirts. Hence, short-circuits may appear and a failure in equipments and materials will be observed. Failure of cutting off a portion of cable after pulling to assure an undamaged end. Five of the six 110 kV bushings failed the tan δ test. Today’s technology allows equipment-temperature differences of one degree Celsius to be detected. Insulation, on the other hand, deteriorates with age. The path to success starts with an understanding of what specifically causes these trouble spots—and how to detect them. Use of improper tools and test equipments. If transformers do not have the same impedance voltage drop, they present a different resistance to the current that flows at each transformer, this meaning that the load will not be equally shared between the transformers, and the transformer(s) that has(have) a lower resistance will support an higher load than the other(s), so a higher current will pass through the transformer(s) with lower resistance. Equipments and materials mounting errors and deficiencies. EP. Electrical systems, equipments and materials are subjected to failures that can cause the total destruction of equipments and severe power outages. Typical manufacturers’ data for MTBF of oil-immersed transformers are 30 years, although experience shows that transformers may have higher MTBF and a useful life of about 50 years, or even more. When transformers working in parallel do not have the same vector group there is a circulation current between the transformers that will cause overheating. Determining which sensor to use depends on the type of signal created and its frequency, something that can range from tens of kilohertz to a few gigahertz. Mechanical properties and dimensions analysis. These transformers may hence have a permanent overload. For a better understanding failures of equipments and materials and the mechanism of these failures is important to understand the concept of Mean Time Between Failures (MTBF) that is used to evaluate reliability of equipments. 11) Keep records of all failures and their causes, as well as the inspections and tests performed in the investigation. Required fields are marked *, All about Electrical & Electronics Engineering & Technology. As a consequence of those wrong procedures (examples: packages and the equipments are exposed to environment conditions that are not suitable; poor fixing and/or locking of the equipment/package are the most common problems in transportation), packages may be destroyed and mechanical shocks and vibration will be amplified with consequences that may be catastrophic to equipments. Mechanical protection of the cable is not implemented and cables may be installed close to heat sources without any type of protection. Micro-circuit analysis including computer boards, circuit boards, chips and other specialty equipment; Motor testing of single and three-phase motors to determine and analyze performance and output for proper operation ; Our experts put all the pieces together and provide all the solutions for Electrical Failure Analysis. The asset can then be taken offline for an inspection to identify the cause of the PD and determine how to deal with it. A typical example of use of inappropriate tools is, Figure 11 shows an example of incorrect crimping of, Another typical error of erection activities that may be responsible for equipments failures is the, Typical examples of use of inappropriate erection accessories are, Another erection error that requires a special attention is, If these conditions were not fulfilled the, The main problem for the installation of conductors of overhead lines, apart from. The first system failed at 100 hours, the second failed at 120 hours and the third failed at 130 hours. The asset can then be taken offline for an inspection to identify the cause of the PD and determine how to deal with it. Also approved lubricants of type compatible with cable jacket to reduce pulling tension are not used. The electrical motor of the rotating system under analysis is analyzed for the failure diagnosis purposes, acting as a transducer in this process. Infringement of manufacturers’ instructions. When the bushings arrived to site and prior to the installation in the transformers tan δ was measured and the results compared with the IEC Standard 60137 acceptance criteria and with FAT results (that were properly conducted and witnessed by the owner representative). Addressing these issues is paramount for personnel tasked with managing and/or maintaining plant equipment. Steve Park is the manager of Technical Services for Vertiv’s (Columbus, OH, Vertivco.com) Electrical Reliability Services business. Basic Electrical; Electrical Laws, Theorems & Rules; Electrical Symbols; Alternating Current Principles; Electrical Engineering Materials; Electrical Measurements; AC & DC Circuit Theory. Forensic inquiry into the failed process or product is the starting point of failure analysis. Fault Trees? This is a very effective way to detect impending failure. This technology compares the speed of the radio-frequency signal to the soundwave of the PD source, or may involve triangulating the sound signal by examining how long the sound takes to travel to different sensors. MTBF is the sum of the operational periods divided by the number of observed failures. The destruction of cable reels is a typical example (see Figure 7), but damages in the insulators (cracks) of high voltage equipment (circuit breakers. As steel and iron are magnetic and conductive materials eddy currents (Eddy currents or Foucault currents are induced currents in conductive materials when subjected to a variable magnetic flux.) Non existence of installation manuals provided by the manufacturer of equipments and even existing they are not generally followed. During this phase, we will conduct tests on the product being analyzed. Manufacturing equipment and machine tools aged and technologically outdated and not properly maintained. We depends on ad revenue to keep creating quality content for you to learn and enjoy for free. Non existence of updated documentation, such as “. Working teams not organized in accordance with the nature and type of work to be performed. For basic IC cross-sectioning capability, the budget should be planned from about $100,000 (used equipment) to $400,000. Once the MTBF of a system is known, the probability that any one particular system will be operational at time equal to the MTBF can be calculated. Poor preparation of the cable, namely conductors’ core (, Use of abrasives and emery clothes with conducting grit or particles (. IR and PD surveys can be partnered and performed online during normal business hours without interrupting a facility’s electrical service. Identifying an asset that is emitting a PD signal may be all the information that operating and/or maintenance personnel need. It was analyzed above that incorrect manufacturing process and use of not suitable materials may cause loss of characteristics of equipments and failures, which can also be a consequence of: Prior to be expedite to site equipments must be subjected to FAT, at the manufacturer installations or at a certified laboratory to verify the electrical and mechanical performances of equipments and to evidence any defect in manufacture and if materials used meet the specifications and the applicable Standards. However, even with such a program, the risk of failure remains high if preventive maintenance program is not correctly established and if one or more of the situations described below occurs: Whenever failures in equipments and materials occur an investigation must be conducted in order to find out the reasons of that failure, to monitor the state of similar equipments and materials and to prevent future failures. • particle discharge. It describes a particular form of the hazard function which comprises three parts: The first part is a decreasing failure rate, known as early failures. Use of a metal alloys with ferrous content higher than what is specified at the applicable standards. Technical improvements in new equipment may as well reduce the economic life time of the existing equipment if the overall outage time is reduced and production losses decreased. MTBF describes the expected time between two failures for a repairable system, while MTTF denotes the expected time to failure for a non-repairable system. This problem is amplified when cable joints and terminations are not installed by trained, experienced and specialized personnel, aware of good safety practices involving high voltage electrical equipment, and when the instructions and the specifications of the manufacturers are not followed. All Rights Reserved. Among the reasons of equipments improper use it must referred: Load changes/additions and circuit changes without equipments characteristics modifications and installation of new equipment and without a detailed study of the new situation may lead to an increase of service currents, causing permanent overloads in cables, busbars and transformers, what means permanent overheating of those equipments, and mismatch of rated currents of switching equipments with new service currents. Updated and approved documents and equipments operation manuals not existent. Excessive torque will cause mechanical stress on materials, which can lead to their destruction. and equipments (See Chapter 5 for the consequences of insufficient tightening of bolts ant nuts on transformers and rotating equipment) or bolts, nuts and rag-bolts of metallic structures, applying insufficient or excessive torque and not using an appropriated and calibrated torque wrench. Today, the reliability of electrical distribution equipment is making owners consider this kind of methodology to minimize system failures. During this Phase, we will conduct tests on the definition of of... Characteristics are not defined important to take the appropriate measures to avoid these failures baseline for comparison. Of methodology to minimize system failures an indefinite period of time upon energizing our website made... 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