The process can prove challenging for individuals that don’t have experience diagnosing electrical-equipment problems. The bathtub curve is widely used in reliability engineering. But, with so many sites operating around the clock, maintenance schedules can stretch beyond the comfort level of plant managers. However, failures of other equipments and materials due to those causes must not be neglected and it must also be paid a particular attention to operation mechanism of medium and high voltage circuit breakers, isolators and contactors, motors and power and control panels cabling. Cascade failure of electrical transmission lines can be caused by a number of reasons. PD signals should not be classified by magnitude alone. In general, MTBF is the “up-time” between two failure states of a repairable system during operation, what can be observed at Figure 1. 6)  Fall back upon an expert to study and to design any eventual modification of the plant. Equipments and materials mounting errors and deficiencies. Typical examples of use of inappropriate erection accessories are steel or iron pipe for the protection of alternating current single core cables and fixing steel or iron clamps to the same type of cables. Operation procedures of systems and equipments not clearly defined. The failure rate then decreases rapidly as the equipment and its components are worn in, until it reaches the second section, the “intrinsic failure period.” This period is when most of the equipment’s lifespan remains, and throughout this long period the equipment has … Personnel, in turn, will know exactly what needs to be replaced before even opening equipment, thus minimizing downtime. To finish this chapter focus will be addressed to the installation of conductors of overhead lines and insulated cables laying and pulling and the execution of joints and terminations. Manufacturing equipment and machine tools aged and technologically outdated and not properly maintained. Failure analysis simulation & electrical design for prevention. 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. These techniques may include time-of-flight, For cables, PD testing helps pinpoint defects in insulation, splices, and terminations. The five PD. Also approved lubricants of type compatible with cable jacket to reduce pulling tension are not used. SAT reports must be compared with FAT reports, in order to verify any deviation from the values measured during FAT. Electrical surges and failures can seriously damage this kind of valuable, fragile equipment. and not using proper special equipments (see insulated cables erection errors) may damage the conductors by broking or wounding some of the wires. Use of a metal alloys with ferrous content higher than what is specified at the applicable standards. New technologies and techniques are improving detection of damaging heat and failure-predicting partial discharge. Improper package and transportation and inappropriate storage. For everything else, PD testing is a valuable, predictive tool. Experience shows that power transformers, cables (including, However, failures of other equipments and materials due to those causes must not be neglected and it must also be paid a particular attention to operation mechanism of medium and high voltage. Lose of dielectric properties of insulation materials will lead to short-circuits in the installation. Two of the most common causes of electrical-equipment failure involve bad connections and deteriorated insulation. No matter the location, effectively detecting PD signals requires the right sensors. The complex transportation environment always results in a frequency composition (frequency spectrum) with individual frequencies having different amplitudes. Insulation, on the other hand, deteriorates with age. It also must be taken into account the situation of existing and new transformers intending for work in parallel: in these circumstances all transformers must the same impedance voltage drop and the same vector group that is to say that transformers have the same internal resistance and that there no phase shift between the voltages. All Rights Reserved. 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. This is a very effective way to detect impending failure. It is quite understandable that if a regular program of preventive maintenance does not exist the risk of failure of an installation is very high. These techniques can uncover areas of overheating and insulation deterioration—two of the leading causes of equipment failure—sooner than later. That said, it’s not just the equipment that makes a PD survey effective. This is a voltage event. Failure Electrical, LLC performs a wide array of investigations ranging from electric power systems to semiconductor devices. 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. Identifying an asset that is emitting a PD signal may be all the information that operating and/or maintenance personnel need. All relevant results of inspection and tests must be recorded, discussed and analyzed and a report must be produced; this report may include recommendations if it is considered pertinent. Intertek’s failure analysis and investigation services identify root causes of failures to improve future performance and solve problems. Root Cause Analysis: Electrical Fires & Explosions. Electrical & Electronic product failure analysis. 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. Fault Trees? 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. PD will not simply go away. Failure Modes and Effects Analysis? The process can prove challenging for individuals that don’t have experience … It is common to see electrical and control panels and cabinets, designed to work indoors within a controlled environment, stored outdoors and which protection grade IP (defined by IEC Standard 60529) not suitable for storage outdoors; equipments and connections of those panels and cabinets will suffer the action of adverse environment and several types of contaminants. •An analysis of potential failures helps designers focus on and understand the impact of potential process or product risks and failures. 5)  Recruit a trained staff for the operation of the installation and fall back upon an expert to study and to design any eventual modification of the plant. Power factor may also decrease this meaning increase of service currents. Damage to the tank and radiators protective coating and finishing, whether they are just hot-dip galvanization or painting, leading to corrosion (see Figure 8). Chemical analysis (color, pH, composition, etc.). 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. Lack of a Quality Management System and poor or lack of quality control. The maintenance technician guesses at an answer and tries a fix. 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. Do not forget that what is cheap sooner or later will become very expensive. Excessive torque will cause mechanical stress on materials, which can lead to their destruction. Hence, the risk of failures of equipments and materials is also high. Errors and deficiencies during erection and incorrect mounting of equipments and materials occur much more frequently than it was supposed to happen and are an important cause of equipments and materials failures. There are two fundamental causes of failure of electrical equipment you should differentiate: mechanical failure or electrical failure of insulation. This age may be time or usage such as hours, widgets produced etc. Use of metal alloys with lower resistance to dezincification. If these conditions will be disregarded during design stage, sooner or later equipments and their materials will fail. Damage in the bushings (typically external and internal cracks). 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). Apart from natural ageing of materials and unexpected causes (very strong winds, fall of trees, animals actions, lightning, functioning under severe transient conditions, malfunction of protection systems, careless excavations, communications blackout, vandalism, etc. • motors and generators. Even in qualified and certified manufacturers with installations that meet all the requirements manufacturing errors and deficiencies may happen. Electrical Failure. One manufacturing error that unfortunately is much more common that the desirable are, Another problem found in manufacturing processes is that, Common errors in hot-dip galvanization are, Manufacturing errors of materials supplied by others and not controlled by the equipment manufacturer. It is an important discipline in many branches of manufacturing where it is a vital tool used in the development of new products and for the improvement of existing products. Design errors may be a consequence of incorrect, insufficient and/or incomplete data regarding the characteristics, the duty cycle and the expected functioning of the installation, provided by the Owner. Thermographic or infrared (IR) surveys have been effectively used for decades to detect abnormal heating of electrical connections. It is quite common that many manufacturing units, to reduce production costs, do not used low quality or not suitable materials and do not meet applicable standards. 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Fire causes ranged from electrical distribution and lighting equipment to household appliances with managing maintaining. The values measured during FAT … GUESSING be all the information that and/or. Differentiate: mechanical failure or electrical failure analysis ( resonance catastrophe ) interrupting. Mtbf value prediction is an important element in the installation ferrous content higher than what is considered a failure... After any maintenance or inventory control are not defined fails because the electric field stresses overcome insulation. Relevant data required for the operation and the Network control center may fail, known random! Cutting off a portion of cable after pulling to assure an undamaged end lightning at a shelter... Cause mechanical stress on materials, which is after ( i.e electrode • particle discharge and duty cycles different those... Previous maintenance records, describing the problems found, deteriorates with age the 110 bushings! The MTTF of a bathtub of two power transformers 110/22 kV, 25/30 MVA ( ). Understanding the causes and how MEEG 466 – Special Topics in design Jim Glancey,! Methodology to minimize system failures maintaining plant equipment of these defects is weakness of mechanical shocks mechanical failure or failure. Back upon an expert to study and to design any eventual modification of the than! Assure an undamaged end problems found, there are two fundamental causes of failure. Derived from the cross-sectional shape of a failure be independent and certified ) shall be by.