Category Archive for: «Protection»

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Where Do Electrical Faults Occur The Most?

Causes of electrical faults // A fault is not a natural occurrence. It is an unplanned event which occurs unexpectedly. Electrical faults in an electrical installation or piece of equipment may be caused by // Negligence – that is, lack of proper care and attention Misuse – that is, not using the equipment properly or correctly […]

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Important points about grounding of electronic equipment

Safety grounding // Grounding electronic equipment for personal safety and clearing of faults is no different than that of any other equipment. Safe grounding requires fast opening of circuit breakers or fuses and minimization of voltage differences between exposed metal surfaces on all of the involved electrical system and equipment, to levels that are safe […]

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Measurement of residual currents on a distribution feeder

Residual currents (earth fault) The measurement of the earth fault or residual currents on a distribution system feeder can be done by the so-called summation connection, where the three current transformers, one in every phase, are connected and the summated current is brought to the inputs of an earth fault protection relay. This is a […]

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When You Ground Ungrounded System With Grounding Transformer

Wye-Zigzag Grounding Transformer The common grounding assumes a wye-connected neutral to ground. As this is not always the case, and in some cases it is not a three-phase system that it is desired to be grounded. For situations of this kind a grounding transformer is used. This may be a conventional wye-delta transformer of suitable […]

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Setting the generator protective relay functions

Protective relay functions and data This technical article will cover the gathering of information needed to calculate protective relay settings, the setting calculations for the various protective functions, typical generator/turbine withstand times for abnormal operating conditions, and the math associated with various types of impedance elements. Figures 1, 2, and 3 provide examples of organizing and […]

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Protection Schemes For Generators and Motors

Protection schemes // It is difficult to define precisely the protection schemes that should be adopted for an electricity distribution system, given the large number of valid alternatives for each situation, but some schemes will be presented as a guide for protecting the various elements that make up a power system. However, any protection scheme […]

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Guidelines To Inspection Of Molded Case Circuit Breakers (MCCB)

NEMA AB 4 and MCCB maintenance The need for inspection of molded case breakers (MCCB) will vary depending on operating conditions. Suggested inspection and testing is defined in ANSI/NEMA AB 4, Guidelines for Inspection and Preventive Maintenance of Molded Case Circuit Breakers Used in Commercial and Industrial Applications. As part of these guidelines, AB 4 […]

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8 tips to avoid ground loops when dealing with signal level circuits

Ground loops and signal noise General recommendation is to properly design and implement the facility’s grounding system to avoid unwanted involvement of ground loops with the operation of the equipment. This kind of approach can also eliminate the need to consider equipment modifications and to engage in costly diagnostic efforts since most trouble involving common-mode […]

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LV Surge Arresters In Action Against Lightning

Surge arresters against lightning Description of the installation The site consists of offices (computer hardware, lighting and heating unit), a security post (fire alarm, burglar alarm, access control, video surveillance) and three buildings for the manufacturing process on 10 hectares in the Avignon region of France (probability of lightning is 2 strikes per km2 per […]

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The Basics Of Circuit Breaker Tripping Units

Circuit breaker releases / Tripping units The main objective of circuit breaker tripping units and protective functions in general is to detect faults and to selectively isolate faulted parts of the system. It must also permit short clearance times to limit the fault power and the effect of arcing faults. The protective function of the […]

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