Category Archive for: «Medium Voltage»

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Inspection, Test and Measurement Procedures for LV and MV (up to 36kV) Switchgears

Importance of checks and maintenance Installed in clean, well ventilated or air-conditioned locations, switchgear will require little routine maintenance. Major inspection should be scheduled for power plant shutdowns and concentrate for low voltage switchboards on identifying contact wear, correct operation of interlocks, correct overload settings and fuse sizes, signs of overheating, and undue dirt or corrosion. For MV […]

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The Consumer Power Substation With Metering On Medium Voltage Side

Nominal voltage 1kV – 35kV A consumer power substation with metering on medium voltage side is an electrical installation connected to a utility supply system at a nominal voltage usually between 1kV – 35kV, which for example may supply a single MV/LV transformer (exceeding generally 1250 kVA), several MV/LV transformers or one or several MV/LV secondary […]

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34 Questions And Answers To Break the Myth About SF6 Gas In Electrical Equipment

Miracle gas or not? There are many published discussions and reports on various aspects of  SF6 gas (sulphur hexafluoride) usage in electrical equipment. Most of them are based on facts and researches, but some are not. Let’s try to answer the 34 questions and break the myth about this ‘miracle’ gas. Note that most of […]

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Rating Definitions Applied to Medium Voltage Fuses

Greater than 2400V and less than 69kV The definition of low voltage fuses is equally applicable to medium voltage fuses. Medium voltage level is defined by standard ANSI C84 as containing standard system voltages from 2400 through 69,000 V, and the high voltage level contains standard system voltages from 115 kV through 230 kV. Strictly-speaking, high voltage fuse standards […]

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Rating Definitions Applied to Medium Voltage Circuit Breaker

MV protection applications The medium voltage circuit breaker is the device of choice when sophisticated system protection at the medium voltage level is required. Most modern medium voltage circuit breakers use a vacuum as the interrupting means, although sulfur-hexafluoride (SF6) based units still exist and in use. Most modern medium voltage circuit breakers are rated on […]

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Microprocessor and conventional secondary systems compared

Reliable operation of the primary system Secondary systems are all those facilities needed to ensure reliable operation of the primary system, e.g. a high voltage substation. They cover the functions of controlling, interlocking, signalling and monitoring, measuring, counting, recording and protecting. With conventional secondary systems, the various functions are performed by separate devices (discrete components) […]

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The role of medium voltage switchgear in power system

Introduction According to international rules, there are only two voltage levels: Low voltage: up to and including 1 kV AC (or 1,500 V DC) High voltage: above 1 kV AC (or 1,500 V DC) Most electrical appliances used in household, commercial and industrial applications work with low voltage. High voltage is used not only to […]

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MV Circuit Breaker Or Vacuum Contactor? (Part 2)

Continued from first part: MV Circuit Breaker Or Vacuum Contactor? (Part 1) When applied properly, both medium-voltage circuit breakers and medium-voltage fused contactors should provide decades of reliable service. Applied incorrectly, either can lead to major headaches. Comparison Table Characteristic Circuit Breaker Contactor (NEMA E2 with fuses) Continuous current High (1200 A, 2000 A, 3000 A […]

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MV Circuit Breaker Or Vacuum Contactor? (Part 1)

Application considerations To compare the application of medium-voltage circuit breakers and of fused contactors, we must understand the basic characteristics of each switching technology. Comparison presented here shows the major characteristics of medium-voltage circuit breakers and medium-voltage fused contactors that influence the application. Of course, the table entries are generalized, and the information varies by […]

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Example of MV/LV network structure with dual fed main MV switchboard

Connected to article: Example of standard MV/LV network structure Network structure: MV consumer substation; The main MV switchboard can be backed up by a generator set and it feeds two MV/LV transformers; MV switchboard can be GIS or AIS and consist of following cubicles: – two incoming feeders (from utility) – two transformer cubicles – […]

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