Category Archive for: «Low 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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Electrical life (durability) of LV circuit breakers due to the switching operations

Test requirements According to the standard IEC 947-2, there is actually no defined stipulation regarding the requirements of electrical life of a circuit breaker. The numbers of switching operations which a circuit breaker under no-load, normal load, overload and short-circuit conditions has to make and/or break are stipulated. These numbers vary between two switchings (O-t-CO) […]

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7 Practical Tips For Installing a Good Measuring System

1. Start from the need: what do I want to measure? A single electric parameter or all the electric parameters There are different product families on the market: instruments that measure a single electric parameter (voltage, current, frequency, phase angle cosϕ), generally used in single phase systems, as instrumentation on the machine, and instruments that enable all the […]

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Guidelines to Maintenance of Low Voltage Switchboard

Maintenance Benefits and Facilities A. Maintenance Program A well-executed maintenance program can provide the following benefits: Longer life of switchboard and fewer replacements; Reduced time on repairs and overhauls, and the option of scheduling them at an opportune time; Fewer failures with unexpected outages; Timely detection of any undesirable operating conditions which require correction; Improved plant […]

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Rating Definitions Applied to Low Voltage Molded-Case Circuit Breaker (MCCB)

For system protection 600V and below The molded-case circuit breaker is the “workhorse” for system protection 600V and below. A circuit breaker is a device designed to open and close by nonautomatic means and to open the circuit automatically on a predetermined overcurrent without damage to itself when properly applied within its rating. The following terms apply […]

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Methods Of Securing LV Circuit Breakers

Methods Circuit breakers are typically secured in place by one of the following methods: Through bolts Bolted to the bus Stab locked to the bus or some type of receptacle connection Din rail mounted Bolted Type Breakers When a longer service life breaker is wanted, a bolted type is typically used. These types have a […]

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Methods Of Mounting LV Circuit Breakers

Three general groups Methods used to mount circuit breakers can be divided into three general groups, those being: Fixed Removable (disconnectable unit), and Drawout (withdrawable) A review of these mounting methods follows. Fixed Mounted Circuit Breakers A circuit breaker that is bolted in its enclosure and wired to the load frame, we can call a […]

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10 Important Precautions When Working On Low Voltage Energized Equipment

Have eyes in the back of head… For most work, the electrical equipment must be de-energized because there is a high risk of injury to workers if they work on energized equipment. It may be possible to schedule such work outside of normal work hours to limit the inconvenience. Sometimes it is not practicable to completely disconnect low-voltage […]

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Harmonic Distortion and High Frequency Applications

Distortion of the fundamental sine wave The presence of harmonic frequencies in addition to the fundamental 50Hz, bring about distortion of the fundamental sine wave. Considerable problems may arise dependant upon the level of this distortion. Sources of harmonic distortion can be: Variable Speed Drives UPS equipment Non linear load (switch mode power supplies) Special […]

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What affects the operating temperature within LV switchgear

Maximum ambient condition BS EN 60439 states a maximum indoor ambient temperature of 40ºC, a maximum daily average of 35ºC and a minimum ambient of -5ºC. As a general guidance rule, the temperature within the low voltage switchgear should not exceed 50/55ºC. If Switchroom/Plant room ambients are typically considered to be up to 25°C this […]

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