Category Archive for: «Protection»

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Current and voltage sensors as an alternative to traditional CTs and VTs

Sensors as alternative As an alternative for traditional primary current and voltage measurement techniques, the use of sensor technique is gaining field. This technique is typically applied to current and voltage measurement in medium-voltage metal-enclosed indoor switchgears. There are many undeniable advantages with sensors when compared to the traditional solutions: Non-saturable High degree of accuracy […]

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Understanding The Ratios Of Magnetic HV Instrument Current Transformers

Primary & secondary windings The primary winding is a part of the network, carrying the actual load current. The transformer’s secondary circuits usually consist of several units, each of them having its own magnetic core and winding. The transformer has a rated current transforming ratio, like for example 200/1 A, stating the rated primary current […]

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Basics of Built-in Motor Protection for Beginners

Why is motor protection necessary? In order to avoid unexpected breakdowns, costly repairs and subsequent losses due to motor downtime, it is important that the motor is fitted with some sort of protective device. This article will deal with built-in motor protection with thermal overload protection to avoid damage and breakdown of motor. The built-in […]

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3 Overcurrent Protective Device Ratings You Must Properly Select

Ampere, voltage and interrupting rating In order for an overcurrent protective device to operate properly, the overcurrent protective device ratings must be properly selected. These ratings include: Voltage rating Ampere rating and Interrupting rating - Minimum Interrupting Rating. If the interrupting rating is not properly selected, a serious hazard for equipment and personnel will exist. Current […]

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A real life analogy of the jurisdiction of the protection relay

To Protect the Transmission Line Under Fault Formally, a relay is a logical element which processes the inputs (mostly voltages and currents) from the system/apparatus and issues a trip decision if a fault within the protection relay‘s jurisdiction is detected. A conceptual diagram of relay is shown in Figure 1 below. Let’s see an example […]

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Voltage Imbalance Protection of Synchronous Generator (ANSI Code 60)

Synchronous Generator Protection In an apparatus protection perspective, generators constitute a special class of power network equipment because faults are very rare, but can be highly destructive and therefore very costly when they occur. If for most utilities, generation integrity must be preserved by avoiding erroneous tripping, removing a generator in case of a serious […]

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Miniature Circuit Breakers (MCBs) For Beginners

Dual functions of a switch and a fuse This technical article focuses on the widely used miniature circuit breakers rated for 240 V or less. These are smaller and lower-rated versions of industrial-grade molded-case circuit breakers rated for 600 V or less. These miniature breakers, called air circuit breakers, are based on thermal, magnetic, or […]

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An Example Of Transformer Overload and Short-Circuit Protection

NEC Article 450 // Transformers Vaults Transformer protection consists of both overload protection and short-circuit protection. Overload protection is usually accomplished via proper selection of the secondary overcurrent protective device. NEC Article 450 gives specific primary and secondary overcurrent device ratings that may not be exceeded. These vary depending upon the accessibility of the transformer […]

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Lightning and surge protection of multi-megawatt wind turbines

Importance of protecting wind turbines There is an unabated trend for the utilisation of regenerative energy gained from wind turbines, solar, photovoltaic and biogas plants or geothermal heat. This is an enormous market potential not only for the energy industry but also for the suppliers and the electrical trade and that worldwide. In Germany meanwhile about 19,000 wind […]

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Danger And Control Of Static Electricity Buildup

Troubles that you can run into… The following are the dangers posed by static electricity: Ignition causing fire or explosion Damage to sensitive electronic components Electric shock to humans followed by accidents such as a fall Damage to mechanical components such as bearings due to sparking through the oil films on bearing surfaces. It is necessary […]

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