Electrical Protection Systems
Electrical power system operates at various voltage levels from 415 V to 400 kV or even more. Electrical apparatus used may be enclosed (e.g. motors) or placed in open (e.g. transmission lines). All such equipment undergo abnormalities in their life time due to various reasons.

For example, a worn out bearing may cause overloading of a motor. A tree falling or touching an overhead line may cause a fault.
A lightning strike (classified as an act of God!) can cause insulation failure. Pollution may result in degradation in performance of insulators which may lead to breakdown. Under frequency or over frequency of a generator may result in mechanical damage to it’s turbine requiring tripping of an alternator.
Even othervise, low frequency operation will reduce the life of a turbine and hence it should be avoided.
Whenever human security is sacrificed or there exists possibility of equipment damage, it is necessary to isolate and de-energize the equipment.
Designing electrical equipment from safety perspective is also a crucial design issue which will not be addressed here.
To conclude, every electrical equipment has to be monitored to protect it and provide human safety under abnormal operating conditions. This job is assigned to electrical protection systems. It encompasses apparatus protection and system protection.
Here, on this page you will find 10+ ABB’s power system protection practices that can be of great help to protection engineers and others. Guides are free to download.
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Note that not all documents in this section are free to download. Navigate through sub-pages to discover all documents.
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It’s very important information for an engineer for details and depth in electrical engineering and mastering the note calculated for each part of the electrical installation Low Voltage and Medium Voltage.
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What is different from kva &kvar
I think your question is: “What is the difference between KVA and KVAr”
KVA is the apparent Power
and KVAr is the reactive power. In case of inductive circuit the current lags behind the voltage and in case of capacitive circuit current leads the voltage..
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Thanks