Tricky but Easy Electrical Engineering!
Strain Gauge is basically a sensor used for the measurement of various physical parameters like stress, strain etc. The working principle of strain gauge is based on Piezoresistive Effect. This is why it is also often called Pizoresistive Gauge. When a metal conductor is stretched or compressed, the dimension of conductor changes. Change in dimension … Read more
Accuracy Limit Factor of Current Transformer is a very important factor while selecting a CT for protection purpose. A current transformer chosen for protection purpose are defined by protection class ‘P’. The whole and sole requirement of a protection class CT is to maintain its measurement accuracy during fault as well as abnormal condition. Such … Read more
You might surprise to hear about HSV & NSV Rating of Electric Equipment. If you ever get a chance to visit a EHV Switchyard, you will notice that HSV / NSV rating is mentioned on every equipment connected to the Switchyard. I was also wondering to see this rating on every connected equipment in EHV … Read more
Instrument Safety Factor Instrument Safety Factor (ISF) is defined as the ratio of CT saturation current to its rated current. Suppose the CT ratio is 2000/1 and the CT gets saturated if there is flow of 10 kA current through its primary, then Instrument Safety Factor is given as Instrument Safety Factor, ISF = CT … Read more
Before discussing “Why PT/VT Secondary Terminal should not be Shorted?”, it is good to have a brief idea of Potential Transformers / Voltage Transformers. PTs/VTs are Instrument Transformer used for the purpose of protection and measurement. The construction of PT/VT is same as that of power transformer except for insulation level, cooling, sealing etc. PTs … Read more
Core Balance Current Transformer or CBCT is a ring type current transformer through center of which a three core cable or three single core cables of three phase system passes. This type of current transformer is normally used for earth fault protection for low and medium voltage system. A typical Core balance Current Transformer is … Read more
Equal Area Criterion is the method of studying the Transient Stability of system of two machines or single machine connected to infinite bus. The study of Transient Stability tells us whether or not synchronism is maintained i.e. whether or not load angle δ settles down to steady state stable value after the clearance of fault … Read more
All Day Efficiency is defined as the ratio of total energy output for 24 hrs i.e. for the whole day to the total energy input for the same day. All Day Efficiency is basically Energy Efficiency of Transformer calculated for a period of 24 hrs. Mathematically we can write, All Day Efficiency = 1 – … Read more
Ammeter Shunt is used for the measurement of heavy current using an Ammeter. Ammeter Shunt is basically a low resistance connected in parallel with the moving coil so that most of the current is bypassed by the Shunt and hence only a small current flows through the moving coil. Why do we need Ammeter Shunt … Read more
A PMMC Instrument can be used as voltmeter by just connecting a series resistance with the moving coil. This series resistance is called Voltmeter Multiplier. This combination of moving coil and multiplier is connected across the point whose voltage is to be measured. There are two main functions of voltmeter multiplier: 1) It limits the … Read more