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...
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December 16, 2017 admin
Measurement and Instrumentation
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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...
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November 9, 2017 admin
Measurement and Instrumentation
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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...
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November 9, 2017 admin
Measurement and Instrumentation
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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...
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November 9, 2017 admin
Measurement and Instrumentation
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Moving Iron Instruments are the most common type of ammeter and voltmeter used at power frequencies in laboratories. These instruments are very accurate, cheap and rugged as compared to other AC instruments. Working Principle of Moving Iron Instruments: In Moving Iron Instruments, a plate or...
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November 9, 2017 admin
Measurement and Instrumentation
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The deflection of needle of moving iron instrument is given in terms of rms value of voltage or current. As the angular deflection of Moving Iron Instrument is proportional to square of operating current, therefore the instrument has basically square law response. Due to this...
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November 9, 2017 admin
Measurement and Instrumentation
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It is a well known fact that Ammeter is always connected in series with the element through which current is to be measured. Figure below shows two cases, in one case ammeter connected in series while in other case, ammeter is connected in parallel. As...
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November 9, 2017 admin
Measurement and Instrumentation
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A Residual Voltage Transformer is used to measure the residual voltage of three phase system during single phase fault. During normal operating condition, the summation of three phase voltage is zero but in case of single phase fault, the scenario changes and there exists a...
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November 9, 2017 admin
Measurement and Instrumentation
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Permanent Magnet Moving Coil or PMMC Instruments are the best for the measurement of DC quantities like voltage and current from accuracy point of view. But there are various factors due to which error in PMMC Instrument reading may develop. To investigate the main sources...
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November 9, 2017 admin
Measurement and Instrumentation
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Permanent Magnet Moving Coil or PMMC Instruments are the most accurate type for the measurement of DC current or voltage. The working principle of PMMC instruments are same as that of d’Arsonaval type of Galvanometer, difference being that a direct reading instrument is provided with...
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November 9, 2017 admin
Measurement and Instrumentation
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