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An air blast circuit breaker is a circuit breaker that interrupts normal load current or fault current by means of a high-pressure blast of air inside the interrupting chamber. Why do we call it an Air Blast Circuit Breaker? A circuit breaker performs two main functions: first, the opening and closing of its contacts, and … Read more
Normally, we do not consider the effects of shunt capacitor bank during calculating the short circuit level. We normally consider 90° lagging power factor for the short circuit currents with respect to the voltage phasor. The utilities generally install shunt capacitor banks in receiving substations. The capacitor banks improve power factor and voltage regulation. Shunt … Read more
Nowadays, utilities connect many power system components in parallel. These components include generating stations, step-up transformers, transmission lines, step-down transformers etc. This arrangement reduces the total reactance of the power system. As a result, the short-circuit level increases. The short-circuit level includes short-circuit current and short-circuit MVA. These values can increase at different points in … Read more
The fault calculation is an essential part of power-system analysis. Because it determines the short circuit rating of different electrical components used in the power system. We also design protective-relaying schemes based on the fault levels. For example, a circuit breaker must be capable of making and breaking the fault currents. Additionally, it must withstand … Read more
We shall discuss the construction, uses and working principle of a potentiometer. Errors in Voltmeters Whenever we connect a voltmeter between two points of a circuit, it takes a shunt current depending on its internal resistance. Ideally, the internal resistance of a voltmeter is infinite. However, practically, this resistance is very high but not infinite. … Read more
Wheatstone bridge is a resistance measurement arrangement. It uses four resistors, out of which one is unknown. It measures the unknown resistance with the help of the rest of the three resistors. The Wheatstone bridge consists of these four resistors as the sides of a square, as shown below. Wheatstone bridge with resistors \(R_1\), \(R_2\), … Read more
Suppose, there is a three-phase network. An earth fault occurs at the red phase. For that fault, let us say current \(I_R\) starts flowing. Since this is an asymmetrical fault, there will be positive, negative and zero sequence currents in the system. Also, let us consider that at the instant of the fault there was … Read more
Nowadays, ester oils have become an alternative to conventional mineral transformer oil. These ester oils provide insulation and cooling to the transformer. We may use them, particularly where fire safety is crucial. Also, we may use ester oil where we essentially require environmental sustainability and improved insulation life. In this article, we have covered natural … Read more
The answer is no. A three-phase star- star or Yy0 transformer does not always demand tertiary delta winding. Let us explain the basic theory behind it. The video Lecture on this Topic Tertiary Delta Winding Suppose, an asymmetrical fault occurs in the LV network of a transformer. Obviously, zero sequence currents start to flow though … Read more
The a operator is one of the most important mathematical concepts used in the analysis of three-phase unbalanced systems and asymmetrical faults. It provides a simple way to represent the phase displacement between the three phases and is extensively used in symmetrical component analysis, sequence networks, and power-system fault calculations. In this article, we will … Read more