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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
In fact, nearly 90% of the faults in transmission and distribution systems are transient faults. Whenever a transient fault occurs, the protective relay detects the fault. It immediately sends a trip command to the circuit breaker. The circuit breaker opens to disconnect the faulty line from the source. Since the fault is transient in nature, … Read more
There are mainly five basic types of operating mechanisms used in high-voltage circuit breakers: Among these five operating mechanisms, the spring-spring mechanism is the most commonly used by electric utilities. This is because it has a comparatively simple construction, fewer mechanical parts, occupies less space, and is more economical than the other operating mechanisms. Disadvantages … Read more
We know that a circuit breaker has two operational positions-open and close. During the closing operation, the circuit-breaker contacts close against few opposing forces. We shall discuss those forces in details here. It is very important to know these forces. Again, during the opening operation, the closed contacts travel back as fast as possible. The … Read more
In this article, we shall discuss the earth fault protection of a balanced three-phase network. Balanced Three-Phase Network Suppose this is a balanced three-phase network. Also, assume this is the representation of a three-phase star-connected winding of a power transformer. Although we can represent all balanced three-phase networks in the same manner, in our case … Read more