Tricky but Easy Electrical Engineering!
Definition: Ideal Transformer is a hypothetical transformer having infinite permeability core and zero core loss and ohmic loss. An ideal Transformer does not exist in reality. This is just a hypothetical transformer for sake understanding the actual transformer. Properties of Ideal Transformer: Following assumption are made to define an ideal transformer: Winding Resistance is negligible. … Read more
Before we jump into the insulation class of Transformer Oil, it is imperative to discuss briefly about the insulation class. Insulation Class basically defines the maximum temperature at which an insulating material will perform its specified duty for the specified life on continuous basis. There are six insulation classes. These are tabulated below: Life of … Read more
Flash Point of Transformer Oil is defined as the temperature at which light hydrocarbon present in the transformer oil starts evaporating causing a flash on introduction of source under specified condition. It is an important parameter which must be maintained above 140 degree Celsius. Light hydrocarbons are already present in the transformer oil and gets … Read more
Protection Current Transformer (CT) and Metering CT are two different types of CT as per their requirement and hence design. Therefore, Protection class CT should not be used as Metering CT. Similarly, a Metering Current Transformer should not be used for protection purpose. Let the discuss the reason behind this. Why can’t we use Protection … Read more
Accuracy Class of Current Transformer (CT) is defined in Indian Standard IS 2705 Part-2 and Part-3. This accuracy class of CT is defined so as to provide the permissible error in the current measurement of CT. As we know that, there are three types of errors defined for a CT: Current Error (or Ratio Error), … Read more
Definition: Composite Error of a Current Transformer (CT) is defined as the rms value of difference between the ideal secondary current and the actual secondary current. It includes ratio error, phase error and the effect of harmonics present in the exciting current. Composite error is used to express the accuracy of protection class CT. You … Read more
Burden of CT is defined as the volt ampere loading which is permissible without errors exceeding the limits for an assigned accuracy class. It is expressed as volt ampere (VA). In simple words, it is the load connected to CT secondary. CT burdens are specified as 10 VA, 15 VA, 20 VA, 30 VA. You … Read more
Earth and Unearth cables are two types of power cables. The selection of cable is decided on the basis of system in which it is to be used. There are two different types of system on the basis of neutral earthing: Earth and Unearth System. Cable used in system where the neutral is grounded is … Read more
Resistive Reach of Distance Relay Characteristics is defined by the fault resistance for which the distance relay characteristics is defined. In MHO type distance relay the major drawback is that resistive reach is defined by the impedance reach and line angle and hence it is not independently settable in the relay. However, it is independently … Read more
LBB protection is often called CB Failure Protection. As per page Schneider P14x Relay Manual, “Circuit breaker failure protection, monitors the circuit breaker for its opening within a reasonable time in case of fault. If the fault current has not been interrupted following a set time delay from circuit breaker trip initiation, breaker failure protection … Read more