Insulation materials used in transformers and motors are classified based on the temperature withstand capability. Some of the insulation classes used in transformers and induction motors are: Class Y, Class A, Class E, Class B, Class F, Class H and Class C. Class Y Maximum hot spot temperature for this type of insulator is 90°C. … Read more
When a transformer is energized after a short interruption, the transformer may draw high inrush currents from the system due to core magnetization being out of synch with the voltage. The inrush currents will be as high as short-circuit currents in the transformer (almost 20 to 40 times the rated normal full load current of … Read more
Gas Insulated Substations (GIS) differ from Air Insulated Substations (substations we usually see) such that all the substation equipment such as busbars, circuit breakers, current transformer, potential transformers and other substation equipment are placed inside SF6 modules filled with SF6 gas. The SF6 gas which has high dielectric property acts as an insulating medium to … Read more
Stones/Gravel is used in Electrical Switchyard because of following reasons 1. During Short circuit current Step and Touch potential increases. (a) Step potential: It is the potential developed between the two feet on the ground of a man or animal when a short circuit occurs. This results in a flow of current in the body … Read more
Mobile Substations are emergency power supply substations employed temporarily to provide power supply in the areas affected by the natural disasters such as storms, cyclones and during wars. These substations will have a maximum rating of about 220kV. Mobile Substation typically contains Trailer for the unit, Distribution Transformer, Cooling system for Transformers, Switchgear equipment (relays, … Read more
A transducer is a device which, when actuated transforms energy from one form to another. Here input quantity is non-electrical quantity. The output quantity may or may not be electrical quantity. When the output quantity is electrical, then transducer is called as Electrical Transducer. An electrical transducer is a device which converts any physical quantity … Read more
Have you ever seen a ring around the Surge Arrester or other EHV equipment? What is the purpose of the Ring around the Extra High Voltage (EHV) equipment? What is the use of big rings at EHV testing centers? This Metal Ring what we see in the substations and other transmission line network is “Corona … Read more
Air Insulated Substation (AIS) or Outdoor Substations have all switchgear equipment, busbars and other switchyard equipment installed outside open to atmosphere. In earlier days for any voltage ratings, AIS or outdoor substation is employed. Indoor Substation type is only employed in places where high pollution or the saline environment exists. Indoor substations are two types … Read more
Sulfur hexafluoride gas (SF6) properties are given below SF6 gas is Heavy, chemically inert, non-toxic SF6 gas has no poisonous effect on the human body but decomposition products are poisonous SF6 gas is Colourless and odourless It is gaseous at normal room temperature and pressure Density is about 6.6g/l at 20°C (5 times denser than air) … Read more
Step Potential and Touch Potentials are very important in substations because during ground faults all the ground current returns to the substation transformer (as the substation transformer is grounded). The current that returns through the earth can create a significant voltage gradient along the ground and between ground and conducting objects. A step potential in … Read more