E-Throttle

From the name itself it may lighten that it’s about the transmission line protection strategy. Ø   When do we need this?      We need to protect a long transmission line with good sensitivity and selectivity Ø     Why not over current Protection? Of course it is possible as it’s a cheaper. But not recommended where we need higher sensitivity and selectivity. That is, if the load current and fault current are almost comparable, overcurrent protection fails to distinguish between the two. Also it is more susceptible in taking action with the change in fault location. Ø     Advantages over other methods ·          Provides faster operation. ·          Has the directional feature. ·          Greater accuracy as more information is using for taking decision. ·          As a backu...

Insulation Resistance All know that the resistance of a pure insulation is infinity. But to no extend we can make a pure insulation. So we have a small leakage current to flow through insulation depending upon the voltage applied. Thus as the result we get a resistance value in the range of Mega Ohms(MΩ) or Giga Ohms(GΩ).   Here the applied voltage is DC. We have separate kit for injecting the DC voltage. Usually that equipment is known as megger. The two windings are connected as in the diagram above and Megger is used to measure the insulation resistance. It applies a high voltage normally 500V or 1kV for time period of minimum 30 seconds to One minute and the respective resistance are noted down. Usually for a new transformer, result value will be in Giga Ohms(GΩ). During the ageing, deposition of dust, moisture and other unwanted particles can cause the megger value to reduce. So to gain the resistance back to normal, the dust deposited should be removed, moisture shoul...

Hey friends! you are familiar with the power system equipment which we discussed earlier.! Now it's time to protect it to total safety. As soldiers protect our country from enemies likewise our system should be protected from fault. The line of control is decided by fixing the current transformers on the right place. So our boundaries is decided by their location. Here in a substation, we have many equipments such as transmission lines, bus-bar, transformers, etc in the system which need atmost care. Starting from the bulkiest, transformers are having different level of protections such as phase to phase and phase to ground. In other words differential protection and earth-fault protection. Over-current protection is also implemented in it. Let's talk about the differential type of protection for transformers. It's quite simple to explain the theory but some complicated while coming into the calculation. The term itself gives a brief idea about the ...

  Did we want to really concerned about the current transformers ? Its just an instrument transformer Yeah!,  that's make it different in protective relaying Lets dig deep                             In the most protective relays the input quantity is current and these current are supplied by current transformers. located on or near to the protected equipment. The main functions of CT are 1. To isolate the power system circuit from protection circuit 2.Reduction of magnitude to a level accessed by relays and meters  When considering Constructional features, these are similar to normal transformers consisting a magnetically coupled primary and secondary windings, wound on a common iron core and the primary is connected in series with  the network and the ratio could be found from basics ie,   Ampere-turns in primary=Ampere-turns in secondary ie, low no. of t...