Recent Blog Entries

  •   Advantages of Underground Cables vs Overhead Lines   There are a number of advantages associated with undergrounding of the transmission line across the development which include the following: Reduced visual impact by removing tower No. 11 in the centre of the development and th...
  •   System short circuits may occur across any two or even three lines, or, if the neutral Point is solidly earthed, between any one line and the earthed neutral the effect of a System short circuit is to produce over currents, the magnitude of which is Dependent on the short-circuit level of ...
  •   Corona   A corona is a partial discharge and takes place at the surface of a transmission line conductor when the electrical stress, that is, the electric field intensity (or surface potential gradient), of a conductor exceeds the breakdown strength of the surrounding air. In such a...
  •     with fire associated with power transformers or oil-filled reactors, where the consequences can be particularly serious and extensive because of the large volume of oil that can catch fire and spread widely (Fig). For more details on protection against fire   ...
View All




Featured Pages

Electrical Network schemes


    Single radial network

    This is the simplest, least costly network scheme and the one with least overall reliability. The single radial scheme for a net-work with several voltage levels has a tree structure, possibly with backbones which supply the loads distributed along the route.


    The main advantages of this network configuration are:


    –  simplicity;

    –  economy.

    Vice versa, the disadvantages are:

    – maintenance (the network must be put out of service on the load side of the maintenance point);

    – vulnerability (in the case of a fault, the whole network on the load goes out of service).


    Double radial network

    The particularity of this scheme consists of having two equal alternative paths, made up by doubling a basic radial type network. Duplication of the scheme can be extended as far as the individual user, or more frequently, as far as one or more distribution nodes (busbars).


    Their major use is in networks of industrial plants with process plants where a high level of service continuity is required.


    The main advantages of this network configuration are:


    –  the limited duration of out of service in the case of a fault;

    – possibility of carrying out maintenance on parts of the plant without causing out of services or plant stoppages.

    On the other hand, the disadvantage is the high costs for its realization.


    Ring network



    Ring networks make it possible to always have two power supplies for each plant substation. In practice, the ring scheme is characterised by the presence of at least one side more (n+1) compared with the minimum needed to connect the loads to the power supply node. Their main use is in networks where there are considerable distances between the users, characterised by small absorbed powers. In the pres-ence of large plant loads, building a ring network can be more onerous than other types of network.


    On the in-out of each substation, the ring networks can be equipped with protection devices (and operating parts) or just with switch-disconnectors (not able to open the circuit in the case of a fault). Obviously in the first case a protection system which only eliminates the faulty trunk from service can be studied, whereas in the second case the only device which can detect a fault in the network and command circuit open-ing will be positioned at the departure of the ring.


    Running ring networks equipped with devices able to identify and interrupt the fault in the ring substations is, in any case, very different according to whether the ring is run open or closed.





What's New

No results found!