Recent Blog Entries

  •   When generator sets operate in parallel, the engine speed governor of each generator set determines the proportional sharing of the total active power requirements (kW) of the system.  For two systems to be paralleled, each must have the following matching characteristics for correct...
  •     Load management systems may prioritize loads based on the load type or importance. Load importance may vary widely depending on the application and facility, but often fall generally within one of the following categories: Non-Critical Loads These are loads that, if removed, will...
  •     When the system is totally isolated from the ground circuit, except through indicating, measuring or protective devices, which are normally grounded and possess a high impedance to ground, the ground fault factor     This may become higher, depending upon the circuit...
  •     Download     What is X/R ("X over R") ratio, and why is it important? First, X/R ratio is simply the ratio of the system reactance to the system resistance, looking back to the power source from any point in a power circuit, assuming that a short circuit is applied t...
View All


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.


    Electrical Network schemes

    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.





Share this article on...