Recent Blog Entries

  • You may have heard of silicone dolls or sex dolls, you may have seen documentation or read an article about an owner. There is a lot of speculation about the love for mini sex doll and the content that people use, but the answer is different for every doll manufacturer and customer. So wha...
  •   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...
View All


Test

Isolated neutral system

  •  

    Isolated neutral system,Resonant grounded system,Non-effectively grounded system,Effectively grounded system,A grounded neutral system,An ungrounded or isolated neutral system

     

    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’s conditions

     

    A grounded neutral system

     

    When the system is grounded through its neutral, either solidly, through a resistance or through an arc suppression coil (inductor), it becomes a grounded neutral system. This type of system grounding may be classified as follows:

     

    • Effectively grounded
    • Non-effectively grounded and
    • Resonant grounded

     

    Effectively grounded system

    This is to achieve a higher level of fault current to obtain a quicker tripping on fault. It is obtained when the system has a ground fault factor not exceeding 1.4 (Vg £ 0.8Ve), as noted above. A solidly grounded system will provide effective grounding . This system will reduce the transient oscillations and allow a current sufficient to select a ground fault protection scheme. It is normally applicable to an LV system.

     

    Non-effectively grounded system

    An impedance grounded system will fall into this category . The GFF may now exceed 1.4 (Vg > 0.8Ve).

     

    Resonant grounded system

    When the system is grounded through an arc suppression coil (reactor) so that during a single phase to ground fault, the power frequency inductive current passing through the inductor coil would almost offset the power frequency leakage capacitive component of the ground fault current. However, such a situation is not allowed to persist for more than 8 hours in any 24 hours or for a total of 125 hours during a year. If it is more, a higher

    level of insulation (BIL) will become necessary for all insulators and terminal equipment. The ground fault factor in this case may also exceed 1.4. This basically falls in the category of ungrounded system

    When the system parameters R0, X0 and X1 are known, the value of GFF may be determined more accurately by the use of , which has been established for different grounding conditions, i.e. for different values of R0, X0 and X1.

     

    Reference: 

    • Kaufmann, R.H. and Halberg, M.M., ‘System over-voltages, causes and protective measures’.

Share this article on...