The neutral of the earthing transformer shall be solidly earthed to provide earthed neutral in the 33 kv systems. The earthing transformer shall have impedance to restrict earth fault current. Grounding transformers used as the only ground source to a distribution circuit should be in service whenever the threephase power source is in service. For this reason, neutral ground resisters are often used in conjunction with the grounding transformer to limit neutral ground fault current magnitude. Because the reactance of source generator or transformer impedance is in series with the neutral circuit, this system cannot be considered a zeroimpedance circuit. Advantage and disadvantage of grounded and ungrounded. Generally the time interval, for which transformer designed to.
Current rating of this transformer is the maximum neutral current in amperes that the transformer is designed to carry in fault condition for a specific time. Advantage and disadvantage of grounded and ungrounded neutral system if this is the first time for you then please read my previous post about electric earthing system. What is earthing transformer or grounding transformer. The rated voltage of an earthing or grounding transformer is the line to line voltage on which it is intended to be used. This is the basic theory of earting transformer, the operation and other features of an earthing transformer is described as follows. Grounding transformer the grounding transformer is used to provide a path to an ungrounded system or when the system neutral is not available for some reason, for example, when a system is delta connected. Contents 1 construction of earting transformer or grounding transformer. If the grounding transformer is lost, a linetoground causes high phasetoneutral voltages on the unfaulted phases, and load unbalances can also cause neutral shifts and overvoltages. It provides a low impedance path to the neutral and also limits the transient overvoltage when the ground faults occur in the system.
Generally connected between ground and neutral of transformers, ners reduce the fault currents to a maximum predetermined value that avoids a network shutdown and damage to equipment, yet allows sufficient flow of fault current to activate protection devices to locate and clear the fault. D static power converter for devices such as rectifiers and inverters, the system grounding is determined by the grounding of the output stage of the converter. To analyze how an electrical shock occurs and how grounding is applied, you need to look at the circuit involved. Grounding system theory and practice ced engineering. A solidly grounded system is one inwhich a generator, transformer or grounding transformer neutral is directly grounded to earth or station ground. C transformer the system grounding on the system fed by the transformer is determined by the transformer secondary winding configuration. Figure 2 illustrates the basic circuit that consists of a source, a transformer or generator for all ac circuits, circuit protection, conductors r1s, and a load rl.
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