Abstract
Electrical network should have proper earthing (grounding) system for its reliable operation and for the safety of operating personnel and connected customers. Good earthing provides a suitable return path for the fault current when a short circuit occurs in the network. In a low-voltage (LV) network mainly terra-terra (TT) and terra-neutral (TN) type network configurations are commonly used. Depending on the agreement between the network operator and the customer, earthing at a customer's point of connection (POC) is provided by a dedicated earth conductor, combined network cable (PEN conductor), or via a separate earth electrode. When an earth retour path is broken or interrupted, it will not be able to provide earth retour circuit and can cause dangerous fault voltage at various exposed parts of the conducting circuit. In this paper, various LV network configurations are discussed. Further, a practical monitoring based case study is presented to analyze the diversity of earth resistance values for different LV network configurations. Also, guiding rules are given to define safe value of circuit impedance and earth resistance path for various configurations. Finally, a proposal is given to optimize the safety needs at a customer's POC.
Highlights
Good earthing provides a suitable return path for the fault current when a short circuit occurs in the network
A practical monitoring based case study is presented to analyze the diversity of earth resistance values for different LV network configurations
The low-voltage (LV) network can be of various configurations depending on network operator’s design strategy and operational philosophy
Summary
The low-voltage (LV) network can be of various configurations depending on network operator’s design strategy and operational philosophy. Good earthing provides a suitable return path for the fault current when a phase to earth short circuit occurs in the network. It is needed for reliable operation of the network components. In a TN system, the network operator provides an earth connection point and the customer can connect his installation to that point for a safe earthing network. As per the Dutch regulation, the short circuit fault voltage in a LV network should be limited to 66 V or the fault has to be cleared within 5 s by the protective device present in the network, as shown in Fig. 1 [2] These guidelines are applicable for the new but could become applicable for the old LV networks in the Netherlands. A proposal is given to optimise the safety needs at a customer’s point of connection (POC)
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