Ensuring the Serviceability of 0.4 kV Electric Networks in Case of Breaks of the Combined Neutral and Earth Conductor

Abstract

Breaks of the neutral conductor are among the most common failures in 0.4 kV networks. At present, to ensure the electrical safety of personnel, grounding loops with standard values of grounding resistance in compliance with Electrical Installation Code (PUE) are set up. Such grounding loops do not have any significant impact on the power quality indicators. Moreover, their construction is quite expensive and requires significant material costs. To maintain power quality parameters within the permissible limits, grounding loops with much lower resistance values are needed, which, however, are much more expensive. One of the ways for solving the problem under consideration is the use of natural grounding conductors for temporarily maintaining the standard electric power quality. The article addresses the problem of ensuring the electric power quality in case of breaks of the neutral conductor and a decrease of its conductance with reference to voltage unbalance. The ways of solving this problem are briefly outlined, in particular, by laying an additional conductor or using the TN-C-S grounding system. One of the alternative solutions to the problem considered is the use of natural grounding conductors, for example, a reinforced concrete foundation or a metal fence. The grounding resistances of such grounding conductors were calculated, the estimated values of which have confirmed the possibility of using them to comply with the PUE requirements. Practical recommendations for implementing the suggested proposals are given. One of them is to develop a device for monitoring the state of the neutral protective and main conductors. The key related issue of the problem considered is to ensure the electrical safety of both personnel and all people staying in the territory in which the grounding is temporarily used as the main neutral conductor. This issue will be addressed in the subsequent publications.