In the dissertation the basic functions and normative requirements for grounding system diagnostics are given, the analysis of the diagnostics results is carried out and the main disadvantages of grounding system are given. The urgency of improvement of the grounding systems of electrical installations with the voltage of more than 1 kV in electric networks with a grounded or effectively grounded neutral is substantiated. The improvement is aimed at ensuring the electromagnetic compatibility of primary and secondary circuits, namely, at ensuring the prevention of damage to the insulation of cables of secondary circuits of measuring current transformers and at ensuring the prevention the false triggers of current protections.
In the work, for the first time, three additional criteria for the implementation of grounding systems of 330 (220) / 150 (110) kV substations are formulated, which are aimed at preventing damage to the insulation of current protection cables with lightning strike and with short circuit, as well as to prevent current protection false triggering in the event of damage to the insulation of the specified cables.
The paper analyzes the experimental data obtained at 80 operating substations 330 (220) / 150 (110) kV of Ukraine, to determine the independent factors as well as insignificant factors from a number of independent ones. As a result of single-factor experiments, it was established that the independent factors are follows: the area of the grounding systems, the equivalent specific soil resistance, the size of the grounding systems mesh cell, the perimeter of the horizontal electrodes section, the depth of the horizontal electrodes, the current of the single-phase short circuit and a constructive coefficient which is the ratio of the distance between the current transformer and the relay panels hall to the diagonal of the grounding system. As a result of single-factor experiments, the depth of the horizontal electrodes was found to be insignificant .
In the paper a complete two-level four-factor and five-factor experiments were carried out to determine the grounding system resistance with short-circuiting. The results of calculation of the grounding system resistance for the real values of the factors of 80 substations based on the formulas obtained and the formulas known from normative and technical literature are presented in the work.
In the paper, for the first time, a complete two-level six-factor experiment was carried out to determine the voltage on the cable insulation of the secondary circuits of the current transformer, which is the most distant from the relay panel hall, with a short circuit. The paper presents the results of calculation of the given voltage for real values of the factors of 80 substations based on the obtained formulas.
In the paper the procedure for the experimental determination of the voltage on the insulation of the secondary circuits cable of the current transformer, which is the most distant from the relay panel hall, when simulating a short circuit on the bus of this current transformer, was formulated.
In the paper a technique was developed and examples of design parameters and material costs for the implementation of grounding system of substations 330 (220) / 150 (110) kV using the mathematical models obtained in the work on the criterion of prevention of insulation damage of current protection cables with short-circuit, as well as the criterion for preventing the false triggering of current protection in the event of a grounding of the phase or zero conductors of the secondary circuits cable.
