Human danger zones in compact and modular air insulated and 110 kV substations
J.H. Kruize (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Dennis van der Born – Mentor (TU Delft - Electrical Engineering, Mathematics and Computer Science)
C.S. Engelbrecht – Mentor (TU Delft - Electrical Engineering, Mathematics and Computer Science)
P.T.M. Vaessen – Mentor (TU Delft - Electrical Engineering, Mathematics and Computer Science)
J. Dong – Graduation committee member (TU Delft - Electrical Engineering, Mathematics and Computer Science)
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Abstract
In the coming years, a large portion of the 110 and 150 kV substations in the Netherlands will be replaced. For this, the Dutch TSO TenneT has introduced the Bay Replacement Program (BRP), in which the old bays are being replaced completely by standard, modular, and compact skid-mounted bays. These bays are, in principle, plug-and-play, except for the busbar disconnector, for which the pantograph has to be aligned to the overhead busbar. To make substations even more compact in the future, this thesis aims to investigate the switching impulse breakdown strength of short air gaps relevant to maintenance of the 110 kV BRP busbar disconnector, in order to determine the minimum safety clearances.
The validity of the Schneider and Weck method for simulating the gap factor of short gaps (gap distance smaller than 2 meters) is investigated. Electric field simulations in COMSOL were compared with the original results from Schneider and Weck. The simulations reproduce the original results with deviations below 5% for gaps larger than 2 meters. For gaps smaller than 2 meters, the results show irregular behaviour. Experiments on a rod-plane and conductor-rod gap show that the simulated gap factor deviates significantly from the experimentally found gap factor, and the Schneider and Weck model is therefore considered to be invalid for air gaps smaller than 2 meters. The experiments on a rod-plane and needle-plane show that the Feser equation best describes the breakdown strength of short rod-plane gaps, while the CRIEPI equation provides a conservative value suitable for clearance determination.
Experiments on the BRP busbar disconnector were conducted in the TU Delft high voltage laboratory to investigate the gap factor that may occur during maintenance. Four different gaps were tested: conductor-rod, pantograph-rod, pantograph-needle, and earthing contact-needle. The results show that the earthing contact-needle gap has the lowest gap factor of 1.20, and hence is the determining gap for the critical clearance. This critical clearance is found to be 45.6 cm, based on a worst-case risk evaluation. The currently enforced critical clearance by TenneT of 47.9 cm is considered to be adequate. A simulation is performed to study the minimum clearances related to the electric field.