Development of the Vacuum Arc Chute for a 110 kV Single-Break Vacuum Circuit Breaker
Requirements for high-voltage vacuum circuit breakers for networks with a grounded neutral, which are stemming from the prospects of using vacuum circuit breakers in networks with the solidly grounded neutral are formulated. The arch chute design for a 110 kV single-break vacuum circuit breaker that takes into account the occurrence of repeated breakdowns is developed. The shielding system equalizes the voltage over the chute casing, decreases the electric field intensity at the “triple point”, protects the casing dielectric from becoming dusted with metallic contact parts erosion products, prevents the occurrence of cascade breakdown between the contact parts and central shield, and eliminates a possible decrease of the chute electric strength as it gradually works out its switching life. It is shown that the chute design includes measures to prevent the possibility of repeated breakdowns during disconnection up to class С1 according to GOST 52565-2006. It has been proven that for vacuum arc chutes for class С2 (for switching a capacitive load) it is necessary to develop a chute with two breaks between the contact parts or to connect two vacuum chutes in series. The shielding system adopted in the chute rules out the possibility of ceramic casing to become metallized, which decreases the chute electric strength as it gradually works out its switching life, and the vacuum arc transfer to beyond the inter-contact gap boundaries onto the central shield, the burnout of which results in that the vacuum arc chute loses its tightness and fully loses its functional properties.