Intra-tank under-oil vacuum primary switches for medium voltage transformer applications

A transformer tank system comprising:

• a) a sealed tank, said sealed tank comprising core and coil assemblies immersed in a dielectric fluid or gas within the tank;
• b) a heat exchanger capable of circulating the dielectric fluid or gas within the sealed tank as the dielectric fluid increases in temperature and expands within the sealed tank, wherein the heat exchanger comprises:
• a hollow panel comprising a first side and a second side, wherein the second side of the hollow panel is connected to the sealed transformer tank at a plurality of ports;
• wherein heated dielectric fluid or gas circulates into the heat exchanger from the transformer tank through a first port and cooled dielectric fluid or gas exits the heat exchanger through a second port back to the transformer tank;
• wherein the hollow panel is capable of expanding in volume to contain electric fault energy that produce a sudden generation of gases which increases the pressure inside the heat exchanger;
• wherein the heat exchanger comprises a preferred release notch on a lower edge of the hollow panel, wherein the preferred release notch comprises a wedge piece that is welded between a notched lower edge of the first side and the second side of the hollow panel, and wherein the wedge piece tapers to a tip at an upper edge of the preferred release notch between the first side and the second side,
• wherein when the dielectric fluid becomes heated and pressure inside the heat exchanger exceeds a rupture pressure of the heat exchanger, a controlled pressure release preferentially initiates at the upper edge of the preferred release notch of the heat exchanger, wherein the preferred release notch is configured to provide a progressive opening that can gradually widen as the pressure intensifies;
• and
• c) a controllable primary switch configured to isolate a transformer from a power grid or network, wherein the controllable primary switch is mountable within the sealed tank and is electrically connected to high voltage feeder cables to allow the transformer to be disconnected from the power grid or network, the controllable primary switch comprising:
• i) one or more vacuum interrupters, wherein each of the plurality of vacuum interrupters comprises:
• (a) a sealed casing, the sealed casing comprising a pair of end caps closing the ends of the casing;
• and
• (b) first and second electrical switch contacts mounted inside the casing, wherein the first switch contact is stationary and the second switch contact is movable relative to the first switch contact;
• ii) an actuator, wherein the actuator moves the second switch contact relative to the first switch contact in each of the one or more vacuum interrupters;
• and
• iii) a handle connected to the actuator, wherein said handle is capable of engaging the actuator to move the second switch contact relative to the first switch contact;
• wherein, when the one or more vacuum interrupters are in an open position, the first and second electrical switch contacts are separated from one another, wherein the feeder cables are isolated and no power is conveyed through the transformer and the transformer is isolated from the power grid or network;
• and
• wherein, when the one or more vacuum interrupters are in a closed position, the first and second electrical switch contacts are in contact with each other, wherein the feeder cables are connected to the transformer and power is conveyed through the transformer.