51results about How to "Lower insulation level" patented technology

The invention relates to an overvoltage protection method and overvoltage protection devices of modular multi-level converters. The overvoltage protection method comprises the following steps of arranging the overvoltage protection devices of the modular multi-level converters between alternating current ends of the modular multi-level converters and the ground, or between direct current ends and the ground, or between the alternating current ends, or between the direct current ends or more than one of the positions at the same time, setting operation voltage parameters of lightning arresters, setting operation voltages of discharging circuits and setting delay operation time of the discharging circuits, wherein each overvoltage protection device comprises the discharging circuit, a voltage-sharing damping circuit and the lightning arrester, the operation voltage parameters of the lightning arresters comprise reference voltages, operation overvoltage protection levels, lightning overvoltage protection levels and steep wave overvoltage protection levels, and the operation voltages of the discharging circuits are set according to expected invasion power frequency overvoltage levels. By means of the overvoltage protection method and the overvoltage protection devices of the modular multi-level converters, economical efficiency and reliability of the modular multi-level converters are improved.

The invention relates to a two-core column transformer which comprises a metal box body with an inner cavity, a square-shaped two-core column iron core of the voltage transformer, and a square-shaped single-core column iron core of an isolation transformer, wherein a high-voltage sleeve and a grounding sleeve are respectively arranged at the top and the bottom of the metal box body, and the metalbox body is filled with inert gas; the square-shaped two-core column iron core of the voltage transformer is arranged at the upper part of the inner cavity of the metal box body and electrically connected with the metal box body, and comprises an upper core column and a lower core column, an upper balancing winding and a first-section primary winding are wound on the upper core column, and a second-section primary winding and a secondary winding of the voltage transformer are wound on the lower core column; the square-shaped single-core column iron core of the isolation transformer is arranged at the lower part of the inner cavity of the metal box body and electrically connected with the metal box body, a primary winding of the isolation transformer is wound on the single-core column ironcore, an annular shielding cover is arranged around the single-core column iron core, and the secondary winding of the isolation transformer is wound in the annular shielding cover; the upper balancing winding is further used for supplying power to the primary winding of the isolation transformer; and the secondary winding of the isolation transformer and the secondary winding of the voltage transformer are connected in series for being used as the secondary output side.

A high-voltage insulating core of epoxy resin-impregnated fiber contains a conductor set up in the center of the insulator core whose peripheral surface is wrapped alternately by an epoxy resin-impregnated fiber layer and a capacity polar plate. The epoxy resin fiber-impregnated insulator is wrapped by an umbrella shaped sheath and the capacity polar plate is made of metal mesh or carbon fiber non-woven fabric having good adhesive strength to the epoxy resin-imprengated fibre layer seldom appearing seams of separation in-between. The metal mesh or carbon fiber non-woven fabric has the performance of high-low temperature resistance and keeps stable in long term operation, avoiding carbon powder dropping or mixing into the liquid epoxy resin to guarantee its isolation ability when they are used as the condense screen in the operation of wet process winding.

A constant magnetic flux voltage regulating structure of ultrahigh voltage self-coupling power transformer, comprising a main transformer body and a voltage regulating transformer body, the main transformer body comprising a series winding (HV), a common winding (MV), an excitation voltage regulating winding (JTV) and a third winding (LV) sleeved on the same iron core, the voltage regulating transformer body comprising a voltage regulating winding (TV) and an excitation winding (JV) sleeved on the same iron core; the series winding is in serial connection with the voltage regulating winding, and is subsequently in serial connection with the common winding; the excitation voltage regulating winding is in parallel connection with the excitation winding; the excitation voltage regulating winding is provided with a voltage regulating switch (K). The self-coupling transformer can connect two ultrahigh power grids, and by utilizing a constant magnetic flux voltage regulating method does not cause a third winding voltage fluctuation and iron over-excitation, reduces the level of insulation of a voltage regulating winding, and reduces cost and difficulty in manufacturing a voltage regulating switch.

The invention discloses an all-insulated on-load voltage-regulating transformer angularly connected on 220-kilovolt high-voltage side. The main body comprises a high-voltage coil, voltage-regulating coils, a low-voltage coil and the like, the voltage-regulating coils in related two phases connected end to end are connected through contacts of a tap selector of an on-load voltage-regulating switch, so that the on-load voltage-regulating switch realizes the voltage-regulating function by using a two-phase switch and a single-phase switch, and the conventional structure with three single-phase switches is replaced. Meanwhile, a right amount of lightning arrester elements are connected between the head end and the tail end of each phase of the voltage-regulating coil so as to limit the potential oscillation of the voltage-regulating coil under the impact of a thunder, the insulation level of the tap selector of the on-load voltage-regulating switch is obviously reduced, and the switch is protected reliably. The invention realizes the purposes of obviously reducing the cost of the on-load voltage-regulating switch with low cost and reliably protecting the on-load voltage-regulating switch at a low cost.