Busbar parts that do not require busbar thermal and electrodynamic effects verification

Busbar parts that do not require busbar thermal and electrodynamic effects verification

 

(1) Adopt fuse protection and connect to the bus bar under the fuse (except current-limiting fuse) copper busbar cut punch bend machine.

(2) Busbar in voltage transformer circuit.

(3) The transformer capacity is 1250KVA and below, and the voltage is 12KV and below, so as not to damage the busbar due to failure. It is mainly used for busbars in non-important electricity consumption places.

(4) Parts that are not exposed to thermal effects and electrodynamic effects, such as the connection wires and sealing wires of surge arresters.

5 Bus selection

5.1 Selection of main bus

The general principle of main busbar selection is to meet the rated current requirements of the main incoming circuit breaker. After selecting the main busbar according to the rated current, check the thermal and electrodynamic effects according to the previous calculation.

5.2 Selection of the next busbar

The selection principle of the next busbar is to determine the current carrying capacity of the busbar according to the rated current of the switchgear and control equipment, and at the same time check whether it meets the requirements of the system's rated short-time withstand current and rated peak withstand current. The rated current of the switchgear and control equipment is the lowest rated current of all the primary equipment in the equipment, usually the rated current of the current transformer.

5.3 A few points to note

(1) According to the provisions of GB3906-1991, the minimum current-carrying capacity of busbars in switchgear and control equipment should have a margin of 10% relative to the rated current.

(2) Under normal circumstances, considering the heat dissipation and increasing the load capacity for the future, the main bus bar in the design drawing is generally larger. At this time, it should be manufactured in strict accordance with the drawing, and the bus bar specifications cannot be reduced at will.

(3) Choose a model with a larger bus width for the same cross-sectional area as much as possible. If you can choose TMY80×6 but not TMY60×8, it is mainly conducive to heat dissipation.

(4) When the operating environment temperature of the switchgear and control equipment is slightly higher than the specified temperature, it is necessary to fully consider whether the current carrying capacity of the bus is sufficient.

GB311.1-1997 "Insulation Coordination of High Voltage Transmission and Transformation Equipment" stipulates:

When the temperature is higher than 40℃, the rated insulation voltage should be multiplied by the temperature correction coefficient Kt=1+0.0033(T-40);

General: Each increase in ambient temperature by 3°C increases the test voltage by 3%. When the ambient temperature increases by 1°C, the rated current should be reduced by 1.8%.