Mechanical Performance Test            Basic test of high voltage electrical apparatus. According to statistics, about 80% of power system accidents are caused by poor mechanical performance of high voltage electrical appliances. The contents of mechanical performance test include: (1) mechanical operation test. It is used to check the performance of products under specified operating energy. (2) Time characteristic test. Measure the action time of the product, such as closing time, opening time, no current time of reclosing operation, metal short connection time, etc. (3) Velocity characteristic test. The split and close speed of switch contacts is one of the important parameters of high voltage switchgear, especially for circuit breakers. The speed of circuit breaker has average speed and instantaneous speed, and the main influence is the instantaneous speed of rigid division and rigid conjunction. Rigid-split instantaneous speed refers to the speed of the moving contact during the process of circuit breaker opening, when the moving contact is just out of contact with the static contact. Rigid closing instantaneous speed refers to the speed of the moving contact during the closing process of the circuit breaker. Mechanical strength test. High-voltage switchgear (together with the operating mechanism) carries out continuous operation tests without being charged to assess the mechanical strength and wear capacity of each part of the product. This test is also called mechanical life test. The term "life" here refers to the minimum number of operations that a manufacturer should ensure that the various mechanical properties remain stable. The real end of product life depends on the operation status of each specific product. So this kind of test is actually mechanical stability test. _Sealing test. To test the sealing performance of products filled with gas or liquid medium. _Rain proof test. The rainproof performance of outdoor products should be tested. _Ice breaking test. Experiments were conducted on outdoor products with external knife gates to assess their ice breaking capacity. _Cold resistance test. _Earthquake resistance test.            Current carrying capacity test            It is used to check the temperature rise and dynamic/thermal stability of conductive circuit after normal working current and short-circuit current are connected. The main points are as follows: 1. Temperature rise test. When high-voltage electrical products pass through the normal working current, because of resistance loss, eddy current loss and hysteresis loss, the electric energy is transformed into heat energy, some of which are lost to the surrounding medium, and some of the current-carrying conductors are heated to raise their temperature. The increase of temperature is determined by two factors: heating and heat dissipation. It is also related to the current passing through the fluid carrying circuit, the cross section of the current carrying circuit and the material, the mechanical structure, the joint quality of the contact surface of the parts and the assembly quality of the products. (2) Circuit resistance measurement. The resistance of current-carrying circuit of high-voltage electrical appliances can reflect the contact state and assembly quality of products, so the method of measuring circuit resistance is often used to judge the technical state of products. (3) Dynamic/thermal stability test. Also known as short-term resistance current test. It is used to test the ability of high voltage electrical apparatus to withstand thermal and electric effects of short circuit current in closed state.            Opening and closing capacity test            A main performance test of high voltage switchgear. Verify the ability of high voltage switchgear to break short circuit (normal) current and turn off short circuit (normal) current at the highest operating voltage. According to the application of high voltage switchgear in power system, the breaking and closing ability test includes: (1) the end short circuit breaking and closing ability test. It refers to the test of breaking and closing ability when short circuit occurs at the outlet of high voltage switchgear. (2) Out-of-step interruption and closing ability test. Also known as reverse interruption and closing ability test. Connection circuit breaker connecting two systems will seriously lose synchronization when serious faults occur in the power system. At this time, the circuit breaker will break the two systems to separate them. This kind of performance break is called out-of-step break. (3) The interruption test of near-zone faults. Short circuit breaking test several kilometers away from the outlet of circuit breaker. Because of a section of line, its short circuit current is smaller than the end short circuit current, but the recovery voltage is stricter than the end short circuit. (4) Capacitance current interruption and closing ability test. Capacitive current refers to no-load long-line charging current, capacitor bank current and cable line charging current. _Small inductance current interruption and closing ability test. Small inductance current refers to excitation current, motor current and reactor current of no-load transformer. Its breaking characteristic is that the circuit breaker is prone to over-voltage due to current closure in the process of breaking. _Developmental fault interruption test. Developmental faults refer to short-circuit faults of power supply caused by overvoltage which endangers the insulation of power equipment when circuit breakers break small inductance current or capacitive current. The characteristic of this fault is that the current flowing through the circuit breaker is a small inductance current or capacitance current, which changes into a large short circuit current due to sudden short circuit of the power supply, which brings great difficulties to the breaking of the circuit breaker, and the explosion accident occurs due to the insufficient mechanical strength of the arc extinguishing chamber. _Parallel interruption test. It refers to a special connection of power system, that is, one output line is supplied by two power supply sources, each power supply line is protected by a circuit breaker. When the output line is short-circuited, both circuit breakers need to be disconnected. Because the operation time of the two circuit breakers always has sequence, the first breaking circuit breaker first breaks, and then the short-circuit current flowing through the breaking circuit breaker will suddenly increase from the original share to all. Similar to developmental faults, it also brings great difficulties to circuit breakers. The interruption test of different phase grounding fault. Short-circuit interruption test with different phase grounding on both sides of circuit breaker. When the breaking voltage of the short circuit on both sides of the circuit breaker is normally interrupted