This paper introduces in detail the debugging of switching appliances in the debugging process of distribution cabinets in Thailand.

During the commissioning of distribution cabinets in Thailand, the commissioning of switchgear mainly includes the following contents:

Circuit breaker debugging

Manual operation test: manually turn on and off the circuit breaker, and check whether its action is flexible and reliable, whether the operating mechanism is jammed or blocked, whether the action of the auxiliary contact is accurate and timely, and whether the cooperation with the main contact is good. For example, when the main contact is closed, the auxiliary contact should be synchronously switched to the corresponding on or off state.

Parameter test: use professional test equipment to measure the closing time, opening time, synchronization and other parameters of the circuit breaker. Generally speaking, the closing time and opening time should be within the range specified by the product technology, and the synchronization error should also meet the requirements, so as to ensure that the circuit can be cut off or connected accurately and quickly when the circuit fails.

Trip characteristic test: the overload trip and short circuit trip functions of the circuit breaker are tested. By adjusting the test current, the overload and short circuit faults are simulated, and it is checked whether the circuit breaker can trip reliably under the set overload current multiple and time, and whether it can trip instantaneously when the short circuit current reaches a certain value, so as to protect the safety of the circuit and equipment.

Overvoltage protection inspection: check whether the circuit breaker is equipped with effective overvoltage protection devices, such as overvoltage relays, and verify whether it can act correctly under overvoltage conditions, cut off the circuit or take other protective measures to prevent overvoltage from damaging the equipment.

Debugging of isolating switch

Manual operation inspection: manually operate the disconnector to switch between the closing and opening positions, and check whether the operation is light and flexible, and whether there is any phenomenon such as jamming and refusing to move. At the same time, observe the contact of the dynamic and static contacts of the disconnector during the opening and closing process, and the contact should be good, without obvious sparks, arcs and other abnormal phenomena.

Contact inspection: use feeler gauge and other tools to check the contact pressure and contact area of the disconnector contact. The contact pressure between contacts should meet the product requirements to ensure good electrical connection; The contact area shall meet the requirements to ensure reliable conduction of current under normal operation and fault conditions.

Interlocking function check: check whether the interlocking relationship between the disconnector and other switching appliances (such as circuit breakers and grounding switches) is correct. For example, when the circuit breaker is in the closing state, the disconnector should not be able to operate, so as to prevent the disconnector from being pulled with load and causing serious electrical accidents.

Load switch debugging

Operation flexibility test: Manually and electrically operate the load switch to check whether its opening and closing actions are flexible and reliable, and whether the operating mechanism works normally. In the process of operation, pay attention to observe whether there is abnormal sound, vibration, etc.

Arc extinguishing performance inspection: check whether the arc extinguishing device of the load switch is in good condition and whether the arc extinguishing performance is normal. Through a certain number of switching operations, the arc extinction can be observed, and the arc should be extinguished quickly within the specified time without reignition.

Matching test with fuse: For load switch equipped with fuse, matching test between them is needed. By simulating different fault currents, the action sequence and coordination of load switch and fuse under overload and short circuit conditions are checked to ensure that the circuit can be effectively cut off and the safety of equipment and lines can be protected.

Commissioning of contactor

Pull-in and release test: Apply rated voltage to the electromagnetic coil of the contactor, and check whether the contactor can be reliably pulled in, whether the contact is closed properly, and whether there is jitter, jamming and other phenomena. Then cut off the power supply of the coil, and observe whether the contactor can be released quickly and whether the contact is completely disconnected.

Contact pressure and contact resistance measurement: use special tools to measure the contact pressure of contactor, which should meet the specified value of the product. At the same time, measure the contact resistance of the contactor, and the contact resistance should be within the allowable range to ensure that the contactor will not affect its performance and life when it is working.

Action time test: measure the pull-in time and release time of the contactor. These parameters are very important for the accuracy and reliability of the contactor in the control system and should meet the design and use requirements.

Thermal stability test: under the condition that the contactor is energized with rated current, run continuously for a period of time to check the heating of the contactor, and the temperature of each component should not exceed the allowable value to verify its thermal stability.

Relay debugging

Parameter setting: according to the design requirements and actual operation needs, the parameters of relay such as action value, return value and delay time are set. For example, the action current value of overcurrent relay should be adjusted according to the rated current and overload protection requirements of the protected line or equipment; The delay time of time relay should be set according to the control logic and process requirements.

Action characteristic test: simulate various faults and operating conditions, input corresponding signals to the relay, and check whether the action of the relay is accurate and reliable. For example, when the overcurrent signal is input, the overcurrent relay should act quickly under the set action current value; When the low voltage signal is input, the undervoltage relay should operate reliably at the set voltage value.

Return characteristic inspection: when the fault signal disappears or the operation condition returns to normal, check whether the relay can return to the initial state in time and whether the return value meets the requirements. For example, when the current of overcurrent relay drops below the return current value, it should be able to return in time and stop acting.