AC motor single-phase grounding fault is defined as insulation damage that occurs only between one phase conductor and the ground in the power system of a three-phase AC motor. Broadly speaking, a single-phase AC motor ground fault includes a single-phase grounding short circuit. Single-phase AC motor grounding short-circuit is a special phenomenon in single-phase AC motor grounding faults. In a narrow sense, single-phase AC motor grounding fault and single-phase grounding short-circuit are two concepts. One is an AC motor failure, and the other is an AC motor accident. So, what method will we use to find the fault of the AC motor? Let's take a look next.
Manual search method
Use grounding line selection device and fault indicator to find
Use feeder automation methods to find
Manual search method
By manually opening the AC motors in turn, it is possible to know which outgoing line of the AC motor substation is grounded, and which phase is grounded through dispatching.
One is to divide the line of the AC motor step by step or to pull the line with frequent faults apart, use a 2.5kV shaker to measure the ground-to-ground insulation, and the insulation resistance is small. The segment is the fault segment, which narrows the scope of finding AC motor faults. The second is to divide the line of the AC motor as much as possible, and then step-by-step the AC motor to try and transmit power, and interact with the dispatcher. When there is a zero-sequence voltage alarm, this section is a fault section.
Use grounding line selection device and fault indicator to find
AC motor substations are generally equipped with grounding line selection devices. Although sometimes inaccurate, they can provide technical references for manual switching. Then install some ground fault indicators on the line to indicate the path of the ground fault. The more reliable AC motor ground fault detection method is the signal source method, and the more sensitive ground fault detection AC motor fault method is the first half-wave method or the DC transient analysis method. It is recommended to use a combination of the two ground fault indicators of AC motors to find ground faults. The signal source method is the main method, and the first half-wave method or the DC transient analysis method is used as a supplement to detect the AC motor.
Use feeder automation methods to find
The substation of the AC motor will cut off the grounding outlet, and the intelligent switch of each section on the line will automatically open. The substation of the AC motor is closed for power transmission, the zero-sequence voltage of the power station does not alarm, and the power transmission of this section is restored successfully. The first smart switch FTU detects the line voltage of the AC motor, but does not detect the zero-sequence voltage of the AC motor, it will automatically close after a delay, and it will be opened immediately if the zero-sequence voltage is detected due to the ground fault. And "locked". The second AC motor smart switch also detects the zero-sequence voltage, the switch does not move and "blocks", canceling the "power delay automatic closing" function. The intermediate contact AC motor switch detects a single-sided power loss of the AC motor and automatically closes after a delay. Because the fault point is not in this section and no zero-sequence voltage is detected, the power transfer to this section is successful. After the contact switch of the AC motor is powered on, the second smart switch detects the line voltage of the AC motor and does not detect the zero-sequence voltage, but there is "blocking" in the front, so the "power delay automatic closing" function is canceled, and the switch Stay in the quintile. At this point, the ground fault point section has been isolated, and the non-faulty sections of other AC motors have been restored or transferred power supply.
Every manufacturer has the responsibility to produce AC motors that meet the standards to ensure the healthy development of the AC motor market. Before leaving the factory, Guangzhou Yuexun Electric Appliance Co., Ltd. has carried out a large number of connection tests on AC motors, reducing the occurrence of AC motor failures and providing solutions. If you are in the AC motor business, you can consider using our cost-effective products.