When the power frequency breakdown voltage of a porcelain insulator in operation is lower than the dry flashover voltage, it is considered a deteriorated insulator. An insulator whose insulation has already been broken down is called a zero value insulator. When there are zero value insulators in the insulator string, the probability of contamination flashover and flashover under overvoltage is high, and even under normal operating voltage, flashover can occur. Short circuit current will pass through the internal gap of the zero value insulator, and the thermal effect of high current may cause porcelain parts to break apart from the head, cast iron caps to burst, steel feet to fall off, and porcelain parts to burn into glass bodies at the head, As a result, a series of accidents such as insulator string dropping and wire dropping occurred. At present, the main methods for detecting zero value insulators in China include voltage distribution method, leakage current measurement method, infrared thermal imaging method, insulation resistance measurement method, etc

Distributed voltage measurement method: When there are zero value insulators in the insulator string, it will significantly affect the voltage distribution of the insulator string. According to this principle, the HB-VD30 insulator distribution voltage tester developed and produced by Hongbo Measurement and Control can efficiently detect zero value insulators in operation with electricity