796 / 2022-03-31 22:52:10

Non-intrusive on-line monitoring technology of UHV on-load tap changer switching sequence

Non-intrusive on-line monitoring,UHV on-load tap changer,switching sequence,UHF signal,vibration signal

Purpose/Aim

On-load tap changer (OLTC) is the key equipment of UHV DC transmission, and the diverter switch is the core component of on-load tap changer. In recent years, almost all OLTC accidents of UHV converter transformer occurred on the diverter switch. The switching sequence test is the key test to detect whether the switching function is normal, but it can only be carried out offline. At present, there is no effective on-line monitoring method of switching sequence. It is more difficult to adopt non-invasive monitoring because the recognition accuracy needs to reach the millisecond level. In order to monitor the operation state of UHV on-load tap changer and avoid faults effectively, it is urgent to accomplish non-invasive on-line monitoring of switching sequence.

Experimental/Modeling methods

This paper presents a non-invasive on-line monitoring method of UHV on-load tap changer switching sequence based on the combination of sound and electricity. By monitoring the electromagnetic wave signals of pre-breakdown arc, arc discharge or spark discharge at the switch fracture during the opening / closing process of each switch in OLTC diverter switch, as well as the mechanical vibration signal generated when the switch is closed, then the switching sequence characteristics are extracted by identifying the action time of each switch. In order to verify the effectiveness of this method, diverting test is carried out at a real test platform of UHV on-load tap changer. UHF sensor is used to measure electromagnetic wave signal, acceleration sensor is used to measure vibration signal, current transformer is used to measure the current signal of driving motor. Finally, the diverting timing characteristics of tap changer is extracted.

Results/discussion

Comparing the diverting timing characteristics obtained by non-invasive monitoring with the test results of off-line switching sequence, the error is less than 1 ms, which verifies the effectiveness of the method.

Conclusions

By monitoring the electromagnetic wave signal and vibration signal in the switching sequence of UHV on-load tap changer, the non-invasive on-line monitoring of diverter switch switching sequence is realized. This method improve the monitoring efficiency of on-load tap changer greatly, which is of great significance for the safe and stable operation of converter transformer.