Field experiences using radio frequency scanning (RFS) to detect partial discharge (PD) in bus duct and metal clad switchgear of electrical generating and transmission substations

It is well known that the occurrence and evolution of partial discharge phenomena within electrical insulation can lead to their destruction. Early detection of this phenomenon can avoid catastrophic failures of electrical equipments installed on transmission, distribution and generating stations. In this paper, two practical experiences using radio frequency scanning to detect partial discharge activity in electrical equipments are described. In the first case, partial discharge activity in two of three phases of a 13.8 kV air isolated bus duct was detected using radio frequency scanning after suspicions of PD activity in a 115 kV GSU power transformer and a 160 MVA generator was detected using acoustic emission and electromagnetic interference measurements tests with radio frequency current transformers. The second case describes the use of radio frequency scanning to detect partial discharge and corona activity inside a 34.5 kV metal clad switchgear located on a 500 kV substation. Although the electrical interference in the area was the main concern to get a reliable measurement, digital filtering and wide band scanning of the radio frequency scanning technique showed high efficacy to discriminate partial discharge activity inside the switchgear. Final results confirmed the abnormal condition of a circuit breaker in the switchgear.