ahmad moradi - Student of Islamic azad university south Tehran branch
mohammad mortazi - Student of Islamic azad university south Tehran branch
alireza nadi polkhabi - Sudent of Islamic azad university of karaj

Online PD testing is performed in a live substation on energized power apparatus which remains in service. It is non-invasive and can be performed safely. It is reliable method of testing insulation in MV and HV substation apparatus. PD tests are highly sensitive to small insulation defects. It is considered to be more probing in detecting initial insulation problems than conventional offline tests such and insulation resistance and tan delta. The offline PD methods described in IEC 60270 are the foundation of online testing, yet online testing is performed without service interruptions or de-energization. When considering the efficiency of testing you must look at the time and cost of testing compared to the value of the information you collect. Usually by the time you can notice something by smell or by temperature, it’s too late. PD testing gives us the only shot we have at finding all types of insulation defects early without needing to take an outage for traditional testing.

partial discharge , UHF sensors , HFCT , PRPD , PRPS , power cables