Ricerc@Sapienza

Healthcare represents a key issue for management in every country. A fundamental problem affects almost every healthcare system: the trade-off between the need to deliver effective healthcare services and the need to control expenses and to ensure the overall sustainability of the system. This problem is a clear expression of management complexity in healthcare systems.

The IEC 61294 Technical Report, published in 1993, describes a simple test procedure to measure the PD Inception Voltage (PDIV) in insulating liquids and doesn't cover any other items related to the PD patterns and their evolution at higher voltages.

IEC 60156 and IEC 60897 were standardized with the purpose of evaluating the breakdown voltage of liquid dielectrics both under AC and impulse voltages. AC breakdown voltage determination is a simple method but only able to provide information on the presence of contaminants. The limit of this test is the large scatter in the results and, for this reason, this IEC standard has been recently revised. Impulse breakdown voltage determination allows discrimination of different dielectric liquids, also in terms of their chemical composition.

The 50-60 Hz breakdown voltage of insulating liquids is not an intrinsic property of the dielectric but strongly depends on the presence of contaminants, such as particles and suspended water. Both IEC and ASTM give tests procedures finalized to determine the 50-60 Hz breakdown voltages. This test is adopted as acceptance on new deliveries, testing of treated liquids prior to or during filling into electrical equipment, and monitoring and maintaining oil-filled apparatus in service. Following the IEC Standards, this test has to be performed following the IEC 60156, Ed.

Partial Discharges (PD) detection in HV components has shown to be a very powerful diagnostic tool. Anyway, also the acquisition of the same signals in simple insulations, like the dielectric liquids, may give additional information for maintenance of HV components in which they are employed, as in the case of liquid insulated transformers.