Limitation of Harmonic Pollution on MV Networks by Means of Proper Connection Criteria and Corrective Devices

Harmonic pollution in some areas of MV distribution network of ENEL, Venice Area Board, have reached by 1991 critical values (THD(V)~15% at HV/MV substation busbars) especially in mountain areas, due to the relatively low short circuit power and to the presence of a large amount of six pulse AC/DC rectifiers (up to 60% of total required power of HV/MV substations) used at ropeway installations. As a consequence ENEL developed, on the basis of digital simulation, proper connection criteria for ASD equipped ropeway installations and planned, realized and tested some correction interventions for existing plants. These criteria, similar to the ones given in IEEE 519 STANDARDS, also assure the respect of CENELEC limits (EN 50160) on voltage harmonic pollution. The paper describes the connection criteria and reports the results of the different measurement campaigns, performed at 1991, 1992, 1993 and 1994 to check, both the effect of connection criteria and the real field behaviour of four different devices to reduce ASD current harmonic emissions, together with some indications about their cost.