9 10 of the filter housing 1a are connected to discrete sources of high voltage energy such sources are high voltage transformer rectifiers 15 16 and 17 which are respectively connected with the corresponding electrodes 11 12 13 by high voltage cables 19 20 22 the cables 19 20 22 respectively pass through suitable insulators 32 33 and 34 in the top portion of the housing 1a the cables 19 20 22 further respectively pass through the control units 23 24 and 26 which are provided with suitable control elements not specifically shown a common regulating line for the electrodes 11 12 and 13 is shown at 27 this line has terminals 28 29 31 which are respectively connected with the control units 23 24 and 26 in accordance with a feature of the invention the filter 1 further comprises a miniature filter 14 which is disposed in the region of an insulator compartment 42 between the zones 9 10 and which also comprises two spaced apart electrodes namely a corona discharge electrode and a collecting electrode of opposite polarity the same as the other filter zones a high voltage cable 21 extends through an insulator 43 to a high voltage aggregate 18 and thence to the common regulating line 27 by way of terminal 30 the reference character 25 denotes a control unit in the cable 21 between the high voltage aggregate 18 and the regulating line 27 the insulator compartment 42 is integrated into the roof beam of the housing 1a the rectifiers 15 16 17 may be of the type manufactured and sold by the west german firm aeg under the designation e 78000 0 9 ce c0v6 the control units 23 24 and 26 may be.