NOVELTY - A test tap adapter for extracting dissolved gases from insulating oil of transformer bushings, comprises a gas diffusing member mounted over the outside portion of a tubular runway; a gas-permeable but liquid impermeable membrane covering the gas diffusing member; a gas storage chamber linked to a tap connector; and a unit to allow the passive diffusion of permeated gases towards the gas storage chamber for determining the presence of gases in the insulating oil.    USE - The adapter is used in providing electrical measurements in a transformer bushing and arranged for extracting samples of gases dissolved in insulating oil present in the transformer bushing so as to determine presence of the gases in the insulating oil (claimed).    ADVANTAGE - The adapter is capable of extracting and determining samples of gas in the insulation oil of the bushing of a transformer while keeping the apparatus functional and without altering the insulating conditions of the bushing. This saves costs in repairing or replacing damaged high-voltage transformers.    DETAILED DESCRIPTION - A test tap adapter (1) for use in providing electrical measurements in a transformer bushing and arranged for extracting samples of gases dissolved in insulating oil present in the transformer bushing so as to determine presence of the gases in the insulating oil, comprises:    (1) a tap connector (5);    (2) a tubular runway (71) axially arranged in the tap connector and having a portion (73) that extends outside the tap connector and is constructed to penetrate into the transformer bushing and to soak in the insulating oil;    (3) an insulated conductor mounted in the tubular runway along its entire length and having a free length (35) for connection to a conductor provided in the transformer bushing;    (4) a unit for connecting an end of the insulated conductor opposite the free length to an electrical measurement unit;    (5) a unit for anchoring the test tap adapter to the transformer bushing through a provided opening, with the outside portion of the tubular runway inside the transformer bushing in contact with the insulating oil;    (6) a gas diffusing member of non-conductive material mounted over the outside portion of the tubular runway;    (7) a gas permeable but liquid impermeable membrane covering the gas diffusing member and arranged to allow permeation of gases that may be present in the insulating oil towards the gas diffusing member;    (8) a gas storage chamber linked to the tap connector, in operative contact with the gas diffusing member; and    (9) a unit to allow passive diffusion of permeated gases present in the gas diffusing member towards the gas storage chamber for determining the presence of gases in the insulating oil.    DESCRIPTION OF DRAWING(S) - The figure is a longitudinal cross-section view of a modified test tap.    Test tap adapter (1)    Tap connector (5)    Free length (35)    Tubular runway (71)    Portion (73)    Circular step (81)