Abstract: A gas chromatographic apparatus having at least two gas separation columns arranged in parallel to each other, the outlet of the first gas separation column being connected to a gas sensor through a column switch valve, and the outlet of the second gas separation column being connected to the column switch valve through a gas detection time-controlling pipe, where when the first gas separation column is communicated with the gas sensor, the outlet of the second gas separation column is made open to the atmosphere by the column switch valve, or when the second gas separation column is communicated with the gas sensor, the outlet of the first gas separation column is made open to the atmosphere by the column switch valve, or the apparatus having a first gas separation column whose inlet is connected to the switch valve and at least two second columns whose inlets are connected to the outlet of the first gas separation column, whose outlets are connected to the gas sensor and which are arranged in parallel to ea

Abstract: A phosphoric triester containing at least one aromatic ring is mixed in an amount of 30 to 80% by weight based on the total constituents with a benzenetricarboxylic acid trialkyl ester or with a polyol ester obtained from trimethylolpropane and a saturated fatty acid to give a fire-retardant insulating oil.

Abstract: A system for monitoring an abnormality of an oil-filled electric device by detecting the components of the gas dissolved in the insulating oil. A gas-in-oil separator which separates the gas from the insulating oil, a gas reservoir where the separated gas is collected, an air feeder which supplies air for delivering out the gas in said gas reservoir, a separating column packed with a gas separating filler whereby the gas supplied from the gas reservoir is separated into the components, a combustible gas detector element disposed in a case which connects at its one end to the outlet of said separating column, and a change-over valve disposed at a location connecting said gas reservoir, are provided. The air feeder and said separating column are adapted to switch a route passing the air from the air feeder into the separating column along with the gas via the gas reservoir to or from a route passing the air directly into the separating column.