A system and method for monitoring a dielectric state of high voltage equipment. It comprises an insert adapted to pass through an opening into a fluid chamber, a support assembly to support the insert, a seal disposed around the insert to seal the opening into the fluid chamber, and a compression mechanism to compress the seal. By means of a first switching means 3 selecting one first vector adjuster 4 and a second switching means 10 selecting a second vector adjuster 11, the frequency band for which distortion component is compensated in the feed forward amplifier is controlled by switching. Purchasing data may also be included in the manifest.