Method and means for supervision of valve units

Method according to any one of the preceeding claims, further comprising the steps of:

• storing of received first indication signals (IP) in respective memory units (150),
• activating an evaluation routine depending on the trigging order signal,
• registering the lack of any first indication signal (IP), and
• resetting the memory units (150),
• storing received second indication signals (SSTP) in the memory units (150),
• registering receival of a second indication signal (SSTP) and resetting the memory units (150).

System for supervising the functioning of a plurality of components in a converter system, in which the system comprises a central control assembly (10) and a plurality of valve units, in which each valve unit has:

• a) an identity (1-N),
• b) a semiconductor element (THY1-N),
• c) a control unit for controlling the semiconductor element,
• d) a trigger order input for receiving a trigger order signal (FP),
• e) an indication output for emitting a first indication signal (IP) for announcing that the semiconductor element in its forward voltage direction has achieved a first predetermined voltage threshold value, said first predetermined voltage threshold value corresponding to a sufficient forward voltage for ensuring effective trigging of the semiconductor element, and
• f) a trigger signal output for emitting a trigger signal to the semiconductor element, and wherein
• g) the control unit comprises means (60, 120, 105, 110) for emitting a second indication signal (SSTP) when the semiconductor element in its forward voltage direction has attained a second predetermined voltage threshold value.

Control unit for activating a semiconductor element (THY) in an HVDC-plant whereby the control unit comprises

• a trigger order input for receiving a trigger order signal (FP), and
• an indication output (111) for emitting a first indication signal (IP) for indicating that the semiconductor element in its forward voltage direction has attained a first predetermined voltage threshold value, said first predetermined voltage threshold value corresponding to a sufficient forward voltage for ensuring effective trigging of the semiconductor element, and
• a trigger signal output (100) for emitting a trigger signal to the semiconductor element, and
• a criteria unit which, in response to the semiconductor element in its forward voltage direction attaining a second predetermined voltage threshold value (U.sub.2), is arranged to generate an activation signal which, in turn, activates the trigging signal, whereby the control unit is set up to emit a second indication signal (SSTP) in response to the activation signal.