Abstract: A method of performing line insulation monitoring of a pair of conductor lines at least partially located in a cable is provided, comprising the steps of providing a first power switch in a first conductor line of the pair and a second power switch in a second conductor line of the pair, providing a line insulation monitor at a first end of the pair of conductor lines, electrically connected to the pair of conductor lines, at the second end of the pair of conductor lines, electrically connecting the first and second conductor lines, placing the first and second power switches into a monitoring configuration wherein the first power switch is closed while the second power switch is open, and using the line insulation monitor to monitor the insulation of the conductor lines.

Abstract: A system for transmitting electrical power and communication signals is provided. The system comprises a transmission line, a source of electrical power for supplying electrical power to the transmission line, a first communication unit configured to supply communication signals to the transmission line, a power extraction unit configured to extract and use electrical power from the transmission line, a second communication unit configured to receive communication signals from the transmission line; and a control unit configured to control operation of the system. The source supplies electrical power to the transmission line for respective periods of time which are different from respective periods of time in which the first communication unit supplies communication signals to the transmission line.

Abstract: A system for transmitting alternating current power and communication signals between a first location and a second location through a communication path which includes at least one inductive load and at least one switch configured to switch power to the at least one inductive load on and off is disclosed herein. The system comprises a control configured to control the at least one switch so that, if the power is switched on during a particular phase of the power, is the power is switched off during the opposite phase of the power, and if the power is switched off during a particular phase of the power, the power is switched on during the opposite phase of the power.

Abstract: A system for transmitting alternating current power and communication signals between a first location and a second location via a communication path which includes at least one inductive load and at least one switching means for switching power to said at least one load on and off, the system including control means adapted for controlling said at least one switching means so that, in response to switching off said power, a direct current is applied to said at least one inductive load and, in response to actuation of said at least one switching means to switch said power on, said power is switched on during a phase of the power which results in a magnetization of said at least one inductive load opposite to that resulting from said direct current.

Abstract: A method of mounting a subsea control module (1) on a mounting plate (10) of an underwater tree of a subsea hydrocarbon well comprises lowering the module to the plate and attaching the module to the plate with an adapter (6) between it and the plate and with portions of the module being coupled with portions of the mounting plate.

Abstract: A method of enabling communication between components of a hydrocarbon extraction plant, the plant having an underwater hydrocarbon extraction installation including at least one hydrocarbon extraction well with an associated tree, comprises providing a plurality of RF communication means at respective components of the installation.

Abstract: A method of enabling communication between components of a hydrocarbon extraction plant, the plant having an underwater hydrocarbon extraction installation including at least one hydrocarbon extraction well with an associated tree, comprises providing a plurality of RF communication means at respective components of the installation.

Abstract: A subsea well control system comprises: a well tree (6 or 7) having a subsea control module (10 or 11); and a power and communications distribution module (5) for communication with the subsea control module via a communication link (8 or 9) between the subsea control module and the distribution module. The link comprises a 4-wire dual twisted copper pair as part of an RS422-based interface.

Abstract: A method of mounting a subsea control module (1) on a mounting plate (10) of an underwater tree of a subsea hydrocarbon well comprises lowering the module to the plate and attaching the module to the plate with an adapter (6) between it and the plate and with portions of the module being coupled with portions of the mounting plate.