Abstract: A vacuum switching device comprising an evacuated envelope including an insulating cylinder, a stationary contact electrode and a movable contact electrode housed within the envelope. The electrodes are adapted to be engaged or disengaged to close or open a circuit in which the device is connected. At least one of the electrodes comprises a coil which, in use, is adapted to generate magnetic fields to control the formation of arcs when the electrodes are disengaged, each electrode having an end face adapted to contact the other electrode when in the engaged condition. At least one of the electrodes has a low resistance electrical path transverse to the axis of the electrode in a region of the end face.

Abstract: A fault protection apparatus is disclosed for use in a time graded fault protection scheme. The apparatus comprises a circuit breaker having a normally closed trip contact provided in a line, current measurement apparatus adapted to produce an output signal indicative to the current in the line at the circuit breaker, and fault signal processing apparatus adapted to process the output signal from the current measurement apparatus to detect an initial fault on the line at a first instance. The fault signal processing apparatus is further adapted to process the output of the current measurement apparatus after the initial fault has been detected and to produce an accelerated opening signal in the event that the output signal meets a predetermined criteria, and a control device which is adapted to open said circuit breaker trip contact in response to said accelerated opening signal.

Abstract: A method of protecting a section of a line is disclosed.

Abstract: A trip circuit supervision circuit is disclosed for use in combination with a trip circuit comprising a circuit breaker trip coil connected in a supply line from a supply voltage and a trip relay contact connected in series with the circuit breaker trip coil. The supervision circuit is connected across the relay trip contact and includes a current sensing device. During normal operation, the supervision circuit draws a constant current from the supply line independent of supply voltage. Thus, changes in the current measured by the current sensing device enable the integrity of the supply voltage to be checked.

Abstract: In a large rotating electrical machine having a rotor comprising conductor bars of copper located in slots in a rotor core and connected together at their ends to form a winding, the conductor bars are electrically insulated from the rotor core by a coating on the conductors of a ceramic-based material. The coating serves to prevent sparking occurring between the conductor bars and the rotor core.

Abstract: A heat exchange unit for hot gas heat recovery has a heat exchange array situated within a heat exchange duct defined between a cylindrical outer casing and an axially slidable inner sleeve. The sleeve, together with a plug valve at the upper end of the unit, forms a variable position sleeve valve arrangement which simultaneously controls the flow of hot gas through the heat exchange duct and the bypass duct.

Abstract: In an arrangement for monitoring the resistance between adjacent rail-ends of a section of railway track, the usual insulating end-post between the ends of adjacent rails is a molded component provided with an embedded conductive mesh or perforated plate situated roughly halfway between the rail-ends. The resistance between each rail-end and the conductive part is monitored to detect any significant decrease in resistance between either rail and the conductive part. When a sufficiently large resistance drop is detected, the normal track signaling circuits associated with the section of line involved are still able to function normally, since the insulation on the other side of the mesh is still unaffected at this stage. Railway personnel are now able to effect a repair to the affected part of the track at their (and the passengers') convenience before the whole end-post fails, disrupting normal service.