Abstract: The present invention is an attachment device and a method for fastening and removing an electrical cable monitoring instrument to an electrical cable. The attachment device comprises monitoring instrument sensor with opening for positioning electrical cable such that said electrical cable can be positioned to pass through the sensitive volume at least partially surrounded by said sensor, at least one elongated elastic member securely attached to said cable monitoring instrument such that, when elastically deformed to a shape characterized by high mechanical energy such that deformed elastic member allows said electrical cable access to and from the sensitive volume at least partially surrounded by said monitoring instruments sensor.

Abstract: The present invention is a method of and an apparatus for measuring resistances of at least one transformer winding (109) in configurations of connected transformers windings. The method is based on increasing driving power from the source of electrical energy (12, 102) until the current reaches a predetermined level, which is below the core saturation current level of the measured transformer or the measuring device current limit, and then controls the power of the source of the electrical energy to maintain predetermined current flowing through the at least one winding over a time period sufficient to cause a L di/dt contribution to a voltage drop across the at least one winding to decrease below a threshold level. The apparatus measures simultaneously the constant current flowing in the at least one winding and the voltage drop over the at least one winding after the predetermined time period has elapsed.

Abstract: An insulation specimen may be analyzed by removing any absorbed charge from the specimen. Test voltage E is applied through system resistance R. I.sub.TOT is sensed at time intervals occurring at selected times multiplied by any three points in a power series while maintaining E constant and R.sub.IR is calculated from the formula: ##EQU1## and displayed. Apparatus consists of a high voltage power supply, current sensing means and specimen terminals for connecting an insulating specimen across the power supply in series with the current sensing means. A voltage comparator is connected across the specimen terminals to sense effective voltage across the specimen. Computation means receives inputs from timing means, the current sensing means and the voltage comparator and is used to calculate insulating current using a formula involving elapsed time measurements of total current through the insulation specimen to calculate insulation current and the insulation resistance of the insulation specimens.

Abstract: Three-phase power equipment while still connected to the three-phase line has the insulation qualities of its various phases tested. All ground connections of said equipment except one are disconnected and that one is reconnected through ground current sensing means. Coupling units which may be capacitors are respectively connected between each of the three phases of the power line to which the power equipment is connected and ground. Each coupler unit is a reference phase current sensing means. Adjustable phase and magnitude adjustor means are used to couple the respective phase current sensing means to a summing means so that they are adding. The ground current sensing means is similarly coupled to the same summing means but opposed to phase current effects. A null detector coupled to the summing unit detects when balance occurs.

Abstract: Insulation is tested by the method of connecting a variable inductive reactor across a voltage supply in parallel with a test specimen. The inductance of the reactor is varied until its reactance equals that of the sample as indicated by the supply current to the parallel circuit.