Abstract: The present invention relates to a test system for a protective relay. The test system comprises a test switch (1) and a test-plug handle (2). The invention comprises supplementing the system with a contact function which is activated when the handle is inserted into the test switch so that, before the testing of the relays in the protective device is initiated, a signal function can be obtained to indicate that testing is in progress. The contact function is brought about by arranging, on the upper and/or lower side(s) of the test switch, two semi-protected, uninsulated and parallel contact pins/slide bars (4, 5) from the front edge to the rear edge of the test switch. At the rear edge contact parts to ordinary conductors are arranged in order to forward the contact function. The contact pins are mounted in a guide structure (10, 11) formed with an inner guide profile adapted to guide two resilient tongues (13, 14) on the test-plug handle.

Abstract: A device for mechanically resetting, by means of a simple manipulation, an optional number of status indicators of the type consisting of an electromagnet with an iron core, a magnetizing winding and some form of permanently magnetized indicating disk capable of rotating through 180.degree.. The device comprises a rail made of a non-magnetic material and being formed so as to enable a desired number of indicators to be mounted side-by-side. The rail has such a profile as to enable a shuttle with a corresponding profile to be in engagement with and be guided by and slide on the rail in its longitudinal direction. The shuttle is provided with a permanent magnet as well as with a pole piece mounted so as to form, together with the core in the electromagnet of each indicator, a magnetic circuit when the shuttle is pushed over the respective indicator whereby the rotatable indicating disk is influenced and is reset to indicate the reset position.

Abstract: The circuitry for generating filter excitation signals from a multi-phase alternating current input is provided with the following circuitry for each phase of the multi-phase alternating current input. A current transformer connected to a respective phase of the multiphase alternating current input is connected to a bridge rectifier having one node connected to a neutral conductor and including a resistor of equal resistance value connected in each parallel branch of the bridge rectifier between the neutral conductor and the input of the current transformer. An operational amplifier having inputs respectively responsive to the voltage across each of the respective resistors in the bridge rectifier generates an output for one phase of the excitation signal to the filter. The filter excitation circuitry has application to two-phase and three-phase systems wherein the excitation circuitry is identical for each phase.

Abstract: A resistance thermometer measuring system for enabling the temperature of a machine to be observed. This measuring system includes a temperature responsive resistance member which is constructed as part of the machine under observation. The resistance of the temperature responsive resistance member varies as the temperature of the member varies, this variance in temperature corresponds to variances in the temperature of the machine. By sensing the voltage across the resistance member, changes in the temperature are detected. When the voltage being sensed exceeds a preset level, an indicating signal can be generated. On the other hand, if a malfunction occurs in the resistance member, such as a break in the resistance element or the leads, then a fallacious indicating signal might be generated. In order to prevent generation of such an improper signal, a second indicating signal is generated upon occurrence of a malfunction within the resistance member.