Abstract: A power interruption detector including a housing, a power input cord, a multi-volt transformer having a 120-208-240 primary winding and a 24 volt secondary winding, a power contactor with an actuating coil, a power plug receptacle, a delay timer, a counting circuit, an alarm circuit, a thumb-wheel switch, a digital trip counter display driver, a display output device, an audible alarm enunciator, and a battery. The power input cord couples line power to the primary winding of the multi-volt transformer and to one side of the power contactor. The other side of the power contactor is wired to the terminals of the power plug receptacle. The power contactor has contacts that close to complete the circuit between the power input cord and the power plug receptacle when the actuating coil is energized. The secondary winding is coupled to the delay timer. The delay timer has a delay timer output coupled to the actuating coil of the contactor.

Abstract: A device for monitoring the safety operation of power switches, in particular vacuum power switches in medium voltage switchboards. The device has a microprocessor unit that consists of a microprocessor, a microprocessor control and process-oriented storage means. The microprocessor is controlled by an angle pulse and a direction of a rotation recognition device. While the movement of the moving part of the power switch under the influence of states of operation is converted, the device detects the available data of the power switches. The device according to the present invention is especially well-suited in medium voltage switchboards for documenting and forecasting the real state of power switches.

Abstract: A binary sensor has a device for detecting the presence or condition of an object. The sensor has circuitry connected to the detecting device to generate a binary output signal that represents the presence or condition of the object. The sensor also includes circuitry that generates a diagnostic signal associated with the sensor. The diagnostic signal is superimposed on the binary output signal. The binary output signal with the superimposed diagnostic signal are simultaneously transmitted to a controller such as a Programmable Logic Controller or a smart drop in a bus network. The diagnostic signal is designed so that it will not interfere with the ability of the controller to recognize the binary output. The controller may be provided with circuitry to detect and interpret the diagnostic signal.

Abstract: An electromagnetic switch for opening and closing a set of contacts has a microprocessor which monitors coil current to determine the state of the contacts. The switch relies on the phenomenon that the inductance of the switch coil changes significantly between the open position of the contacts when the switch armature carrying the moveable contact is spaced by an air gap from the core of the electromagnet, and the closed position in which the armature abuts the core. For an AC energized coil, which is self-limiting in that the increase in inductance from closing of the contacts reduces the current to the holding value automatically, a coil current of less than about one/half of the nominal open contact value is an indication that the contacts are closed.

Abstract: The electronic switching device serves to control the connection of a load to a voltage source by a switch which is controlled in a first operating mode directly by a binary signal furnished by a signal processing circuit and in a second operating mode inverted. The switching device has three terminals, of which the first permanently remains connected to a first terminal of the voltage source and to a first terminal of the load, whilst of the other two switching device terminals the one is connected to the second terminal of the voltage source and the other to the second terminal of the load. The switching device is configured so that it can be changed over from the one operating mode into the other by interchanging the connections between these two other switching device terminals and the second terminals of the voltage source and of the load, respectively.

Abstract: An energization indicator for a solenoid includes an electrically operable signaler (70) having a coil (72) for energizing the signaler (70) when a magnetic flux field sweeps such coil, with the coil (72) being mounted in the magnetic flux path of the solenoid coil. The indicator includes the hold-down member (116) for rotatable positioning of the bobbin assembly on the hold-down member independently of the rotated position of the hold-down member to locate the lamp as desired on the solenoid.

Abstract: Switching components with contact parts that are mounted on a contact carrier in a switch housing may include devices for monitoring the contact erosion. The contact carrier may be split (sub-divided) and contact parts can be slotted at the rear and mounted on the sub-divided contact carrier. Thus, the oscillation response (vibration response) of the contact carrier in particular can be used as a measure of the erosion of the contact parts.

Abstract: An apparatus for monitoring the vacuum of a vacuum switch having at least one vacuum switch tube with a switch chamber and switch contacts is provided. The apparatus has a remotely interrogatable pressure measurement sensor in the form of a piezocrystal or surface acoustic (SAW) device arranged in the interior of the vacuum switch tube and a remote interrogation device placed external to the vacuum switch for monitoring the vacuum via the sensor.

Abstract: An electromagnetic relay, such as an electromechanical RF switch, which is operated by an electromagnetic coil, is provided with an indicating circuit which responds to the position of the electromagnetic armature as well as the application of driving current to the coil. A magnetically activated reed switch is mounted adjacent to the electromagnetic coil at a distance selected so that the magnetic field of the coil will operate the reed switch when current is applied to the coil and the armature is driven into a position closing a magnetic circle.

Abstract: An electrical contact position indicator assembly is operatively coupled to an electrical device, such as a recloser, for indicating the relative position of the contacts of the electrical device, i.e., opened or closed, at any given time during operation of the electrical device. The position indicator assembly includes a movable indicator having first indicia to indicate that the contacts are opened, and second indicia to indicate that the contacts are closed. Each of the first and second indicia of the indicator lies in more than one plane. Preferably, each of the first and second indicia of the indicator lies on a three-dimensional, curvilinear or spherical surface. In the preferred embodiment, the indicator includes a mechanical linkage to the contact opening and closing assembly.

Abstract: An apparatus and method for determining the state of a switch for use in an HVAC system. The apparatus and method are advantageously configured for use within a heating, ventilation and air conditioning (HVAC) system, in which the sensing of the state of safety switches external to a controller is desirable. A current sensor coupled in series between a current source, a safety switch, and a current load, detects the flow of current from the current source and through the switch and load. A status signal, indicative of the flow of current through the current sensor, is generated for sampling by a microprocessor. The presence or absence of current flow through the current sensor provides an indication as to whether the remotely-located switch is in an open or closed state.

Abstract: The duty ratio range of a duty signal DCN transmitted from a high-voltage load controller 12 to a field current controller 103 is divided into several subranges, which are assigned to zones, such as a normal voltage control zone, high-voltage control zone, and power generation stop and failure signal zone. The duty signal of a duty ratio in each zone is transmitted to the field current controller 103 for controlling the power generation mode of a generator 2. When a failure in a high-voltage circuit 16 is detected, the duty signal of a duty ratio in the power generation stop and failure signal zone causes power generation of the generator to stop and a pilot lamp 10 to go on for warning. The pilot lamp 10 is also used to warn the operator to a power generation error of the generator 2.

Abstract: A binary sensor including a binary sensing circuit, a logic circuit and an adaptive interface card adapted to matingly engage the binary sensor. The binary sensing circuit and logic circuit are operatively coupled for communication with external circuits. The adaptive interface card includes bus network interface circuitry that disables the logic circuit and enables the bus network interface circuitry upon matingly engaging the interface card with the binary sensor. The bus network interface circuitry also becomes operatively coupled with the sensing circuit upon matingly engaging the adaptive interface card with the binary sensor. The bus network interface circuitry of the adaptive interface card provides a means for the binary sensor to communicate with bus networks.

Abstract: A drive circuit fault detection device comprising a discriminating circuit generating a digital signal, the level of which indicates a fault; and an identifying circuit generating a binary-coded signal indicating the type of fault, i.e. ground shorting of the drive circuit or an open load. The discriminating circuit comprises a resistive network connected to the output of the drive circuit, for generating a voltage indicating correct connection of the load or a fault on the drive circuit and a comparator for comparing the generated voltage with a reference voltage and supplying the digital signal at its output. The identifying circuit comprises a current mirror circuit generating an output voltage having two different logic levels in the event of short circuiting or an open load, respectively, and a combination circuit for generating the binary-coded output signal.

Abstract: A circuit configuration for a signalling device in circuit breaker units, in particular in power circuit breakers, which have an electronic tripping device and which become effective in the event of a fault in an electrical system to be protected, whereby the electronic tripping device includes a microcontroller which performs a fault evaluation, and for each type of fault makes available an output pin, from which the corresponding fault signal is amplified and transmitted to an electrical relay. The fault signal (FM, FM1 . . . FMn) is transmitted to the circuit configuration (SA, SA1 . . . SAn), and by means of logic operation with the action of a static standard signal and of a clock pulse signal (Clock Pulse) acts on the electrical relay, which is realized in the form of a bistable relay (RB, RB1 . . . RBn) the contact system of which corresponds to a make function or a break function, depending on the signal status of the standard signal.

Abstract: A device for monitoring the switch position of a switch including an auxiliary voltage source, which is connected to the switch, a device for converting the switch position into an electrical signal, a device for transmitting the electrical signal and a device for evaluating the transmitted information. The converting device uses a pulse-duration modulation, the duty cycle of which becomes higher as the voltage U.sub.0 of the auxiliary voltage source becomes smaller. This enables the monitoring device to be used for different auxiliary voltages, without any need for adaptation.

Abstract: A composite switch is constituted by a series or parallel association of at least two simple switches. Each simple switch includes an element for measuring the current in the simple switch in the case of a parallel association; an element for measuring the voltage across the simple switch in the case of an association in series; and a control circuit receiving the information provided by the measuring elements as well as a control signal from the simple switch, and providing an active failure signal if the measured voltage is high or the measured current is low while the simple switch is controlled to be turned on, or if the measured current is high or the measured voltage is low while the simple switch is controlled to be turned off.

Abstract: A fault control apparatus is disclosed having elements that provide for an easily reconfigurable fault response. When the fault detection circuit signals that a fault has occurred, an alarm is triggered, switching means are automatically set to their fault positions, and a control output circuit is activated. The flexibility of fault response is made possible by the use of a matrix of switched connections to preset the fault positions of the relays. Additional flexibility is provided by providing an adjustable level for the control output.

Abstract: In order to provide a dependable check on the reliable functioning of contacts of switches or relays which control a control device, to ascertain whether they occupy the desired rest contact position and/or have a sufficiently high mains voltage, the rest contacts of the two switches can be connected in parallel by way of a respective electrical resistor to a pole of the voltage source and both resistors can be connected in series to a charging capacitor which, upon the attainment of a given electrical charge or voltage (threshold voltage) activates the control device and in particular feeds a threshold switch or itself serves as such.

Abstract: A safety switching arrangement for the switching on and off of the power supply (11) of two actors (12a, 12b) for example relays, which, in dependence on the switching on of the current, and in dependence on a sensor switching signal (13a, 13b) jointly set a working apparatus (22) in operation, the safety switching arrangement comprising two main switches (14a, 14b) arranged between the power supply (11) and each preferably earthed actor (12a, 12b).

Abstract: An off state demonstrating device on a line-pulling switch for a ceiling fan, is characterized in that a display or demonstrating device is jumper connected at the off position of the switch, so that when the switch is in an off state, the display or demonstrating device can be turned on and a user can be advised that the ceiling fan is in an off state.

Abstract: A method for determining mechanical parameters of an electric switching device exposed to environmental influences in which a measuring transmitter is provided for detecting the speed of a component of the drive means of the switch device at at least two consecutive times. In the case of vacuum power switches, the time of contact of the switch members and the time of the latching in the switched-on condition are preferably considered. If measurement values from comparative measurements of a given number of switches are available, the maximum intensity of a given environmental influence at which test sample can reliably operate is determined from a measurement of a test sample under normal environmental conditions.

Abstract: In one aspect of the present invention, an apparatus detects a shorted winding condition of a solenoid coil. The apparatus includes a reference solenoid that is connected to a test solenoid. A sine generator drives the reference solenoid with a sinusoidal waveform to cause an induced voltage across the test solenoid. A meter determines the voltage difference between the solenoids and compares the voltage difference to a predetermined value.

Abstract: A method for sensing the on/off status condition of a power switch in an appliance includes applying a series of alternating current (AC) voltage pulses to an appliance with an on/off switch that are synchronized to a source of AC power, sensing the presence of any series of AC current pulses that result if said appliance switch is closed, analyzing any AC current pulses detected in the step of sensing to determine if they resulted from the application of the AC voltage in the step of applying, and outputting an on/off status indication for the appliance switch.

Abstract: Electrical and mechanical operation of a bistable magnetically latching solenoid is diagnosed by monitoring induced voltage across the one of a pair of solenoid coils not energized. Energization of one of the pair of coils induces voltage across the other of the coils not energized and plunger actuation in response to energization induces another voltage therethrough. The various induced voltages are distinguishable as between those caused by energization of a coil or motion of the plunger.

Abstract: The operating parameters of a proximity switch can differ depending on the type of switch and also because of manufacturing tolerances. To make it possible for one to react to new developments in ultrasonic transducers and to customer-specific solutions without requiring additional space, data such as operating parameters are able to be input into a microprocessor of a prefabricated proximity switch with little expenditure of time and energy. A proximity switch may contain an enabling input and an overcurrent-detection device including a microprocessor. An overcurrent across the switching output can be identified by a pulse provided to a first input of the microprocessor. A programming device is provided through which such an overcurrent condition is simulated and the corresponding pulse is generated which represents information about an operating parameter in the form of a bit pattern. The microprocessor is loaded with this bit pattern.

Abstract: A circuit which gives a continuous voltage output indication of whether a contact is open or closed. The circuit senses the voltage across the contact to detect whether the contact is open or closed. When there is a significant voltage, the circuit indicates that the contact is open. When the voltage is negligible, the circuit indicates that the contact is closed. Alternatively, the current through the contact can be sensed to provide an indication of whether the contact is conducting or not. The circuit can be used to indicate the welding close of a relay contact in which case power to the load can be turned off or the contact can be opened by other than normal corrective actions. One application is to discontinue closing movement of a garage door when the motor relay switch does not open as desired, but there are innumerable other applications.

Abstract: An improved monitoring system which identifies the particular event (contact operation) and therefore the particular electromechanical relay (20, 22, and 24 which operated). This information is output from a MCU (30), along with the relative time the event occurred, to a PC and an LCD display (40). In addition, the relative occurrence time is recorded to the thousandths of a second.

Abstract: An annunciator for indicating the removal of an electrical plug from the electrical receptacle. The electrical receptacle includes neutral switching contacts actuated in response to the insertion of a plug into the receptacle. An input circuit in the annunciator apparatus monitors the state of the neutral switching contacts and couples signals produced when a plug is removed to a latching circuit thereby to produce an audible or electrical indication of plug removal. The input Circuit and latching circuit are electrically isolated, and the annunciator detects any attempts to disconnect the apparatus from an external power supply or to remove any internal battery.

Abstract: A monitoring device is provided for use in association with a limit switch or similar mechanically actuated device in order to permit its end of life to be predicted. The system uses nonvolatile random access memory to store a count which represents the number of occurrences of one of two alternative events. The first event is the occurrence of a number of switch actuations and the second event is the lapse of a predetermined period of time. When either of these two events occurs, a microprocessor increments a count in the nonvolatile memory unit and clears both the clock and the volatile memory parameter. When the number stored in the nonvolatile memory represents a number of actuations estimated to be appropriately equal to the total life of the switch, this condition can be signaled to a sensor bus by a communication circuit. Alternatively, a light emitting diode can be alternately energized and de-energized to represent the number of actuations having exceeded the predicted end of life total.

Abstract: An apparatus for testing an industrial machine safety system that allows the machine to begin operation only when a plurality of safety push buttons have all been depressed, and that stops the machine's operation when any safety push button is released. The apparatus includes an artificial hand that can depress and, upon command, release one of the safety push buttons, and has a release detector for detecting the release of the artificial hand. The release detector operates optically. A lamp directs a light beam along a path that is blocked by a plunger when releasing the safety push button and not blocked when depressing the safety push button. A photodetector detects interruption of this light beam. Thus release of the safety push button is detected upon detection of interruption of the light beam. The machine begins to stop upon release of the safety push button. A motion detector detects the stoppage of the machine.

Abstract: An improved input module is able to sense the ON and OFF states associated with an external signal, wherein that signal complies with standards denoting the ON and OFF condition thereof. The improved input module includes a fixed impedance and a parameter sensor, such as a voltage sensor, which senses at least a portion of the voltage drop across the impedance. In addition, the module includes a current limiter in series with the impedance so as to limit the current flow through the impedance when the threshold parameter has been exceeded. An additional embodiment of the input module includes a second current limiter which is able to selectively detect broken wires associated with the connection of the external signal to the input module.

Abstract: A device for determining the state of an apparatus capable of existing in a first state and a second state. The apparatus is provided with auxiliary contacts (CAO1, . . . , CAF1, . . . ) which provide binary state signals that depend on the current state of the apparatus. The device includes at least one first state auxiliary contact CAO1), that provides a "1" state signal when the apparatus is in its first state, and at least one second state auxiliary contact CAS1) providing a "1" state signal when the apparatus is in its second state. The device also has a programmed microcontroller (MP) having inputs on which it receives the state signals from the auxiliary contacts (CAO1, . . . , CAF1, . . . ) and also instructions (OO, OF) requesting the apparatus to switch from one state to the other.

Abstract: A circuit breaker arranged with overload sensing, switches and LED indicators. Provided is a green LED (42) which when lit indicates that the circuit is blown and so the electrical wires from the breaker are not powered--the wires are "dead"; a red LED is also provided to indicate, when lit, that the electrical wires are powered or "live", in addition there is an amber third LED (52) which, when lit, indicates that a short circuit overload is still connected to the breaker output terminals.

Abstract: A circuit breaker locator comprises a housing having a plunger projecting outwardly at one end and reciprocably moveable within the housing. The plunger is coupled to a spring urged retractable contact at the opposite end of the housing. The housing also includes, at the end with the retractable contact, a pair of contacts extending outwardly therefrom which are coupled to a fuse and a pilot light connected in parallel with the fuse. In operation, the pair of contacts are inserted into an electrical outlet and the plunger is actuated forcing the retractable ground contact into the outlet. The device automatically trips a circuit breaker related to the particular outlet so that it is possible to check which circuit breaker is connected to the outlet. If the breaker fails to trip, the alarm light, which is connected parallel with the fuse, is activated indicating a faulty circuit breaker. The circuit breaker locator provides a ready and safe means of determining what circuit breaker is related to what outlet.

Abstract: A circuit is provided for detecting abnormal conduction of current conducted through a solenoid in response to the pulse width modulation signal. The circuit includes a measuring means, for detecting conduction current conducted through the solenoid in response to the pulse width modulation signal and measuring continuous conduction time of the conduction current, and determining means, for determining a conduction to be an abnormal conduction when the continuous conduction time is longer than a predetermined time. Thus, the circuit can be miniaturized and the accuracy of the circuit is not affected by the accuracy of its components. And, the circuit is capable of detecting the half short state of the transistor driving the solenoid and not malfunctioning even if tile power is turned off.

Abstract: A tamper detection system for promptly warns a utility that it has lost control of a load which is part of a load management system, and may be giving price incentives to a customer without receiving the corresponding benefit arising from the intended control of the load. A monitor circuit automatically determines whether the load management device is connected to the load by detecting whether a current is passing via the load control device to the load, and generates a warning signal when no current is detected for a first predetermined period of time. The load current is detected either by inductively coupling a conductor to the load with a sensing conductor, or by sensing current induced in the load control relay as the load current passes through the relay contacts. The tamper detection feature operates without any activity of the load management device, and detects disconnection of the load even when the load management device itself is powered up and working properly.

Abstract: The invention relates to a method for the supervision of a switch, in which a switch supervision signal (CA1, CA2, CB1, CB2) is generated and transmitted to the switch contact to be supervised, and in which the switch supervision signal (CA1, CA2, CB1, CB2) returning from the switch contact is detected and compared with the emitted signal. A coded signal is used as switch supervision signal (CA1, CA2, CB1, CB2) and this coded signal is transmitted serially to the switch contact to be supervised.

Abstract: Load driver system (10) preferably uses a microprocessor controller (20) to generate write/read signals and command signals received by a circuit at write/read and command/status input terminals (16, 17). The circuit (15) responds to the input signals and controls a semiconductor switch (11) that controls the operative state of a load (14). The circuit (15) includes a load shorted high detector (28), a load shorted low detector (29) and a load open detector (30) which are used to detect various faults and provide a predetermined sequence of logic states at the command/status input terminal (17) during read cycles implemented by the controller (20). Thus one input line (terminal 17) is used to both send commands to the semiconductor switch (11) and receive a sequence of logic states indicative of various fault modes. This permits the controller to determine which of several types of faults, if any, has occurred, while minimizing the number of controller-circuit interconnections.

Abstract: A circuit configuration is provided for monitoring an electromagnetically actuated device, such as an electromagnetic clutch. The circuit comprises a switchable power source connected to the winding of the electromagnet; the power source supplies a composite voltage formed of a direct voltage part and a periodic alternating voltage part superimposed on one another. Engage and disengage signals are issued for the clutch and the direct voltage part assumes distinctly different levels in dependence on the engage and disengage signals. A precision resistor is connected in series with the winding of the electromagnet and a voltage sensor is connected at a node between the winding and the precision resistor. An evaluation circuit is connected to the voltage sensor for evaluating the alternating voltage part acting on the precision resistor and receiving therefrom information regarding the functionality of the electromagnetic device.

Abstract: An energization indicator for a solenoid includes an electrically operable signaler (70) having a coil (72) for energizing the signaler (70) when a magnetic flux field sweeps such coil, with the coil (72) being mounted in the magnetic flux path of the solenoid coil (53).

Abstract: An annunciator for indicating the removal of an electrical plug from an electrical receptacle. The electrical receptacle includes neutral switching contacts actuated in response to the insertion of a plug into the receptacle. An input circuit in the annunciator apparatus monitors the state of the neutral switching contacts and couples signals produced when a plug is removed to a latching circuit thereby to produce an audible or electrical indication of plug removal. The annunciator circuit does not provide an alarm in response to the insertion of a plug or to an absence of a plug.

Abstract: A computerized relay tester is provided which comprises a bar code reader, a test circuit for determining an actual value of an operational characteristic of the relay, and a memory for storing reference values for the operational characteristic for a plurality of relays. The test circuit is operative to automatically measure the actual voltage or current values at which "pickup" or "drop away" occurs in the relay under test, by sensing an inductive voltage "spike" caused by movement of the relay armature. Based on signals from the bar code reader, a reference value for the particular operational characteristic under test are retrieved from memory. The actual value is then compared with the reference value to determine whether the relay is functioning properly, and the relay tester outputs an indication of the operational state or condition of the relay.

Abstract: A circuit is provided for detecting the deposition of an electromagnetic contactor which opens and closes a drive circuit connecting a power source to a load. A load current of the drive circuit and an operating current for operating the electromagnetic contactor are detected and applied to a detection circuit. The thus detected load current and operating current are used to determine the deposition of the electromagnetic contactor. Further, in the event of a detected malfunction in the electromagnetic contactors, a breaker of the drive circuit is automatically opened.

Abstract: When a solenoid has been turned on by supplying current to a coil thereof, the solenoid operation is checked by temporarily ceasing the supply of current to the coil to temporarily deenergize the solenoid. The current flowing in the coil is detected while the solenoid is temporarily deenergized, and the characteristics of the thus detected current are used to discriminate the position of a movable iron core of the solenoid. On the other hand, when the solenoid has been turned off by ceasing the supply of current to the coil, the solenoid operation is checked by temporarily supplying current to the coil to thereby temporarily energize the solenoid. The current flowing in the coil while the solenoid is temporarily energized is detected, and the characteristics of the thus detected coil current are used to determine the position of the movable iron core of the solenoid.

Abstract: A fusion detecting system for relays is provided for detecting a fusion of relay contacts. Two fully-interlocked or semi-interlocked relays are connected in such a manner that they operate under identical conditions, and a fused state is detected based on the states of signals sent from series-connected make contacts and series-connected break contacts of the two relays. In the case of semi-interlocked relays (R1, R2), if a make contact (r12) is fused during a current supply to a coil, the other contact (r22) remains in an open state or at a make-contact side after the current supply to the coil is cut off, and if a break contact (r11) is fused, the other contact (r21) remains in an open state or at break-contact side after a current is supplied to the relay coil.

Abstract: In a triac power switching system, two triacs are connected in series between an AC power source and a load. Each time power is applied to a load, the triacs are tested by first turning on one of the triacs while maintaining the other triac turned off, then turning on both triacs to apply power to the load for a set time interval and then turning off one of the triacs and determining whether power is still applied to the load. If power is applied to the load while either one of the triacs is supposed to be off, an alarm is sounded. In addition, if power is not applied to the load when both triacs are turned on, an alarm is sounded.

Abstract: An abnormality diagnosing system and method for high voltage power apparatus wherein a plurality of detectors for detecting abnormalities of the high voltage power apparatus and providing outputs indicative thereof are disposed to detect predetermined phenomena indicative of at least an insulation abnormality, power supply abnormality, and foreign matter among abnormalities existing inside of the high voltage power apparatus. A monitoring arrangement responsive to the outputs of the detectors provides at least one of an output and display of the kind of abnormality detected.

Abstract: The switch condition of two switches (S1, S2) connected in parallel to a single transmission line (11) is detected by the signals output from two Schmitt triggers (10a, 10b) which are arranged to operate at different switching threshold levels by virtue of the output (WA) of one of the triggers (10a) being connected to the threshold level control input (F) of the other trigger (10b). Closure of one of the switches (S1 or S2) causes a reference voltage (UR) to the applied to the inputs of the triggers (10a, 10b) which is turn causes the upper threshold trigger (10a) to operate. Closure of both switches (S1 and S2) reduces the level of the voltage applied to the inputs of the triggers which is turn causes the lower threshold trigger to operate. Preferably, the signal input to the lower threshold trigger is converted into a current prior to application to the trigger due to the relatively small difference in threshold levels.

Abstract: A system and method for detecting partial discharge of gas-insulated switchgear wherein a high-frequency component and the fundamental wave component of the voltage applied to the conductor of the gas-insulated switchgear are detected, the zero-cross point of the fundamental wave component is set as the starting point for the voltage, and the presence of partial discharge and the reason for the occurrence of partial discharge are ascertained based on the phase difference between the phase of the detected high-frequency component and the phase of the starting point of the voltage.