Siemens Aktiengesellschaft

Klaus Renz

Michael Becker

Hermann Waldmann

Dusan Povh

Alfons Fendt

Gerhard Schuch

Manfred Weibelzahl

A device to locate internal faults in a high-voltage capacitor battery that has a plurality of symmetrically parallel and series-coupled capacitor banks arranged in parallel branches coupled by shunt branches. The phase angles of the shunt currents flowing in the shunt branches relative to the total current flowing in the parallel branches are determined. A fault is located in one of the capacitor banks based upon these determined phase angles.

Device for locating internal faults in a high-voltage capacitor battery

A monitoring device connected to an LC filter circuit for determining the occurrence of faults therein includes sensors for measuring the voltage drop across the LC filter circuit and the current flow therethrough. The monitoring device includes simulation circuits for estimating the voltage drop and current flow in response to the actual values of the current flow and voltage drop, respectively. In one position of the double-throw switch, the actual value of the current is compared with an estimated value thereof while in another position of the double-throw switch, an estimated value of the voltage drop is compared with the actual value thereof. Differences between the compared values are detected by a multiplicity of Y-connected limit and counting stages activatable by voltages of different magnitudes and directions for indicating different kinds of faults and for selectively disconnecting the LC filter circuit from a power supply network.

Monitoring device for detecting faults in an electrical device,

A monitoring system for detecting earth contact of at least one phase of a polyphase network. Each of the phases in the network is connected by a capacitive-inductive filter to a neutral node which is connected to earth. In one embodiment of the invention, the current flowing from the neutral node to earth is detected by an induction current transformer which provides a signal responsive to said earth current. The output signal of the induction current transformer is conducted through at least one low pass filter for suppressing harmonics, and rectified to produce a direct current voltage signal, the amplitude of which is proportional to the amplitude of the fundamental frequency component of said signal. A fault indicating signal is produced when the direct voltage signal exceeds a predetermined value.

Earth contact monitoring device for a polyphase three-phase filter

A system for monitoring the capacitor batteries of a three-phase filter circuit. Each capacitor battery is formed of a plurality of parallel legs each having a plurality of sectional capacitors which are connected in series with fuses. Adjacent ones of the sectional capacitors are coupled to one another. In a three-phase system, three capacitor batteries are coupled to one another in a Y-circuit configuration, the Y-circuit node being coupled to a reference potential, illustratively ground. The magnitude and phase of the fundamental frequency component of the current flowing from the Y-circuit node to the reference potential is monitored, variations therein being evaluated to identify defective sectional capacitors. Only variations in the Y-circuit node current which occur rapidly will trigger fault signals, thereby preventing false indications resulting from variations in temperature.

Monitoring system for the capacitor batteries of a three-phase filter

A monitoring system for measuring the phase currents of a filter circuit, the monitoring system having current measuring transformers coupled to respective filter sections for suppressing the harmonic content. Voltage measuring transformers are provided for measuring the network phase voltages, each such voltage measuring transformer being coupled to an electronic filter simulator and a filtering section for suppressing harmonic content. The fundamental frequency component of the measured phase currents and the simulated phase currents are conducted to transient comparator circuitry which is coupled to indicating and triggering circuitry having individual counter stages. Only rapid variations between the measured and simulated phase currents will result in fault indications, thereby preventing false indications resulting from variations in temperature.

Monitoring system for an LC filter circuit in an AC power network

A monitoring system for a capacitor battery, the capacitor battery having a plurality of parallel legs, each with a plurality of sectional capacitors connected in series with fuses. Adjacent ones of the sectional capacitors are connected to one another by continuous cross lines. Electronic simulation circuitry is provided for producing a signal corresponding to the fundamental frequency component of a simulated capacitor voltage. A transient comparator circuit compares the fundamental frequency component of the simulated capacitor voltage with the fundamental frequency component of a measured capacitor voltage. Only rapid changes between the simulated capacitor voltage and the measured capacitor voltage are signaled as indicative of failures of one or more sectional capacitors in the capacitor battery. Slowly occurring voltage changes, which may correspond to variations in ambient temperature, do not lead to fault signaling.

Monitoring system for a capacitor battery in an AC voltage network

A circuit for monitoring the voltage stress of a capacitor which produces an over-stress indicator signal responsive to the over-voltage history of the capacitor. If the measured voltage stress of the capacitor exceeds a predetermined over-voltage value, a characteristic-curve generator, having a predetermined transfer function, produces an output signal which is responsive to the measured voltage stress of the capacitor and the transfer function of the characteristic-curve generator. This signal is combined with a further signal which is responsive to a predetermined permissible continuous operation voltage value. The combined signals are conducted to an integrator having a predetermined integration time constant for producing an overload signal. The overload signal at the output of the integrator is a measure of the state of stress of the capacitor. Circuitry may be provided for disconnecting the capacitor from a transmission line in response to the output signal of the integrator. Also, plural capacitor voltage stress monitoring stages may be combined to monitor the capacitor voltage stress in a plurality of over-voltage ranges.

Circuit for monitoring the voltage stress of a capacitor

A circuit for monitoring the capacitor battery of a filter circuit connected to a transmission line, the capacitor battery consisting of at least two parallel legs, each with a number of series-connected capacitors. A first signal is produced which corresponds to the total alternating current flowing through the capacitor battery. A second signal is produced which corresponds to the difference between the currents flowing through the respective parallel legs of the capacitor battery. The current difference signal is compared with a respective fraction of the total current signal. A fault indicator signal is produced if the difference between the difference current signal and the fractional total current signal exceeds a predetermined threshold value. Further circuitry is provided for correcting drift in the difference current signal, which may be caused by temperature variations or acceptable capacitor failures. Automatic ranging circuitry may be provided in embodiments of the invention in which the total capacitor battery current varies in amplitude over a large range.

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Furth, Germany

Klaus Renz