The solid-state trip device of a protective circuit breaker of a three-phase mains system comprises a fault type detection circuit comparing the currents flowing in the mains system conductors with a first threshold and a second threshold, higher than the first one. It supplies a signal representative of a certain type of fault, single-phase or two series pole, when a first number of currents are lower than the first threshold and a second number of currents are higher than the second threshold.

Solid-state trip device for a protective circuit breaker of a three-phase mains system, enabling the type of fault to be detected

The currents flowing through high voltage conductors in a network or switchyard are monitored by magnetic field sensors in the form of air-cored epoxy-filled coils which are electrostatically shielded by discontinuous shields. The magnetic field sensors are located a safe working distance away from the conductors being monitored to remain substantially at earth potential and are orientated to maximize the magnetic field influence from the conductors being monitored. The value of the magnetic field detected by the sensors are sampled instantaneously and the sampled value is processed, having regard to calibration and cross linking effects of the network being monitored to calculate the instantaneous current flowing through the network.

Monitoring and fault protection of high voltage switchyards

A method and an apparatus for testing an electrical heating cable of the self-limiting type which is out of operation. The cable comprises a pair of parallel electrical conductors. An auxiliary voltage is applied at least periodically across the two electrical conductors. The resulting current flowing through either of the two conductors is compared with the current flowing back from the other conductor. The most recent value of the currents flowing through either of the two conductors is stored. In the next test of the cable, it is established whether the instantaneous current value through the respective conductor lies beyond a given range relatively to the stored current value.

A method and an apparatus for testing self-limiting electrical heating cables which are out of operation

The invention provides a power supply open-phase detection method and device, a storage medium and an electric appliance. The method comprises the following steps of sampling an input voltage of a power supply within a preset sampling time, averaging the sampled input voltage sampling values to obtain an average sampling value of the input voltage, determining whether a voltage fluctuation periodexists or not according to the sampled input voltage sampling value and the average sampling value, and if the voltage fluctuation period is determined to exist, determining whether the power supply is open-phase according to a comparison result of the input voltage sampling value sampled each time and the average sampling value. According to the scheme provided by the invention, the abnormality of the input voltage can be detected through a software algorithm, and the cost is reduced.

Power supply open-phase detection method and device, storage medium and electric appliance

The static trip device of a circuit breaker for protecting a three- phase network comprises a detection circuit of the fault type comparing the currents (I1, I2, I3,IN) travelling along the conductors of the network to a first threshold (S1) and to a second threshold (S2) greater than the first. It supplies a signal (A) representing a certain type of fault, single-phase or two-pole series, when a first number of currents is less than the first threshold (S1) and a second number of currents greater than the second threshold (S2).

Static trip device for a circuit breaker, protecting a three-phase network, allowing the detection of the fault-type

A method of identifying faults in a polyphase alternating current electric power transmission system wherein determination of the type of fault occurring is effected by monitoring the amplitudes and relative phases of fault current quantities derived from the phase currents of the system. The current quantities are preferably phase fault currents and quantities derived by addition and subtraction of phase fault currents. Apparatus for carrying out the method is also disclosed.

John Victor Harold Sanderson

Papers

Method and apparatus for fault identification in electric power transmission systems