A method for determining the operating status of a MV switching device (1), which comprises one or more electric poles, each comprising a movable contact and a fixed, contact adapted to be coupled or uncoupled during the switching operations of said switching device, and an electromagnetic actuator comprising a magnetic core, a test coil wound around said magnetic core and a movable plunger operatively coupled to the movable contact of each electric pole. The method comprises: providing a test signal (ST) to said test coil for an observation period of time (T.sub.O), said test signal having a waveform adapted to excite said magnetic core; obtaining measuring data (V.sub.M, I.sub.M) indicative of the voltage at the terminals of said test coil and of the current circulating along said test coil during said observation period of time; calculating observation data (R.sub.N, I.sub.M) indicative of the electric behaviour of said test coil at the end of said observation period of time on the base of said measuring data; selecting at least a transformation function (F.sub.1, F.sub.2) indicative of the electromagnetic behaviour of said electromagnetic actuator; and calculating first estimation data (P, T) indicative of the operating status of said electromagnetic actuator on the base of said observation data (R.sub.N, L.sub.N) by using said transformation function, said first estimation data comprising, a first estimation value (P) indicative of the position of the movable plunger of said electromagnetic actuator.

There is a need to monitor and control the state of relays and circuit breakers within power distribution systems. The monitoring of a relay state, i.e. open or closed, is often performed by applying a monitoring signal to sensing contacts added to the relay. Manufactures of such systems have chosen many different voltages for their own. monitoring systems making it difficult to interconnect dissimilar monitoring systems. A signal conditioning circuit is provided that can cope with a large input voltage range and can be configured to allow may items of equipment(which may be new item or legacy items) to be connected to a controller.

There is a need to monitor and control the state of relays and circuit breakers within power distribution systems. The monitoring of a relay state, i.e. open or closed, is often performed by applying a monitoring signal to sensing contacts added to the relay. Manufactures of such systems have chosen many different voltages for their own. monitoring systems making it difficult to interconnect dissimilar monitoring systems. A signal conditioning circuit is provided that can cope with a large input voltage range and can be configured to allow may items of equipment(which may be new item or legacy items) to be connected to a controller.

One embodiment describes a three-phase electromechanical switching device, which includes three single-phase switching devices mechanically and electrically coupled in parallel with one another, each single-phase switching device including a direct current electromagnetic operator that in operation receives a direct current control signal for switching of the device, stationary contacts disposed in a respective device housing, and a movable assembly that in operation is displaced by energizing the operator and that include movable contacts that open and close, with the stationary contacts, a single current carrying path through the respective single-phase switching device; in which each of the single-phase switching devices receives control signals from control circuitry coupled to the operators of the respective single-phase switching devices to cause at least one of the single-phase switching devices to open or close the single current carrying path at a desired time coordinated with a current zero-crossing or a predicted current zero-crossing of a phase of three-phase power.

One embodiment describes a three-phase electromechanical switching device, which includes three single-phase switching devices mechanically and electrically coupled in parallel with one another, each single-phase switching device including a direct current electromagnetic operator that in operation receives a direct current control signal for switching of the device, stationary contacts disposed in a respective device housing, and a movable assembly that in operation is displaced by energizing the operator and that include movable contacts that open and close, with the stationary contacts, a single current carrying path through the respective single-phase switching device; in which each of the single-phase switching devices receives control signals from control circuitry coupled to the operators of the respective single-phase switching devices to cause at least one of the single-phase switching devices to open or close the single current carrying path at a desired time coordinated with a current zero-crossing or a predicted current zero-crossing of a phase of three-phase power.

A design of a protection relay, and interface with an operator of a protection relay, are disclosed. The protection relay can include a base relay for measurement of line current and for generation of a trip signal, a base Human Machine Interface (HMI) for user specifying of a base setting of an operating parameter of the protection relay, and an optionally active Human Machine Interface (HMI) unit having a processing unit to manage plural activities with controlled power consumption.

A design of a protection relay, and interface with an operator of a protection relay, are disclosed. The protection relay can include a base relay for measurement of line current and for generation of a trip signal, a base Human Machine Interface (HMI) for user specifying of a base setting of an operating parameter of the protection relay, and an optionally active Human Machine Interface (HMI) unit having a processing unit to manage plural activities with controlled power consumption.

A phase sequence switching device for a three-phase power supply is disposed in a power feed path from a three-phase power supply to a load and includes a power-supply side relay including two Form C contact relays connected to two phases of the power supply respectively, a load side relay including two Form C contact relays connected between the power-supply side relay and the load, and a switching circuit connected between the power-supply side relay and the load side relay and wired to be capable of switching by a relay action from a standby state where no power is supplied to the load to either a state where the power supply is connected to a positive phase so that power is supplied to the load side or a state where the power supply is connected to a reverse phase so that power is supplied to the load side.

A phase sequence switching device for a three-phase power supply is disposed in a power feed path from a three-phase power supply to a load and includes a power-supply side relay including two Form C contact relays connected to two phases of the power supply respectively, a load side relay including two Form C contact relays connected between the power-supply side relay and the load, and a switching circuit connected between the power-supply side relay and the load side relay and wired to be capable of switching by a relay action from a standby state where no power is supplied to the load to either a state where the power supply is connected to a positive phase so that power is supplied to the load side or a state where the power supply is connected to a reverse phase so that power is supplied to the load side.

A power conversion circuit includes a high-side switch and a low-side switch connected in series with one another and configured to control a load current flowing through a load, wherein at least one of the high-side switch and the low-side switch comprise a power relay circuit for switching the load current, and wherein the power relay circuit comprises a micro-electro-mechanical system switch, and a semiconductor power switch, wherein the MEMS switch and the semiconductor power switch are connected in series with the load.