Digital multifunction relay

The present invention relates to a digital multifunction relay having improved characteristics. Digital multifunction relays are well known in the state of the art. They are generally used, in a power distribution network, for controlling the operation of protection devices that have the aim of protecting the power distribution network from fault events for example tripping devices or disconnectors or the like, particularly in the voltage range from 1 KV to 35 KV). Digital multifunction relays can control the operating state of these protection devices and can host many different protection functions, that can be software objects consisting generally of a processing stage and of a state machine stage. Digital multifunction relays generally comprise a digital signal processor DSP which is generally connected to an analog digital AD converter. The A/D converter receives signals from sensors positioned on the power distribution network. These sensors measure some predefined power distribution quantities for example current and/or voltage. The DSP receives, from the A/D converter, sampled values of these predefined quantities and processes the sampled values, in order to obtain some calculated values. The calculated values are used for detecting the presence of a fault event. Based on the calculated values, the DSP generates signals for regulating, the operating state of the protection devices, by means of the mentioned protection functions. For example, the DSP can perform mathematical calculations, such as FFT Fast Fourier Transform algorithms, or determine other quantities such as the transmitted electric power or the equivalent resistance of a branch of the power distribution network. All these described processing activities, performed by the DSP, are commonly defined as "foreground processing activity". It is known that all the foreground processing activity must be executed in a period of time, which elapses between the acquisition of two consecutive sampled values hereinafter defined as "sampling period". Referring to , the two instants of acquisition of the sampled values 8 are indicated with T and T , while the sampling period is indicated with T . The period of time for executing the foreground processing is indicated with T . After having completed the entire foreground processing, the DSP is kept in a state of idle, for the period of time T , remaining before the instant Tc. A digital multifunction relay, for controlling one or more protection dev