Method for generating a trigger signal according to the current differential protection principle and current differential protection arrangement

The method as claimed in one of the preceding claims, characterized in that

• the smallest value (ismin) of the stabilization current (is) is determined in each case in a time range in which the first measurement quantity (isd) becomes less than zero,
• its largest value (ismax) is determined in each case in a time range in which the first measurement quantity (isd) becomes greater than zero, and
• a check is made to determine whether the stabilization current (is) is greater than KMIN times the smallest value (ismin), where 1<KMIN<{square root}2, and 0.5 times the value of the largest value (ismax), and,
• if appropriate, the trigger signal (A) is generated.

The method as claimed in one of the preceding claims, characterized in that,

• in the absence of a trigger signal (A), an internal inhibit signal (B) is generated if
• the first measurement quantity (isd) is greater than the limit value of this quantity (igd2),
• furthermore the second measurement quantity (idd) is less than the instantaneous value—weighted with the k factor—of the first measurement quantity (k*isd) and, at the same time, the instantaneous value of the stabilization current (is) is greater than
• a limit value (ish),
• a first reweighted limit value (idg/k),
• a second reweighted limit value (1.5*idg), and
• a comparison value calculated as mean value from previous values (isrms comparison value).

A current differential protection arrangement for a section (E) of an electrical power supply system having

• a measured value preprocessing device (MV), in which respective differential current values (id) and stabilization current values (is) respectively assigned thereto are formed continuously from currents (i1, i2) detected at the ends of the section (E), having
• an evaluation device (AW) connected downstream of the measured value preprocessing device (MV), —in which evaluation device the differential current (id) is checked to determine whether it exceeds a predetermined differential current limit value (idg), and having
• a logic circuit (L1), which, on the input side, is connected to the evaluation device (AW) and has an output for outputting a trigger signal (A),
• characterized in that the measured value preprocessing device (MV) is designed in such a way that it generates differential current instantaneous values and stabilization current instantaneous values (is),
• a first limit value stage (Gs) is arranged downstream of a first differentiator (Ds), to which stabilization current instantaneous values (is) are applied, which limit value stage is also connected to a differential current quotient limit value transmitter (Gl) on the input side,
• a second limit value stage (Gd) is arranged downstream of a second differentiator (Dd), to which differential current instantaneous values are applied, which limit value stage is also connected to the differential current quotient transmitter (Gl9) on the input side, and
• the logic circuit (L1) is arranged downstream of the limit value stages and generates the trigger signal (A) when output signals of the limit value stages are present.