REX010 HESG324426R0001 Injection unit

The earth fault protection is based on the injection of a coded signal. The resulting offset voltage is utilized to calculate the earth resistance (Rf).
The injection signal is produced in the injection unit REX010 and applied to the generator through the transformer unit REX011. For the coupling to the protected unit resistors (RE, RP) are used. For the rotor earth fault protection two capacitors are required in addition.
The measurement signals for earth fault protection are processed by the REG216 or the REG316*4 respectively.
The equipment described protects 100% of the generator stator winding. Two independent protection functions are applied: one for 95% and one, using a different algorithm, for 100% of the stator winding. The 100% function is calculating the earth resistance and the 95% function is measuring the neutral voltage displacement of the generator.
a) The 100% function protects 35% of the stator windings from the neutral point for Rf = 0 and I0max = 15 A
b) The 95% function (U>) protects 95% of the generator stator winding from the terminals. This results in an overlap
(redundancy) of the two protection functions as seen in Fig. 1.
The 100% function increases in sensitivity with increasing earth fault resistance and decreasing earth fault current.

REX010