Experience in the Detection of High Impedance Faults in the Line Macagua-Callao-Claritas 400 kV

On day 28-03-02 at 12:37, line Macagua-Callao-Claritas 400 kV tripped, additionally the autotransformer 1 400/230 kV, the reactances 1 and 2 of 50 MVAr of the Claritas substation, and the transformers 230/69/13.8 kV in Boa Vista substation tripped too. According to the carried out analysis, a fault of high resistance was detected in the phase "A" of the line Macagua-Claritas, near to Claritas substation, which was not detected by the distance protections of the line, this fault should be cleared by the high impedance protections in 200 ms. This scheme did not operate because the relays of the Macagua end did not detect the fault and they did not send the signals of high frequency to the end of Claritas to complete its performance. Finally the fault was cleared in 4.4 sec. by the relay of high impedance (67N) in their back-up scheme. All the other equipments (transformers and reactors) that were tripped by correct performance of the ground overcurrent protection in back-up for the fault duration. This work explains the behavior of the power system and the protections equipments for the fault in reference, additionally some proposals of improvements are indicated to achieve a better performance of the protections devices