Negative-sequence overcurrent protection (NSPTOC) - Arc protection - Merging unit - Transformer protection - 2 winding - Product Guide - RET615 Transformer Protection and Control - Relion 615 series - 5.0 FP1 IEC - IEC - 24.05.2023

RET615 Product Guide

Table 1. Negative-sequence overcurrent protection (NSPTOC)
Characteristic Value
Operation accuracy Depending on the frequency of the measured current: f n
±1.5% of the set value or ±0.002 × I n
Start time Minimum Typical Maximum

I Fault = 2 × set Start value

I Fault = 10 × set Start value

23 ms

15 ms

26 ms

18 ms

28 ms

20 ms

Reset time Typically 40 ms
Reset ratio Typically 0.96
Retardation time <35 ms
Operate time accuracy in definite time mode ±1.0% of the set value or ±20 ms
Operate time accuracy in inverse time mode ±5.0% of the theoretical value or ±20 ms
Suppression of harmonics

DFT: -50 dB at f = n × f n, where n = 2, 3, 4, 5,…

1 Negative sequence current before fault = 0.0, f n = 50 Hz, results based on statistical distribution of 1000 measurements
2 Includes the delay of the signal output contact
3 Maximum Start value = 2.5 × I n, Start value multiples in range of 1.5...20