This document is a user manual for ABB 41-178S type negative sequence time overcurrent relay. The relay is mainly used for the protection of rotating machinery such as generators and synchronous capacitors to prevent overheating damage caused by prolonged current imbalance.
The SOQ negative sequence time overcurrent relay is designed to protect rotating machinery such as turbine generators and synchronous condensers from excessive heating caused by prolonged current unbalance. The relay provides an alarm feature that can be set between 0.03 and 0.20 per unit to alert operators of abnormal negative‑sequence current levels.
The bulletin details the relay’s internal construction, including input, timer, control, and power‑supply boards, as well as the indicating contactor switch and optional remote readout instrument. It also describes how to set the per‑unit pickup, K‑setting, alarm level, and timer characteristics, with selectable time‑constant values of 38 s or 80 s.
| Ambient Temperature Range | -20°C to +55°C |
|---|---|
| Current Transformer Continuous Rating | 10 amperes |
| Burden (ac) | 1.6 V·A (max.) at 5 A, 60 Hz |
| Trip Pickup Adjustment Range | 0.1 to 1.0 per unit |
| Timer Reset Exponential Time Constant | 38 s or 80 s (selectable) |
| K‑Setting Range | 2 to 40 |
It protects rotating machinery against excessive heating damage caused by prolonged current unbalance.
The timer can be set to an exponential reset constant of either 38 seconds or 80 seconds via a link on the Timer Board.
The relay operates from –20 °C to +55 °C.