PANAJI
Goa’s power system experienced a brief outage on Saturday following the tripping of key high-voltage circuits at the Goa-Tamnar Transmission Project Limited (GTTPL) sub-station.
The incident occurred when the 400 kV Xeldem–Mapusa Circuit-2, along with the 220 kV Xeldem–Xeldem Circuits-1 and 2, automatically tripped due to the operation of the Over-Voltage Protection (OVP) scheme.
GTTPL officials said the situation could have been mitigated had the NXTL Narendra double-circuit line (400 kV Xeldem–Narendra Line-1 and Line-2) been operational. The additional transmission corridor would have provided stronger grid support to the GTTPL 400 kV bus, enabling improved voltage regulation, enhanced short-circuit strength, and better reactive power balancing.
The presence of this parallel evacuation path would also have reduced voltage sensitivity to the Mapusa line and minimised the likelihood of OVP operation, thereby strengthening the stability and operational resilience of the Goa power grid.
According to GTTPL officials, the 400 kV Xeldem–Mapusa Circuit-2 tripped along with 220 kV Xeldem–Xeldem Circuits-1 and 2 following the activation of the protection mechanism designed to safeguard the system against excessive voltage levels.
At present, the power flow from Mapusa towards Xeldem is being routed through the GTTPL pooling point, where the 400 kV bus at GTTPL is radially charged from the Mapusa (PGCIL) end. Under this arrangement, the GTTPL bus remains electrically dependent on the Mapusa source for voltage support. This creates a weak-end bus condition with limited capacity to absorb reactive power.
Officials explained that due to this radial configuration, any voltage rise at the Mapusa end—often caused by light load conditions, the Ferranti effect, or surplus reactive power in the upstream network—is directly reflected at the GTTPL 400 kV bus. As a result, the bus voltage crossed the preset threshold of the Over-Voltage Protection scheme.
This triggered the automatic tripping of the 400 kV Xeldem–Mapusa Circuit-2, which subsequently led to the tripping of the downstream 220 kV Xeldem–Xeldem Circuits-1 and 2, as per the configured protection logic.
The affected circuits tripped at 17:32 hrs and were restored at 19:16 hrs after system parameters were normalised. During the nearly two-hour interruption, approximately 150 MW of power supply remained affected, impacting system reliability and supply continuity.
