Hydro-Quebec uses real-time simulation to study line protection

Hydro-Quebec recently used its IREQ simulator to conduct real-time technical tests of three line protection systems being considered for a 500-kV series-compensated transmission system in Vietnam. The line will link Hao Binh substation at the northern tip of the country to Phu Lam substation in the south, covering 1,500 kilometers (km).

The network includes a portion of the 200-kV network located near the 500-kV substations and network equivalents valid up to 500 Hz for lower voltage levels. Two configurations of the network were studied, the first using a heavy load similar to what will be experienced during the country`s rainy season and the second demonstrating the lighter load anticipated in the dry season.

More than 7,500 faults and switching operations were simulated on each of four sections of the line with results showing that the relays offer good protection for the network. Several malfunctions were noted but most were corrected through adjustments to settings or connections.

The three line protection schemes assessed included one based on the current-differential principle and two based on impedance measurement. The performance of the current-differential-based scheme was “impeccable,” according to Hydro-Quebec, with the exception of a few reliability problems on the longest section, which stretches 496 km from Pleiku to Phu Lam.

Impedance relays also performed well, but not as well as the current-differential scheme. Also, the settings of these relays were more complex and more critical for a series-compensated line.