High speed earthing switch (HSGS) rated operating sequence according to IEC standard (for>550kv)

High - Speed Earth Switches (HSES) have two rated operating sequences:

• C–ti1–O

• C–ti1–O–ti2–C–ti1–O

where:

• ti1 represents a time period that is longer than the time needed for secondary arc extinction and for the dielectric recovery of air insulation at the fault location. ti1 is determined by users while taking system stability into account. The recommended value of ti1 is 0.15 s.

• ti2 is the intermediate time specified by the system protection. ti2 encompasses the closing time of the circuit breakers after the HSES open, the duration of a new line fault, and the breaking time of the circuit breakers. After this ti2 period, the HSES can be reclosed. The recommended value of ti2 is 0.5 s. In this situation, the HSES should be capable of operating without any intentional time delay.

The figure depicts the time chart for the rated operating sequence of C–ti1–O–ti2–C–ti1–O with a circuit breaker (CB) in the grid.

In the figure:

• Energizing of the closing circuit of the HSESs

• Current start in HSESs

• Contact touch of HSESs

• Energizing of the opening release of the HSESs

• Contact separation of HSESs

• Arc extinction in HSESs

• Fully open position of HSESs

The closing time of the HSES is typically less than 0.2 s.