Series‐compensated transmission lines utilize series capacitors to cancel a portion of the inductive reactance of the line, thereby improving the power transmission capability of the line.
Do series capacitors affect the overall protection used on series compensated lines?
A discussion of their effect on the overall protection used on series compensated lines. First, however, a brief review will be presented on the application and protection of series capacitors. Series capacitors are applied to negate a percentage of and hence reduce the overall inductive reac-tance of a transmission line.
Why are series capacitors used in transmission systems?
Load Division among Parallel Line – Series capacitors are used in transmission systems for improving the load division between parallel lines. When the new line with large power transfer capability is paralleled with an already existing line, then it is difficult to load the new line without overloading the old line.
Series capacitor banks consist mainly of the capacitors as well as their protection system and function to increase power flow on an existing system by reducing line impedance. Their first application dates back to 1928 when GE installed such a bank – rated 1.2 MVar – at the Ballston Spa Substation on the 33 kV grid of New York Power and Light.
Distance protection is widely used in transmission lines, but it can be strongly affected by series capacitors. This section briefly describes some special phenomena that can occur during faults in series compensated lines, and their adverse effect on distance protection.
What is a series capacitor?
Typically, series capacitors are applied to compensate for 25 to 75 per-cent of the inductive reactance of the transmission line. The series capacitors are exposed to a wide range of currents as depicted in Figure 1, which can result in large voltages across the capacitors.
As for the series capacitor, it will be pro-tected once the current levels increase beyond the protective level of the bypass equipment. The presence of the transients may also excite one or more of the natural torsional frequencies of the mechanical shaft system of the generator(s).