Surge Impedance
If the line is loss-less, i.e. the resistance and conductance are zero, then the characteristic impedance reduces to √(L/C), a pure resistance. When dealing with high frequencies or with surges due to lightening, losses are often neglected and surge impedance becomes important.
Surge Impedance Loading (SIL)
It is the power delivered to a line by a purely resistive load equal to its surge impedance. When so loaded, line supplies a current of
Current is in Amperes (A) and |V| is line-to-line voltage at the load. Since, load is pure resistance,
in Watts (W)
or, with |V| in kVs,
It is sometimes convenient to express power transmitted in terms of per unit of SIL, i.e, the ratio of power transmitted to the surge impedance loading. For eg., permissible loading may be expressed as a function of SIL, and SIL provides a comparison of load carrying capabilities of lines.
If the line is loss-less, i.e. the resistance and conductance are zero, then the characteristic impedance reduces to √(L/C), a pure resistance. When dealing with high frequencies or with surges due to lightening, losses are often neglected and surge impedance becomes important.
Surge Impedance Loading (SIL)
It is the power delivered to a line by a purely resistive load equal to its surge impedance. When so loaded, line supplies a current of
or, with |V| in kVs,
It is sometimes convenient to express power transmitted in terms of per unit of SIL, i.e, the ratio of power transmitted to the surge impedance loading. For eg., permissible loading may be expressed as a function of SIL, and SIL provides a comparison of load carrying capabilities of lines.
In other way
1) Transmission lines produce reactive power depending on line's capacitive reactance and the voltage at which the line is working at.
2)Transmission lines also absorb reactive power. This depends on the current that flows in the line and the line's reactance.
So Surge Impedance loading of a line is just the MW loading at UPF when
reactive power used = reactive power produced
