Consider a $$HVDC$$ link which uses thyristor based line commutated converters as shown in the figure. For a power flow of $$750$$ $$MW$$ from System $$1$$ to System $$2,$$ the voltages at the two ends, and the current, are given by: $${V_1} = 500\,kV,\,\,{V_2} = 485\,kV\,\,$$ and $$\,{\rm I} = 1.5\,kA.\,\,$$ If the direction of power flow is to be reversed (that is, from System $$2$$ to System $$1$$) without changing the electrical connections, then which one of the following combinations is feasible?

A moving average function is given by $$y\left(t\right)=\frac1T\int_{t-T}^tu\left(\tau\right)d\tau$$. If the input u is a sinusoidal signal of frequency $$\frac1{2T}Hz$$, then in steady state, the output y will lag u (in degree) by ________.

The impulse response g(t) of a system G, is as shown in Figure (a). What is the maximum value attained by the impulse response of two cascaded blocks of G as shown in Figure (b)?

The signum function is given by $$$\mathrm{sgn}\left(\mathrm x\right)=\left\{\begin{array}{l}\frac{\mathrm x}{\left|\mathrm x\right|};\;\mathrm x\neq0\\0\;;\;\;\mathrm x=0\end{array}\right.$$$ The Fourier series expansion of sgn(cos(t)) has