Asc 45 D10/3/H 0 (12.31)
whereDis the diameter of the tunnel (in m).
The maximum upsurge and downsurge should be contained within
the chamber. For simple surge tanks the following equations may be used
to calculate these maximum surges. For a sudden 100% load rejection,
maximum upsurge
Z*max 1 2 K*0/3K^2 *0/9 (for K*00.7), (12.32)
whereZ*Z/Zmax, K*0P 0 /Zmax,ZmaxQ 0 /Asrandr(gAt/LtAs)1/2, and
maximum downsurge
Z*min 1/(1 7 K*0/3). (12.33)
For a sudden 100% load demand, maximum downsurge
Z*max 1 0.125K*0 (forK*00.8) (12.34)
whereZis the surge amplitude with respect to the reservoir level, Asis the
cross-sectional area of the surge tank and P 0 is the head loss in the tunnel.
The range of surge levels (amplitudes) must not be too large to minimize
the governing difficulties. The maximum upsurge and downsurge are com-
puted for extreme conditions, i.e. the top level of the surge chamber is
governed by the maximum upsurge level when the reservoir level is at its
maximum and the bottom level of the chamber is controlled by the
maximum downsurge level when the reservoir is at its lowest drawdown
level.
526 HYDROELECTRIC POWER DEVELOPMENT
Fig. 12.20 A typical power plant layout: steady state conditions
