*3.3.3. Emergency control procedures*

Since WSS are spatially distributed, the power supply of valves and pumps in different parts of the system is delivered by a nearly-independent power supply. Therefore, local con‐ trol systems may continue operating normally, after a power failure has occurred some‐ where else in the network. The control systems may have a positive or negative effect on the propagation of hydraulic transients. The distributed nature of WSS and the presence of con‐ trol systems may be exploited to counteract the negative effects of emergency scenarios.

If a centralised control system is available, valves may start closing or other pumps may ramp up as soon as a pump trip is detected. Even without a centralised control system, emergency control rules may be developed to detect power failures. These emergency con‐ trol rules should be defined in such a way that false triggers are avoided during normal op‐ erations. An example of an emergency control rule is: *ESD valve closure is initiated if the discharge drops by more than 10% of the design discharge and the upstream pressure falls by at least 0.5 bar within 60 seconds.*
