Critical infrastructure components are digitally controlled and operate alongside setups of interconnected machinery, computers and network devices, i.e. as cyber-physical systems. As such they became a frequent target of cyber-attacks. In this paper we investigate the physical impact of time delay attacks on Industrial Control Systems (ICS) protocols. The study is conducted using a testbed emulating a power generation station. Its generating facility consists of low-power machinery, however, the rest of the instrumentation (real-time programmable logic controllers (PLCs), sensors, actuators, and network devices) are fully consistent with the instrumentation that could be found in industry. To simulate a time delay attack over the network, the Dummynet kernel module is used. Our experimental results show how a time delay attack can affect control system performance and may result in a failure of the entire power generation facility.