A New Digital Relay for Dispersed Storage and generation (DSG) Units
Brown, Dewayne Randolph
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A dispersed storage and generation system consists of both a source of energy for conversion to electricity and a means to interconnect this unit to the electric utility system. Most dispersed generators connected to the utility distribution system are less than 5 MW. A new emerging problem arises when a utility circuit breaker is opened while a capacitor-bank bus and load bus is energized very near a dispersed storage and generation unit. A new resonant- detecting relay will be developed that has the ability to trip if dangerously high off-nominal frequency voltages are produced at the capacitor-bank bus or load bus during this condition (self-excitation). Self-excitation may lead to severe overvoltages, and may induce undesirable transients in neighoring circuits (low power and control circuits being particularly vulnerable) on the connected network. It can create harmonics that can fail surge arrestors or cause transformer saturation. The new relay will be able to detect this condition at the inter-tie and trip the cogeneration facility. In order to make this multifunction relay cost effective, it includes protection functions for traditional relay functions such as directional inverse time-delay overcurrent, directional instantaneous overcurrent, islanding, loss-of- excitation, differential, overfrequency, underfrequency, overvoltage, undervoltage, negative-sequence current, check-synchronism, and directional power. Also, the new relay will have metering capability.
- Doctoral Dissertations