How and why the phase angle decreases with respect to time during faults in power system (leading to negative instantaneous frequency in the power system during the faults) ?
Siddharth Kamila During a power system malfunction, the phase angle, also known as the angle between the voltage and current waveforms, can decrease over time. This might result in a negative instantaneous frequency, referred to as a frequency dip.
1. A abrupt fall in the system's impedance during a malfunction causes the phase angle to decrease. When a failure occurs, the impedance of the system decreases, enabling greater current to flow through the system. This rise in current generates a drop in voltage, which reduces the phase angle between the voltage and current waveforms.
2. This reduction in phase angle results in a negative instantaneous frequency. A power system's frequency is defined as the number of cycles of the voltage or current waveform that occur in one second. When the phase angle falls, it indicates that the voltage waveform is lagging behind the current waveform, resulting in fewer cycles per second. The frequency falls below its usual value as a result, resulting in a negative instantaneous frequency.
It should be noted that a frequency drop is a sign of a power system malfunction, and it may occur in both balanced and unbalanced problems. It is a hazardous phenomena that can cause equipment damage as well as power outages for clients. As a result, systems are intended to detect frequency dips and isolate the problematic piece from the rest of the system.
Power system has two main energy-storing components: line/transformer/generator inductance and system capacitance. As we all know, whenever there is a change in state in a system with such energy storage components (Think L,C circuit in network analysis), there will always be some oscillation following the state change (Hence phase angle also varies).
Regarding the second part, I am not sure the frequency will always dip. Suppose, there is a large loss of load following a fault in the system. I expect the instantaneous frequency to increase.
It is not clear if your question regards the the shift of the current with respect to rhe voltage or if it regards the phase of the voltage with respect to a reference segnal.
Best regards. Giulio
- Badges
- Science topic
- Similar topics
- Engineering
- Control Theory
- Control Systems
- Control Systems Engineering