Voltage Transient
Voltage transients refer to sudden and brief spikes in voltage that can range from just a few volts to several thousand volts, lasting from microseconds to milliseconds. Unlike short-term overvoltages (swells), which persist for several cycles, voltage transients are much shorter in duration, typically occurring in less than half a cycle of the voltage waveform. Despite their short lifespan, voltage transients can have high magnitudes, making them potentially more damaging to electrical equipment, especially by degrading insulation and other sensitive components.
Causes of Voltage Transients
The primary source of voltage transients is external events that cause a sudden release of stored energy within the power network. Common causes include:
- Lightning Strikes: A direct or nearby lightning strike can induce a powerful transient in the electrical network, potentially affecting equipment even when not directly hit.
- Switching Operations: Actions such as switching transmission lines or transformers in or out of service can generate transients by releasing stored electrical energy.
- Capacitor Banks: The sudden switching of capacitor banks can lead to voltage transients, disrupting the network.
- Electric Arc Furnaces: Industrial operations like electric arc furnaces generate significant transients due to the electrical arcs they create.
- Loose or Faulty Connections: Poorly maintained or faulty electrical connections can cause irregular voltage changes, leading to transients.
Preventing Voltage Transients
To mitigate the risks of voltage transients and protect equipment from potential damage, the following strategies can be employed:
a) Preventing Transient Propagation
One of the most effective methods of mitigating voltage transients is to prevent their spread at the source. Installing surge protection devices (SPDs) or similar protective equipment can help. For instance, installing a surge protector at the terminal of an electric arc furnace can block the transient from propagating through the network. Surge protectors need to be appropriately rated and fast enough to respond to transient spikes.
b) Recording and Monitoring Transients
Continuous monitoring of the network is crucial for identifying and addressing transient issues. Power quality analyzers can record essential data, such as:
- Time and date of the event
- Duration of the transient
- Intensity and magnitude of the transient
- Voltage and current waveforms during the transient
These recordings help diagnose the root cause of the transient and assist in determining the appropriate protective measures. Since each type of transient has a unique signature in its voltage and current waveform, this data can be invaluable in preventing future incidents.