What is Power Line Transient?
A power line transient is a temporary rise in voltage &/or current on an electrical power line (or) system that can harm electrical and electronic equipment linked to it. It may affect AC & DC systems.
Electrical transients can also travel via data or communication links. Power line transients are caused by
- Load Switching,
- Capacitor Bank Switching,
- Device Failures,
- Power Grid Switching,
- Inductive Load Interruption,
- Relay Contact Bounce,
- AC/DC Switching Operation,
- Circuit Breakers Switched,
- Lightning Discharges, etc.
Power line transients are destructive high voltages (a few volts to several thousand volts) that drive significant currents in low-voltage electrical systems/circuits for a few microseconds to several milliseconds.
These transients are temporary and unwanted.
Ex: If an inductive load is abruptly interrupted by switching operation, the magnetic field collapses, causing voltage impulses (or) transients
E = - N × dϕ/dt
E = - L × di/dt
Higher current change rates cause greater transient voltage spikes.
Transient voltages in the KV range can severely harm electrical and electronic devices near the line.
On transmission lines, cables, bus sections, etc., power line transients (switching & lightning surges) travel at light speed (3 x 108 m/s).
Line transients are termed as conducted electromagnetic interference/disturbances.
Due to capacitive, inductive, and radiated electromagnetic disturbance (EMI), these transients can couple with surrounding power lines, data cables, & communication lines.
Power line transients can interfere (i.e., induce overvoltage) with connected and nearby electrical & electronic devices, such as
• Computers,
• Telecommunication equipment,
• Sensitive electronic circuits, and others,
causing malfunction or failure.
Electromagnetic compatibility (EMC) is the study of how electrical and electronic devices operate in their electromagnetic environment without interfering with or being impacted by other devices.
The electromagnetic compatibility of electrical and electronic devices connected to power line/system can be affected by power line transients.
Products must be developed and tested to tolerate EMI, such as power line transients, to be electromagnetically compatible.
Utilizing surge protection devices, correct grounding and shielding during device design and production, and EMC norms and regulations may be required.
Power line transient related to EMC must be considered in electrical and electronic system design, installation, & operation to ensure reliability and interference-free operation.
Types of Transients
According to IEEE 1159, Transients divides into
- Impulsive Transient and
- Oscillatory Transient.