What is Overvoltage?
Overvoltage is the state in which the voltage in an electrical system exceeds its normal rated level.
This unexpected voltage spike may be transitory or transient, and if not managed, it can cause catastrophic damage to electrical equipment.
Overvoltage occurrences are particularly hazardous to sensitive electronics, control systems & industrial equipment.
Causes of Overvoltage
Overvoltage can arise for a variety of causes.
Lightning strikes if direct (or) indirect, are a primary source of high-energy surges entering the system.
Overvoltages can also be generated during switching processes such as
- Capacitor bank switching,
- Motor starting, and
- Circuit breaker operations.
Network problems such as short circuits and neutral failures, contribute to unexpected voltage spikes.
Additionally, electrostatic discharges can cause localized overvoltage problems in sensitive circuits.
Characteristics of Overvoltage
Overvoltages are distinguished by their extraordinarily quick rising time, which is commonly measured in kilovolts per microsecond.
They emit harmful quantities of energy which can damage insulation, limit device life and create problems.
Because overvoltage accidents can occur repeatedly, they hasten the premature aging of electrical equipment and might cause irreparable damage if no safety is provided.
Types of Surge Protection Devices (SPD)
Surge Protective Devices are categorized into three categories.
- Type 1 Devices are utilized in installations with external lightning protection systems such as lightning rods (or) mesh cages & are intended to discharge direct lightning currents.
- Type 2 Devices are the most prevalent, mounted on the main distribution board (MDB) to protect against switching surges & indirect lightning strikes.
- Type 3 Devices are additional protectors positioned near sensitive equipment to provide local protection when the distance from the main SPD exceeds thirty meters.
Installation
Surge protection requires careful installation procedures. Surge arresters are connected in parallel with the power supply and should be located as close as possible to the equipment they safeguard.
Cable lengths must be kept as short as possible, ideally fewer than fifty centimeters, because each meter of cable might cause additional overvoltage during a surge.
Proper earthing & bonding are required for successful surge dissipation & the cable cross-section must meet standard criteria.
Upstream Protection
Surge arresters are meant to divert transient currents to ground in microseconds, however they cannot handle long-term overvoltage conditions such as phase-neutral inversion (or) neutral failure.
For this reason, an upstream protection device, such as a circuit breaker (or) fuse should always be present.
This breaker is selected based on the installation’s short-circuit withstand capacity and the surge arrester’s maximum discharge current rating.
Proper synchronization between the surge arrester & its upstream protection provides both safety and service continuity.
Longevity of Surge Protective Devices
A surge arrester’s lifetime is determined by the number and intensity of the surges it absorbs. Repeated exposure gradually diminishes its efficacy.
Most current devices include an end-of-life indicator which indicates when the arrester is no longer functional and must be replaced.
Regular inspection and replacement are required to ensure reliable protection.
Overvoltage protection is essential for guaranteeing the safety and dependability of electrical infrastructure.
Electrical systems can be protected against lightning strikes, switching surges & other overvoltage occurrences by selecting the appropriate type of surge protective device assuring proper installation and providing adequate upstream protection.
This not only protects against equipment damage & costly downtime, but also ensures long-term operational safety.
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