What is Inrush Current?
Inrush current is a residual current which exist in the transformer at the time of switching on the supply.
Such phenomenon is experienced because magnets have been placed at the transformer core and also by the fast rise and fall of voltage in the windings.
The inrush current may be several times above the transformer’s rated current; therefore, it poses several problems like voltage irregularities, tripping of circuit breakers, and even destruction of equipment if not well handled.
They reminded stakeholders of inrush current which is conspicuous in the distribution transformers during start-up or at the time of energization.
To mitigate the effects of inrush current on distribution transformers, various methods and devices can be used:
Inrush Current Limiting Devices
Prevention methods like
- Inrush current limiter,
- Reactor etc
can be employed to minimize the value of inrush current when transformer energization takes place.
They escalate the ability to regulate the rate of rise of current while reducing the disturbances introduced to the system.
Soft Starting
The application of soft starting strategies can help improve the manner which the voltage supplied to the transformer is escalated thus minimizing on the effect of inrush current.
Soft starters can be employed to reduce the amount of the inrush current and hence the impacts of the same to the electrical network.
Core Design
Due to the effect of core saturation, special core design transformers including those produced with lower saturation flux density can minimize inrush current values by reducing the levels of magnetic flux caused by energization.
The factors of the core design can also affect the inrush current level, and thus, the transformer performance.
Synchronization
This implies that when energizing several transformers in the context of a distribution system the effects of inrush current can be minimized.
This strategy of energization ensures that the transformers are energized at different time intervals thus greatly improving the prevention of simultaneous occurrence of inrush currents.
Proper Sizing
Inrush current problems can be controlled if an adequate distribution transformer for the connected load is installed.
Large transformers may, at times, carry large inrush currents, which amounts to difficulties in operations and possible system failures.
Through these strategies and taking into account distinctive features, related to inrush current in distribution transformers, operators can maximize inrush current control, reducing its impact on the systems operation and thereby, decreasing inrush current negative influence on electrical systems.