Managing Fault Current in Electrical System: Switchgears and Transformers

 

Adjusting transformer impedance can help reduce the fault current of low voltage switchgear2. 

The transformer impedance is determined by short-circuiting the transformer secondary and increasing the voltage on the primary until full load current flows. However, it is important to note that decreasing the transformer impedance while increasing the efficiency can have a downside, which is the tendency to increase the fault current3. Therefore, adjusting transformer impedance can be an effective method to reduce the fault current of low voltage switchgear, but it should be done carefully to avoid any negative consequences.

How does transformer impedance affect fault current in Low Voltage Switchgear

Transformer impedance affects fault current in low voltage switchgear. Transformer impedance is determined by short-circuiting the transformer secondary and increasing the voltage on the primary until full load current flows1. By increasing the transformer impedance, the fault current can be reduced2. The added impedance of the transformer reduces the arc fault current in the event of an arc flash in the switchgear2. However, it is important to note that faults in low voltage bus structures are not self-clearing, and fault arcs do not show the drastic current-limiting effect which they are frequently assumed to exert upon short-circuit currents4. Therefore, while adjusting transformer impedance can help reduce fault current in low voltage switchgear, it is not the only factor that affects fault current.

What is the relationship between fault current and switchgear Selection

The relationship between fault current and switchgear selection is that the selection of switchgear is based on the calculation of possible fault current in the system1. The maximum fault current that can occur due to a fault in the system is necessary to find out for the proper selection of circuit breaker2. The fault current interrupting device is the switchgear or the circuit breaker, and it should withstand the dynamic effects of short circuits3. The short-circuit withstand current rating of the circuit breakers used in the switchgear should coordinate with the short-circuit rating of the switchgear4. Therefore, the fault current is an important factor to consider when selecting switchgear for a particular application.

What is the importance of fault current analysis in switchgear Selection

Fault current analysis is important in switchgear selection because it helps to determine the possible fault current in the system123. Fault current is the abnormal amount of current flowing in a circuit to the location of a short-circuit, and the magnitude of the fault current is decided by the impedances of the network components1. The proper selection of switchgear in any application requires the calculation of possible fault current in the system1. Fault current calculations are necessary to properly select the type, interrupting rating, and tripping characteristics of protective devices45. Therefore, fault current analysis is a crucial step in switchgear selection to ensure that the switchgear can operate under fault events and protect the rest of the power system from fault currents.