|
https://voltage-disturbance.com/power-engineering/broken-delta/#:~:text=Broken%20delta%20refers%20to%20the,fault%20detection%20of%20ungrounded%20systems.
Broken Δ refers to the connection of Voltage Transformers (VT) or Potential Transformers (PT) in a series fashion to calculate the zero-sequence voltage of the system. Three VTs are required for this connection. This connection is primarily used in ground fault detection of ungrounded systems.
When a ground fault occurs in an ungrounded system, the fault current will be close to zero making it difficult to locate and isolate ground fault using traditional ground overcurrent relay. A parameter that can be used to our advantage in the detection and isolation of ground fault on ungrounded system is the zero-sequence voltage during ground fault.
When a single line to ground fault occurs on ungrounded system, the faulted phase voltage will collapse to zero while the other two phases remain healthy. From sequence components theory, we know that when we add the three phase voltages, we get three times the zero-sequence voltage (V0). This is sometimes also referred to as 3V0 protection though the term is not very common.
Flip on the left SPST switches on the primary side of the transformers to activate the broken Δ transformer.
On the secondary side of the transformers, a changeover relay is placed. When there's no ground fault, the green LED will emit light.
When 1 of the SPST swithes, on the top right is switched on, the voltage on the secondary side of the transformers will be high enough to trip the relay. Now, the red LED will emit light.
|
