How to determine CT Saturation?
- Amount of fault current
- CT Secondary Resistance
- Wire resistance that connects CT and the protection relay
- The Burden resistance of the relay.
A protection relay is to be installed to a motor with full load current rating of 290. A CT with conversion ratio of 300:5 will be used and it has a total distance of 20 meters from the relay. The wire has a resistance of 1.5 ohms per kilometers. If the CT secondary resistance is 0.09 ohms and the relay burden resistance is 0.005 ohms. Determine if the CT ratio will saturate based on the curve given below.
- CT to be used is 300 : 5
- Fault current = 3,500 Amperes
- CT secondary resistance = 0.090 ohms
- Wire distance to relay = 20 mtrs rated @ 1.5 ohms/ km
- Relay burden resistance = 0.006 ohms