I am confused about how a residual CT arrangement on a 3wire system with 3CT's works. If the secondary of these 3 CT's are connected in a wye arrangement will there be neutal current flowing in the CT secondary neutral for unbalanced current flowing in the primary circuit due to unbalanced L-L loads causing unbalanced current in the primary?
I know that this arrangement is used for detecting ground faults because phase current will not be balanced as ground fault current will not be returning through any of the phase CT's. I would expect the same for unbalanced currents on the primary?
If there is no neutral element on the CT secondary circuit and a relay calculates this value is this done simply by vectorally adding the 3 primary phase currents. For example if the 3 phase currents are balanced in magnitude and angles then they will sum to zero when added vectorally. If these primary currents are unbalanced and have different magnitudes or angles then when adding them vectorally they will result in some magnitude representing a neutral current which would be seen by a relay. Is this correct?
How does the above now compare to a core CT or zero sequence CT around all three phases? Will this core CT see unbalanced current similar to a residual arrangement or will this CT only see ground fault current?
I know that this arrangement is used for detecting ground faults because phase current will not be balanced as ground fault current will not be returning through any of the phase CT's. I would expect the same for unbalanced currents on the primary?
If there is no neutral element on the CT secondary circuit and a relay calculates this value is this done simply by vectorally adding the 3 primary phase currents. For example if the 3 phase currents are balanced in magnitude and angles then they will sum to zero when added vectorally. If these primary currents are unbalanced and have different magnitudes or angles then when adding them vectorally they will result in some magnitude representing a neutral current which would be seen by a relay. Is this correct?
How does the above now compare to a core CT or zero sequence CT around all three phases? Will this core CT see unbalanced current similar to a residual arrangement or will this CT only see ground fault current?