Current Transformer Selection - janitza SVG Series User Manual

5.5.1 Current transformer selection

The current transformer (CT) is of considerable importance in the operation with the SVG,
which means that the selection of an external current transformer (CT) is very important.
3-phase conductor system without N-conductor:
Two CTs are required and they must be installed on phase A (L1) and C (L3) respectively.
3-phase conductor system with N-conductor:
Three CTs are required and they must be installed in the current circuits of phases A (L1), B
(L2) and C (L3).
Minimum permissible ratio of an external CT:150:5,
Maximum permissible ratio: 10000:5.
The current transformer ratio must be selected to suit the load current. To achieve more
accurate compensation, the present magnitude of the load current must be taken into
account when selecting the CT ratio. A selection of 1.5 times the maximum current in
operation is recommended, whereby a reasonable tolerance is also recommended.
Example: If the maximum detected load current is 1000 A, the best selection for the CT
ratio will be between 1500:5 to 2000:5.
The accuracy rating of the external CT should be at least 0.2 (closed loop) or 0.5 (open
loop). Poorer ratings can have a negative effect on the compensation accuracy.
The current transformer (CT) can be installed as an accessory part either in closed or open
loop configuration.
• When selecting a CT, be sure the CT ratio is supported.
• Before commissioning, check to be sure that the set-up of the "CT Ratio" on the inter-
face of the monitor is identical to the current CT ratio (see chapter 4).
NOTE
SVG 50/100
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