A range of core balance transformers for use with the Delta and RD range of earth leakage relays. Standard encapsulated or split-core versions are available. The lowest level of earth leakage that may be set on the earth leakage relay is determined by the size of core balance transformer selected. The transformers have two sets of windings, measurement and test.
Choice of Transformer
According to lowest value of residual current to be detected and hole diameter in which shall pass all the active conductors of line to be protected. If insulation or dimension problems for cables or bars for line to be protected do not allow to use ring current transformer, it is possible to use current transformers chosen with homogeneous errors and connected with a special transformer
Ring Current Transformer - Relay Connection
Preferably to carry out with a shielded cable; this protection is very important when high-sensitivity residual current device (I∆n ≤ 0,1A) are used. Besides, a great attention must be paid to the distance between the ring transformer and residual current device (that has to be as short as possible) and to the nearness of power conductors or other devices that may induce noise on the system. In case the shielded- conductor cable cannot be used, we suggest to twist the wires connecting the current transformer to the residual current device.
Specifications
- Primary/secondary measuring ratio : 1/700
- Primary circuit : conductors of line to be protected that cross toroid hole
- I∆n lowest current (I∆n lowest value that can be set on earth leakage relay connected with toroid) : see table.
- Test current corresponding to 6 In : Imax (shown values are valid only for conductors passing exactly in the middle of toroid).
- Ith short circuit thermal current : 90kA according to EN/IEC 61869-1, 61869-2
Insulation
- Rated voltage of the monitored circuit Un : 720V (phase-neutral)
- Rated power frequency withstand voltage : 3kV (50Hz / 1min)
- The test voltage is applied between primary, bus bar / cables and earth
- The secondary terminals connected to earth
- Rated impulse withstand voltage Uimp : 8kV 1.2/50μs
- The test voltage is applied between primary, bus bar / cables and earth
- The secondary terminals connected to earth
DIMENSIONS
