Differential Relay SPAD 330

Outdated product since 2009.

The differential relay SPAD 330 C is designed to be used as a fast interwinding short-circuit and interturn fault protection for two-winding power transformers and power plant generator-transformer units. The relay is also adopted for three-winding power transformers provided that the power transformer is characterized by a unidirectional flow.


  • Three-phase biased differential relay for the protection of power transformers and generator-transformer units.
  • Matching of the power transformer vector group with DlL switches and the electronics. No intermediate current transformers are needed.
  • The transforming ratio errors of the C.T.s separately correctable on the HV and LV side of the power transformer.
  • Separately adjustable differential current high-set instantaneous stage.
  • Stabilized operating principle prevents spurious function on faults occurring outside the area of protection.
  • Blocking function, for prevention of spurious operations caused by connection inrush currents, based on the occurrence of the second harmonic.
  • Local display of measured and set values on relay front panel.
  • Continuous self-supervision of the electronic circuitry and the operation of the microprocessor.

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    ABB contact for United States of America

    Sales: Paula Ortiz
    Service: Rolando Solis
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