Protection and Control

The DTP is a digital relay that provides high-speed differential and backup instantaneous differential three-phase protection for power transformers with two, three or four windings.

Differential Protection

For high-magnitude external faults, the DTP uses a current differential with percentage restraint to compensate for unbalance caused by variation in CT outputs. The DTP differential unit has programmable dual-slope percentage restraint with adjustable slope breakpoint. Discrete Fourier Transformation (DFT) provides excellent frequency filtration, making the differential current measurement immune to noise, DC components and wave distortion. This gives the digital DTP relay a clear advantage over other analog and hybrid models. The algorithm used to calculate the RMS value permits a high level of accuracy in the through current measurement. Phase Shift Compensation Internal compensation is selected to adjust for the phase shift across the protected transformer. This selection allows the DTP to make the proper phase adjustments to the applied currents and eliminates the zero-sequence component of the current. Conventional external compensation can also be selected. This setting is useful for testing the relay with single and three-phase test sources that supply in-phase currents.

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