The HRU harmonic restraint relay is a high speed relay used for the supervision of differential, overcurrent, or pilot relays. It is applied in various transformer protection schemes to provide security against false tripping on transformer magnetization inrush.

HARMONIC-RESTRAINT UNIT (HRU) The harmonic restraint unit of the HU and HU-1 relays consists of an air-gap operating transformer, a second harmonic block filter, a fundamental block-second harmonic pass filter, two full-wave rectifiers, indicating instantaneous trip unit, varistor, and a dc polar unit.

The type HRU relay is connected to operate for faults internal to the differential zone of the transformer but not on magnetizing inrush currents associated with energization of the transformer. Magnetizing inrush current waves have various wave shapes. A typical wave appears as a rectified half wave with decaying peaks.

The type HRU harmonic restraint relay is a high speed relay used for supervising overcurrent, differ-ential or pilot relays to avoid magnetizing inrush trip-ping.

ough-current restraint in the relay. This application can safely be made only when the additional circuit has no in-feed or is at best a very weak source an needs

2021年3月8日 · 对HRU Definition四个选项的解释如下： Dominant Land Use,Soil,Slop:每个子流域中只有一个HRU,子流域里面积比最大的Land Use,Soil,Slop将会参与模拟。

ABB HRU Electromechanical relay instruction, support, forum, description, manual

2024年4月5日 · Test the relay in the case if possible. Make small adjustments to the left then the right and then the left and then the right... Until the unit is calibrated. The time to trip is directly proportional to the final distance of the left and right contacts to the moving contact. page 9 of the attached shows time characteristics.

Type HU, HU-1 and HU-4 Transformer Differential Relays These instructions are supplementary to the HU and All possible contingencies which may arise during installation, operation or maintenance, and all details and

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