Advanced Three-Phase Winding Resistance Meters – Overview

The TWA Standard series has LCD displays. Both models are capable of testing six transformer windings with a one-time cable connection, as well as three-phase automatic transformer demagnetisation. The stored magnetic energy is safely and automatically discharged at the end of the test. The built-in tap changer control unit enables automated test mode, where the instrument operates the tap changer without operator input and records winding resistance results based on pre-selected stabilisation criteria. Both models can output test currents from 5 mA to 30 A DC for the purpose of winding resistance measurement. TWA40D has a special test mode for checking the synchronisation of on-load tap changers with three phases simultaneously tested in parallel, in which the total test current can rise to up to 40 A DC. The unique DVtest method enables checking the moving contacts of on-load tap changers during the transition, measuring the transition time, detecting open circuits, and many other types of faults. It is performed with a 0.1 ms sampling rate, simultaneously with the measurement of the tap changer motor current, which helps with the detection of motor and mechanical issues. An algorithm is used for testing tap changers connected through a built-in series (booster) transformer. The DVtest can be performed either on one phase or on three phases simultaneously. It can also be performed as an additional test, simultaneously with the winding resistance test in all tap positions.

Advanced Three-Phase Winding Resistance Meters  – Features

• Resistance measurement of all tap positions in all six windings performed in a single test
• True three-phase on-load tap changer (OLTC) DVtest (dynamic resistance measurement)
• Quick measurement, single-step cable setup
• Rapid automatic demagnetisation
• Fully automated test mode
• Built-in tap changer control unit
• Temperature measurement channel