Video: TWR250B

Video transcript

What the TWR250B measures on a power transformer, how all its windings are connected in a single step and which tests then run without touching a cable. Testing a power transformer usually means one instrument for ratio, another for winding resistance, and a new set of cables for each test, on a large transformer that has hours of work up and down the bushings. The TWR250B connects to all the terminals once, and every test runs from there. Up to 250 V AC for turns ratio and up to 25 A DC for winding resistance.

Ratios from 0.8 to 50,000 and resistances from 0.1 micro-ohm to 100 kilo-ohms, with an internal battery for sites without mains. tests share the same connection, winding resistance, the dynamic test of the on-load tap changer, demagnetization, turns ratio, phase angle, and excitation current. The vector group is also detected automatically. connection panel has 4H sockets for the high-voltage side and 4X sockets for the low-voltage side, color-coded.

Beside them, the earth stud, the temperature input, the discharge lamp, the tap changer control and motor current sockets, the printer, and the emergency stop. In the lid, the 10.1-inch touchscreen. Test templates prepared in the office make the field work a few touches. Beside it, the USB and Ethernet interface to the PC, the flash drive port, and the socket for the safety strobe light. It ships with the PC software, the USB, Ethernet,

mains and earth cables, and a 5-meter tap changer control cable. The standard set adds 4H and 4X test leads of 10 meters with TTA clamps and the current clamp. Five, 15, and 20-meter leads, a temperature sensor, a test shunt, and a verification calibrator are options. a three-phase transformer, earth first. Then the 4H leads to the high-voltage bushings. Red to H1, yellow to H₂, blue to H3, and black to the neutral H0.

Then the 4X leads to the low-voltage side in the same colors. Every bushing is now connected. On an auto transformer, 4H and 4X leads again. The difference is the neutral. Both the H and the X neutral leads go to the common neutral bushing, H0X0. It also tests current transformers. Because the primary has only one or two turns, the leads are reversed. H to the secondary winding, X to the primary.

With no primary terminals, the X1 and X0 leads are joined and passed through the core. Winding resistance is measured with true, ripple-free direct current up to 25 amps. With all six windings connected, the instrument injects through the high and low-voltage windings on the same core limb at once, so the core saturates sooner and the reading settles faster. Four turns ratio, the instrument applies up to 250 volts to the high -voltage windings and measures the open-circuit voltages on the other side.

Pick the vector diagram and it runs the right test for star, delta, or zigzag without moving a lead and works out the deviation from the nameplate. A DC test can leave the core magnetized, and so can taking the transformer out of service. That remnants distorts later tests. The TWR250B removes it with a controlled direct current of alternating polarity, decreasing step by step down to zero. built-in control unit drives the on-load tap changer through the control cable,

and the motor current is recorded on its own channel. So one operator can test every tap position automatically, and the dynamic test records each transition with a resolution of one millisecond. Results appear as numbers and graphs on the screen, and print straight away on the 58 mm printer. The 32 GB card holds tens of thousands of results. The PC software, with free updates, exports them to Excel and builds the report in PDF.

It is made for the commissioning and maintenance of power transformers and autotransformers, three-phase and single-phase, for tap changer diagnostics, for current transformers, and for the winding resistance of motors and generators. Transformer testing from Amperis.