1.LCD interface

1.1. Main menu interface As shown in figure 1.

Figure 1. Main menu

When the tester is started up, the main menu will be displayed as shown in figure 1.

There are 8 function options, namely parameter setting, three-phase TTR, three-phase turns ratio, single-phase transformer, Z-type transformer, Scott transformer, Anti-Scott transformer, history data, which can be chosen by pressing "↑", "↓", "←", "→", and the chosen item will be displayed highlightedly, then press "Enter" to enter into corresponding function; State parameters is displayed at the top of screen, including program version No.,date, time etc. Voltage amplitude and residual capacity of internal battery are displayed at the top of screen at the same time, in order that operator can observe the state of instrument battery at any time. In case finds battery with insufficient voltage, he can charge it timely; Prompts bar is located at the bottom of screen, which is aimed at providing simple operation prompts to user, so that user can operate it correctly.

2．Parameter setting screen

Press "parameter setting"function, enter into the screen of parameter setting at first, as shown in figure 2.

The items, need to be set on the parameter setting screen, include testing sample No., rated turns ratio, tapping amount, equal tapping level, date setting, time setting etc..Prompts bar is located at the bottom of LCD, to prompt operator how to operate. On the interface as shown in figure 4, press "↑" and "↓" to move cursor; press "Enter", then the color of chosen parameter will be changed, at this time press digit key to input required parameters and press "Enter", the setting parameter take effect and color of the parameter items return to normal; after parameter setting, press "Exit" to return. The meaning and function of each parameter item are as follows:

Testing sample No.: the No.of transformer (to be tested), it can be input not more than 6 digits.

Rated TTR: at rated gear, the voltage turns ratio value of transformer (to be tested) on the high voltage side and low voltage side.

Equal tapping level：voltage percent regulated at each gear of transformer.

Date setting: to set current date.

Time setting: to set current time.

3.Three-phase transformer turns ratio test

Figure 3. Prompts screen of 3-phase TTR test connection

   Set parameter before 3-phase transformer turns ratio test. Press "Set" or choose "Parameter setting" item, then press "Enter" to parameter setting screen, after parameter setting, press "Exit" to return to main menu interface, choose "3-phase transformer turns ratio test" item and press "Enter" to connection prompts screen (as shown in figure 3). Detailed connection diagram is displayed on the screen, so that operator can connect wire according to the shown diagram.

After connection, press "Enter" to test automatically. When the automatic counting of test is up to 57 times, the counting will cease automatically. At the time, testing is over and its results will be displayed. Screen of prompts bar and testing results is shown as figure 4.

Figure 4. Screen of 3-phase transformer turns ratio testing results 

   After testing, its result will be displayed on LCD, as shown in figure 6: data of testing is displayed on the left side of screen, including 3-phase voltage value on the HV side, 3-phase voltage value on the LV side, phase angle between 3-phase HV and LV(the above items are the data of testing process), current tapping TTR value of each phase, 3-phase actual measuring rated TTR, error percent of 3-phase TTR, group judgment, times of testing count, and testing state. Vector diagrams of each setting parameter and group are displayed on the right side of screen, as shown in figure 6: when the current group is zero point, angle and direction of HV side vector diagram(see figure 3: big triangle in the outer ring) coincide with LV side vector diagram(see figure 6: big triangle in the inner ring). After testing, press "Save" to store testing results. Press "Exit" to return; press "Enter" to test again.