Basler UFOV 250A/260A protection module

2. Circuit breaker reset and fault analysis

After the circuit breaker trips, it needs to be manually reset before it can be put back into operation. If the circuit breaker repeatedly trips after load shedding, the most likely reason is that the overvoltage setting value is too low, causing the transient overvoltage peak value to touch the trip threshold when the load suddenly changes. At this point, the setting value should be adjusted appropriately to be higher than the normal transient peak, while ensuring that it does not exceed the equipment's tolerance limit.

3. Special applications of bipolar circuit breakers

When the regulator is SR-A series (using "A" terminal) or SR-F/SR-H series (using "F0" terminal), a bipolar circuit breaker (P/N 05391) must be used to simultaneously cut off both power lines and achieve complete isolation. The external dimensions of the bipolar circuit breaker are shown in Figure 3-3 of the manual.

Installation and Wiring Engineering Guide

1. Installation position and direction

The module can be installed in any direction without affecting performance. The installation method of the backboard should refer to Figure 3-1 for drilling and fixing. The circuit breaker is an independent component, installed in the appropriate position on the panel or cabinet according to Figure 3-2/3-3.

2. Change the voltage tap connection

If the input voltage is not 120V, the module needs to be opened and the wire connecting the primary of the transformer needs to be changed from the "120" tap to the corresponding tap (208/240/416/480/600). Be sure to disconnect all power sources when changing connections.

3. Coordination with EMI filters

When the system is equipped with an EMI filtering package (such as EMI 248/208), the N terminal of the UFOV module must be directly connected to the F+terminal of the regulator (or the F+terminal of the filter), and this connection must not be grounded. Please refer to Figures 3-8 and 3-9 for detailed wiring.

4. Key points for wiring verification

The manual provides wiring diagrams for up to 6 different regulator series (Figure 3-4 to Figure 3-9), including SR4A/SR8A, SR32A, SR4F/SR8F, SR32F, etc. When replacing on site, it is necessary to check each line according to the corresponding model's drawing, paying special attention to the differences in terminal definitions between UFOV 250A (new part number 9 1051 00 106) and the old model (9 0400 00 104): the old model uses terminals 3, 4, and 6, while the new model uses P, C, D, and N. Terminal N is newly added and used to connect the common end of the circuit breaker coil (see the terminal comparison table on page 15 of the manual for details).

On site tuning and functional verification

1. Underfrequency action verification

Start the generator to the rated speed, and the regulator works normally.

Slowly reduce the speed of the prime mover and observe that when the frequency drops to the rated value minus 4-7 Hz, the terminal voltage should start to decrease according to the curve in Figure 1-1.

If the voltage does not decrease, check if the wrong model (50/60Hz) is selected or if the input voltage tap is incorrect.

If the voltage drops too early or too late, it is necessary to confirm whether the action threshold is within the 4-7 Hz window (this threshold is fixed and cannot be adjusted, and if there is a deviation, the module needs to be replaced).

2. Overvoltage setting adjustment

The overvoltage potentiometer (located inside the module and usually labeled as "OV ADJ") can be adjusted within the range of 125% to 150%.

Recommended tuning steps: Run the generator without load, gradually increase the excitation to raise the voltage to 135% of the rated value (or target value), slowly adjust the potentiometer until the circuit breaker just trips, and then slightly adjust it back (about 2-3% margin) to avoid normal transients.

During the load rejection test, if the circuit trips, the setting value needs to be increased.

3. Dynamic performance considerations

The manual clearly states that overvoltage circuits are sensitive to voltage change rates - instantaneous spikes during load shedding may be higher than the steady-state set point. Therefore, the setting value should be adjusted based on the transient characteristics of the system, and if necessary, an oscilloscope can be used to observe the load shedding waveform to determine the optimal threshold.

Troubleshooting Logic and Typical Cases

Chapter 4 of the manual provides a troubleshooting table for the system. The following are typical fault scenarios and processing procedures:

Fault phenomenon 1: Underfrequency circuit malfunctions at normal speed

Inspection steps: ① Check if the model matches the system frequency; ② Check if the input voltage is at the correct tap; ③ Replace the module.

Root cause: Mostly due to model mismatch (50Hz module used for 60Hz system, action threshold offset).

Fault phenomenon 2: The frequency has dropped to the operating zone, but the voltage has not decreased

Inspection steps: ① Verify the model and input voltage; ② Confirm that the frequency is indeed below the threshold (4-7 Hz); ③ Check if the wiring is complete (especially if the control terminals P/C/D/N are connected to the corresponding end of the regulator); ④ Replace the module.