DL/T 294.3-2019Specification for equipment of de-excitation and overvoltage protection for generators Part 3��Rotor overvoltage protection (English PDF)

4.1 Operating environment requirements

a) Ambient temperature. -5°C~45°C.

b) Relative humidity. is not higher than 95% (no condensation).

c) The altitude does not exceed.2000m (relevant parameters should be revised if it exceeds.2000m).

4.2 Basic requirements

4.2.1 The insulation resistance value of the rotor overvoltage protection device should not be less than 1Mohm. For the measurement method, refer to DL/T 489.

4.2.2 The withstand voltage of the rotor overvoltage protection device and the circuit connected to the rotor should not be lower than the rotor withstand voltage level;

4.3 Rotor overvoltage protection setting value

4.3.1 Should be higher than 1.2 times of the peak value of the normal maximum output voltage of the rectifier bridge;

4.3.2 Should be lower than 0.95 times of the reverse repetitive peak voltage value of the rectifier bridge thyristor;

4.3.3 Should be higher than the maximum voltage on the excitation winding during de-excitation;

4.3.4 It should be ensured that the instantaneous value of the overvoltage at both ends of the excitation winding is not higher than 70% of the voltage amplitude of the winding-to-ground withstand voltage test.

4.3.5 For units that allow asynchronous operation, it should be higher than the maximum voltage on the excitation winding during asynchronous operation.

4.4 Selection of overvoltage protection components

4.4.1 The voltage value when the component is operating should not be higher than the setting value of the jumper; it should not be lower than the voltage amplitude of the winding-to-ground withstand voltage test during the factory test.

50% (no requirement when de-excitation and over-voltage protection are shared).

4.4.2 Non-linear resistors should be used for overvoltage protection components;

4.4.2.1 Using zinc oxide non-linear resistance.

a) The design value of the zinc oxide resistance charge rate is generally not greater than 0.6, when it is greater than 0.6, a jumper should be configured;

b) Other requirements shall comply with DL/T 294.2.

4.4.2.2 Using silicon carbide nonlinear resistance.

a) Jumper should be configured;

b) Can be shared with demagnetization resistance.

4.5 When the instantaneous overvoltage is greater than the rotor overvoltage protection setting value, the overvoltage protection circuit should be turned on. When the overvoltage disappears, the overvoltage protection the protection circuit should be automatically shut off.

4.6 The rotor overvoltage protection device should have an overvoltage action alarm signal output function.

4.7 Electronic jumper.

a) When the over-voltage protection element is zinc oxide, the electronic jumper should adopt the parallel connection of forward thyristor and reverse diode;

b) When the over-voltage protection element is silicon carbide, the electronic jumper should be connected in parallel with thyristors in the forward and reverse directions;

c) The rated voltage of the thyristor and diode should be higher than the maximum voltage that the jumper circuit can withstand;

d) Thyristors and diodes should be able to withstand the current flowing through various rotor overvoltage protection actions;

e) The operating voltage value of the jumper should be higher than the voltage value when the overvoltage protection element is turned on.

4.8 Temperature rise of rotor overvoltage protection device

a) The maximum temperature rise of over-voltage protection components should not exceed 80K, and the temperature rise of other components should not exceed the allowable temperature rise of the product itself;

b) The maximum temperature rise of the jumper control board is not more than 30K.

5.1 Insulation withstand voltage test

The voltage value of the insulation withstand voltage test is shown in Table 1, and the test method is shown in DL/T 489.

5.2 Non-linear resistance test

Refer to DL/T 489 implementation.

5.3 Rotor overvoltage setting test

Refer to Appendix A for the test method of rotor overvoltage setting value.

6.1 Type test

Type test should be carried out when one of the following conditions exists.

a) When the device is finalized;

b) When changes in device design, technology or materials used will affect product performance;

c) When the device resumes production after a long-term shutdown;

d) When requested by the national quality supervision agency.

6.2 Factory test

The rotor overvoltage protection device should be tested before leaving the factory.

6.3 Handover test

The handover test should be carried out before the rotor overvoltage protection device is put into production.

6.4 Periodic inspection test

According to the unit maintenance cycle arrangement or according to the operation of the device, regular inspections and tests should be carried out.

6.5 Test items

6.5.1 Non-linear resistance test

a) The zinc oxide resistance handover test and periodic inspection test items are shown in Table 2, and the type test and factory test items are shown in DL/T 294.2.

b) SiC resistance handover test and regular inspection test items are shown in Table 3, type test and factory test items see DL/T 294.2.

Note. When using silicon carbide resistors, the test is carried out in accordance with the manufacturer's relevant standards.

6.5.2 Electronic jumper test items

The jumper test items are shown in Table 4.

8.1 Packaging

When packaging, sealed plastic products should be used as the inner packaging, and the surrounding should be cushioned with shockproof materials and placed in the outer packaging box. The packaging of the device should conform to the provisions of GB/T 191.

8.2 Transportation

Transportation should comply with the regulations of GB/T 191.

8.3 Storage

According to DL/T 294.2 regulations.

Appendix A

(Informative appendix) Rotor overvoltage setting value test method A.1 Test method for overvoltage setting value of zinc oxide resistor rotor

a) Check whether the installation and assembly of various components in the product meet the requirements of the product's drawings and process; check the electroplated parts and spray the surface quality of painted parts and plastic parts, if there are scratches, bumps and deformation.

b) Use a voltage regulating transformer and apply a test voltage to both ends of the overvoltage protection branch through the step-up transformer, adjust the voltage regulator steadily, and observe the oscilloscope Calculate the over-voltage protection setting value, compare with the design value, check the accuracy of the over-voltage protection action voltage value, and the actual over-voltage protection the deviation between the set value and the design value should not exceed ±10%. The test wiring is shown in Figure A.1, and the action waveform diagram is shown in Figure A.2.

A.2 Test method for overvoltage setting value of silicon carbide resistor rotor

a) Check whether the installation and assembly of various components in the product meet the requirements of the product's drawings and process; check the electroplated parts and spray the surface quality of painted parts and plastic parts, if there are scratches, bumps and deformation.

b) Use a voltage regulating transformer and apply a test voltage to both ends of the overvoltage protection branch through the step-up transformer, adjust the voltage regulator steadily, and observe the oscilloscope Calculate the over-voltage protection setting value, compare with the design value, check the accuracy of the over-voltage protection action voltage value, and the actual over-voltage protection the deviation between the set value and the design value should not exceed ±10%. The test wiring is shown in Figure A.3, and the action waveform diagram is shown in Figure A.4.

Figure A.3 Wiring diagram of silicon carbide rotor overvoltage action value test

Figure A.4 Schematic diagram of rotor overvoltage action waveform