DL/T 294.3-2019 in English
VALIDSpecificanon for equipment of de-excitation and overvoltage protection for generators Part 3: Rotor overvoltage protection
- Issued on:2019-06-04
- Implemented on:2019-10-01
- File Format:PDF
- Delivery:Via email within 1~3 business days
$156.00
Introduction
Analysis of the core content of the standard
| Technical elements | Zinc oxide resistor solution | Silicon carbide resistor solution |
|---|---|---|
| Charge rate requirements | ≤0.6 (jumper is required if exceeding the limit) | No clear restrictions |
| Jumper configuration | Forward thyristor + diode is recommended | Bidirectional thyristor is required to be connected in parallel |
| Residual voltage characteristics | Residual voltage ratio≤1.4 | Residual voltage ratio≥1.8 |
Key technical requirements
The standard stipulates that the rotor overvoltage protection setting value must simultaneously meet the following three constraints: higher than 1.2 times the peak value of the rectifier bridge output voltage, lower than 0.95 times the reverse withstand voltage of the thyristor, and not exceeding 70% of the winding withstand voltage test value.
Actual application case
When a 300MW hydropower station adopts the zinc oxide nonlinear resistor solution, the actual rotor winding withstand voltage to ground is 4500V, then the protection action value should be set to less than 3150V (4500×70%), and at the same time, it must be ensured to be higher than 1.2 times the peak value of the rectifier bridge output voltage (the calculated value is 2850V).
Analysis of Standard Evolution
Compared with the earlier version, the 2019 version adds:
- Temperature rise limit of electronic jumper trigger circuit (≤30K)
- Special requirements for asynchronous operation units
- Quantitative index of zinc oxide resistor charge rate
Implementation suggestions
1. When selecting non-linear resistors, the following should be carried out:
- Varistor voltage test (zinc oxide)
- Leakage current comparison (replacement is required for acceptance test ≥50μA)
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