Surge protection of generators
- Rensselaer Polytechnic Inst., Troy, NY (USA)
Generator windings may be stressed beyond their normal power frequency duty by a variety of disturbances. Steep-fronted surge sources include lightning, nearby faults, circuit breaker closing, reignitions and restrikes. Medium frequency oscillatory overvoltages include the transfer of lighting induced surges through transformers, line faults, fault clearing, multiple reignitions, arcing bus faults, series arcing on busses, and HV switching. Power frequency overvoltages include self excitation, harmonic line resonance, HV to LV faults in transformers, stuck breaker pole and bus faults and several kinds of ferroresonance. The overvoltages for each contingency were modeled in detail, typically using the ElectroMagnetic Transient Program, with the results also quantified in terms of simpler formulas. The probabilities controlling these contingencies were estimated. Stress distributions within windings were simulated for single-turn and multi-turn coil machines. This includes internal winding resonances in the 20-kHz range and amplification of a steep-fronted surge at the end of the first winding slot. The groundwall insulation breakdown strength was tested for more than 100 coils in five machines with varying service ages using dc, power frequency and impulses. These results were compared with specified withstands for generators. The vulnerability of metal oxide arresters to temporary overvoltages and the high ambient temperatures found in generating stations was studies. Historical methods for calculating overvoltages were critically reviewed. A utility survey uncovered weakness in the present design of surge protection. Results of extensive low voltage and full power field tests were used to develop improved models for simulations. 170 refs., 150 figs., 10 tabs.
- Research Organization:
- Electric Power Research Inst., Palo Alto, CA (USA); Ontario Hydro, Toronto, ON (Canada); Rensselaer Polytechnic Inst., Troy, NY (USA)
- Sponsoring Organization:
- EPRI
- OSTI ID:
- 6587461
- Report Number(s):
- EPRI-GS-6936
- Country of Publication:
- United States
- Language:
- English
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CIRCUIT BREAKERS
ELECTRIC DISCHARGES
ELECTRIC GENERATORS
ELECTRICAL EQUIPMENT
ELECTRICAL FAULTS
ENERGY SYSTEMS
EQUIPMENT
EQUIPMENT PROTECTION DEVICES
LIGHTNING
POWER GENERATION
POWER PLANTS
POWER SYSTEMS
SURGES
TRANSFORMERS