Methods for Handling Abnormalities and Accidents in Substations

1. What is accident handling? What are the common types of operations used in accident handling?

Answer: Accident handling refers to a series of operational actions taken in response to an emergency that endangers personal, power grid, or equipment safety, or when a power grid or equipment accident occurs. The goal is to quickly rescue personnel, isolate faulty equipment, adjust operating modes, and restore normal operation as soon as possible.

Common operation types include: test energizing, forced energizing, load shedding, tripping for load limitation, securing power supply, and restoring load.

2. Under what abnormal conditions should a circuit breaker be immediately de-energized?

Answer: A circuit breaker should be immediately de-energized under the following abnormal conditions:

• Severe damage to the bushing accompanied by discharge phenomena;
• Explosive sounds inside a bulk-oil circuit breaker;
• Smoke from the arc-extinguishing chamber or abnormal internal noises in a minimum-oil circuit breaker;
• Severe oil leakage in an oil circuit breaker, making the oil level invisible;
• Severe gas leakage in an SF₆ chamber, accompanied by an operation lockout signal;
• A "hissing" sound indicating vacuum failure in a vacuum circuit breaker;
• Sudden hydraulic pressure loss to zero in the operating mechanism;
• Equipment enclosure rupture, severe deformation, overheating, or smoking.

3. Under what abnormal conditions should a main transformer be immediately shut down?

Answer: A main transformer should be immediately shut down under the following abnormal conditions:

• Emitting strong and uneven noise, or internal cracking and spark discharge sounds;
• Top oil temperature exceeds historical records by more than 10°C under the same load, ambient temperature, and cooling conditions, with the oil temperature continuously rising (confirming the temperature gauge is functioning correctly);
• Rupture of the oil conservator or explosion-proof pipe with oil spraying (confirm that the breather passage is unobstructed);
• Severe deterioration of oil color, with carbon particles appearing in the oil;
• Bushing rupture accompanied by severe discharge;
• Severe oil leakage causing the oil level in the conservator and Buchholz relay to become invisible;
• Transformer on fire;
• Conditions requiring shutdown as specified in the "Infrared Thermography Work Standards."

4. Under what abnormal conditions should a current or voltage transformer be immediately taken out of service?

Answer: A current or voltage transformer should be immediately taken out of service under the following abnormal conditions:

• Internal discharge sounds;
• Presence of a burnt odor, smoking, or oil spraying;
• Bushing rupture or flashover discharge;
• Continuously rising temperature that is worsening;
• Severe oil leakage.

5. How should a circuit breaker with a hydraulic mechanism be handled when hydraulic pressure drops to zero during operation?

Answer: When the hydraulic pressure of a circuit breaker with a hydraulic mechanism drops to zero due to a fault during operation, handle it as follows: First, use a mechanical lockout plate to secure the circuit breaker in the closed position, then disconnect the control power fuse.

• If a bypass circuit breaker is available, immediately change the operating mode to transfer the load via the bypass, open the disconnect switches on both sides of the faulty circuit breaker, and then investigate the cause;
• If no bypass circuit breaker is available and power outage is not permitted, on-load handling may be performed while the breaker is mechanically locked.

6. How should a circuit breaker with a hydraulic mechanism be handled when a "trip lockout" signal is issued?

Answer: When a "trip lockout" signal is issued by a circuit breaker with a hydraulic mechanism, operating personnel should promptly check the hydraulic pressure value. If the pressure is indeed below the trip lockout threshold, immediately disconnect the oil pump power supply, install the mechanical lockout plate, withdraw the relevant protection trip links, report to the on-duty dispatcher, and prepare for load transfer.

7. Under what abnormal conditions should a surge arrester be immediately taken out of service?

Answer: A surge arrester should be immediately taken out of service under the following conditions:

• Severe overheating of the arrester body or significant temperature difference between sections, with visible cracks in the porcelain housing;
• Leakage current increasing by more than 20% compared to historical records, or inter-phase difference reaching 20% in the current reading.

8. How should a transformer be handled when the oil level is too high or oil is overflowing from the conservator during operation?

Answer: First, check whether the transformer load and temperature are normal. If they are, the high oil level may be a false indication caused by blockage of the breather or oil-level gauge. After obtaining approval from the dispatcher, change the heavy gas protection to alarm mode, then clear the breather or oil-level gauge. If oil overflow is due to excessively high ambient temperature, perform oil draining.

9. How should an overloading alarm from a transformer during operation be checked and handled?

Answer: Operating personnel should check whether the transformer's currents on all sides exceed the specified limits and report the overload magnitude to the on-duty dispatcher. Simultaneously, verify whether the oil level and oil temperature are normal, activate all cooling units, follow the on-site procedures for overload operation, conduct regular patrols, and increase special inspections if necessary.