Substation Fault Handling: Core Principles & Response Guide
The substation is the key hub of the power system, and its safe and stable operation is of great importance. When a fault occurs, quickly and accurately judging and dealing with it is the core of ensuring the safety of the power grid and reducing the loss of power outages. Combining with the common scenarios of substation operation, this paper sorts out the core principles, processes and typical fault response methods of accident handling.
I. Basic principles and procedures for handling accidents
Core principles: The fundamental goal of accident handling is to limit the development of accidents, eliminate the root causes, ensure the safety of personnel and equipment, and, under the premise, restore power supply to users as soon as possible.
General procedure:
Act quickly: immediately restore the alarm signal, record the time and phenomenon of the fault (light board, meter, protective action signal, etc.), and briefly report to the dispatcher.
Accurate judgment: Based on the inspection results, comprehensively analyze the nature and scope of the fault.
Safety first: remove threats to people and equipment, ensure the safety of station power, and prevent the expansion of accidents.
Isolate the fault: take safety measures to isolate the fault point.
Restore power supply: Adjust the operation mode to restore the operation of non-faulty equipment and user power supply as a priority.
Record and report: Record the processing process in detail and report to superiors and dispatchers in a timely manner.
II. Typical fault phenomena and handling points
1. Single-phase grounding in a small-current grounding system
Phenomenon: When the alarm bell rings, the "grounding" light word sign lights up; One phase voltage is zero or reduced, and the other two phase voltages are increased to the line voltage.
Feature: The system can run with grounding for 1-2 hours, but it is easy to cause overvoltage or two-point grounding short circuit.
Processing:
Report the dispatch, check if there are any obvious fault points in the station equipment.
Use the "pull test method" to find the grounding line: first pull the secondary, light load, long line, and then pull the important line.
It should be distinguished from phenomena such as fuse melting in voltage transformers.
2. Line-to-line short circuit (transient/permanent)
Phenomenon: When the accident alarm sounds, the protection (speed break/overcurrent) and reclosing signal lights up, and the meter recovers or resets after the impact.
Processing:
Record the phenomenon, restore the signal, and print the fault report.
Check the equipment at the station (circuit breakers, CTs, etc.) for any abnormalities.
Transient fault: Re-synchronization is successful, and normal operation is restored.
Permanent failure: reclosure failure, switch tripping. We need to report to the dispatcher and decide whether to force the power supply based on the command.
3. Line fault in the large current grounding system (110 kV/220 kV)
Protection configuration: Usually equipped with phased distance, zero-sequence protection and automatic reclosing. The 220 kV line also has a longitudinal main protection.
Handle the key points:
After the 110 kV line is tripped, if the recloser is not moved, after checking for no abnormalities, it can be tested for power supply once according to the dispatch order.
After the 220 kV line is tripped, it is strictly forbidden to forcibly send electricity without authorization! After conducting a detailed inspection of the protection action information and fault recording report, and clarifying the nature of the fault (single-phase/phase-to-phase, instantaneous/permanent), the subsequent operations (such as checking the synchronization and closing the circuit, trial delivery, etc.) should be carried out strictly in accordance with the dispatch order.
4. The bus is out of power.
Cause: Fault in the bus itself, protection misoperation, or fault in the lower-level line causing the circuit breaker to trip.
Key judgment: Check whether the differential protection has been triggered and whether there are any obvious signs of failure in the equipment within the range of the loss of pressure busbar.
Processing:
Maternal deviation action and obvious fault: Isolate the fault point, restore the power supply of the non-fault part with backup power or reverse bus method.
Maternal deviation action but no sign of fault: need to be vigilant about protection misoperation (such as DC ground caused), after withdrawing the maternal deviation protection inspection, try to send the mother line.
Caused by over-voltage trip: Isolate the non-operating switch or faulty line, and restore the bus operation.
5. System frequency and voltage anomalies
Frequency abnormality: caused by unbalanced active power in the system. The treatment is mainly to increase the active power of the generator or to cut off part of the load in the order of pulling off the circuit breaker in case of an accident to prevent frequency collapse.
Voltage abnormality: caused by unbalanced reactive power in the system. Measures to deal with it include putting in capacitors, adjusting the transformer tap, and instructing users to reduce load.
6. System oscillation
Phenomenon: Periodic violent oscillation of various electrical meters, rhythmic roar of the generator.
Distinguish from short circuit: The three phases are always symmetrical during oscillation, without negative sequence or zero sequence components.
Treatment: Each power plant should immediately increase reactive power output without waiting for the dispatch order, and adjust active power according to the frequency situation to calm the oscillation.
Summary
The handling of substation faults is a systematic work that requires strictness, speed, and collaboration. On-duty personnel must be familiar with the equipment, master the procedures, and remain calm and composed.The core process can be summarized as follows: "signal recovery → record and report → inspection and judgment → isolate the fault → restore power supply → summarize and report."We must always adhere to the principle of "safety first", and under the unified command of dispatching, we can respond to all kinds of sudden failures efficiently and correctly, and guard the lifeline of power grid safety.
