High-voltage circuit breaker failure to close—90% of electricians have encountered this pitfall!

1、 Voltage issue: the most common 'mastermind behind the scenes'

The closing action of the Circuit Breaker is driven by the electromagnet, and once the voltage is not within the appropriate range, it cannot be considered successful.

Common situation: Low voltage: When the 220V closing power supply drops below 150V, the electromagnet cannot move. The DC system battery float charge is insufficient, dropping below 195V and refusing to close.

Voltage too high: The coil may be burnt out.

The AC power supply fluctuates greatly: especially when the factory uses its own power, the voltage drops absurdly low at the moment of closing.

Experience:

The first step, don't panic, take a meter to measure the voltage first. Check if it is within the rated range of 80% to 105%. Not enough? Just check float charging and AC power supply. If it can't be closed, you can do it manually first, but you must trace the power problem to the end, otherwise something will happen sooner or later.

2、 Chain failure in the closing circuit

The voltage is normal, but still not suitable? Most likely, there is a problem with the circuit.

Common reasons: Loose wiring or burnt contacts: When the contact resistance increases and the voltage drops, the coil cannot be fully charged.

Button and relay damaged: If you press them down, the signal doesn't even arrive.

Circuit disconnection or fuse failure: common in old stations.

Case: I encountered it in a 35kV station and couldn't close it no matter what. In the end, I found that the closing contact was severely oxidized and the voltage dropped significantly. Spray some electric oil, wipe it, and immediately restore it.

3、 Mechanical jam: there is no electrical problem, and the mechanism is not awesome

Don't just focus on the electrical system, the mechanical mechanism inside the circuit breaker is also a major component.

Common situations:

The spring has not stored enough energy and its movement is not thorough;

Inadequate lubrication and jamming;

The lock buckle is stuck and the connecting rod cannot move.

Suggestion: There is no shortcut to mechanical work, it must be watched, touched, and disassembled by someone. One time during our maintenance, we found that the mechanism shaft pin was completely rusted, and it was only after a complete overhaul that the issue was resolved.

4、 Auxiliary contacts: small parts, big trouble

Many people overlook auxiliary contacts, which are actually the key to ensuring the continuity of the closing circuit.

Once the contact is poor, the electromagnetic coil will lose power as soon as it is pulled, resulting in the iron core returning and refusing to close.

So during maintenance, I usually have to check these small contacts, and if they don't work, I'll replace them with new ones. Don't worry.

5、 Fault in the closing circuit itself

The closing circuit is complex and has many problems.

Several typical scenarios:

• High voltage drop in the circuit: with long wires and multiple contacts, the voltage drop exceeds the standard, and the closing current is insufficient.
• Short term current shortage: The current required for the design of the operating mechanism has not been reached, and the closing iron core cannot absorb it.
• Excessive circuit resistance: Especially when the contactor coil and plug are loose, it directly leads to failure.

Troubleshooting method:

1. Measure the voltmeter and ammeter first;
2. For those with light monitoring, observe the opening and closing positions;
3. If necessary, simulate live testing and investigate section by section.

6、 Iron core malfunction

Sometimes when the power supply and circuit are connected, but still cannot be closed, it is mostly due to the iron core movement being stuck.

Frequently Asked Questions:

• Iron core rust or foreign objects, incomplete suction;
• The force of the reaction spring is too strong, and the magnetic force of the coil is insufficient;
• The assembly gap is not qualified, causing friction.

How to treat it?

1. First, disassemble and clean, then lubricate;
2. Adjust the spring tension;
3. If it really doesn't work, replace it.

7、 Summary of Refusal Inspection Process

The dry running summarizes the "three axes":

First, let's look at the voltage: float charging, AC source, and ensure the quantity is in place.

Recheck the circuit: contacts, relays, fuses, and screen them one by one.

Finally, pay attention to the mechanism: lubrication, springs, iron cores, and do not overlook any details.

Many young masters forcefully join in as soon as they arrive, which is actually a waste of time. Following this process, almost everything can be done.

The circuit breaker refuses to close, don't blame it for getting angry.

Simply put, it's three words: electricity, electricity, and machinery.

Once the power supply is stable, the circuit is connected, and the machinery is smooth, it can obediently obey.

One sentence: Don't be impatient, check in order, all rejections are traceable!