Determination and elimination of the causes of failure to close the main switch of the ship generator and fault tripping

First, the main switch failed to close the cause of judgment and exclusion

1. Main switch closing failure reason judgment

Conditions for manual closing of the main switch: the striker does not operate and the energy storage spring stores energy normally. Main switch electric closing conditions: to meet the conditions of manual closing, and then the closing coil and the closing control circuit work normally.

When the circuit breaker is closed, the sound of internal mechanism action and contact closure can be clearly heard. Main switch closing is indicated on the front panel of the circuit breaker and on the switchboard.

(1) Electric closing, after pressing the button, the main switch does not respond while the manual mode closing is normal.

The fault lies in the closing control circuit. You can confirm this by pressing the close button and using a multimeter to measure whether the close signal reaches the corresponding terminals of the circuit breaker. If the closing signal reaches the circuit breaker terminals, then the internal control circuit of the circuit breaker is faulty.

(2) Electric and manual closing, both can hear the switch internal mechanism action, but not close the gate.

The point of failure is in the main switch mechanism, which needs to be further inspected; the protective tripping device, electrical interlock, etc. are functioning. The generator's protective tripping device will be inoperative or not reset after operation, or interlocked with the shore power, etc., which will cause the main switch to be in a decoupled state. Protection tripping device, electrical interlocking, etc., generally through the circuit breaker release coil is energized to achieve, the use of a multimeter to measure the under-voltage release coil and the excitation release coil of the external terminals to confirm the tripping signal, the signal may be a problem: overload current, short-circuit current, ground-fault current, the transient current is too large at the time of closure.

Simple expression:

(1) Loss of pressure off-trigger does not act: check whether the fuse is blown; check whether the button contact is good; check the coil of the loss of pressure off-trigger, if it is broken, it should be repaired or replaced with a new one.

(2) overcurrent disconnectors out of adjustment (action value is too small): correction, adjustment to the specified value.

(3) Serious wear and tear of the disconnecting mechanism, can not be hooked: Repair the disconnecting mechanism or replace it with a new one.

(4) No reset after thermal release action: stop for a few seconds and wait for the thermal element to reset.

2. Main switch close gate failure fault demonstration

As an example, the DW95 has a solenoid energy storage method to set up a fault.

(1) Setting the point of failure: the contact of the closing coil control circuit is disconnected.

Phenomenon: can move the handle to close the gate, press the close button does not respond.

Analysis: can be manually closed, indicating that the energy storage part, contact part, and then buckle part of the normal; press the close no response, indicating that the fault in the closing control circuit.

Inspection and repair method: control circuit, press the closing button while using a multimeter to measure whether the closing signal reaches the corresponding terminals of the circuit breaker, focusing on confirming whether the closing contactor has action or not.

(2) Setting the point of failure: Loss of pressure coil circuit contact is disconnected.

Phenomenon: Closing action occurs when the handle is moved and the closing button is pressed, but is immediately disconnected.

Analysis: the energy storage spring is normal, but the release mechanism can not be buckled again, indicating that the release device failure, may be a mechanical failure (such as the release mechanism is badly worn, hooks can not be), may also be an electrical failure (such as the loss of voltage release device loss of power or the shunt release device abnormally powered).

Inspection and repair methods: first check the electrical circuit, can soon be found in the loss of voltage coil is not electric, find the disconnection point can be.

Expansion: trip device malfunction or failure to reset after action, and shore power interlocking, etc., generally by making the main switch of the loss of voltage release coil power failure to achieve, can be confirmed by using a multimeter to measure the loss of voltage release coil of the external terminals with or without the trip signal.

(3) Setting the point of failure: overcurrent detent parameter is turned down.

Phenomenon: sometimes the generator can be closed, sometimes it can not be closed, after closing, the load increases and immediately tripped.

Analysis: Load changes can lead to tripping, generally caused by overcurrent detent parameter disorders, random changes in the inrush current during the closing time leads to the closing of the gate sometimes closed, sometimes not.

Inspection and repair method: Correct and adjust the overcurrent release value to the specified value.

(4) Setting the point of failure: Mechanical failure.

After eliminating electrical faults, mechanical faults can be identified. This fault generally requires factory service.

Common mechanical failures are:

① Loose mechanical connecting rod: tighten it;

②The release mechanism is worn out: it needs to be replaced;

③ Closing solenoid jamming: adjust loosely;

④Inflexible rotation of the detacher lever or aging of the reaction spring: adjust accordingly.

Second, the main switch fault tripping reason judgment and exclusion

1. Main switch fault tripping reason judgment

If the system is not short-circuit or direct grounding phenomenon, the relay protection does not act, the circuit breaker automatically tripped circuit breaker “false jump”. The analysis, judgment and treatment of “false tripping” are generally divided into the following three steps.

(1) Based on the following characteristics of the accident phenomenon, it can be judged as a “false jump”.

Before tripping, the main switch is located in the generator control panel meter readings, insulation on the distribution board is normal, indicating that the system has no short-circuit faults; after tripping, the generator control panel on the voltmeter, ammeter and power meter indication is zero.

(2) Identify the cause and deal with it separately.

In case of “false tripping” caused by personnel accidentally touching or operating the circuit breaker, or the protection panel being vibrated by external force, the cause of the switch failure should be eliminated and the power should be restored immediately. For other electrical or mechanical faults, if it is not possible to restore power supply immediately, contact the chief engineer to explain the situation, and deactivate the “false tripping” circuit breaker for maintenance.

(3) “False jump” circuit breaker for electrical and mechanical fault checking and analysis.

Electrical faults: protection error or improper positioning, or current or voltage transformer circuit faults; poor insulation performance of the secondary circuit, two-point grounding of the DC system (two-point grounding of the tripping circuit).

Mechanical causes of failure: The closing maintenance bracket and the breaking latch cannot be maintained, resulting in tripping.

2. Main switch false trip fault demonstration

(1) Setting the point of failure: simulating ship vibration.

Phenomenon: Only power loss alarm, but no specific fault alarm.

Analysis: If it is not relay protection, it is possible that the operator may have touched or operated it by mistake, or it may have been subjected to mechanical vibration because the release mechanism could not be maintained, causing a “false jump”.

Handling method: you can immediately close the gate to send power.

(2) Setting the point of failure: overcurrent detent parameter is turned down.

Phenomenon: When the generator load power is large, it is very easy to jump the power.

Analysis: Increased load can lead to tripping, usually caused by overcurrent detent parameters are out of adjustment, but also may be the current transformer, voltage transformer circuit failure or secondary circuit insulation performance caused by false tripping signal.

Inspection and repair method: Correct and adjust the overcurrent release value to the specified value.

(3) Setting the point of failure: Loss of pressure release device reaction spring tension is too large.

Phenomenon: Generator trips when high power asynchronous motor is started.

Analysis: In the high-power asynchronous motor start-up, will cause a large drop in instantaneous voltage, if the loss of voltage release device reaction spring tension is too large, will lead to loss of voltage release device false operation.

Treatment: Reduce the tension of the reaction spring.

Third, the main switch off not open the reason judgment and exclusion

In the case that the main switch cannot be electrically tripped, first try to manually trip the main switch by pressing the trip button on the circuit breaker panel; if manual tripping can be successful, the main switch can be withdrawn and the main switch electric trip control circuit can be further checked; if manual tripping cannot be accomplished, then consider manually disconnecting the contact switches between the two sections of the manifolds or disconnecting the isolation faulty main switch on the manifolds to which the main switch is connected and isolating the faulty main switch from the main switch. If manual breaking cannot be accomplished, consider manually disconnecting the contact switch between the two sections of the manifold or disconnecting the isolating faulty main switch from the manifold to which the main switch is connected, and isolating the faulty main switch from the section of the manifold to which the main switch is connected.

1 . Judgment of the reason why the main switch cannot be disengaged

Frame-type automatic air circuit breakers can also be tripped in two ways, electrically and manually. The motorized method is normally used, i.e., the circuit breaker is tripped by means of a trip control circuit using a trip button on the switchboard or a signal from an automatic control system. As a back-up, the main switch is normally retained in the manual tripping mode, whereby the main switch mechanism is tripped by direct actuation of a pushbutton on the circuit breaker panel.

(1) If neither electric nor manual means can be used to break the gate, further inspection of the main switching mechanism is required.

(2) If the switch can be manually opened but not electrically opened, the point of failure is in the switching control circuit. Motorized trip control is also achieved by de-energizing the undervoltage detent coil of the switch or by energizing the shunt detent coil, which can be confirmed by pressing and holding the trip button on the switchboard and measuring the external terminals of the undervoltage detent coil and the shunt detent coil with a multimeter.

Common causes and treatments for failure to disengage the gate:

(1) The release coil does not act: check whether the working voltage of the release coil is normal, whether the fuse is blown; check whether the contact of the release button is good; check the release coil, if it is broken, it should be repaired or replaced with a new one.

(2) The main contact is burned out and sticking: check, repair or replace the main contact.

(3) Transmission mechanism stuck: check, repair transmission mechanism.

2. Failure Demonstration (Take DW95 as an example, with magnet storage)

(1) Setting the point of failure: The contact of the shunt coil circuit is open.

Phenomenon: can manually split the gate, but press the split button does not respond.

Analysis: Generally remote control tripping is realized through the shunt release. Remote control tripping also has a special trip circuit. Failure may occur in the trip control circuit or shunt coil circuit.

Troubleshooting method: utilize a multimeter to measure the power failure to detect the open point.

(2) Setting the point of failure: The reaction spring force is adjusted down.

Phenomenon: The generator has an undervoltage and reverse power fault without tripping.

ANALYSIS: Undervoltage and reverse power protection are both tripped by causing the loss of voltage detent to operate. If there is no tripping, it means that the voltage striker does not operate, it may be that the voltage coil is not disconnected, such as the normally closed contacts do not operate, or it may be that the lever is mechanically jammed or the reaction spring force is too small.

Inspection and repair method: After eliminating the electrical line faults, you can manually press the armature of the detacher to detect whether the mechanical rotation of the detacher is flexible and the size of the reaction spring force. By adjusting the reaction spring force to solve the problem.

(3) Setting the point of failure: other failures.

Analysis: The drive mechanism of the main switch can also be jammed, resulting in the release of the gate. The locking mechanism can be tested first to see if there is a problem. If the main contact is burned out and sticking, it can also lead to not being able to release the gate.