Predictive Maintenance Talk

Circuit breaker is the common equipments that you can see on many industries. due to circuit breakers are always have a current that flows to feed the electricity to the load, circuit breakers need to be testing periodically to ensure it’s reliability and availability. The circuit breakers testing need special consideration because of their importance for routine switching and for protection of other equipment. Electric transmission system breakups and equipment destruction can occur if a circuit breaker fails to operate because of a lack of preventive maintenance. The need for maintenance of circuit breakers is often not obvious as circuit breakers may remain idle, either open or closed, for long periods of time. Breakers that remain idle for 6 months or more should be made to open and close several times in succession to verify proper operation and remove any accumulation of dust or foreign material on moving parts and contacts. The inspection schedule should be based by the interrupting duty imposed on the breaker. It is advisable to make a complete internal inspection after the first severe fault interruption. If internal conditions are satisfactory, progressively more fault interruptions may be allowed before an internal inspection is made.

CIRCUIT BREAKER MAINTENANCE AND TESTING PROCEDURE. Manufacturer’s instructions for each circuit breaker should be carefully read and followed. The following are general procedures that should be followed in the maintenance of low-voltage air circuit breakers:
a. An initial check of the breaker should be made in the TEST position prior to withdrawing it from to enclosure and perform corcuit breaker testing.
b. Insulating parts, including bushings, should be wiped clean of dust and smoke.
c. The alignment and condition of the movable and stationary contacts should be checked and adjusted according to the manufacturer’s instruction book.
d. Check arc chutes and replaces any damaged parts.
e. Inspect breaker operating mechanism for loose hardware and missing or broken cotter pins, etc. Examine cam, latch, and roller surfaces for damage or wear.
f. Clean and relubricate operating mechanism with a light machine oil (SAE-20 or 30) for pins and bearings and with a non hardening grease for the wearing surfaces of cams, rollers, etc.
g. Set breaker operating mechanism adjustments as described in the manufacturer’s instruction book before perform circuit breaker testing. If these adjustments cannot be made within the specified tolerances, it may indicate excessive wear and the need for a complete overhaul.
h. Replace contacts if badly worn orburned and check control device for freedom of operation.

After visual and mechanical inspection usually maintenance person performing such circuit breaker testing:

Insulation Resistance Test . This is the first circuit breaker testing method that used. A megohmmeter is used to make tests between phases of opposite polarity and from current-carrying parts of the circuit breaker to ground. A test should also be made between the line and load terminals with the breaker in the open position. Load and line conductors should be dis­connected from the breaker under insulation resistance tests to prevent test mesurements from also showing resistance of the attached circuit. Resistance values below 1 megohm are considered unsafe and the breaker should be inspected for pos­ sible contamination on its surfaces. For the tumb of rule a rated voltage + 1 is the minimal resistance value that acceptable

Contact Resistance  Test. A contact resistance test is included in circuit breaker testing method that you can do. It can disclose several abnor­mal conditions inside a breaker such as eroded contacts, contaminated contacts, or loose internal connec­ tions. The contact resistance test should be made at a nominal direct-current volt­age at 50 amperes or 100 amperes for large breakers, and at or below rating for smaller breakers. The contact resitance test is compared against manufacturer’s data for the breaker being tested.

Connections Resistance Test .The connections to the circuit breaker should be inspected to determine that a good joint is present and that overheating is not occurring. If overheating is indi­ cated by discoloration or signs of arcing, the connections should be re­ moved and the connecting surfaces cleaned.

Secondary Relay Function test. The proper action of the overload tripping components of the circuit breaker can be verified by applying 300 percent of the breaker rated continuous current to each pole. The significant part of this test is the automatic opening of the circuit breaker and not tripping times as these can be greatly affected by ambient conditions and test condi­ tions.

Lets check the video of someone that performed circuit breaker testing on his company

source : HYDROELECTRIC RESEARCH AND TECHNICAL SERVICES GROUP

Speaking about industrial battery, it’s talk about a back up system for supporting your critical equipments at your. Battery system become important part to your maintenance program because it will backup your critical equipments during emergency situation such as blackout condition or another disturbances. Proper treatment for your lead battery will guarantee that your system will safe during blackout condition, until the disturbance is eliminated or backed up by your standby generator

Battery design is depends of your plant requirements. It can be dry cells battery (VRLA) or wet cells battery(flooded type). Both of them can meet your requirement to build a reliable backup system. The differences are VRLA battery need less maintenance than wet battery.

VRLA Battery construction

During plant operation. It is important to set up good maintenance program to monitor and maintain your battery system health. Regular battery cell measurement and testing is needed to know each battery cell condition and monitor the battery internal resistance, so that if one of them show the defect sign, you can take action to replace the bad battery. The measurements that you can do during your routine maintenance are battery  conductance test and battery impedance test. Both of them are quite reliable and you can easy know your cell internal condition and know which cells that have high resistance value. For the value deviation you can check with the battery manufacture datasheet.

battery aging graph

It is also interesting to know that do we have to replace the battery that already defect one by one or replacing all the batteries with the new one in the same time due to budget constraint or you want to save your money. I said that it is wise to replace the batteries together as a system than you replace the battery one by one. The reason is if you just replacing the battery one by one as per your maintenance results, the new battery must handle the charging rate longer because it connected together with old battery and the old batteries need longer charging rate. The result is you will decrease the lifetime of the new battery.

Another thing that you have to do is perform battery capacity testing. You can do it once per year to know the battery capacitance decline value. You can do the test by connecting the battery with dummy load. Based on IEEE, the minimum value that the battery can handle the system in good condition is 80%. It’s mean that if you battery capacitance below the standard, you should replace the battery soon.