Maintenance of Electrical Systems
Regular maintenance of Electrical Distribution System is required for compliance with statutory / regulatory requirements and it is essential to prevent unexpected failures, improve system efficiency, and maximize the lifespan of equipment.
Statutory / Regulatory Requirements:
- Electrical Act 2001 , abstract of Part 3, Section 20 (3) , …it is the duty of a retail electricity licensee to develop and maintain a reliable, efficient, coordinated and economical electricity retail business in accordance with such applicable codes of practice and other standards of performance as may be issued or approved by the Authority, etc.
- EMA (Energy Market Authority) states that every high voltage apparatus in the installation shall be maintained according to the manufacturer’s recommendation.
- Singapore Standard SS538: Code of practice for maintenance of electrical equipment of electrical installations.
Table 1.1 - Maintenance of Frequency Matrix (SS538)
Table 1.1 to be used with conjunction with inspection and test records to determine the frequency of maintenance in terms of year of intervals.
| Maintenance of Frequency Matrix (Year Intervals) | ||||
|---|---|---|---|---|
|
Equipment Condition
|
||||
| Poor | Average | Good | ||
|
Equipment Criticality
Category |
Low | 1.0 | 2.0 | 2.5 |
| Medium | 0.5 | 1.0 | 2.0 | |
| High | 0.5 | 0.75 | 1.0 | |
Criticality
Residential / Shop Houses / Religious / Ware House
Do not operate on daily 24 hours, Office/ Small Factories / Hotels / Entertainment / Commercial Buildings, etc.
Hospital, Hotels , Factories and Offices with 24 operations, commercial building with international standing.
Condition
- Equipment installed in dusty , humid , poorly ventilated location
- High load (above 70%), above 12 years usage.
- Equipment installed in location with environment between Good and Poor condition
- Average Load (50%-70%)
- Regular maintenance carried out, more than 5 years and less than 12 years usage.
- Equipment installed in clean, dust free, well ventilated location
- Low load (below 50%) , regular maintenance carried out, less than 5 years usage
Maintenance Methods
There are 3 methods to maintenance, namely:
- Routine Inspection
- Shutdown Maintenance
- Condition Monitoring (CM) Tests.
Routine inspection can be monthly / quarterly / bi yearly depending on the criticality and condition of the equipment. The inspection includes thorough examination of the various components such as relays, recording of electrical loading , etc. It is typically conducted to ensure the safety, reliability, and efficiency of the electrical distribution system.
EMA states that the licensed electrical installation has to be inspected and certified fit for operation by LEW.
The frequency of inspection is shown in table below
| Type of Installation | Inspection Frequency | Remarks |
|---|---|---|
| Construction Worksites | At least once per month | Electrical installations at construction worksites are subjected to more wear and tear and shall be inspected at least once a month to ensure they remain safe to use. |
| Trade Fairs, Mini-Fairs, Festive Lightings, Etc. | Daily | Safety inspection should be carried out daily to ensure all parts accessible to the public remain safe and all protective devices in good working conditions. |
| Multi-tenanted buildings, condominiums, etc. | At least once in six months | Communal electrical services such as risers, lightings, socket-outlets, protective systems, etc., should be inspected to prevent causing danger to the public. |
| High Voltage9 installations | Inspection and maintenance schedule shall be worked out by the appointed LEW, but inspection shall be carried out at least once a year. | The manufacturers of high voltage equipment/apparatus should be consulted on the maintenance requirements. |
| Others | Annually | Inspection shall be carried out before renewal of the electrical installation license |
Shutdown Maintenance
Shutdown Maintenance refers to a period during which a facility, plant, or equipment is taken offline or temporarily shut down for the purpose of conducting maintenance activities.
It involves a comprehensive inspection, repair, and replacement of components, systems, or equipment to ensure their continued functionality, reliability, and safety. Shutdown maintenance typically involves a thorough assessment of the equipment, cleaning, lubrication, calibration, and replacement of worn-out parts. It may also include activities such as testing, upgrading, or modifying systems to improve performance or comply with regulatory standards. The duration of a shutdown maintenance can vary depending on the complexity of the equipment or system and the scope of work required.
Condition Monitoring
Condition Monitoring Tests are conducted while the power supply remains uninterrupted, allowing for the detection of electrical defects like hot spots in electrical equipment. This enables the identification of defects that can subsequently be addressed during a scheduled shutdown maintenance. It’s important to note that while CM tests are valuable, they cannot replace shutdown maintenance, as both methods are necessary for ensuring the optimal functioning of the system.
The following Condition Monitoring (CM) tests are conducted without any disruption to the power supply:
- Partial Discharge Testsof HT Switchgears / Transformers – Identifies electrical arcing.
- Transformers Oil Test DGA / Furan – Detects electrical arcing and assesses the condition of the oil.
- Thermal Scanning of LT Switchboards / Busbars / Transformers – Detects hot spots on switchboards.
- Lightning / Electrical Earthing Audit Test – Inspects and tests the reliability of the lightning and earthing systems.
Efficient maintenance of electrical distribution systems is vital for ensuring safe and reliable operation. Adhering to regulatory requirements and conducting regular maintenance activities, including annual shutdown maintenance and implementing various condition monitoring tests, is essential. By prioritizing maintenance efforts, organizations can enhance the lifespan of equipment, minimize downtime, and mitigate the risk of electrical failures.
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