When performing maintenance work on substations, professionals must be qualified and authorized for the task, as well as equipped with the necessary collective protection equipment (CPE) and personal protective equipment (PPE).
The professionals must also have received technical training related to the task they will perform and training on the safety standard NR-10 from the Ministry of Labor and Employment. The workers’ clothing must be appropriate, and they should not wear watches, rings, bracelets, or any other personal adornments, as mandated by NR-10.
Any equipment that is isolated within a substation is only considered de-energized when it is:
1. Turned off,
2. Isolated,
3. Locked out,
4. Tested,
5. Grounded,
6. Tagged.
This sequence of operations is defined in Chapter 5.1 of NR-10.
Maintenance of electrical equipment is necessary to ensure their continuous availability and to prolong their service life, which must comply with:
. Pre-established criteria by the equipment manufacturer;
. Technical standards;
. Specifications from the company’s engineering department.
These criteria must consider the equipment installation location, operational frequency, maintenance periodicity, physical-chemical conditions, voltage, and equipment load.
Maintenance is characterized as any service of control, preservation, and restoration of an item or installation with the objective of keeping it in satisfactory working condition and preventing anomalies that could render it unavailable. Maintenance can be preventive, corrective, or predictive.
.Preventive maintenance is all control, preservation, and restoration on a scheduled item following pre-established criteria, aiming to keep it in satisfactory operating condition and protect it against occurrences that may increase its unavailability.
. Corrective maintenance applies to an item that is either unavailable or available, with or without restrictions, and aims to repair a fault or defect. Corrective maintenance can be:
. Emergency corrective maintenance: immediate intervention on an item to restore normal operating conditions.
. Urgent corrective maintenance: intervention on an item to correct faults or defects as soon as possible, restoring normal operation.
. Scheduled corrective maintenance: intervention on an item to correct faults or defects at any time, returning it to normal operation.
.Predictive maintenance consists of control and inspection activities intended to verify the operational condition of installations and equipment. If any anomaly is detected during predictive maintenance, a corrective maintenance can be scheduled, or the monitoring frequency increased until preventive maintenance is possible.
In all types of maintenance, a report must be prepared analyzing the equipment’s condition, test values, and checking if any changes compared to previous reports are within pre-established limits. This report should be part of the installation’s documentation as required by NR-10.
Each equipment manufacturer may have a different maintenance procedure. What is presented below are the basic procedures, inspections, tests, and sequence that can be used for all equipment.
For performing substation maintenance services, certain documents must be provided, as listed below:
. TRN (Technical Responsibility Note) completed and signed by a legally qualified professional;
. Equipment manufacturers’ manuals;
. Technical test and inspection report forms for the equipment;
. Record sheet of previous maintenance reports;
. Standardized work procedure according to item 10.11 of NR-10;
. Authorization document proving the qualifications of the professionals, according to item 10.8 of NR-10.
In the maintenance of substation equipment, it is important to have a more accurate diagnosis of the condition of the installed equipment. Electrical tests provide the status of the equipment, assessing its current condition and identifying any anomaly that may render the equipment unavailable.