Electrical Substation Maintenance 

Visual Inspection

Visual inspection is a critical aspect of substation maintenance, It provides an initial assessment of the overall condition of the substation equipment structures and the general site. This inspection is typically conducted by well trained qualified personnel who visually examine various parts of the substation to identify signs of wear, damage, potential theft , vegetation growth, the state of the substation gravel and mechanical protection or potential issues. Here are key aspects of a visual substation inspection:

1. General Site Inspection: Evaluate the overall condition of the substation site, including the fencing, access points, and landscaping. Ensure that there are no unauthorized personnel or animals within the vicinity.
   
   
2. Security Measures: Check the security measures in place, such as locked gates and surveillance cameras, to prevent unauthorized access and ensure the safety of the substation.
   
   
3. Structural Integrity: Inspect the structural integrity of buildings, towers, and support structures (hydro poles) within the substation. Look for signs of corrosion, rust, or other forms of deterioration.
   
   
4. Grounding System: Examine the grounding system, including ground rods and conductors, to ensure proper grounding. A well-maintained grounding system is essential for safety and electrical performance.
   
   
5. Fencing and Signage: Check the condition of the perimeter fencing and signage. Ensure that the fencing is intact and that warning signs are visible, providing clear information about the potential dangers of entering the substation.
   
   
6. Equipment Condition: Perform a visual inspection of individual substation components, including transformers, circuit breakers, switchgear, disconnect switches, and other electrical equipment. Look for signs of overheating, leaks, corrosion, or physical damage.
   
   
7. Insulator Inspection: Inspect insulators for cracks, contamination, or other issues that could affect their insulating properties. Damaged insulators may compromise the integrity of the electrical system.
   
   
8. Conductor and Busbar Inspection: Examine conductors and busbars for signs of corrosion, loose connections, or damage. Proper electrical conductivity is crucial for efficient power transmission.
   
   
9. Oil-Filled Equipment Inspection: For oil-filled equipment such as transformers, visually check for oil leaks, discoloration, and the overall condition of the oil. A well-maintained oil-filled system is essential for efficient cooling and insulation.
   
   
10. Environmental Considerations: Assess the substation environment for potential issues such as vegetation overgrowth, accumulation of debris, or the presence of animals. Ensure that the substation is free from conditions that could compromise safety or equipment performance.
    
    
11. Emergency Response Equipment: Verify the presence and condition of emergency response equipment, such as fire extinguishers and first aid kits. Ensure that personnel have access to necessary safety gear.
    
    
12. Record Keeping: Maintain records of the visual inspection findings. This documentation is valuable for tracking the condition of the substation over time and planning future maintenance activities.

Transformer oil Analysis

Transformer oil analysis is a diagnostic technique used to assess the condition of the insulating oil in power transformers. The insulating oil in transformers serves multiple purposes, such as providing insulation, cooling, and suppressing corona discharge. Over time, the oil can degrade due to various factors, including oxidation, contamination, and thermal stress. Transformer oil analysis helps in monitoring the health of the transformer and identifying potential issues before they lead to equipment failure.

Key parameters analyzed during transformer oil analysis include:

1. Dielectric Strength:   This measures the insulating properties of the oil. A decrease in dielectric strength may indicate the presence of contaminants or degradation of the oil.
   
   
2. Moisture Content:   Excessive moisture in transformer oil can lead to a decrease in dielectric strength and accelerate the aging of the insulation. Moisture is typically measured in parts per million (ppm).
   
   
3. Acidity:   The acidity of the oil is an indicator of the degree of oxidation. Increased acidity suggests that the oil is breaking down chemically, which can impact the transformer's insulation.
   
   
4. Power Factor:   Power factor is a measure of the dielectric losses in the insulation system. An increase in power factor may indicate the presence of contaminants or deterioration of the insulation.
   
   
5. Dissolved Gas Analysis (DGA): This involves analyzing the gases dissolved in the transformer oil. The presence and concentration of specific gases, such as methane, ethane, acetylene, and hydrogen, can provide insights into potential issues, such as overheating, partial discharge, or arcing within the transformer.
   
   
6. Furan Analysis:   Furan compounds are formed during the thermal degradation of cellulose insulation. Furan analysis can help assess the condition of the solid insulation in the transformer.
   
   
7. Interfacial Tension: This measures the cleanliness of the oil and can indicate the presence of contaminants.
   
   
8. Color and Appearance: Visual inspection of the oil for changes in color or appearance can reveal contamination or degradation issues.

Transformer oil analysis is typically part of a comprehensive predictive maintenance program for power transformers. Regular monitoring and interpretation of the test results allow maintenance professionals to identify potential problems early, schedule maintenance or repairs, and extend the life of the transformer. It is important to follow industry standards and guidelines for sampling and analysis and to compare results against established benchmarks for the specific transformer and oil type.

Thermographic imaging

Thermographic imaging is widely used in electrical systems for preventive maintenance and troubleshooting. The application of thermography in electrical inspections involves using infrared cameras to detect and visualize temperature variations in electrical components. Here's how thermographic imaging is utilized in electrical systems:

1. Identifying Hotspots: Thermographic imaging is particularly useful for identifying hotspots in electrical components, such as circuit breakers, fuses, switches, and electrical panels.
   
   Hotspots may indicate problems like loose connections, overloaded circuits, or imbalanced loads, all of which can lead to electrical failures or fires.
   
   
2. Preventive Maintenance:   Regular thermographic inspections of electrical equipment are part of preventive maintenance programs. By detecting potential issues early, maintenance personnel can address problems before they escalate, reducing the risk of unplanned downtime and equipment damage.
   
   
3. Loose Connections: Loose electrical connections can create resistance and generate heat. Thermographic imaging helps identify loose connections in terminals, bus bars, and other components.
   
   Early detection of loose connections is crucial for preventing overheating, arcing, and equipment failures.
   
   
4. Overloaded Circuits: Thermography can reveal overloaded circuits by highlighting areas with elevated temperatures. Overloaded circuits can lead to overheating and pose a fire hazard.
   
   Monitoring temperature variations allows for the adjustment of loads, or the installation of additional capacity as needed.
   
   
5. Phase Imbalance: Imbalances in current distribution among phases can lead to overheating in electrical systems. Thermographic imaging helps identify phase imbalances by detecting temperature variations across phases.
   
   Addressing phase imbalances improves the overall efficiency and lifespan of electrical equipment.
   
   
6. Switchgear and Panel Inspections: Thermography is used to inspect switchgear, distribution panels, and other electrical enclosures for anomalies. It helps ensure that all components are operating within safe temperature ranges.
   
   Detecting issues in these components early on prevents equipment failures and extends the life of the electrical infrastructure.
   
   
7. Transformers and Motor Inspections: Thermographic imaging is applied to transformers and electric motors to monitor their temperature profiles. Overheating in these components may indicate problems such as insulation breakdown or mechanical issues.
   
   Regular inspections using thermography help identify potential failures before they cause major disruptions.
   
   
8. Recording and Analysis: Thermographic images are recorded and analyzed over time to track temperature trends and changes in electrical components. This historical data aids in predicting potential issues and planning maintenance schedules.

It's important to note that proper training and interpretation skills are essential for effective thermographic inspections. Professionals performing these inspections should understand the electrical system, know the expected thermal patterns, and be able to differentiate normal operating conditions from potential problems. Regular thermographic surveys of electrical systems contribute significantly to the safety, reliability, and efficiency of industrial and commercial electrical installations.

Electrical Power Study/ Power System Study

Electrical Power Study/ Power System Study Performing an electrical power study, also known as a power system study or electrical power analysis, is crucial for various reasons in the design, operation, and maintenance of electrical power systems. Here are some key reasons why electrical power studies are conducted:

1. System Design and Planning: Electrical power studies help in designing power systems with the appropriate capacity, redundancy, and reliability to meet the present and future demands. These studies aid engineers in determining the optimal configuration of the power system.
   
   
2. Load Flow Analysis: Load flow studies assess how electrical power flows through a network under normal operating conditions. This information is essential for optimizing the distribution of power, ensuring balanced loading, and preventing overloads in the system.
   
   
3. Voltage Drop Analysis: Voltage drop studies evaluate the voltage levels at various points in the power distribution system. This is critical for ensuring that electrical devices receive the required voltage to operate properly and that there are no excessive voltage drops.
   
   
4. Short Circuit Analysis: Short circuit studies assess the behavior of the power system under fault conditions. This helps in determining the magnitude of fault currents and selecting protective devices such as circuit breakers and fuses to safeguard the system and connected equipment.
   
   
5. Protective Device Coordination: Coordination studies are performed to ensure that protective devices, such as relays and circuit breakers, are appropriately coordinated to isolate faults and minimize the impact on the rest of the system. Proper coordination enhances system reliability and reduces downtime.
   
   
6. Arc Flash Hazard Analysis: Arc flash studies evaluate the potential for arc flash incidents within the electrical system. This is essential for determining appropriate safety measures and personal protective equipment (PPE) for personnel working on or near electrical equipment.
   
   
7. Harmonic Analysis: Harmonic studies assess the presence and impact of harmonics in the power system. Harmonics can lead to issues such as equipment overheating and increased losses. Mitigation strategies can be implemented based on the results of harmonic analysis.
   
   
8. Transient Stability Analysis: Transient stability studies evaluate the system's ability to recover from transient disturbances, such as sudden load changes or faults. This analysis is crucial for ensuring the stability and reliability of the power system.
   
   
9. Energy Efficiency Optimization: Power studies help identify opportunities for improving energy efficiency in the power system. This may involve adjusting operating parameters, upgrading equipment, or implementing energy-saving technologies.
   
   
10. Compliance with Standards and Regulations: Electrical power studies ensure that the power system design and operation comply with industry standards, codes, and regulations. Compliance is essential for safety, reliability, and legal requirements.
    
    
11. Asset Management and Maintenance Planning: By understanding the performance of the power system through studies, maintenance activities can be planned more effectively. This helps in extending the life of equipment and reducing the likelihood of unexpected failures.

In summary, electrical power studies are conducted to optimize the design, operation, and maintenance of power systems. They provide critical insights into the performance, reliability, and safety of electrical networks, allowing for informed decision-making and effective management of electrical infrastructure.

What are the common components of an electrical substation?

Electrical substations play a crucial role in the power distribution network, transforming and distributing electrical energy from high voltage to low voltage or vice versa. Substations consist of various components that work together to ensure the efficient and safe transmission of electricity. The specific components in an electrical substation can vary based on factors such as the type of substation, its purpose, and its location. However, common components found in many electrical substations include:

Main or Primary Feeder: 

The High voltage cable where on the primary voltage is transported to the Electrical substation usually owned by the local distribution company. Most common voltage are 44,000V, 27.600V and 13.800V.

The electrical system starts off with a feeder that is owned, operated and controlled by the customer LDC (Local Distribution Company). This feeder is usually brought in overhead on wire or underground through cable.

Overhead wire will be mounted on Hydro poles held in place by insulators (Example #1)

The underground cable will be installed on a hydro pole (Dip pole) mounted down the side transitioning into an underground raceway (Duct bank) (Example #3); the Cables and conduit are usually protected by steel cable guards.

Usually the LDC owned equipment will have markings on the closest hydro pole (example #2) to identify what equipment is on them or where in their system this equipment is located this is useful information to know in conversations for shutting down the electricity to the customers site.

Metering​:

• Secondary  Metering:  Secondary metering is the most common from of metering It consists of PT and CT installed on the Load side of the Main disconnect of the Secondary switchboard. The costumers will have a meter socket with a hydro meter installed in close approximation where the secondary electrical service is located that usually is accessible from the outside this possible. This way of collecting data is done on sites that have only  one service or multiple services that have different primary feeders.
• Main or Primary Metering:  Main or Primary metering could exist on a costumer if there is multiple service on site or if there is any renewable source of energy available, always owned and installed by the LDC (Local distribution company) if its installed for revenue metering and not part of the maintenance. If installed to meter for metering renewable source customer installed and customer owned. Most common voltage are 44,000V, 27.600V and 13.800V and can be Pole Mounted (Example #4) or metal enclosed (Metering Cell) (Example #5).

Means of Disconnect: 

The Main or Primary disconnect is a piece of equipment that will isolate the sub-station from the main or primary feeder. Disconnect can come in many different forms:

1. Isolation Switches
2. 1. Options include, Pole mount, Structure mount and Metal enclosed.
3. Circuit Switcher
4. 1. Most common voltage are 44,000V, 27.600V and 13.800V
5. Isolating Switches:
6. 1. Load Break Switch (LBS): Designed for making and breaking of loaded circuits. They can interrupt the current when the switch is opened and have arc suppressors.
   2. Air Break Switch: Utilizes air as the interrupting medium, often used in outdoor applications and can not be operated underload, so they are usually accompanied with an interlock scheme.These Switches can be horizontal (Example #6) and vertical (Example #7) pole or Structure mounted (Example #8)
7. Metal enclosed: Metal enclosed is the final option (Example #9). These are used if a single customer has multiple services on site with a common point where the LDC is collecting the data (metering point/primary metering) on customer electrical usage.

Circuit Brea​kers: 

Circuit breakers are devices that interrupt or break the flow of electric current in the event of a fault or overload. They play a crucial role in protecting the electrical system from damage and ensuring the safety of the equipment. Includes protection relays.

1. Vacuum Circuit Breaker (VCB): Uses a vacuum as the interrupting medium, providing reliable switching for medium and high voltage applications.
2. SF6 Circuit Breaker: Uses sulfur hexafluoride gas as the interrupting medium, commonly used in high-voltage applications. SF6 breakers are usually only found in bigger and more complex electrical substations with higher voltages that require additional protection.

Surge Arre​stors: 

Surge arresters (LA’s) protect the substation equipment from voltage surges caused by lightning or other transient events. They redirect excess voltage to the ground. They usually come in distribution class or Station class. Older surge arrestors are manufactured out of Porcelain while newer once are usually Polymer (Example #10 and #11).

Transformers: 

Transformers are essential components that change the voltage level of electrical power. Step-up transformers increase voltage for long-distance transmission, while step-down transformers decrease voltage for distribution to end-users. Transformers can come in many different forms.

1. Pole or structure mount transformer: Usually smaller transformers up to Single Phase 167kV that can be installed as a cluster of three and are always Oil filled (Example #12).
2. Ground mount: Any size greater than Single or Three Phase 167kV, can be Oil filled or Dry Type (Example 13).
3. Station Class or Tamperproof: The main difference between Station class and tamperproof is Station Class Transformers have exposed electrical parts and require additional barriers to prevent contact with live parts.

Configuration of Transformers:  Delta/Delta, Delta/Wye and Wye/Wye, Layout of the primary and secondary bushings and internal core         connections. Configuration depends on Customer and LDC requirements.

• Delta (Δ) Configuration:
• • In a delta configuration, the windings are connected in a triangular (delta) shape.
  • Each winding is connected to the next one in series, forming a closed loop.
  • The line voltage is the same as the phase voltage, and the phase current is the line current.
  • The phase angle between the primary and secondary voltages is zero degrees.
• Wye (Y) Configuration:
• • In a wye configuration, the windings are connected in a Y shape.
  • One end of each winding is connected to a common point called the neutral, and the other ends are connected to the three phases.
  • The line voltage is √3 times the phase voltage, and the line current is the same as the phase current.
  • The phase angle between the primary and secondary voltages is 30 degrees.

    Location of Live Parts:  (Primary and secondary bushings). Top/Top, Top/Side Side/Side and Dead Front.

    Most common Primary voltages:   44,000V, 27.600V and 13.800V

    Most common Secondary voltages:   600V, 347V and 208V

Switchgear​:

Switchgear includes various switching devices such as switches, disconnectors, and fuses. It allows for the control, protection, and isolation of electrical equipment within the substation.

Disconnect Switches: 

Disconnect switches are used to isolate sections of the electrical system for maintenance or in the event of a fault. They provide a way to de-energize specific components without affecting the entire substation always includes fuses.

Capacitor Banks:

Capacitor banks are used for power factor correction to improve the efficiency of the electrical system. They help maintain a balanced and efficient power flow.

Instrument Transformers:

Current transformers (CTs) and voltage transformers (VTs) are instrument transformers that provide reduced and isolated signals for measurement and protection devices. They allow for safe monitoring of current and voltage levels.

Control and Protection Systems:

These systems include relays, control panels, and communication equipment that monitor and control the operation of various components within the substation. They also provide protection against abnormal conditions.

Grounding System:

The grounding system includes ground rods, conductors, and grids that provide a path for fault currents to safely dissipate into the ground. It helps maintain proper safety levels and equipment functionality.

Control Building or Enclosure:

Many substations include a control building or enclosure (E-House) that houses control panels, monitoring equipment, and sometimes personnel for managing and overseeing substation operations.

Battery and Charger Systems:

Batteries and chargers provide backup power for control and protection systems in case of a power outage. They ensure that critical components remain operational during emergencies.

These components work together to transform, distribute, and control electrical power within the substation. The specific configuration and design of a substation depend on factors such as its size, capacity, location, and the purpose it serves in the overall power grid.

What documentation is provided after electrical substation maintenance is performed?

After each electrical maintenance is completed, the customer is provided with a detailed copy of all the test results and observations including:

• ESA Substation report
• Oil Sample
• Test Sheets:
• • High Voltage disconnect data and test heet
  • Transformer Data and test sheets
  • Circuit breaker Data and test sheet
  • Low Voltage Device data and test sheet