How to: Isolation, maintenance, and restoration of a 132kV GIS Transformer Bay and Line Bay

Operating 132kV GIS Transformer Bay & Line Bay

This article aims to provide a comprehensive guide to the standard operating procedures (SOPs) for the isolation, maintenance, and restoration of a 132kV GIS Transformer Bay and Line Bay. It will delve into detailed safety checks, specific steps to be followed during the isolation process, and the restoration protocols to be adhered to post-maintenance.

Additionally, the article will cover the procedures for handling transformer oil sampling, a critical aspect of maintaining transformer health and performance.

As yo already know, high Voltage (HV) substations are critical components of the electrical grid, playing a pivotal role in ensuring the reliability and stability of power transmission and distribution. Among these, the 132kV Gas Insulated Switchgear (GIS) substations are particularly significant due to their compact design, enhanced safety features, and superior operational efficiency.

By systematically outlining these procedures, this article seeks to serve as a valuable resource for electrical engineers, maintenance personnel, and safety officers involved in the operation and upkeep of 132kV GIS substations.

The meticulous application of these SOPs not only enhances operational efficiency but also significantly mitigates the risks associated with high-voltage electrical systems.

Table of Contents:

1. Standard Operating Procedure for Isolation and Maintenance of a 132kV GIS Transformer Bay:
   1. Isolation Procedure
   2. Checking for Live Parts
   3. Restoration Procedure
   4. Detailed Safety Checks
2. SoP for 132kV Power Transformer Trip & Restoration:
   1. Objective
   2. Scope
   3. Circuit Breaker Trip Response:
      1. Differential Relay Operation
      2. Mechanical Protection Operation
      3. General Steps
   4. Conclusion
3. SoP for 132kV Line Trip & Restoration:
   1. Objective
   2. Scope
   3. Elaboration on Procedures: (132KV Line Bay Operation):
      1. Line Circuit Breaker Trip Response
      2. Differential Relay Operation
      3. Distance Relay Operation
      4. General Steps
   4. Conclusion
4. SOP for Transformer Oil Sampling:
   1. Objective
   2. Scope
   3. Procedure
   4. Oil Sampling in Aluminium Bottle
   5. Oil Sampling in Glass Bottle
   6. Bottle Samples for Screen Tests
   7. Syringe Samples for Dissolved Gas Analysis
5. BONUS (PDF) 🔗 Download 132kV GIS Drawings of HV Devices and LCC + Design & Execution Guide (PDF)

1. Standard Operating Procedure For

Isolation and Maintenance of a 132kV GIS Transformer Bay

The primary aim of this procedure is to provide a comprehensive guide for the operation, isolation, and restoration of the 132kV transformer bay within a high-voltage (HV) substation.

This procedure outlines the specific steps required to isolate and restore the 132kV transformer bay, ensuring that all activities are conducted safely and effectively. Isolation is necessary for performing maintenance, repairs, or upgrades, and it involves de-energizing and securing the transformer bay to protect personnel and equipment.

This procedure aims to minimize downtime, prevent accidents, and maintain the reliability and stability of the electrical supply.

Figure 1 – Single Line Diagram for the 132kV Transformer Bay at Substation

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1.1 Isolation Procedure

Step No.1 – Open the E02 Q0 Transformer Bay Circuit Breaker:

1. Navigate to the control panel corresponding to the E02 Q0 Transformer Bay.
2. Locate the circuit breaker control switch and set it to the “Open” position.
3. Verify that the circuit breaker has successfully opened by checking the indicator lights on the control panel.

Step No.2 – Open the E02 Q1 Bus Isolator:

1. Identify the E02 Q1 Bus Isolator, which disconnects the busbar from the transformer bay.
2. Operate the control mechanism to move the isolator to the “Open” position.
3. Confirm that the bus isolator is fully open, ensuring there is no physical connection between the busbar and the transformer.

Step No.3 – Open the E02 Q9 Line Isolator:

1. Locate the E02 Q9 Line Isolator, which isolates the transmission line from the transformer bay.
2. Actuate the isolator to the “Open” position using the control handle or switch.
3. Check the status indicators to verify that the line isolator is completely open.

Step No.4 – Close the E02 Q51, E02 Q53, and E02 Q8 Earthing Switches:

1. Identify the earthing switches E02 Q51, E02 Q53, and E02 Q8, which ground the disconnected equipment for safety.
2. Operate each earthing switch to the “Close” position.
3. Ensure that each earthing switch is securely closed, and that the equipment is properly earthed, providing a safe work environment for maintenance personnel.

Figure 2 – Isolation of 132kV GIS Transformer Bay

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1.2 Checking for Live Parts

Step No.1 – Verify De-energization with a Live Line Tester:

1. Use a live line tester to check that no part of the MV bushing and busbar is live.
2. Perform the test on the MV bushing first, ensuring no voltage is present.
3. Repeat the test on the busbar, confirming complete de-energization.
4. Record the test results and proceed only if both tests confirm that the equipment is de-energized.

Watch Video – Voltage Detectors MV Medium Voltage

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1.3 Restoration Procedure:

Step No.1 – Ensure the LCC is in Remote Position:

1. Verify that the Local Control Cubicle (LCC) for the E02 Q0 Transformer Bay is set to the remote position.
   This setting ensures that operations are conducted from the control room, minimizing the risk of manual errors during the restoration process.

Step No.2 – Confirm Interlocking is Enabled:

1. Check the interlocking system to ensure it is active. Interlocking prevents simultaneous operations that could cause unsafe conditions, such as closing an isolator while the earthing switch is closed.
2. Verify the status of interlocks using control room indicators or interlock status panels.

Step No.3 – Open the E02 Q51, E02 Q53, and E02 Q8 Earthing Switches:

1. From the control room, operate the switches to open the earthing connections.
2. Confirm that each earthing switch (E02 Q51, E02 Q53, and E02 Q8) is fully open, ensuring there is no ground path that could cause an electrical fault.

Step No.4 – Close the E02 Q1 Bus Isolator and E02 Q9 Line Isolator:

1. Actuate the E02 Q1 Bus Isolator to the “Close” position to reconnect the busbar to the transformer bay.
2. Operate the E02 Q9 Line Isolator to the “Close” position to reconnect the transmission line to the transformer bay.
3. Check the control room indicators to confirm that both isolators are securely closed and making proper electrical contact.

Step No.5 – Close the E02 Q0 Transformer Circuit Breaker:

1. Finally, set the E02 Q0 Transformer Bay Circuit Breaker to the “Close” position.
2. Verify the closure by checking the breaker status indicators and ensure the transformer bay is energized and operational.

Good Reading – Practical guidelines for protection system engineering

Practical Design Rules for Protection System Engineers

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1.4 Detailed Safety Checks:

Step No.1 – Pre-Isolation Checks:

1. Notify relevant personnel and departments of the impending isolation.
2. Ensure that load transfer or load shedding has been completed as necessary to avoid system disruptions.
3. Review and follow any site-specific safety protocols or lockout/tagout procedures.

Step No.2 – Post-Restoration Checks:

1. Confirm the operational status of the transformer bay through control room monitoring systems.
2. Perform a visual inspection to ensure all equipment is operating correctly and there are no abnormal conditions.
3. Inform all relevant personnel and departments that the transformer bay has been restored to service.

By following these detailed steps, the isolation and restoration of the 132kV transformer bay are conducted safely and efficiently, minimizing risks and ensuring the integrity of the electrical system.