It is common for a slight hissing sound to occur when high-voltage breakers or switches are connected to an energized source. This phenomenon is typically associated with the flow of electrical current and is considered a normal part of the operation. It should not be a cause for immediate concern or a reason to halt the operation. Instead, the operation should continue until the breaker or switch is securely and fully engaged in its position. This ensures proper electrical connection and functionality.
High Voltage Safe Work Practices
1. Operating High-Voltage Circuit Breakers, Contactors, and Switches – Verification of Isolation
Operating the isolation mechanism of high-voltage circuit breakers, contactors, and switches requires a meticulous verification process to ensure the safe isolation or connection of the energy source. The following guidelines outline the verification steps, and the appropriate methods for different equipment designs:
1. Indicating Lights:
- Check for the presence of indicating lights on the exterior of the equipment. These lights are designed to convey the status of the breaker/contactor/switch.
- If the equipment is connected to the high-voltage bus, the light will be illuminated.
- If the equipment is isolated from the high-voltage bus, the light will not be lit.
- Note any changes in the light status (from off to on or vice versa) during the switching operation.
2. Visual Inspection:
- For equipment with a visual inspection window, verify that the breaker/contactor/switch is in the connected position when it’s connected to the high-voltage bus and in the disconnected position when isolated from the high-voltage bus.
- Examine the appropriate contacts, such as main and arcing contacts, for their positions.
3. Voltmeter:
- If the equipment is equipped with a voltmeter, observe the voltage reading to determine the presence or absence of voltage.
- Presence of voltage should be confirmed when the equipment is connected to the high-voltage bus.
- Absence of voltage should be confirmed when the equipment is isolated from the high-voltage bus.
4. Caution for Equipment with Cubicle Doors:
- Some equipment designs necessitate opening the cubicle door to verify the breaker’s position using an indicating device.
- Ensure that the appropriate Personal Protective Equipment (PPE) specified in Appendices A, B, C, or D is worn until the door is securely closed and fastened.
5. Addressing Verification Challenges:
- In cases where verification methods pose challenges or problems, especially those identified during plant operator training, it is essential to contact Electrical Engineering for assistance and guidance.
Additional Considerations for HV Motors or Equipment:
- Work on high-voltage (HV) motors or equipment that draw power from multiple sources requires a thorough identification and implementation of lockout and tagout procedures for all energy sources.
- For instance, a high-voltage motor receiving both HV power and low voltage for field excitation, speed control, space heating, etc., necessitates the lockout and tagging of all these power sources before any work is allowed on the equipment.
- Similarly, in switchgear cubicles with multiple feeds (AC PTs, DC, control circuits, etc.), all sources must be locked out and tagged out before work inside the cubicle is permitted. Internal cubicle fuses or circuit breakers may serve for cubicle isolation.
- Mechanical or process sources of energy that could potentially allow motor rotation (e.g., barring devices, process reverse flow) should also be isolated and tagged out as part of the safety measures.
These verification and isolation procedures are critical to ensuring the safety of personnel working with high-voltage equipment and preventing accidents or electrical hazards.
2. Inspections and Meter Readings During Equipment Starting
When it becomes necessary for an individual to stay within an electrical room to oversee the instrumentation during the startup of equipment, it is imperative to adhere to specific safety precautions:
1. Personal Protective Equipment (PPE):
- Purpose: Ensure the safety of personnel overseeing equipment startup by requiring the use of appropriate PPE.
- Procedure:
- All individuals involved in monitoring the equipment must wear the specified Personal Protective Equipment (PPE) as outlined in Appendix A.
2. Access Door and Panel Closure:
- Purpose: Prevent unauthorized access and maintain a safe environment during equipment startup.
- Procedure:
- High-voltage access doors and panels within the electrical room must be securely closed and locked to restrict entry.
3. Limited Personnel Presence:
- Purpose: Restrict access to only those individuals directly involved in monitoring the equipment during startup.
- Procedure:
- Only personnel with a role in monitoring the equipment are permitted to remain within the electrical room during the startup process.
4. Alternative Monitoring Method:
- Purpose: Enhance safety by minimizing personnel presence in the electrical room.
- Procedure:
- It is recommended to utilize an alternative method for monitoring instrumentation during equipment startup, such as using a video camera directed at the instrumentation.
- This approach eliminates the need for personnel to remain inside the electrical room, further reducing potential risks.
By following these precautions, the safety of personnel can be assured during equipment startup, and the potential hazards associated with high-voltage equipment can be mitigated effectively.
3. High-Voltage Motors in Flammable-Gas Atmospheres Without Permanent Pre-Start Purging Systems
The operation of high-voltage motors in areas containing flammable gases carries inherent risks, as there is a potential for ignition if these motors are started in the presence of such gases. To prevent accidents and ensure safety, plant personnel must adhere to specific safety measures when dealing with high-voltage motors in areas with flammable gas installations.
These precautions are outlined in Appendix B and are designed to mitigate the associated risks and hazards effectively. Personnel should refer to Appendix B for detailed guidance on safe practices and procedures for starting high-voltage motors in these environments. This proactive approach helps safeguard both personnel and the equipment from potential dangers related to flammable gas atmospheres.
4. Protective Relays – Safe Handling and Operation
Handling and operating protective relays require strict adherence to safety protocols to minimize the risks associated with energized circuits. The following guidelines are essential to ensure the safety of personnel and equipment:
1. Withdrawal of Protective Devices:
- It is strictly prohibited to withdraw protective devices from their cases while the circuit is energized (breaker/contactor closed). Any exceptions to this rule must be explicitly approved by Electrical Engineering management or their authorized representative.
2. Operation or Interrogation from Faceplate:
- Operating or interrogating electronic relays from their faceplate is also prohibited when the circuit is energized (breaker/contactor closed). Similar to the above point, any deviations from this protocol require explicit approval from Electrical Engineering management or their authorized representative.
3. Communication with Relays:
- When the breaker or contactor is closed, personnel communicating with the relay from a local PC must use a cable that is at least 5 meters in length.
- This task is restricted to Qualified Electrical Leader or Fire Alarm authorized personnel.
These stringent safety measures are essential to prevent accidents, ensure proper equipment operation, and protect the well-being of personnel working with protective relays. Compliance with these guidelines is paramount for maintaining a safe working environment.
5. Temporary Electric Power Supply – Safety Protocols
Utilizing temporary electric power supplies, such as generators, batteries, or customer feeds, to connect to a permanent plant electrical system for temporary power requirements demands strict adherence to safety measures. These precautions are essential to prevent any risks associated with back-feeding electrical equipment that must remain de-energized during maintenance outages or upgrades. Below are the key safety procedures to be followed:
1. Implement Physical Breaks:
- To ensure isolation and prevent back-feeding, create a physical break in the electrical supply system. This can be achieved through actions such as:
- Withdrawing a withdrawable circuit breaker
- Removing bus links in a bus duct
- Removing fuses in a fused switch
- Removing cable terminations, etc.
- Opening a non-withdrawable device, like a disconnect switch or molded-case breaker, is acceptable for this purpose as long as the device can be locked in the open position and is approved by Electrical Engineering.
2. Ground De-Energized Bus or Section:
- When work is being performed on a de-energized bus or any upstream device that is to remain de-energized during the temporary condition, ensure that the bus or section is properly grounded.
3. Pre-work Review:
- Prior to connecting a temporary electrical supply or generator, a comprehensive review must be conducted.
- Task descriptions should be utilized to configure the system for the upcoming work, with reference to Appendix D1, which can be attached to the Safety Work Permit. Appendix E provides examples of marked-up electrical diagrams.
4. Management of Change (MOC):
- An approved Management of Change (MOC) process is mandatory before connecting a temporary electric power supply. This helps assess and document the changes in the electrical system.
5. Restoration Process:
- After the temporary electrical supply is no longer required, a second set of task descriptions should be used to restore the electrical system to its normal state. Reference Appendix D2, which can be attached to the Safety Work Permit.
6. Safety Work Permits:
- A Safety Work Permit is essential for the connection of a temporary electric power supply.
- A second Safety Work Permit must be issued for the work necessary to return the system to its normal operation.
7. Scope Changes:
- If the scope of work changes during the process, the work must cease immediately.
- The existing Safety Work Permit and checklist (Appendix D1) will be canceled.
- A new Safety Work Permit, along with a revised set of task descriptions and checklist (Appendix D1), must be issued based on the updated work scope.
These stringent safety measures are crucial to ensure the safety of personnel and the integrity of the electrical systems when working with temporary electric power supplies. Adherence to these protocols is fundamental in maintaining a secure work environment.
6. Batteries and Battery-Charging Installations – Safety Guidelines
Working with batteries and battery-charging installations requires strict adherence to safety protocols to prevent accidents and ensure the well-being of personnel. Here are the key safety measures:
1. Wet-Cell Battery Types:
- Personal Protective Equipment (PPE): When cleaning batteries or handling battery fluids, the PPE specified in Appendix A must be worn. Additionally, chemical gloves and an apron are required for these tasks. For all other battery work, the PPE from Appendix A and a chemical apron are mandatory.
- No Open Flames or Smoking: Prohibit open flames or smoking in battery areas, as hydrogen gas is vented during charging, posing an explosion risk.
- Warning Signs: Avoid using metal warning signs above battery charging installations. Instead, utilize plastic signs or labels.
- Eyewash Station: Battery charging areas where maintenance and servicing occur (excluding installations solely for charging) must have a 15-minute eyewash station installed nearby. If the charging installation is located in electrical rooms, the eyewash should be a self-contained (not plumbed) model. It must be designed to contain used water in a reservoir or prevent it from draining onto the floor.
2. Sealed Battery Types:
- PPE: When cleaning or testing sealed batteries, the PPE outlined in Appendix A should be worn. An eyewash station is not required for this battery type.
Adhering to these safety guidelines is crucial to protect personnel when working with batteries and battery-charging installations and to mitigate potential hazards associated with these tasks.
7. Housekeeping and Cleaning Solvent Restrictions – Safety Guidelines
Maintaining proper housekeeping and using approved cleaning solvents are essential for electrical safety. Here are the key guidelines:
Housekeeping Restrictions:
- Permissible Housekeeping Activities: Routine housekeeping activities like floor cleaning can be carried out without the need for a Safety Work Permit.
- Authorization Required: For housekeeping activities other than routine cleaning, a Safety Work Permit is mandatory, and appropriate precautions must be taken.
- Avoid Electrically-Conductive Materials: Electrically-conductive cleaning materials, including steel wool, silicon carbide, and conductive liquid solutions such as water, should not be used, as they can pose electrical hazards.
Approved Cleaning Solvents:
- Use Approved Solvents: Only cleaning solvents that have been approved by Electrical Engineering should be used when cleaning or working around electrical equipment.
Adhering to these guidelines is crucial to prevent electrical hazards and ensure the safety of personnel when performing housekeeping and cleaning tasks in areas with electrical equipment.