Okay, this is definitely a head-scratcher. "Ghost tripping" is never fun, especially when it cascades. Given the cold weather and the synchronized tripping, here's a breakdown of possible causes, mitigation strategies, and further troubleshooting steps

I. Possible Causes (Prioritized):
Temperature-Related Contraction/Expansion

This is your prime suspect, and it's affecting multiple components:

Fuse Holder/Linkage

The cold can cause the metal in the fuse holders, trip bar mechanisms, and linkages to contract. This contraction, even if minimal, could be enough to: Slightly alter the position of the trip bar, enough to actuate the safety switch. Change the fuse-to-clip contact pressure, causing increased resistance and heat cycling that weakens the fuse, leading to failure. Impact tolerances in the mechanical linkage, causing binding or sticking.

Wiring

Low temperatures can make wiring more brittle. Any existing loose connections, marginal insulation, or corrosion can be exacerbated by the cold, leading to intermittent shorts or open circuits.

Relay Logic

While less likely, extreme temperature swings can affect the internal components of the Siemens Siprotec relays themselves. This is usually a gradual drift in accuracy rather than a sudden, synchronous tripping.

Condensation/Humidity

While it might be cold, humidity levels can still fluctuate. If there's any air infiltration into the MV room, moisture can condense on the cold equipment, especially when temperatures start to rise slightly. This condensation can lead to tracking across insulation surfaces, corrosion, and ultimately, spurious trips.

Vibration

Vibration from operating equipment (especially the running pulverizer) can be transmitted through the building structure to the switchgear cabinets. If the mechanical linkages are already sensitive due to cold-induced contraction or loosening, vibration could be the final trigger.

Power System Disturbance/Transients

While less likely given the specific symptoms, a voltage sag, surge, or transient on the power system could potentially trigger the relays, especially if they have marginal settings. This would likely trigger more widespread issues, not just those related to these specific circuits.

Ground Faults

While not directly indicated by the fuse blown indication, it’s still worth consideration. A ground fault, even intermittent, could potentially affect the relay logic and cause a trip.

Relay Setting Issues

Someone may have inadvertently changed relay settings recently.

II. Mitigation Strategies (Prioritized)



Improve MV Room Temperature Stability

This is the MOST CRITICAL immediate step.

Heating

Install temporary space heaters (carefully, ensuring adequate clearance from equipment and proper ventilation). Focus on maintaining a consistent temperature above freezing. Aim for 40-50°F (4-10°C) if possible. Monitor the temperature regularly.

Insulation

Identify any sources of cold air infiltration (gaps around doors, windows, cable penetrations) and seal them. Consider temporary insulation around the switchgear cabinets themselves (being extremely careful to avoid blocking ventilation).

Dehumidification

If humidity is suspected, use dehumidifiers in conjunction with the heaters.

Temporary Relay Setting Changes



Disable "flx01" Trip Function

As a temporary troubleshooting step, if you are confident that the "flx01" function is the primary cause of the trips, consider temporarily disabling it. This is only if doing so does not compromise the protection of the equipment.

Document this clearly and reinstate the function as soon as the root cause is identified and corrected. Increase Time Delays (Siprotec)

If possible and appropriate, slightly increase the time delays on the affected relay functions. This might filter out some of the spurious trips caused by intermittent issues. Again,

document and revert to original settings ASAP. Fuse Inspection and Replacement (Strategic)



Prioritize Running Equipment

Inspect and replace fuses in the actively running equipment first. This is the most critical.

Visual Inspection

Carefully inspect the fuse holders, clips, and fuse bodies for any signs of corrosion, discoloration, overheating, or mechanical damage.

Tighten Connections

Ensure that all fuse clips are making good, tight contact with the fuses.

Torque Values

Use a calibrated torque wrench to tighten connections to the manufacturer's recommended torque values.

Wiring Inspection (Focus on Terminations)



Visually inspect accessible wiring terminations within the switchgear cabinets for looseness, corrosion, or signs of overheating. Gently tug on wires at terminations to check for tightness. Consider thermal imaging (IR scanning) of accessible terminations to identify potential hot spots. Vibration Dampening (if feasible)

If you suspect vibration is a contributing factor, try to identify the source and implement vibration dampening measures (e.g., rubber pads under the switchgear, isolating supports).

III. Further Troubleshooting Steps (Immediate and Longer-Term)



Detailed Event Logs (Siprotec)

Download the detailed event logs from the Siprotec relays for the days leading up to and including the trips. These logs can provide valuable information about the sequence of events, relay settings, and any other anomalies.

Oscillography (if available)

If your Siprotec relays have oscillography capabilities, enable them. Oscillography captures waveform data during a trip, which can be invaluable for analyzing the cause of the trip.

Trend Monitoring

Set up trend monitoring of key parameters within the Siprotec relays, such as voltage, current, frequency, and relay operating times. This can help identify any trends that might be contributing to the trips.

Safety Switch Testing

As soon as possible, when conditions allow, perform a thorough test of the safety switches and associated linkages. Ensure proper operation and adjustment.

Mechanical Linkage Inspection and Adjustment

This is a longer-term task, but essential. When you can safely shut down the equipment, carefully inspect the mechanical linkages for any signs of wear, corrosion, or misalignment. Adjust or replace components as needed.

Insulation Resistance Testing (Megger)

When safe and possible, perform insulation resistance tests (Megger tests) on the cables connected to the switchgear. This can help identify any insulation degradation that might be contributing to ground faults.

Review Relay Settings

Double-check all relay settings to ensure they are correct and appropriate for the application. Consider having a qualified protection engineer review the settings.

Consult Siemens

Contact Siemens technical support for assistance. They may have seen similar issues with the Series 81000 contactors and Siprotec relays. Provide them with detailed information about the problem, including the event logs and oscillography data.

Root Cause Analysis

Once the immediate problem is under control, conduct a thorough root cause analysis to identify the underlying causes of the "ghost tripping" and prevent future occurrences.

IV. Safety Considerations



De-energize and Lockout/Tagout (LOTO)

Always follow proper de-energization and LOTO procedures before working on any electrical equipment.

Qualified Personnel

Ensure that all work is performed by qualified and experienced personnel.

PPE

Wear appropriate personal protective equipment (PPE), including arc flash-rated clothing and gloves.

Hot Work Permits

Obtain hot work permits before performing any work that could create a fire hazard.

Confined Space Entry

If you need to enter any confined spaces (e.g., cable vaults), follow proper confined space entry procedures.

V. Communication

Keep your management and other stakeholders informed of the situation and the steps you are taking to address it. Document all troubleshooting steps and findings.* Share information with other power plants that may be experiencing similar issues.

In summary, prioritize temperature stabilization in the MV room, conduct a thorough inspection of the fuses and their holders, review relay settings, and document everything. Contact Siemens for support and conduct a thorough root cause analysis to prevent future occurrences.

Please provide the pictures/drawings when you can. Good luck, and stay safe! Let me know if you have any further questions. Flag for review