8.3 Risk Assessment & Restoring Installations to Service

8.3 Risk Assessment & Restoring Installations to Service

Periodic inspection and testing often takes place on legacy, deteriorated, or severely neglected electrical installations. Inspectors preparing for City & Guilds 2391-51 must possess the skill to evaluate physical hazards before applying test voltages and must know how to safely manage immediate dangers. Furthermore, returning an installation to service following testing requires a methodical, step-by-step verification sequence to ensure safety is maintained.

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1. Risk Assessment on Aged, Fragile & Hazardous Installations

Under the Management of Health and Safety at Work Regulations 1999 and EAWR 1989, inspectors have a statutory duty to assess risks before carrying out physical work. Applying high test voltages (e.g., 500V or 1000V DC) or physically disturbing old switchgear can trigger insulation failure, flashovers, or electrical fires.

Identifying High-Risk Legacy Wiring & Materials

1. Vulcanised India Rubber (VIR) Cables:

   • Common in pre-1960s installations. Rubber insulation becomes extremely dry, hard, and brittle over time.
   • Hazard: Flexing or disturbing VIR cables during distribution board cover removal causes the rubber to crumble instantly, leaving bare conductors in close proximity and creating immediate short circuits.
   • Mitigation: Perform visual checks first. If VIR insulation is severely perished, do not disturb conductors. Record a Code C2 or C1 defect and omit invasive dead testing under an operational limitation.

2. Asbestos Hazards in Legacy Switchgear:

   • Older rewirable fuse carriers (e.g., MEM, Bill, or Crabtree units), arc chutes, and distribution board backing pads often contain asbestos fibers.
   • Hazard: Inhaling airborne asbestos fibers during fuse removal or enclosure cleaning.
   • Mitigation: Do not vacuum or brush switchgear containing asbestos. Follow specialist asbestos risk controls; if friable asbestos is identified, cease work and inform the Duty Holder.

3. Green Goo (Plasticiser Exudation):

   • Early PVC wiring (1965–1971) can exude a green sticky liquid (di-octyl phthalate plasticiser reacting with copper).
   • Hazard: Green goo lowers insulation resistance, causes tracking across terminal blocks, and severely degrades accessory contacts.

4. High Test Voltage Hazards:

   • Applying a 500V DC insulation resistance test across damp, carbonised, or cracked insulation can induce dielectric breakdown or arc tracking.
   • Mitigation: Always start insulation testing at 250V DC on suspect legacy circuits before stepping up to 500V DC.

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2. Immediate Danger Protocol: Managing Code C1 Conditions

If during periodic inspection and testing the inspector discovers a condition that presents immediate danger to person or property, an immediate safety protocol must be executed.

+------------------------------------------------------------------+
|                    CODE C1 DANGER PROTOCOL                       |
|                                                                  |
| 1. Stop / Make Safe -> 2. Verbal Warning -> 3. Written Notice   |
|                                                                  |
| 4. Record in EICR -> 5. Issue UNSATISFACTORY Overall Assessment   |
+------------------------------------------------------------------+

Definition of Code C1

• C1 – Danger Present: Risk of injury. Immediate remedial action required.
• Examples: Exposed live conductor accessible to touch (missing DB blanking plate), metal switchgear casing energised due to missing Earth, broken socket faceplate exposing live terminals.

Mandatory Action Sequence

1. Make Safe Immediately: With the Duty Holder's permission, isolate the dangerous circuit or fit an immediate protective barrier (e.g., install a temporary DIN-rail blanking plate).
2. Verbal Notification: Immediately inform the client or Duty Holder on site verbally of the exact nature of the danger.
3. Issue Written Warning Notice: Issue a formal Dangerous Condition Notification form (or immediate written notification letter) to the Duty Holder before leaving the site.
4. Record on EICR: Log the observation in Section K (Observations) with a Code C1 classification.
5. Overall Assessment: Assign an overall outcome of UNSATISFACTORY in Section E of the EICR.

Critical Legal Point: If the Duty Holder refuses to allow the inspector to isolate a Code C1 dangerous circuit, the inspector must not leave the danger unrecorded. The inspector must document the refusal in writing on the Dangerous Condition Notification, request the Duty Holder to sign it, and formally warn them of their legal liabilities under EAWR 1989.

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3. Pre-Energisation Checks & Re-Commissioning

Before restoring power to an isolated installation or distribution board following testing, a strict pre-energisation checklist must be executed to prevent catastrophic short circuits upon re-energisation.

Pre-Energisation Checklist

• Removal of Temporary Test Connections: Verify that all temporary shorting links, $R_1+R_2$ crossover jumpers, earth test leads, and neutral disconnection links have been completely removed.
• Enclosure Ingress Protection (IP) Verification:
  • Top horizontal surfaces of enclosures must meet IP4X minimum (protection against solid objects $> 1 ext{mm}$, preventing wires or small screws falling in).
  • Side and front accessible surfaces must meet IP2X or IPXXB minimum (protection against finger contact).
• Tool & Foreign Object Audit: Perform a visual inspection inside switchgear enclosures to confirm no hand tools, loose screws, wire offcuts, or metallic debris remain inside.
• Protective Device Audit: Confirm all MCBs, RCDs, and fuses are returned to their correct switch positions and carry correct ratings.
• Reinstatement of Barriers & Covers: Ensure all internal arc shields, terminal covers, and main dead-front panels are securely refitted.

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4. Controlled Re-Energisation & Post-Energisation Checks

Restoring power must follow a controlled, logical sequence to manage inrush currents and verify system operational integrity.

  RE-ENERGISATION SEQUENCE:
  
  [1. Remove LOTO & Notify Site]
               |
               v
  [2. Close Main Switch / Isolator]
               |
               v
  [3. Close Sub-Main Isolators]
               |
               v
  [4. Close Final Circuit MCBs (One by One)]

Step-by-Step Re-Energisation

1. LOTO Lock Removal: Remove all padlocks and warning tags. Formally notify site personnel that power restoration is commencing.
2. Controlled Switching Sequence:
   • Close the Main Supply Switch / Isolator first.
   • Close sub-main isolators.
   • Energise final circuit MCBs/RCBOs one by one. Closing circuit breakers sequentially prevents a massive combined inrush current from tripping the upstream main circuit protective device or utility supply fuse.

Post-Energisation Verification

1. Phase Rotation Testing: On three-phase (TP&N) supplies, use a phase rotation meter to verify that the phase sequence remains clockwise (L1-L2-L3) before re-connecting three-phase motors or HVAC plant.
2. Supply Voltage & Polarity Check: Verify correct nominal voltage ($230 ext{V}$ single-phase / $400 ext{V}$ three-phase) and correct phase-to-neutral polarity at main intake terminals.
3. RCD Functional Testing: Test all RCDs and RCBOs using their integral test button (T) to confirm mechanical tripping functionality under normal line voltage.