1、Lessons Learned Entry: 1716Lesson Info:a71 Lesson Number: 1716a71 Lesson Date: 2004-10-1a71 Submitting Organization: JSCa71 Submitted by: Ron Montaguea71 POC Name: Shelia Powella71 POC Email: shelia.k.powellnasa.gova71 POC Phone: 281-483-3142Subject: Configuration control of electrical conductors du
2、ring facilities installations Abstract: Power cables in tight power cabinets are susceptible to damage from penetrating fasteners.Description of Driving Event: An electrician suffered burns from an electrical arc when a pre-existing condition in a power distribution panel ultimately led to a ground
3、fault in a 3-phase 480-volt power supply. The pre-existing condition was believed to be an access panel fastener that had penetrated conductor insulation. Power distribution panel designs must allow sufficient internal space within the panel enclosure to route the conductor cables away from fastener
4、s. In the case of this mishap, it appeared that the conductor cables were routed close to the front access panels and dead front where there are multiple fasteners capable of penetrating the cable insulation. A combination of too small a panel plus overcrowded cabling ultimately resulted in fastener
5、 penetration of conductor insulation. Control of the cables was complicated further by the sinuous, unrestrained routing of the cables from the floor to the breaker connections (see picture). Periodic power surges (such as by operating high-voltage breakers or by operating pre-programmed power line
6、surge control devices such as reclosures) can physically jar cables (much like a water or air hose experiencing a sudden pressure increase), moving them incrementally closer to fasteners. Short and straight runs of unrestrained cables would not experience this type of response. Repeated removal and
7、reinstallation of the fasteners for panel access due to construction and maintenance activity may have jeopardized the integrity of the electrical cable insulation. Each Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-removal and reinstallation cycle
8、 may have further penetrated the insulation. Lesson(s) Learned: Ensure that design and acceptance criteria are adequately developed and implemented to route conductors in panel enclosures away from fasteners and sharp edges.Recommendation(s): 1. Ensure that adequate design and inspection criteria ar
9、e developed to provide for sufficient cable clearance within an enclosure. Implement the inspection criteria in both acceptance and preventative maintenance inspections. 2. Conduct a site-wide survey and identify all panels meeting the following criteria: a. Locations between the building transforme
10、r and the main service entrance panel where the secondary cables have no low voltage protective device coverage (excludes switchgear and motor control centers or any panel with upstream low voltage protective device). Low voltage is defined as above 50 volts and below 600 volts. b. Locations where f
11、ire pumps are fed directly from the transformer secondary and do not have any low voltage protective device coverage. This is required by National Fire Protection Agency standards. Locate pump panels without upstream low voltage protection and add warning labels to panel. 3. Using proper PPE, de-ene
12、rgize all identified panels and inspect for: a. Proper conductor strain relief per manufacturers recommendations b. Conductor routing away from sharp panel edges and access panel fastener penetrations. Bundle, saddle, or provide non-conductive isolation barriers as necessary to properly route conduc
13、tors. 4. Include specific instructions for inspections of physical service entrance cable routing and clearances from panel enclosure contact in all scheduled maintenance and repair procedures. 5. Evaluate present five-year maintenance cycle of main service entrance panels and determine if this cycl
14、e should be shortened with respect to usage conditions, i.e., recloser operations, vibration, etc. 6. Future project designs must locate the incoming conduits in relation to the termination at the main breaker such that the number of electrical cable bends is minimized and proper clearances from pan
15、el enclosure are maintained. 7. Establish schedule and procedure to survey similar panels or service feed configurations for locations of electrical cables within panel and proximity to dead front. Schedule outages, perform field investigations and make necessary adjustments.Evidence of Recurrence C
16、ontrol Effectiveness: Photos of rerouted cables were taken after panel was rebuilt and similar panels inspected.Documents Related to Lesson: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 E
17、ngineering Design (Phase C/D).a71 Engineering Design (Phase C/D).Powera71 Manufacturing and Assemblya71 Safety and Mission Assurance.a71 Safety and Mission Assurance.Maintenancea71 Safety and Mission Assurance.Qualitya71 Additional Categories.a71 Additional Categories.Configuration Managementa71 Add
18、itional Categories.Energya71 Additional Categories.Facilitiesa71 Additional Categories.Personal Protective Equipmenta71 Additional Categories.Risk Management/AssessmentAdditional Info: a71 Project: N/AApproval Info: a71 Approval Date: 2006-12-06a71 Approval Name: ghendersona71 Approval Organization: HQProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
