ELECTRIC OPERATING PROCEDURES Date: 11/01/06

Transcription

1 Doc No.: NG-USA EOP D001 Page: 1 of 5 ELECTRIC OPERATING PROCEDURES SUBJECT: Cutouts Open/Enclosed Type SECTION: Distribution/Overhead REFERENCE: National Grid Retail Company Safety Manuals National Grid Safety and Health Policies & Procedures OSHA National Grid Distribution Construction Standards National Electric Safety Code (NESC) Applicable Work Procedures GENERAL INFORMATION: The purpose of this procedure is to provide information and work methods for working on (operation or replacement) or in the vicinity of open or enclosed cutouts. Failure of any in-service distribution equipment is an eventuality. Adherence to proper work procedures must always occur to minimize the risk of any hazard that could occur from failure. National Grid continues to evaluate improved or alternate materials and designs for distribution equipment requirements. PROGRAM ADMINISTRATOR: SCOPE: Distribution Engineering Services I. Background Open or Enclosed Type Fused Cutouts II. Jobsite Hazard Evaluation III. Work Process Requirements IV. Cutout Removal/Replacement APPLICABILITY: This procedure will apply to all qualified workers (see definition) who may perform work on or near exposed energized parts. DEFINITIONS: Qualified Workers (as defined in ) Workers shall be trained in and familiar with the safety related work practices, safety procedures and other safety requirements that pertain to their respective job assignments. Workers shall also be trained in and familiar with any other safety practices, including applicable emergency procedures (such as pole top/bucket rescue). Qualified workers shall be trained and competent in: Supersedes Document Dated: 08/01/06 Authorized By: Director-Distribution Engineering Svcs. Approved By: VP- Engineering Services.

2 Skills and techniques necessary to distinguish exposed live parts. Determining nominal voltage of exposed live parts. Knowledge of minimum approach distances. Proper use of precautionary techniques, use of PPE including insulating and shielding materials and properly rated insulated tools for working on or near energized parts of electrical equipment. I. BACKGROUND OPEN OR ENCLOSED TYPE FUSED CUTOUTS The general design of cutouts has undergone modification over time. This work procedure is intended to highlight the progression and limitation resulting in the transition from enclosed style cutouts, to banded style cutouts, to potted style cutouts, and finally polymeric style cutouts. Enclosed cutouts are designed to enclose the fuse tube with top, bottom and center mounting assemblies cemented into the cavity in the porcelain body. Banded style cutouts have the center mounting pin, top, and bottom assemblies U bolted to the porcelain fuse body. Potted style cutouts have the top, bottom and center mounting assemblies cemented into a cavity in the porcelain body. The Polymeric cutout is designed using a fiberglass rod with attachments either bolted or molded to the rod with a covering of polymeric material (silicone rubber and/or EDPM). The failure mode of each type of cutout differs; however, all have a finite life expectancy. General failure modes for the different types of cutouts are as follows: Enclosed type cutouts fail due to internal contamination/tracking and porcelain breakage. Banded type cutouts fail with fuse tube burning up. Potted type cutouts fail due to tracking, cracking, and porcelain breakage. The failure mode for Polymeric type cutouts has not been established, but may be via leakage/tracking. Enclosed Porcelain Banded Cutout Potted Cutout Polymeric Due to the mechanical failure mode and potential hazard associated with potted porcelain cutouts, National Grid is no longer purchasing this style of cutout. National Grid s preferred cutout style is the polymeric style. These materials have performed well in electrical testing, and do not exhibit the mechanical failure mode seen in the potted porcelain cutouts. Page 2 of 5

3 II. JOB SITE HAZARD EVALUATION Whether the job entails routine line work, operating a cutout, replacing a cutout, or work on or near a cutout due to an emergency situation, a thorough inspection of poles and pole top must be conducted and documented on a written job brief. Any defective equipment found as part of the job site hazard evaluation must be repaired or replaced. At a minimum, the following items shall be reviewed/evaluated/during the hazard evaluation: All appropriate Personal Protective Equipment, which includes, but is not limited to hard hat, eye protection, flame retardant clothing, and rubber gloves and sleeves must be utilized as required by the National Grid Retail Company Safety Manuals and applicable work procedures. Insulating protective equipment such as rubber blankets, line hose and fiberglass barrier guards must be utilized as required. Minimum approach distance and proximity of equipment to be worked on. The condition and location of all cutouts on the pole/poles with particular attention to the tap lead length and possible items that could be contacted during a cutout failure. Condition of the cutout (inspect for cracks or fractures, tracking evidence or discolored connections). The condition of the crossarms and pole top with particular attention to any signs of burning. Any hazards from non-standard construction. Delta system or potential back-feed. Upon completion of the Job Site Evaluation the qualified worker will be prepared to take the necessary precautions to eliminate, avoid or mitigate any foreseeable or unforeseeable hazards. The qualified worker will be prepared to take additional electrical safeguards, including the use of hot stick/live line equipment, the use of additional line and equipment cover-up, the placement of circuits or portions of circuits on non-reclosing/hot line tag, or the de-energization of customers, circuits, or parts of circuits, in order to safely complete the work. III. WORK PROCESS REQUIREMENTS The replacement of both good and defective potted porcelain cutouts will be accomplished as part of any work performed on poles or structures. Specific conditions and work requirements for cutout replacements are listed below: Prior to performing routine or emergency work in the primary area, all potted porcelain cutouts on poles or structures shall be thoroughly inspected for visible hazards and replaced. Additional precautions should be taken if defects were identified as part of the inspection process.. Prior to performing routine or emergency work in the secondary area all potted porcelain cutouts on the poles or structures shall be thoroughly inspected for visible hazards. A defective cutout must be replaced prior to work being performed. When no apparent defects are visible the cutout should be replaced, provided equipment, material, and crew qualification allow. Work can proceed at or below the secondary level using class O gloves when no apparent cutout defects or hazards associated with the cutout are found. Page 3 of 5

4 Cut and kick pole work shall require a thorough inspection of the potted porcelain cutouts. If the inspection reveals that the potted porcelain cutout is defective, then the cutout must be replaced prior to the cut and kick process. In the rare case where a defective cutout of any type is NOT immediately replaced, no work shall be performed at this pole or structure. The worker (authorized person) shall immediately report the condition to the system operator and notify his/her supervisor. A hold tag must also be placed at the location per NG-USA EOP G014, and the cutout is to be scheduled for replacement within 48 hours. Potted porcelain or enclosed porcelain cutouts shall not be used as a visable open for grounding or isolation. When the requirement to replace potted porcelain cutouts impact safety to the worker or public, or compromises system continuity (storm restoration), or customer business continuity, work may proceed, provided a thorough inspection of the cutout shows no apparent defects. Replacement of energized primary cutouts requires a minimum of two qualified workers. Cutouts may be de-energized by a single worker using hot stick/live line tools as shown below in the single worker excerpt from Standard 29 CFR (1) (ii) A, B, C. A) Routine switching of circuits, if the employer can demonstrate that conditions of the site allow this work to be performed safely. B) Work performed with live-line tools if the employee is positioned so that he or she is neither within reach of nor otherwise exposed to contact with energized parts, and C) Emergency repairs to the extent necessary to safeguard the general public. Jumpers of any type shall not be used to keep transformers, or transformer banks energized for the purpose of changing potted porcelain cutouts. Where practical, approved 15kV jumpers can be utilized for bypassing a cutout when replacing main line cutouts or cutouts feeding tap lines. (Jumpers must not be placed on cutout tap conductors). Refer to National Grid Retail Company Safety Manual and Work Procedures to determine when it may be necessary to place a circuit or portion of a circuit on non-reclosing/hot line tag and obtain a NRA. IV. CUTOUT REMOVAL/REPLACEMENT Removal All exposed energized conductors, grounds and neutrals within reaching and falling distance shall be rubbered-up or guarded. The cutout fuse holder will be opened and removed. (The condition of the cutout and the results of the inspection will dictate whether this can be done safely). When disconnecting the cutout from an energized circuit by means of a conducting wire, employees shall remove the source end first from the source conductor. (Note: delta transformer configurations will have both source and load connection points energized with door removed). Care must be taken to control any loose lead from contacting conductors, parts or equipment that are at a different potential. The alternate method is to remove the source lead from the cutout body using hot stick tools (Method is dictated by configuration and condition of installation). The lead must be controlled at all times. The method of removal and replacement of the lead must be discussed in detail during the documented Job Brief. All leads must be kept as short as possible and controlled. After removal and prior to replacing the new cutout, the position of the cutout must also be evaluated to ensure that the mounting location is in the least hazardous space. Page 4 of 5

5 Replacement Install the load side lead first and then install the source side lead, keeping the tap lead controlled and as short as possible. Depending on the configuration of the pole top construction, remove rubber and/or barriers. Install the fuse holder in the cutout and close using a hot stick/live line tool. If a line jumper has been applied, remove the jumper after closing the cutout. RESPONSIBILITIES: TRAINING: 1. Distribution Engineering Services A. Update procedure as necessary. B. Provide T&D personnel guidance when requested. 2. Customer Operations A. Ensure the components of the procedure are implemented. B. Ensure T&D personnel are trained in this procedure. C. Provide revision input as necessary. 3. Employee A. Demonstrate the understanding of the procedure. B. Comply with the requirements of the procedure. Provided by appropriate National Grid Training Program. Page 5 of 5

6 NG-USA EOP D001 Cutouts Open/Enclosed Type 11/01/06 This document is revised throughout.