INTRODUCTION TO PROTECTION GRUARANTEE Objectives (1) To explain some terms used in connection with protection guarantees. (2) To identify the different forms of protection which may be provided. (3)To point out the space of the operators responsibility with respect to protection. INFORMATIONThe electrical operator is responsible for all operating equipment owned by PHCN. He is the one person responsible for placing PHCN operating equipment in service, taking it out of service, isolating it for work by other departments and restoring it to service for full or partial use during testing periods.

Whether it is a lighting circuit, a compressor, a governor pump, an 11-kv breaker, a generator, a 330-kv breaker, or auxiliary equipments, the operator has the responsibility for releasing it from service making it safe to work on and restoring it to service. Only in few Instance may he delegate any or all of these responsibilities. In releasing apparatus for works, the operator must be aware of what effect its loss will have on the security of the station, system, supply to the customer or auxiliary equipments. Terms used in protectionApparatusAliveOperating ControlSupervisory Control Isolated

For explanation see the list of special definitions which appears in the beginning of the standard protection code.Forms of Protection Provided1.Hold-off (OF 12) See Fig.1 This is to used when work is being carried out near line apparatus or when live-line crews are working on the transmission line. The purpose of 12 protection is to prevent any apparatus, which might trip out of service as a result of any worker or apparatus Making contact with it, from being re-energized until the workers can report to the operator the details of what has happened.

Hold off protection is not to be used when:-The circuit or equipment can be taken out of service and protection guarantee issued it does not provide safe working condition for the work to be performedwhen suitable constant communication is not available between the operator and the man in charge. Hold-off protection is largely used by the line maintenance department for replacement of insulators, clamps or cross-arms on transmission circuits and by other maintenance departments when they are moving equipment closed by live apparatus.

It must be emphasized that a constant dependable means of communication has to be in effect during the period that the hold-off is in effect. For procedure to be followed in issuing and surrendering hold-off Protection refer to the standard protection cod rule 2003. SELF-PROTECTION (of 11) See Fig. 2 This form of protection is to be used by maintenance departments for work on shop equipment, minor auxiliary plant equipment and lighting circuits. It may, in cases where no communication is available between the operator and the workman be used as a substitute for a protection guarantee.

Procedure for the use of self protection is outlined in the standard protection code rules 2004, -5, -6, -7. In most cases, the workman receives the tags from the operator, performs the necessary switching to remove the apparatus from service places and removes the tags and restores the apparatus to service. The operator, where it is mutually agreed, may perform a part of or all the switching and may place and remove the tags on behalf of the workman. The main function of the operator is to ensure that the removal of any such apparatus will not affect the operating security of his station.

To do this he must know the function of the apparatus and what alternate supplies or equipment may be used to substitute for the apparatus removed. TAKE-OVER TAGS (OF 10) SEE FIG. 3 The use of these tags is not strictly as protection for work in the accepted sense. Rather they are used to identity apparatus whose control has been transferred from a contractor to the operating department.Generally an entire generating unit is not transferred at the same time. As portions are turned over of 10 tags are placed on all valves, switches and other control sources associated with that equipment by the operators.

The tags are placed to prevent the operation of these devices by person other then operators. They are removed when these devices is placed in service or may be replaced by suitable protection tags if work is to continue on the apparatus.CAUTION TAGS (OF 13) see fig 4These tags are used solely to protect equipment which is to be left out of service or restricted in its use. It is never used to provide protection for work.It is placed usually by an operator but may be placed by any qualified employee.

The tags are removed when the restriction on or danger to the equipment is rectified. It is replaced by a suitable protection tag while work is being carried out .PROTECTION GUARANTEEThese guarantee are used to protect workman during all work on apparatus under control of the operating authority which is not permissible under OF 11 or OF 12 protection. It is written certificate which guarantee that safe working condition have been established on the apparatus covered (in the case of a work permit or work and test permit) or that isolation and de-energizing of the apparatus has been effected from all sources of energy under the control of the issuing operator (in case of a station guarantee).

Briefly the requirement of each form of protection guarantee are:-(i) WORK PERMIT (OF 2) see Fig 5it is printed on blue paper. It guarantee complete isolation and de-energizing. It lists all equipment covered on which the workman are permitted to work. It lists all of the isolation and de-energizing devices used to effect the protection by name and specifies whether they have been locked and tagged. On the form are spaces in which special instructions may be given to the man in charge (Permit Holder) regarding safe working clearances; neighboring live apparatus and other helpful data.

It must be signed both by the permit holder and the issuing operator before work can commence and signed again by the permit holder and the operator when work is completed form to the work permit except that it authorizes specified testing of the apparatus during the outage. These test may or may not make the equipment alive and may only be carried out with the knowledge and approval of both the permit holder and the operator. Rule 2028 further explain the use of OF 14 as part of the procedure the tests.(ii) Station Guarantee (OF 4) see Fig 7This is printed on white paper. It is issued when the apparatus on which work is to be carried out cannot be completely isolated and de-energized by means of devices under the control of the issuing operator i.e

when some other neighbor station/s has to co-operate in effecting complete isolation and or de-energizing of such apparatus.It is generally used to support a work permit or work and test permit to be issued at a master station. With regard to jobs such as those on transmission lines or line terminal equipment, it is issued by the operator of the assisting station to the operator of the master station who will issue the proper work permit or work and test permit.Another application is when work is being carried out on equipment part of which is under PHCN control and part of which is still controlled by a contractor. This might be on a generating unit or a station bus. In such instance the operator issues the contractor a station guarantee covering the isolation and de-energizing devices over which he does exercise control. (Rule 2045)

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